weixin_34236497
weixin_34236497

SpringBoot2.x Data JPA 多数据源爬坑

环境版本：

  • SpringBoot 2.1.3

JPA 官方文档

官方文档

5.1.2. Annotation-based Configuration

The Spring Data JPA repositories support can be activated not only through an XML namespace but also by using an annotation through JavaConfig, as shown in the following example:

Example 51. Spring Data JPA repositories using JavaConfig

@Configuration
@EnableJpaRepositories
@EnableTransactionManagement
class ApplicationConfig {

  @Bean
  public DataSource dataSource() {

    EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();
    return builder.setType(EmbeddedDatabaseType.HSQL).build();
  }

  @Bean
  public LocalContainerEntityManagerFactoryBean entityManagerFactory() {

    HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
    vendorAdapter.setGenerateDdl(true);

    LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
    factory.setJpaVendorAdapter(vendorAdapter);
    factory.setPackagesToScan("com.acme.domain");
    factory.setDataSource(dataSource());
    return factory;
  }

  @Bean
  public PlatformTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {

    JpaTransactionManager txManager = new JpaTransactionManager();
    txManager.setEntityManagerFactory(entityManagerFactory);
    return txManager;
  }
}
复制代码

文档中说明，基于注解的配置包含三个关键Bean：

  • PlatformTransactionManager——事务管理
  • LocalContainerEntityManagerFactoryBean——实体类管理
  • DataSource——数据源

同时还有一个关键注解@EnableJpaRepositories

SpringBoot官方文档

官方文档

多数据源使用@Primary指明优先级

You can even go further by leveraging what DataSourceProperties does for you — that is, by providing a default embedded database with a sensible username and password if no URL is provided. You can easily initialize a DataSourceBuilder from the state of any DataSourceProperties object, so you could also inject the DataSource that Spring Boot creates automatically. However, that would split your configuration into two namespaces: url, username, password, type, and driver on spring.datasource and the rest on your custom namespace (app.datasource). To avoid that, you can redefine a custom DataSourceProperties on your custom namespace, as shown in the following example:

@Bean
@Primary
@ConfigurationProperties("app.datasource")
public DataSourceProperties dataSourceProperties() {
	return new DataSourceProperties();
}

@Bean
@ConfigurationProperties("app.datasource.configuration")
public HikariDataSource dataSource(DataSourceProperties properties) {
	return properties.initializeDataSourceBuilder().type(HikariDataSource.class)
			.build();
}
复制代码

84.2 Configure Two DataSources

If you need to configure multiple data sources, you can apply the same tricks that are described in the previous section. You must, however, mark one of the DataSource instances as @Primary, because various auto-configurations down the road expect to be able to get one by type.

If you create your own DataSource, the auto-configuration backs off. In the following example, we provide the exact same feature set as the auto-configuration provides on the primary data source:

@Bean
@Primary
@ConfigurationProperties("app.datasource.first")
public DataSourceProperties firstDataSourceProperties() {
	return new DataSourceProperties();
}

@Bean
@Primary
@ConfigurationProperties("app.datasource.first.configuration")
public HikariDataSource firstDataSource() {
	return firstDataSourceProperties().initializeDataSourceBuilder()
			.type(HikariDataSource.class).build();
}

@Bean
@ConfigurationProperties("app.datasource.second")
public BasicDataSource secondDataSource() {
	return DataSourceBuilder.create().type(BasicDataSource.class).build();
}
复制代码

或者使用两个EntityManagers，并结合@EnableJpaRepositories进行配置

84.10 Use Two EntityManagers

Even if the default EntityManagerFactory works fine, you need to define a new one. Otherwise, the presence of the second bean of that type switches off the default. To make it easy to do, you can use the convenient EntityManagerBuilder provided by Spring Boot. Alternatively, you can just theLocalContainerEntityManagerFactoryBean directly from Spring ORM, as shown in the following example:

// add two data sources configured as above

@Bean
public LocalContainerEntityManagerFactoryBean customerEntityManagerFactory(
		EntityManagerFactoryBuilder builder) {
	return builder
			.dataSource(customerDataSource())
			.packages(Customer.class)
			.persistenceUnit("customers")
			.build();
}

@Bean
public LocalContainerEntityManagerFactoryBean orderEntityManagerFactory(
		EntityManagerFactoryBuilder builder) {
	return builder
			.dataSource(orderDataSource())
			.packages(Order.class)
			.persistenceUnit("orders")
			.build();
}
复制代码

The configuration above almost works on its own. To complete the picture, you need to configure TransactionManagers for the two EntityManagers as well. If you mark one of them as @Primary, it could be picked up by the default JpaTransactionManager in Spring Boot. The other would have to be explicitly injected into a new instance. Alternatively, you might be able to use a JTA transaction manager that spans both.

If you use Spring Data, you need to configure @EnableJpaRepositories accordingly, as shown in the following example:

@Configuration
@EnableJpaRepositories(basePackageClasses = Customer.class,
		entityManagerFactoryRef = "customerEntityManagerFactory")
public class CustomerConfiguration {
	...
}

@Configuration
@EnableJpaRepositories(basePackageClasses = Order.class,
		entityManagerFactoryRef = "orderEntityManagerFactory")
public class OrderConfiguration {
	...
}
复制代码

源码分析

自动装配类中声明了配置Bean和条件装配顺序

package org.springframework.boot.autoconfigure.data.jpa;

/**
 * {@link EnableAutoConfiguration Auto-configuration} for Spring Data's JPA Repositories.
 * 

 * Activates when there is a bean of type {@link javax.sql.DataSource} configured in the
 * context, the Spring Data JPA
 * {@link org.springframework.data.jpa.repository.JpaRepository} type is on the classpath,
 * and there is no other, existing
 * {@link org.springframework.data.jpa.repository.JpaRepository} configured.
 * 

 * Once in effect, the auto-configuration is the equivalent of enabling JPA repositories
 * using the {@link org.springframework.data.jpa.repository.config.EnableJpaRepositories}
 * annotation.
 * 

 * This configuration class will activate after the Hibernate auto-configuration.
 *
 * @author Phillip Webb
 * @author Josh Long
 * @see EnableJpaRepositories
 */
@Configuration
@ConditionalOnBean(DataSource.class)
@ConditionalOnClass(JpaRepository.class)
@ConditionalOnMissingBean({ JpaRepositoryFactoryBean.class,
		JpaRepositoryConfigExtension.class })
@ConditionalOnProperty(prefix = "spring.data.jpa.repositories", name = "enabled", havingValue = "true", matchIfMissing = true)
@Import(JpaRepositoriesAutoConfigureRegistrar.class)
@AutoConfigureAfter({ HibernateJpaAutoConfiguration.class,
		TaskExecutionAutoConfiguration.class })
public class JpaRepositoriesAutoConfiguration {

	@Bean
	@Conditional(BootstrapExecutorCondition.class)
	public EntityManagerFactoryBuilderCustomizer entityManagerFactoryBootstrapExecutorCustomizer(
			Map taskExecutors) {
		return (builder) -> {
			AsyncTaskExecutor bootstrapExecutor = determineBootstrapExecutor(
					taskExecutors);
			if (bootstrapExecutor != null) {
				builder.setBootstrapExecutor(bootstrapExecutor);
			}
		};
	}

	private AsyncTaskExecutor determineBootstrapExecutor(
			Map taskExecutors) {
		if (taskExecutors.size() == 1) {
			return taskExecutors.values().iterator().next();
		}
		return taskExecutors
				.get(TaskExecutionAutoConfiguration.APPLICATION_TASK_EXECUTOR_BEAN_NAME);
	}

	private static final class BootstrapExecutorCondition extends AnyNestedCondition {

		BootstrapExecutorCondition() {
			super(ConfigurationPhase.REGISTER_BEAN);
		}

		@ConditionalOnProperty(prefix = "spring.data.jpa.repositories", name = "bootstrap-mode", havingValue = "deferred", matchIfMissing = false)
		static class DeferredBootstrapMode {

		}

		@ConditionalOnProperty(prefix = "spring.data.jpa.repositories", name = "bootstrap-mode", havingValue = "lazy", matchIfMissing = false)
		static class LazyBootstrapMode {

		}

	}
}
复制代码

引入的配置类中声明了EnableJpaRepositories注解

package org.springframework.boot.autoconfigure.data.jpa;

class JpaRepositoriesAutoConfigureRegistrar
		extends AbstractRepositoryConfigurationSourceSupport {

	private BootstrapMode bootstrapMode = null;

	@Override
	protected Class getAnnotation() {
		return EnableJpaRepositories.class;
	}

	@Override
	protected Class getConfiguration() {
		return EnableJpaRepositoriesConfiguration.class;
	}

	@Override
	protected RepositoryConfigurationExtension getRepositoryConfigurationExtension() {
		return new JpaRepositoryConfigExtension();
	}

	@Override
	protected BootstrapMode getBootstrapMode() {
		return (this.bootstrapMode == null) ? super.getBootstrapMode()
				: this.bootstrapMode;
	}

	@Override
	public void setEnvironment(Environment environment) {
		super.setEnvironment(environment);
		configureBootstrapMode(environment);
	}

	private void configureBootstrapMode(Environment environment) {
		String property = environment
				.getProperty("spring.data.jpa.repositories.bootstrap-mode");
		if (StringUtils.hasText(property)) {
			this.bootstrapMode = BootstrapMode
					.valueOf(property.toUpperCase(Locale.ENGLISH));
		}
	}
    
	@EnableJpaRepositories
	private static class EnableJpaRepositoriesConfiguration {}
}
复制代码

EnableJpaRepositories注解定义

package org.springframework.data.jpa.repository.config;

/**
 * Annotation to enable JPA repositories. Will scan the package of the annotated configuration class for Spring Data
 * repositories by default.
 *
 * @author Oliver Gierke
 * @author Thomas Darimont
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(JpaRepositoriesRegistrar.class)
public @interface EnableJpaRepositories {

	String[] value() default {};

	String[] basePackages() default {};

	Class[] basePackageClasses() default {};

	Filter[] includeFilters() default {};

	Filter[] excludeFilters() default {};

	String repositoryImplementationPostfix() default "Impl";

	String namedQueriesLocation() default "";

	Key queryLookupStrategy() default Key.CREATE_IF_NOT_FOUND;

	Class repositoryFactoryBeanClass() default JpaRepositoryFactoryBean.class;

	Class repositoryBaseClass() default DefaultRepositoryBaseClass.class;

	/**
	 * 实体管理工厂
	 * @return
	 */
	String entityManagerFactoryRef() default "entityManagerFactory";

	/**
	 * 事务管理
	 * @return
	 */
	String transactionManagerRef() default "transactionManager";

	boolean considerNestedRepositories() default false;

	boolean enableDefaultTransactions() default true;

	/**
	 * Configures when the repositories are initialized in the bootstrap lifecycle. {@link BootstrapMode#DEFAULT}
	 * (default) means eager initialization except all repository interfaces annotated with {@link Lazy},
	 * {@link BootstrapMode#LAZY} means lazy by default including injection of lazy-initialization proxies into client
	 * beans so that those can be instantiated but will only trigger the initialization upon first repository usage (i.e a
	 * method invocation on it). This means repositories can still be uninitialized when the application context has
	 * completed its bootstrap. {@link BootstrapMode#DEFERRED} is fundamentally the same as {@link BootstrapMode#LAZY},
	 * but triggers repository initialization when the application context finishes its bootstrap.
	 * 
	 * @return
	 * @since 2.1
	 */
	BootstrapMode bootstrapMode() default BootstrapMode.DEFAULT;
}
复制代码

查找关键Bean的注册时机

package org.springframework.boot.autoconfigure.orm.jpa;

@Configuration
@ConditionalOnClass({ LocalContainerEntityManagerFactoryBean.class, EntityManager.class })
@Conditional(HibernateEntityManagerCondition.class)
@EnableConfigurationProperties(JpaProperties.class)
@AutoConfigureAfter({ DataSourceAutoConfiguration.class })
@Import(HibernateJpaConfiguration.class)
public class HibernateJpaAutoConfiguration {}
复制代码

进入配置Bean

package org.springframework.boot.autoconfigure.orm.jpa;

@Configuration
@EnableConfigurationProperties(HibernateProperties.class)
@ConditionalOnSingleCandidate(DataSource.class)
class HibernateJpaConfiguration extends JpaBaseConfiguration {}
复制代码

在其父类JpaBaseConfiguration中声明了装配时机和条件

package org.springframework.boot.autoconfigure.orm.jpa;

/**
 * 该类在2.0版本进行了重构
 * @since 2.0.0
 */
@Configuration
@EnableConfigurationProperties(JpaProperties.class)
@Import(DataSourceInitializedPublisher.Registrar.class)
public abstract class JpaBaseConfiguration implements BeanFactoryAware {
    
    @Bean
	@ConditionalOnMissingBean
	public PlatformTransactionManager transactionManager() {
		JpaTransactionManager transactionManager = new JpaTransactionManager();
		if (this.transactionManagerCustomizers != null) {
            // 默认使用方法名称
			this.transactionManagerCustomizers.customize(transactionManager);
		}
		return transactionManager;
	}

	@Bean
	@ConditionalOnMissingBean
	public JpaVendorAdapter jpaVendorAdapter() {
		AbstractJpaVendorAdapter adapter = createJpaVendorAdapter();
		adapter.setShowSql(this.properties.isShowSql());
		adapter.setDatabase(this.properties.determineDatabase(this.dataSource));
		adapter.setDatabasePlatform(this.properties.getDatabasePlatform());
		adapter.setGenerateDdl(this.properties.isGenerateDdl());
		return adapter;
	}

	@Bean
	@ConditionalOnMissingBean
	public EntityManagerFactoryBuilder entityManagerFactoryBuilder(
			JpaVendorAdapter jpaVendorAdapter,
			ObjectProvider persistenceUnitManager,
			ObjectProvider customizers) {
		EntityManagerFactoryBuilder builder = new EntityManagerFactoryBuilder(
				jpaVendorAdapter, this.properties.getProperties(),
				persistenceUnitManager.getIfAvailable());
		customizers.orderedStream()
				.forEach((customizer) -> customizer.customize(builder));
		return builder;
	}

	@Bean
	@Primary
	@ConditionalOnMissingBean({ LocalContainerEntityManagerFactoryBean.class,
			EntityManagerFactory.class })
	public LocalContainerEntityManagerFactoryBean entityManagerFactory(
			EntityManagerFactoryBuilder factoryBuilder) {
		Map vendorProperties = getVendorProperties();
		customizeVendorProperties(vendorProperties);
		return factoryBuilder.dataSource(this.dataSource).packages(getPackagesToScan())
				.properties(vendorProperties).mappingResources(getMappingResources())
				.jta(isJta()).build();
	}
}
复制代码

测试

爬完文档和源码，对需要配置Bean有了基本了解，新建工程进行多数据源测试

以当前最新版本SpringBoot进行测试

maven

xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.1.3.RELEASEversion>
        <relativePath/> 
    parent>
    <groupId>top.fjy8018groupId>
    <artifactId>jpadatasourceartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>jpadatasourcename>
    <description>Demo project for Spring Bootdescription>

    <properties>
        <java.version>1.8java.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-data-jpaartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>

        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <scope>runtimescope>
        dependency>

        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
        dependency>

        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
    dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>

project>
复制代码

实体类

通过包路径区分主库和备份库

主库实体类

package top.fjy8018.jpadatasource.entity.primary;

import lombok.Data;

import javax.persistence.Entity;
import javax.persistence.Id;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:11
 */
@Data
@Entity
public class Product {

    @Id
    private Integer id;

    private String name;

    private Integer price;
}
复制代码

备份库实体类

package top.fjy8018.jpadatasource.entity.backup;

import lombok.Data;

import javax.persistence.Entity;
import javax.persistence.Id;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:36
 */
@Data
@Entity(name = "tb_order")
public class Order {

    @Id
    private Integer id;

    private String orderName;

    private Integer price;
}
复制代码

坑一：表名关键字冲突

若此处不指定表名为tb_order则会与MySQL关键字冲突导致建表失败

报错：

org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "
    create table Order (
       id integer not null,
        orderName varchar(255),
        price integer,
        primary key (id)
    ) engine=InnoDB" via JDBC Statement
    ...
复制代码

DAO

package top.fjy8018.jpadatasource.repository.backup;

import org.springframework.data.jpa.repository.JpaRepository;
import top.fjy8018.jpadatasource.entity.backup.Order;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:12
 */
public interface OrderRepository extends JpaRepository<Order, Integer> {
}
复制代码
package top.fjy8018.jpadatasource.repository.primary;

import org.springframework.data.jpa.repository.JpaRepository;
import top.fjy8018.jpadatasource.entity.primary.Product;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:12
 */
public interface ProductRepository extends JpaRepository<Product, Integer> {
}
复制代码

配置Bean

官方配置样例：

Both data sources are also bound for advanced customizations. For instance, you could configure them as follows:

app.datasource.first.url=jdbc:mysql://localhost/first
app.datasource.first.username=dbuser
app.datasource.first.password=dbpass
app.datasource.first.configuration.maximum-pool-size=30

app.datasource.second.url=jdbc:mysql://localhost/second
app.datasource.second.username=dbuser
app.datasource.second.password=dbpass
app.datasource.second.max-total=30
复制代码

You can apply the same concept to the secondary DataSource as well, as shown in the following example:

@Bean
@Primary
@ConfigurationProperties("app.datasource.first")
public DataSourceProperties firstDataSourceProperties() {
	return new DataSourceProperties();
}

@Bean
@Primary
@ConfigurationProperties("app.datasource.first.configuration")
public HikariDataSource firstDataSource() {
	return firstDataSourceProperties().initializeDataSourceBuilder()
			.type(HikariDataSource.class).build();
}

@Bean
@ConfigurationProperties("app.datasource.second")
public DataSourceProperties secondDataSourceProperties() {
	return new DataSourceProperties();
}

@Bean
@ConfigurationProperties("app.datasource.second.configuration")
public BasicDataSource secondDataSource() {
	return secondDataSourceProperties().initializeDataSourceBuilder()
			.type(BasicDataSource.class).build();
}
复制代码

The preceding example configures two data sources on custom namespaces with the same logic as Spring Boot would use in auto-configuration. Note that each configuration sub namespace provides advanced settings based on the chosen implementation.

参照编写配置文件，此处注意SpringBoot 2.x的驱动变化

坑二：mysql驱动类名变化

详见：SpringBoot mysql驱动问题

spring:
  datasource:
    first:
      driver-class-name: com.mysql.cj.jdbc.Driver
      username: financial_adminer
      password: financial_adminer_pass
      url: jdbc:mysql://localhost/jpa_test?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
      configuration:
        maximum-pool-size: 30
    second:
      driver-class-name: com.mysql.cj.jdbc.Driver
      username: financial_adminer
      password: financial_adminer_pass
      url: jdbc:mysql://localhost/jpa_test_bak?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
      configuration:
        maximum-pool-size: 20

  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    database-platform: org.hibernate.dialect.MySQL55Dialect
    properties:
      hibernate:
        format_sql: true
        use_sql_comments: true
复制代码

配置类

package top.fjy8018.jpadatasource.config;

import com.zaxxer.hikari.HikariDataSource;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:24
 */
@Configuration
public class DataAccessConfig {
    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first")
    public DataSourceProperties firstDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first.configuration")
    public HikariDataSource firstDataSource() {
        return firstDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second")
    public DataSourceProperties secondDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second.configuration")
    public HikariDataSource secondDataSource() {
        return secondDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }
}
复制代码

配置完成后发现只在主库自动建表，备份库无变化，属于预期情况，因为目前仅配置了三个必须Bean的其中一个

继续配置实体管理和事务管理Bean

官方文档样例

84.10 Use Two EntityManagers

Even if the default EntityManagerFactory works fine, you need to define a new one. Otherwise, the presence of the second bean of that type switches off the default. To make it easy to do, you can use the convenient EntityManagerBuilder provided by Spring Boot. Alternatively, you can just theLocalContainerEntityManagerFactoryBean directly from Spring ORM, as shown in the following example:

// add two data sources configured as above

@Bean
public LocalContainerEntityManagerFactoryBean customerEntityManagerFactory(
		EntityManagerFactoryBuilder builder) {
	return builder
			.dataSource(customerDataSource())
			.packages(Customer.class)
			.persistenceUnit("customers")
			.build();
}

@Bean
public LocalContainerEntityManagerFactoryBean orderEntityManagerFactory(
		EntityManagerFactoryBuilder builder) {
	return builder
			.dataSource(orderDataSource())
			.packages(Order.class)
			.persistenceUnit("orders")
			.build();
}
复制代码

The configuration above almost works on its own. To complete the picture, you need to configure TransactionManagers for the two EntityManagers as well. If you mark one of them as @Primary, it could be picked up by the default JpaTransactionManager in Spring Boot. The other would have to be explicitly injected into a new instance. Alternatively, you might be able to use a JTA transaction manager that spans both.

If you use Spring Data, you need to configure @EnableJpaRepositories accordingly, as shown in the following example:

@Configuration
@EnableJpaRepositories(basePackageClasses = Customer.class,
		entityManagerFactoryRef = "customerEntityManagerFactory")
public class CustomerConfiguration {
	...
}

@Configuration
@EnableJpaRepositories(basePackageClasses = Order.class,
		entityManagerFactoryRef = "orderEntityManagerFactory")
public class OrderConfiguration {
	...
}
复制代码

工程配置

package top.fjy8018.jpadatasource.config;

import com.zaxxer.hikari.HikariDataSource;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import top.fjy8018.jpadatasource.entity.backup.Order;
import top.fjy8018.jpadatasource.entity.primary.Product;
import top.fjy8018.jpadatasource.repository.backup.OrderRepository;
import top.fjy8018.jpadatasource.repository.primary.ProductRepository;

import javax.sql.DataSource;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:24
 */
@Configuration
public class DataAccessConfig {
    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first")
    public DataSourceProperties firstDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first.configuration")
    public HikariDataSource firstDataSource() {
        return firstDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second")
    public DataSourceProperties secondDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second.configuration")
    public HikariDataSource secondDataSource() {
        return secondDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean firstEntityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("firstDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .packages(Product.class)
                .persistenceUnit("first")
                .build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean secondEntityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("secondDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .packages(Order.class)
                .persistenceUnit("second")
                .build();
    }

    @Bean
    public PlatformTransactionManager primaryTransactionManager(
            @Qualifier("firstEntityManagerFactory") LocalContainerEntityManagerFactoryBean entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory.getObject());
    }

    @Bean
    public PlatformTransactionManager backupTransactionManager(
            @Qualifier("secondEntityManagerFactory") LocalContainerEntityManagerFactoryBean entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory.getObject());
    }

    @EnableJpaRepositories(basePackageClasses = ProductRepository.class,
            entityManagerFactoryRef = "firstEntityManagerFactory")
    @Primary
    public class PrimaryConfiguration {
    }

    @EnableJpaRepositories(basePackageClasses = OrderRepository.class,
            entityManagerFactoryRef = "secondEntityManagerFactory")
    public class secondConfiguration {
    }
}
复制代码

坑三：官方文档样例有误

此时配置直接启动会报错

Method requestMappingHandlerMapping in org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$EnableWebMvcConfiguration required a single bean, but 2 were found:
	- firstEntityManagerFactory: defined by method 'firstEntityManagerFactory' in class path resource [top/fjy8018/jpadatasource/config/DataAccessConfig.class]
	- secondEntityManagerFactory: defined by method 'secondEntityManagerFactory' in class path resource [top/fjy8018/jpadatasource/config/DataAccessConfig.class]


Action:

Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

复制代码

意思是自动装配时发现两个类型一致的Bean，主要指定优先级，而官方文档对此处可能出现的问题并未提示

指定firstEntityManagerFactory为优先Bean，同时文档样例创建了事务管理器但未配置到@EnableJpaRepositories注解中，此处也一并配置

最终配置类如下

package top.fjy8018.jpadatasource.config;

import com.zaxxer.hikari.HikariDataSource;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import top.fjy8018.jpadatasource.entity.backup.Order;
import top.fjy8018.jpadatasource.entity.primary.Product;
import top.fjy8018.jpadatasource.repository.backup.OrderRepository;
import top.fjy8018.jpadatasource.repository.primary.ProductRepository;

import javax.sql.DataSource;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:24
 */
@Configuration
public class DataAccessConfig {
    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first")
    public DataSourceProperties firstDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first.configuration")
    public HikariDataSource firstDataSource() {
        return firstDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second")
    public DataSourceProperties secondDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second.configuration")
    public HikariDataSource secondDataSource() {
        return secondDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean firstEntityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("firstDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .packages(Product.class)
                .persistenceUnit("first")
                .build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean secondEntityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("secondDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .packages(Order.class)
                .persistenceUnit("second")
                .build();
    }

    @Bean
    public PlatformTransactionManager primaryTransactionManager(
            @Qualifier("firstEntityManagerFactory") LocalContainerEntityManagerFactoryBean entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory.getObject());
    }

    @Bean
    public PlatformTransactionManager backupTransactionManager(
            @Qualifier("secondEntityManagerFactory") LocalContainerEntityManagerFactoryBean entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory.getObject());
    }

    @EnableJpaRepositories(basePackageClasses = ProductRepository.class,
            entityManagerFactoryRef = "firstEntityManagerFactory", transactionManagerRef = "primaryTransactionManager")
    @Primary
    public class PrimaryConfiguration {
    }

    @EnableJpaRepositories(basePackageClasses = OrderRepository.class,
            entityManagerFactoryRef = "secondEntityManagerFactory", transactionManagerRef = "backupTransactionManager")
    public class secondConfiguration {
    }
}
复制代码

坑四：JPA不会自动建表

配置完成后启动

发现日志中建表SQL没有输出，同时查看数据库，确认表未创建

但官方文档对多数据源的配置说明已经结束，令人疑惑

自动建表语句没生成猜想可能由于与ddl相关的属性未配置导致

进入配置文件查看ddl配置，发现默认为false

将其配置为true后总配置文件如下

spring:
  datasource:
    first:
      driver-class-name: com.mysql.cj.jdbc.Driver
      username: financial_adminer
      password: financial_adminer_pass
      url: jdbc:mysql://120.79.226.26/jpa_test?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
      configuration:
        maximum-pool-size: 30
    second:
      driver-class-name: com.mysql.cj.jdbc.Driver
      username: financial_adminer
      password: financial_adminer_pass
      url: jdbc:mysql://120.79.226.26/jpa_test_bak?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
      configuration:
        maximum-pool-size: 20

  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    database-platform: org.hibernate.dialect.MySQL55Dialect
    properties:
      hibernate:
        format_sql: true
        use_sql_comments: true
    generate-ddl: true
复制代码

启动工程发现自动建表生效

查看数据库情况，与预期一致，主库只包含主库的表，备份库只包含备份库的表，多数据配置完成

坑五：hibernate默认配置被覆盖

若在单数据源配置下应当无需配置该项，同时发现本应该默认将驼峰属性名映射为_拼接名称策略也失效，说明自定义配置源时覆盖了默认配置或者导致默认配置失效

查询源码分析原因，发现hibernate相关配置均在HibernateProperties配置类中

package org.springframework.boot.autoconfigure.orm.jpa;

/**
 * Configuration properties for Hibernate.
 *
 * @author Stephane Nicoll
 * @since 2.1.0
 * @see JpaProperties
 */
@ConfigurationProperties("spring.jpa.hibernate")
public class HibernateProperties {}
复制代码

而该类在HibernateJpaConfiguration中进行注入，但配置类中进行了条件装配注解@ConditionalOnSingleCandidate标注，导致在多数据源情况下不满足该配置，类没有被装配到Spring Bean中

package org.springframework.boot.autoconfigure.orm.jpa;

/**
 * {@link JpaBaseConfiguration} implementation for Hibernate.
 * @since 2.0.0
 */
@Configuration
@EnableConfigurationProperties(HibernateProperties.class)
@ConditionalOnSingleCandidate(DataSource.class)
class HibernateJpaConfiguration extends JpaBaseConfiguration {

	private final HibernateProperties hibernateProperties;

	HibernateJpaConfiguration(DataSource dataSource, JpaProperties jpaProperties,
			ConfigurableListableBeanFactory beanFactory,
			ObjectProvider jtaTransactionManager,
			ObjectProvider transactionManagerCustomizers,
			HibernateProperties hibernateProperties,
			ObjectProvider> metadataProviders,
			ObjectProvider providers,
			ObjectProvider physicalNamingStrategy,
			ObjectProvider implicitNamingStrategy,
			ObjectProvider hibernatePropertiesCustomizers) {
		super(dataSource, jpaProperties, jtaTransactionManager,
				transactionManagerCustomizers);
		this.hibernateProperties = hibernateProperties;
		this.defaultDdlAutoProvider = new HibernateDefaultDdlAutoProvider(providers);
		this.poolMetadataProvider = new CompositeDataSourcePoolMetadataProvider(
				metadataProviders.getIfAvailable());
		this.hibernatePropertiesCustomizers = determineHibernatePropertiesCustomizers(
				physicalNamingStrategy.getIfAvailable(),
				implicitNamingStrategy.getIfAvailable(), beanFactory,
				hibernatePropertiesCustomizers.orderedStream()
						.collect(Collectors.toList()));
	}
    ...
}
复制代码

解决方法就只能自己工程内实现该类的配置，注意，Spring 2.x版本自动装配变化较大，当前配置基于最新版2.1.3有效，并不代表对后续版本一定兼容

工程配置

package top.fjy8018.jpadatasource.config;

import com.zaxxer.hikari.HikariDataSource;
import org.hibernate.boot.model.naming.ImplicitNamingStrategy;
import org.hibernate.boot.model.naming.PhysicalNamingStrategy;
import org.hibernate.cfg.AvailableSettings;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties;
import org.springframework.boot.autoconfigure.orm.jpa.HibernatePropertiesCustomizer;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateSettings;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.EmbeddedDatabaseConnection;
import org.springframework.boot.jdbc.SchemaManagement;
import org.springframework.boot.jdbc.SchemaManagementProvider;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.hibernate5.SpringBeanContainer;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.util.ClassUtils;
import top.fjy8018.jpadatasource.entity.backup.Order;
import top.fjy8018.jpadatasource.entity.primary.Product;
import top.fjy8018.jpadatasource.repository.backup.OrderRepository;
import top.fjy8018.jpadatasource.repository.primary.ProductRepository;

import javax.sql.DataSource;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

/**
 * @author F嘉阳
 * @date 2019-03-30 9:24
 */
@Configuration
public class DataAccessConfig {

    private final ObjectProvider providers;

    private final HibernateProperties hibernateProperties;

    private final JpaProperties properties;

    private final ObjectProvider physicalNamingStrategy;

    private final ObjectProvider implicitNamingStrategy;

    private final ConfigurableListableBeanFactory beanFactory;

    private final ObjectProvider hibernatePropertiesCustomizers;

    @Autowired
    public DataAccessConfig(ObjectProvider providers, HibernateProperties hibernateProperties, JpaProperties properties, ObjectProvider physicalNamingStrategy, ObjectProvider implicitNamingStrategy, ConfigurableListableBeanFactory beanFactory, ObjectProvider hibernatePropertiesCustomizers) {
        this.providers = providers;
        this.hibernateProperties = hibernateProperties;
        this.properties = properties;
        this.physicalNamingStrategy = physicalNamingStrategy;
        this.implicitNamingStrategy = implicitNamingStrategy;
        this.beanFactory = beanFactory;
        this.hibernatePropertiesCustomizers = hibernatePropertiesCustomizers;
    }

    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first")
    public DataSourceProperties firstDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.first.configuration")
    public HikariDataSource firstDataSource() {
        return firstDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second")
    public DataSourceProperties secondDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.second.configuration")
    public HikariDataSource secondDataSource() {
        return secondDataSourceProperties().initializeDataSourceBuilder()
                .type(HikariDataSource.class).build();
    }

    @Bean
    @Primary
    public LocalContainerEntityManagerFactoryBean firstEntityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("firstDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                // 加入规约配置
                .properties(getVendorProperties(dataSource))
                .packages(Product.class)
                .persistenceUnit("first")
                .build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean secondEntityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("secondDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .properties(getVendorProperties(dataSource))
                .packages(Order.class)
                .persistenceUnit("second")
                .build();
    }

    @Bean
    public PlatformTransactionManager primaryTransactionManager(
            @Qualifier("firstEntityManagerFactory") LocalContainerEntityManagerFactoryBean entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory.getObject());
    }

    @Bean
    public PlatformTransactionManager backupTransactionManager(
            @Qualifier("secondEntityManagerFactory") LocalContainerEntityManagerFactoryBean entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory.getObject());
    }

    @EnableJpaRepositories(basePackageClasses = ProductRepository.class,
            entityManagerFactoryRef = "firstEntityManagerFactory", transactionManagerRef = "primaryTransactionManager")
    @Primary
    public class PrimaryConfiguration {
    }

    @EnableJpaRepositories(basePackageClasses = OrderRepository.class,
            entityManagerFactoryRef = "secondEntityManagerFactory", transactionManagerRef = "backupTransactionManager")
    public class secondConfiguration {
    }

    /**
     * 获取配置文件信息
     *
     * @param dataSource
     * @return
     */
    private Map getVendorProperties(DataSource dataSource) {
        List hibernatePropertiesCustomizers = determineHibernatePropertiesCustomizers(
                physicalNamingStrategy.getIfAvailable(),
                implicitNamingStrategy.getIfAvailable(), beanFactory,
                this.hibernatePropertiesCustomizers.orderedStream()
                        .collect(Collectors.toList()));
        Supplier defaultDdlMode = () -> new HibernateDefaultDdlAutoProvider(providers)
                .getDefaultDdlAuto(dataSource);
        return new LinkedHashMap<>(this.hibernateProperties.determineHibernateProperties(
                properties.getProperties(),
                new HibernateSettings().ddlAuto(defaultDdlMode)
                        .hibernatePropertiesCustomizers(
                                hibernatePropertiesCustomizers)));
    }

    /**
     * 命名策略自动判断
     *
     * @param physicalNamingStrategy
     * @param implicitNamingStrategy
     * @param beanFactory
     * @param hibernatePropertiesCustomizers
     * @return
     */
    private List determineHibernatePropertiesCustomizers(
            PhysicalNamingStrategy physicalNamingStrategy,
            ImplicitNamingStrategy implicitNamingStrategy,
            ConfigurableListableBeanFactory beanFactory,
            List hibernatePropertiesCustomizers) {
        List customizers = new ArrayList<>();
        if (ClassUtils.isPresent(
                "org.hibernate.resource.beans.container.spi.BeanContainer",
                getClass().getClassLoader())) {
            customizers
                    .add((properties) -> properties.put(AvailableSettings.BEAN_CONTAINER,
                            new SpringBeanContainer(beanFactory)));
        }
        if (physicalNamingStrategy != null || implicitNamingStrategy != null) {
            customizers.add(new NamingStrategiesHibernatePropertiesCustomizer(
                    physicalNamingStrategy, implicitNamingStrategy));
        }
        customizers.addAll(hibernatePropertiesCustomizers);
        return customizers;
    }

    /**
     * 自动进行建表操作
     */
    class HibernateDefaultDdlAutoProvider implements SchemaManagementProvider {

        private final Iterable providers;

        HibernateDefaultDdlAutoProvider(Iterable providers) {
            this.providers = providers;
        }

        public String getDefaultDdlAuto(DataSource dataSource) {
            if (!EmbeddedDatabaseConnection.isEmbedded(dataSource)) {
                return "none";
            }
            SchemaManagement schemaManagement = getSchemaManagement(dataSource);
            if (SchemaManagement.MANAGED.equals(schemaManagement)) {
                return "none";
            }
            return "create-drop";

        }

        @Override
        public SchemaManagement getSchemaManagement(DataSource dataSource) {
            return StreamSupport.stream(this.providers.spliterator(), false)
                    .map((provider) -> provider.getSchemaManagement(dataSource))
                    .filter(SchemaManagement.MANAGED::equals).findFirst()
                    .orElse(SchemaManagement.UNMANAGED);
        }

    }

    private static class NamingStrategiesHibernatePropertiesCustomizer
            implements HibernatePropertiesCustomizer {

        private final PhysicalNamingStrategy physicalNamingStrategy;

        private final ImplicitNamingStrategy implicitNamingStrategy;

        NamingStrategiesHibernatePropertiesCustomizer(
                PhysicalNamingStrategy physicalNamingStrategy,
                ImplicitNamingStrategy implicitNamingStrategy) {
            this.physicalNamingStrategy = physicalNamingStrategy;
            this.implicitNamingStrategy = implicitNamingStrategy;
        }

        /**
         * 数据库命名映射策略
         *
         * @param hibernateProperties the JPA vendor properties to customize
         */
        @Override
        public void customize(Map hibernateProperties) {
            if (this.physicalNamingStrategy != null) {
                hibernateProperties.put("hibernate.physical_naming_strategy",
                        this.physicalNamingStrategy);
            }
            if (this.implicitNamingStrategy != null) {
                hibernateProperties.put("hibernate.implicit_naming_strategy",
                        this.implicitNamingStrategy);
            }
        }
    }
}
复制代码

配置Bean完成后则规约配置会生效，便无需在配置文件显示配置DDL语句执行开关

启动日志也可看出结果符合预期

总结

由此发现，在SpringBoot版本迁移过程中不一定互相兼容，同时官方文档尽管全面，但随着版本变化文档也有不准确情况。而如果完全依靠爬源码复制源码配置也是无法实现最简单化的配置，需要结合文档、源码、日志逐一分析

工程源码已开放，注意配置自己的数据库连接地址，工程内的连接地址已经失效

GitHub源码

转载于:https://juejin.im/post/5c9f52de51882567c94e7184

你可能感兴趣的:(SpringBoot2.x Data JPA 多数据源爬坑)

  • WPF中的ComboBox控件几种数据绑定的方式 互联网打工人no1 wpfc#
    一、用字典给ItemsSource赋值（此绑定用的地方很多，建议熟练掌握）在XMAL中：在CS文件中privatevoidBindData(){DictionarydicItem=newDictionary();dicItem.add(1,"北京");dicItem.add(2,"上海");dicItem.add(3,"广州");cmb_list.ItemsSource=dicItem;cmb_l
  • 将cmd中命令输出保存为txt文本文件 落难Coder Windowscmdwindow
    最近深度学习本地的训练中我们常常要在命令行中运行自己的代码，无可厚非，我们有必要保存我们的炼丹结果，但是复制命令行输出到txt是非常麻烦的，其实Windows下的命令行为我们提供了相应的操作。其基本的调用格式就是：运行指令>输出到的文件名称或者具体保存路径测试下，我打开cmd并且ping一下百度：pingwww.baidu.com>./data.txt看下相同目录下data.txt的输出：如果你再
  • Linux MariaDB使用OpenSSL安装SSL证书 Meta39 MySQLOracleMariaDBLinuxWindowsssllinuxmariadb
    进入到证书存放目录，批量删除.pem证书警告：确保已经进入到证书存放目录find.-typef-iname\*.pem-delete查看是否安装OpenSSLopensslversion没有则安装yuminstallopensslopenssl-devel开启SSL编辑/etc/my.cnf文件（没有的话就创建，但是要注意，在/etc/my.cnf.d/server.cnf配置了datadir的，
  • 网络编程基础 记得开心一点啊 网络
    目录♫什么是网络编程♫Socket套接字♪什么是Socket套接字♪数据报套接字♪流套接字♫数据报套接字通信模型♪数据报套接字通讯模型♪DatagramSocket♪DatagramPacket♪实现UDP的服务端代码♪实现UDP的客户端代码♫流套接字通信模型♪流套接字通讯模型♪ServerSocket♪Socket♪实现TCP的服务端代码♪实现TCP的客户端代码♫什么是网络编程网络编程，指网络上
  • K近邻算法_分类鸢尾花数据集 _feivirus_ 算法机器学习和数学分类机器学习K近邻
    importnumpyasnpimportpandasaspdfromsklearn.datasetsimportload_irisfromsklearn.model_selectionimporttrain_test_splitfromsklearn.metricsimportaccuracy_score1.数据预处理iris=load_iris()df=pd.DataFrame(data=ir
  • 4.C_数据结构_队列 荣世蓥 数据结构数据结构
    概述什么是队列：队列是限定在两端进行插入操作和删除操作的线性表。具有先入先出(FIFO)的特点相关名词：队尾：写入数据的一段队头：读取数据的一段空队：队列中没有数据，队头指针=队尾指针满队：队列中存满了数据，队尾指针+1=队头指针循环队列1、基本内容循环队列是以数组形式构成的队列数据结构。循环队列的结构体如下：typedefintdata_t;//队列数据类型#defineN64//队列容量typ
  • vue项目element-ui的table表格单元格合并 酋长哈哈 vue.jselementuijavascript前端
    一、合并效果二全部代码exportdefault{name:'CellMerge',data(){return{tableData:[{id:'1',name:'王小虎',amount1:'165',amount2:'3.2',amount3:10},{id:'1',name:'王小虎',amount1:'162',amount2:'4.43',amount3:12},{id:'1',name:'
  • python tif转png Python与遥感 python开发语言
    importosfromosgeoimportgdalimportnumpyasnpfromPILimportImage#提取432三波段fromspectralimport*#输入文件夹路径defget_img(dataset_img):width=dataset_img.RasterXSize#获取行列数height=dataset_img.RasterYSizebands=dataset_i
  • MongoDB知识概括 GeorgeLin98 持久层mongodb
    MongoDB知识概括MongoDB相关概念单机部署基本常用命令索引-IndexSpirngDataMongoDB集成副本集分片集群安全认证MongoDB相关概念业务应用场景：传统的关系型数据库（如MySQL），在数据操作的“三高”需求以及应对Web2.0的网站需求面前，显得力不从心。解释：“三高”需求：①Highperformance-对数据库高并发读写的需求。②HugeStorage-对海量数
  • Vue中table合并单元格用法 weixin_30613343 javascriptViewUI
    地名结果人名性别{{item.name}}已完成未完成{{item.groups[0].name}}{{item.groups[0].sex}}{{item.groups[son].name}}{{item.groups[son].sex}}exportdefault{data(){return{list:[{name:'地名1',result:'1',groups:[{name:'张三',sex
  • uniapp map组件自定义markers标记点 以对_ uni-app学习记录uni-appjavascript前端
    需求是根据后端返回数据在地图上显示标记点，并且根据数据状态控制标记点颜色，标记点背景通过两张图片实现控制{{item.options.labelName}}exportdefault{data(){return{storeIndex:0,locaInfo:{longitude:120.445172,latitude:36.111387},markers:[//标点列表{id:1,//标记点idin
  • 博客网站制作教程 2401_85194651 javamaven
    首先就是技术框架：后端：Java+SpringBoot数据库：MySQL前端：Vue.js数据库连接：JPA(JavaPersistenceAPI)1.项目结构blog-app/├──backend/│├──src/main/java/com/example/blogapp/││├──BlogApplication.java││├──config/│││└──DatabaseConfig.java
  • vue + Element UI table动态合并单元格 我家媳妇儿萌哒哒 elementUIvue.js前端javascript
    一、功能需求1、根据名称相同的合并工作阶段和主要任务合并这两列，但主要任务内容一样，但要考虑主要任务一样，但工作阶段不一样的情况。（枞向合并）2、落实情况里的定量内容和定性内容值一样则合并。（横向合并）二、功能实现exportdefault{data(){return{tableData:[{name:'a',address:'1',age:'1',six:'2'},{name:'a',addre
  • Python实现TIFF 文件转换为 PNG 和 JPG 格式 sand&wich python开发语言
    在日常的图像处理工作中，可能会遇到需要将TIFF格式的图像转换为其他格式的情况，例如PNG和JPG。下面，本文将介绍如何使用Python和GDAL库实现这一功能。准备工作在开始之前，请确保已经安装了必要的库：GDAL（GeospatialDataAbstractionLibrary）可以使用以下命令安装GDAL：pipinstallgdal代码实现以下是一个将TIFF文件转换为PNG文件的示例代码
  • 使用datepicker和uploadify的冲突解决（IE双击才能打开附件上传对话框） zhanglb12
    在开发的过程当中，IE的兼容无疑是我们的一块绊脚石，在我们使用的如期的datepicker插件和使用上传附件的uploadify插件的时候，两者就产生冲突，只要点击过时间的插件，uploadify上传框要双才能打开ie浏览器提示错误Missinginstancedataforthisdatepicker解决方案//if(.browser.msie&&'9.0'===.browser.version
  • golang获取用户输入的几种方式 余生逆风飞翔 golang开发语言后端
    一、定义结构体typeUserInfostruct{Namestring`json:"name"`Ageint`json:"age"`Addstring`json:"add"`}typeReturnDatastruct{Messagestring`json:"message"`Statusstring`json:"status"`DataUserInfo`json:"data"`}二、get请求的
  • 【Java】已解决：org.springframework.jdbc.datasource.lookup.DataSourceLookupFailureException 屿小夏 java开发语言
    文章目录一、分析问题背景问题背景描述出现问题的场景二、可能出错的原因三、错误代码示例四、正确代码示例五、注意事项已解决：org.springframework.jdbc.datasource.lookup.DataSourceLookupFailureException在使用Spring框架进行开发时，数据源的配置和使用是非常关键的一环。然而，有时候我们可能会遇到org.springframewo
  • el-table实现全选整表，单元一页复选框功能 周bro vue.jselementuijavascript前端
    全选整表单选一页0":popper-append-to-body="false":total="tableData.length":page-size="pageObj.pagesize":page-sizes="[10,50,100]"layout="total,sizes,prev,pager,next"@size-change="handleSizeChange"@current-chang
  • Vue + Express实现一个表单提交 九旬大爷的梦
    最近在折腾一个cms系统，用的vue+express，但是就一个表单提交就弄了好久，记录一下。环境：Node10+前端：Vue服务端：Express依赖包：vueexpressaxiosexpress-formidableelement-ui（可选）前言：axiosget请求参数是：paramsaxiospost请求参数是：dataexpressget接受参数是req.queryexpresspo
  • Kubernetes部署MySQL数据持久化 沫殇-MS KubernetesMySQL数据库kubernetesmysql容器
    一、安装配置NFS服务端1、安装nfs-kernel-server：sudoapt-yinstallnfs-kernel-server2、服务端创建共享目录#列出所有可用块设备的信息lsblk#格式化磁盘sudomkfs-text4/dev/sdb#创建一个目录：sudomkdir-p/data/nfs/mysql#更改目录权限：sudochown-Rnobody:nogroup/data/nfs
  • Hadoop架构 henan程序媛 hadoop大数据分布式
    一、案列分析1.1案例概述现在已经进入了大数据(BigData)时代，数以万计用户的互联网服务时时刻刻都在产生大量的交互，要处理的数据量实在是太大了，以传统的数据库技术等其他手段根本无法应对数据处理的实时性、有效性的需求。HDFS顺应时代出现，在解决大数据存储和计算方面有很多的优势。1.2案列前置知识点1.什么是大数据大数据是指无法在一定时间范围内用常规软件工具进行捕捉、管理和处理的大量数据集合，
  • 使用input[type=file]遇上的一些问题 刘圣凯
    项目遇到一个需要，如下image.png功能大致就是添加图片，展示出来，然后在用户点击提交的时候把图片传给后台，在和后台交涉之后，决定在用户选择图片之后转成formdata传给后台，后台返回一个url，提交的时候将url返回给后台/**转formdata*/varformdata=newFormData();formdata.append("file1",$("#pic")[0].files[0]
  • 详解mybatis的一二级缓存以及缓存失效原因 仰望天花板 缓存数据库mybatisjavamysql
    数据库的大部分场景下是从磁盘读取，如果数据从内存进行读取，速度较比磁盘要快得多。但因为内存的容量有限，所以一般只会把使用和查询较多的数据缓存起来，以便快速反应，其他使用率不太多的继续存放在磁盘。mybatis分为一级缓存和二级缓存1.一级缓存一级缓存存放在SqlSqeeion上，默认开启1.1pojo@DatapublicclassRole{privateLongid;privateStringr
  • 小程序通过js控制页面字体颜色属性 祈澈菇凉
    需求：当电量少于百分之20的时候，显示电量的字体显示为红色。1：在wxml里面设置属性batStyle：style="{{item.batStyle}}"电量:{{item.battery}}%2：当复合逻辑条件的时候，在js里面carList[i].batStyle="color:red";success:function(res){constcarList=res.data.list;for(
  • Golang Channel PandaSkr golang
    Channel解析1.Channel源码分析1.1Channel数据结构typehchanstruct{qcountuint//channel的元素数量dataqsizuint//channel循环队列长度bufunsafe.Pointer//指向循环队列的指针elemsizeuint16//元素大小closeduint32//channel是否关闭0-未关闭elemtype*_type//元素类
  • matlab游标标注移动,matlab实现图形窗口的数据游标 莫白想 matlab游标标注移动
    DatacursorsforfigurewindowSeveralrelatedfunctions:CreateCursorsetsupaverticalcursoronallaxesinafigure.Thecursorscanbemovedaroundusingthemouse.MultiplecursorsaresupportedineachfigureGetCursorLocationre
  • 使用FPGA接收MIPI CSI RX信号并进行去抖动、RGB转YUV处理：FX3014 USB3.0 UVC传输与帧率控制源代码，FPGA实现MIPI CSI RX接收，去Debayer， RGB转 kVfINoSzdrt fpga开发程序人生
    fpgamipicsirx接收去debayer,rgb转yuv,fx3014usb3.0uvc传输与帧率控制源代码，具体架构看图，除dphy物理层外，mipi均为源码sensorimx219mipi源码mipi4lanecsirxraw10fpgamachXO3lf-690usb3.0fx301432bityuvdatawithframesync测试模式3280*246415fps1920*108
  • 数据结构 1 五花肉村长 数据结构算法开发语言c语言visualstudio
    1.什么是数据结构数据结构（DataStructure）是计算机存储和组织数据的方式，是指相互之间存在的一种或多种特定关系的数据元的集合。2.什么是算法算法（Algorithm）就是定义良好的计算过程，他取一个或一组的值为输入，并产生出一个或一组值作为输出。简单来说算法就是一系列的计算步骤，用来将输入数据转化成输出结果。3.数据结构和算法的书籍资料学习完数据结构知识，可以去看《剑指offer》和《
  • 好看的vue登录页面(附 源代码 背景图) 小小薛定谔 vue.jsjavascriptcss前端
    一、效果展示二、代码你好!欢迎回来登录忘记密码?注册exportdefault{name:"MedLogin",data(){return{confirm_disabled:false,loginForm:{no:'',password:''},rules:{no:[{required:true,message:'请输入账号',trigger:'blur'},{min:3,max:6,messag
  • 36. MyBatis如何支持多数据库操作？如何配置不同的数据源？ 这孩子叫逆 Mybatis笔记mybatis数据库
    在许多企业级应用中，可能需要访问多个数据库。MyBatis可以通过配置多个数据源和动态切换数据源来支持多数据库操作。下面介绍如何在MyBatis中配置和使用多个数据源。1.多数据源的基本配置1.1配置多个数据源要支持多个数据源，首先需要在Spring或SpringBoot中配置不同的数据源。假设我们要连接两个数据库db1和db2，可以通过以下步骤进行配置。SpringBoot示例：applicat
  • PHP，安卓，UI，java，linux视频教程合集 cocos2d-x小菜 javaUIlinuxPHPandroid
    ╔-----------------------------------╗┆                           
  • zookeeper admin 笔记 braveCS zookeeper
      Required Software 1) JDK>=1.6 2)推荐使用ensemble的ZooKeeper(至少3台)，并run on separate machines 3)在Yahoo!，zk配置在特定的RHEL boxes里，2个cpu，2G内存，80G硬盘   数据和日志目录 1)数据目录里的文件是zk节点的持久化备份，包括快照和事务日
  • Spring配置多个连接池 easterfly spring
    项目中需要同时连接多个数据库的时候，如何才能在需要用到哪个数据库就连接哪个数据库呢？ Spring中有关于dataSource的配置：     <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"   &nb
  • Mysql 171815164 mysql
    例如，你想myuser使用mypassword从任何主机连接到mysql服务器的话。 GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'%'IDENTIFIED BY 'mypassword' WI TH GRANT OPTION; 如果你想允许用户myuser从ip为192.168.1.6的主机连接到mysql服务器，并使用mypassword作
  • CommonDAO（公共/基础DAO） g21121 DAO
            好久没有更新博客了，最近一段时间工作比较忙，所以请见谅，无论你是爱看呢还是爱看呢还是爱看呢，总之或许对你有些帮助。         DAO(Data Access Object)是一个数据访问（顾名思义就是与数据库打交道）接口，DAO一般在业
  • 直言有讳 永夜-极光 感悟随笔
      1.转载地址:http://blog.csdn.net/jasonblog/article/details/10813313   精华: “直言有讳”是阿里巴巴提倡的一种观念，而我在此之前并没有很深刻的认识。为什么呢？就好比是读书时候做阅读理解，我喜欢我自己的解读，并不喜欢老师给的意思。在这里也是。我自己坚持的原则是互相尊重，我觉得阿里巴巴很多价值观其实是基本的做人
  • 安装CentOS 7 和Win 7后，Win7 引导丢失 随便小屋 centos
    一般安装双系统的顺序是先装Win7，然后在安装CentOS，这样CentOS可以引导WIN 7启动。但安装CentOS7后，却找不到Win7 的引导，稍微修改一点东西即可。 一、首先具有root 的权限。      即进入Terminal后输入命令su，然后输入密码即可 二、利用vim编辑器打开/boot/grub2/grub.cfg文件进行修改 v
  • Oracle备份与恢复案例 aijuans oracle
    Oracle备份与恢复案例 一. 理解什么是数据库恢复当我们使用一个数据库时，总希望数据库的内容是可靠的、正确的，但由于计算机系统的故障（硬件故障、软件故障、网络故障、进程故障和系统故障）影响数据库系统的操作，影响数据库中数据的正确性，甚至破坏数据库，使数据库中全部或部分数据丢失。因此当发生上述故障后，希望能重构这个完整的数据库，该处理称为数据库恢复。恢复过程大致可以分为复原(Restore)与
  • JavaEE开源快速开发平台G4Studio v5.0发布 無為子
      我非常高兴地宣布,今天我们最新的JavaEE开源快速开发平台G4Studio_V5.0版本已经正式发布。   访问G4Studio网站 http://www.g4it.org   2013-04-06 发布G4Studio_V5.0版本 功能新增 (1). 新增了调用Oracle存储过程返回游标，并将游标映射为Java List集合对象的标
  • Oracle显示根据高考分数模拟录取 百合不是茶 PL/SQL编程oracle例子模拟高考录取学习交流
    题目要求: 1,创建student表和result表 2,pl/sql对学生的成绩数据进行处理 3,处理的逻辑是根据每门专业课的最低分线和总分的最低分数线自动的将录取和落选     1,创建student表,和result表 学生信息表; create table student( student_id number primary key,--学生id
  • 优秀的领导与差劲的领导 bijian1013 领导管理团队
    责任 优秀的领导：优秀的领导总是对他所负责的项目担负起责任。如果项目不幸失败了，那么他知道该受责备的人是他自己，并且敢于承认错误。 差劲的领导：差劲的领导觉得这不是他的问题，因此他会想方设法证明是他的团队不行，或是将责任归咎于团队中他不喜欢的那几个成员身上。 努力工作 优秀的领导：团队领导应该是团队成员的榜样。至少，他应该与团队中的其他成员一样努力工作。这仅仅因为他
  • js函数在浏览器下的兼容 Bill_chen jquery浏览器IEDWRext
      做前端开发的工程师，少不了要用FF进行测试，纯js函数在不同浏览器下，名称也可能不同。对于IE6和FF，取得下一结点的函数就不尽相同：   IE6：node.nextSibling,对于FF是不能识别的；   FF：node.nextElementSibling,对于IE是不能识别的； 兼容解决方式：var Div = node.nextSibl
  • 【JVM四】老年代垃圾回收：吞吐量垃圾收集器(Throughput GC) bit1129 垃圾回收
    吞吐量与用户线程暂停时间   衡量垃圾回收算法优劣的指标有两个： 吞吐量越高，则算法越好 暂停时间越短，则算法越好 首先说明吞吐量和暂停时间的含义。   垃圾回收时，JVM会启动几个特定的GC线程来完成垃圾回收的任务，这些GC线程与应用的用户线程产生竞争关系，共同竞争处理器资源以及CPU的执行时间。GC线程不会对用户带来的任何价值，因此，好的GC应该占
  • J2EE监听器和过滤器基础 白糖_ J2EE
    Servlet程序由Servlet，Filter和Listener组成，其中监听器用来监听Servlet容器上下文。 监听器通常分三类：基于Servlet上下文的ServletContex监听，基于会话的HttpSession监听和基于请求的ServletRequest监听。   ServletContex监听器 ServletContex又叫application
  • 博弈AngularJS讲义(16) - 提供者 boyitech jsAngularJSapiAngularProvider
      Angular框架提供了强大的依赖注入机制，这一切都是有注入器(injector)完成. 注入器会自动实例化服务组件和符合Angular API规则的特殊对象，例如控制器，指令，过滤器动画等。   那注入器怎么知道如何去创建这些特殊的对象呢？ Angular提供了5种方式让注入器创建对象，其中最基础的方式就是提供者(provider), 其余四种方式(Value, Fac
  • java-写一函数f(a,b)，它带有两个字符串参数并返回一串字符，该字符串只包含在两个串中都有的并按照在a中的顺序。 bylijinnan java
    public class CommonSubSequence { /** * 题目：写一函数f(a,b)，它带有两个字符串参数并返回一串字符，该字符串只包含在两个串中都有的并按照在a中的顺序。 * 写一个版本算法复杂度O(N^2)和一个O(N) 。 * * O(N^2)：对于a中的每个字符，遍历b中的每个字符，如果相同，则拷贝到新字符串中。 * O(
  • sqlserver 2000 无法验证产品密钥 Chen.H sqlwindowsSQL ServerMicrosoft
    在 Service Pack 4 (SP 4), 是运行 Microsoft Windows Server 2003、 Microsoft Windows Storage Server 2003 或 Microsoft Windows 2000 服务器上您尝试安装 Microsoft SQL Server 2000 通过卷许可协议 (VLA) 媒体。 这样做, 收到以下错误信息CD KEY的 SQ
  • [新概念武器]气象战争 comsci
           气象战争的发动者必须是拥有发射深空航天器能力的国家或者组织....        原因如下:        地球上的气候变化和大气层中的云层涡旋场有密切的关系,而维持一个在大气层某个层次
  • oracle 中 rollup、cube、grouping 使用详解 daizj oraclegroupingrollupcube
    oracle 中 rollup、cube、grouping 使用详解 -- 使用oracle 样例表演示 转自namesliu -- 使用oracle 的样列库，演示 rollup, cube, grouping 的用法与使用场景    --- ROLLUP ， 为了理解分组的成员数量，我增加了 分组的计数  COUNT(SAL)   
  • 技术资料汇总分享 Dead_knight 技术资料汇总 分享
    本人汇总的技术资料，分享出来，希望对大家有用。 http://pan.baidu.com/s/1jGr56uE 资料主要包含： Workflow->工作流相关理论、框架(OSWorkflow、JBPM、Activiti、fireflow...) Security->java安全相关资料(SSL、SSO、SpringSecurity、Shiro、JAAS...) Ser
  • 初一下学期难记忆单词背诵第一课 dcj3sjt126com englishword
    could 能够 minute 分钟 Tuesday 星期二 February 二月 eighteenth 第十八 listen 听 careful 小心的，仔细的 short 短的 heavy 重的 empty 空的 certainly 当然 carry 携带；搬运 tape 磁带 basket 蓝子 bottle 瓶 juice 汁，果汁 head 头；头部
  • 截取视图的图片, 然后分享出去 dcj3sjt126com OSObjective-C
    OS 7 has a new method that allows you to draw a view hierarchy into the current graphics context. This can be used to get an UIImage very fast. I implemented a category method on UIView to get the vi
  • MySql重置密码 fanxiaolong MySql重置密码
    方法一:  在my.ini的[mysqld]字段加入： skip-grant-tables 重启mysql服务，这时的mysql不需要密码即可登录数据库  然后进入mysql mysql>use mysql;  mysql>更新 user set password=password('新密码') WHERE User='root'; mysq
  • Ehcache（03）——Ehcache中储存缓存的方式 234390216 ehcacheMemoryStoreDiskStore存储驱除策略
    Ehcache中储存缓存的方式   目录 1     堆内存（MemoryStore） 1.1     指定可用内存 1.2     驱除策略 1.3     元素过期 2   &nbs
  • spring mvc中的@propertysource jackyrong spring mvc
      在spring mvc中，在配置文件中的东西，可以在java代码中通过注解进行读取了： @PropertySource  在spring 3.1中开始引入 比如有配置文件 config.properties mongodb.url=1.2.3.4 mongodb.db=hello 则代码中   @PropertySource(&
  • 重学单例模式 lanqiu17 单例Singleton模式
    最近在重新学习设计模式，感觉对模式理解更加深刻。觉得有必要记下来。 第一个学的就是单例模式，单例模式估计是最好理解的模式了。它的作用就是防止外部创建实例，保证只有一个实例。 单例模式的常用实现方式有两种，就人们熟知的饱汉式与饥汉式，具体就不多说了。这里说下其他的实现方式 静态内部类方式: package test.pattern.singleton.statics; publ
  • .NET开源核心运行时，且行且珍惜 netcome java.net开源
    背景 2014年11月12日，ASP.NET之父、微软云计算与企业级产品工程部执行副总裁Scott Guthrie，在Connect全球开发者在线会议上宣布，微软将开源全部.NET核心运行时，并将.NET 扩展为可在 Linux 和 Mac OS 平台上运行。.NET核心运行时将基于MIT开源许可协议发布，其中将包括执行.NET代码所需的一切项目——CLR、JIT编译器、垃圾收集器（GC）和核心
  • 使用oscahe缓存技术减少与数据库的频繁交互 Everyday都不同 Web高并发oscahe缓存
    此前一直不知道缓存的具体实现，只知道是把数据存储在内存中，以便下次直接从内存中读取。对于缓存的使用也没有概念，觉得缓存技术是一个比较”神秘陌生“的领域。但最近要用到缓存技术，发现还是很有必要一探究竟的。   缓存技术使用背景：一般来说，对于web项目，如果我们要什么数据直接jdbc查库好了，但是在遇到高并发的情形下，不可能每一次都是去查数据库，因为这样在高并发的情形下显得不太合理——
  • Spring+Mybatis 手动控制事务 toknowme mybatis
    @Override    public boolean testDelete(String jobCode) throws Exception {       boolean flag = false;  &nbs
  • 菜鸟级的android程序员面试时候需要掌握的知识点 xp9802 android
    熟悉Android开发架构和API调用 掌握APP适应不同型号手机屏幕开发技巧 熟悉Android下的数据存储  熟练Android Debug Bridge Tool 熟练Eclipse/ADT及相关工具  熟悉Android框架原理及Activity生命周期 熟练进行Android UI布局 熟练使用SQLite数据库； 熟悉Android下网络通信机制，S
按字母分类： ABCDEFGHIJKLMNOPQRSTUVWXYZ其他