SpringBoot 2.x 整合 jpa实现多数据源

SpringBoot 2.x 在jpa中配置多数据源，与1.x还是存在稍许差别的，本示例基于SpringBoot2.0.6

1. 下载依赖

<dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <optional>trueoptional>
            <scope>providedscope>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <scope>runtimescope>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-data-jpaartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>

lombok是一款插件，可以自动生成setter，getter等方法，适应起来十分方便可有减少编码量。

2. 配置多数据源配置信息

application.properties

#主
spring.datasource.jdbc-url=jdbc:mysql://192.168.2.222:3306/test1?useSSL=false&useUnicode=true&characterEncoding=utf-8
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=Haloo2018@
#从
spring.slave.datasource.jdbc-url=jdbc:mysql://192.168.2.222:3306/test1?useSSL=false&useUnicode=true&characterEncoding=utf-8
spring.slave.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.slave.datasource.username=root
spring.slave.datasource.password=Haloo2018@

spring.jpa.database-platform=org.hibernate.dialect.MySQL5Dialect
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=create

spring.jpa.hibernate.ddl-auto=create-drop是hibernate.hbm2ddl.auto的简称，create-drop代表创建的时候自动生成表，会话结束删除表.
注意:SpringBoot2.x默认使用的数据源是HikariCP，它使用的连接参数是jdbc-url而不是url.

编写数据源配置类

@Configuration
public class DataSourceConfig {
    @Bean("master")
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSource dataSource(){
        return DataSourceBuilder.create().build();
    }
    @Bean("slave")
    @ConfigurationProperties(prefix = "spring.slave.datasource")
    public DataSource dataSourceSlave(){
        return DataSourceBuilder.create().build();
    }
}

必须有一个@Primary作为主数据源，生成的@Bean都将交给Spring容器进行管理，所以在同类型有多个注册的情况下需要在@Bean上定义别名，到时候注入的时候可以通过名称来进行注册，以免报错无法注入bean。

配置数据源的JPA信息

前面的数据源仅仅配置的是一些连接参数，现在我们的JPA需要使用datasource,所以需要对不同的数据源配置不同的JPA属性。

主：

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef = "entityManagerFactoryMaster",//配置连接工厂 entityManagerFactory
        transactionManagerRef = "transactionManagerMaster", //配置 事物管理器  transactionManager
        basePackages = {"com.ztemap.datasource.repository"}
)
public class MasterDataSourceConfig {
    @Autowired
    @Qualifier("master")
    private DataSource dataSourceMaster;
    @Autowired
    private JpaProperties jpaProperties;

    @Bean("entityManagerMaster")
    @Primary
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactoryBean(builder).getObject().createEntityManager();
    }
    @Bean("entityManagerFactoryMaster")
    @Primary
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryBean(EntityManagerFactoryBuilder builder) {
        return builder.dataSource(dataSourceMaster)
                .properties(getVendorProperties())
                .packages("com.ztemap.datasource")
                //持久化单元名称，当存在多个EntityManagerFactory时，需要制定此名称
                .persistenceUnit("masterPersistenceUnit")
                .build();

    }
    private Map getVendorProperties() {
        HibernateSettings hibernateSettings = new HibernateSettings();
      //  hibernateSettings.ddlAuto(ddlAuto);
        return jpaProperties.getHibernateProperties(hibernateSettings);
    }
    @Bean("transactionManagerMaster")
    @Primary
    public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactoryBean(builder).getObject());
    }
}

从：

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef="entityManagerFactorySlave",
        transactionManagerRef = "transactionManagerSlave",
        basePackages = {"com.ztemap.datasource.slave"}
)
public class SlaveDataSourceConfig {
    @Autowired
    @Qualifier("slave")
    private DataSource dataSource;
    @Autowired
    private JpaProperties jpaProperties;
    @Bean("entityManagerFactorySlave")
    public LocalContainerEntityManagerFactoryBean localContainerEntityManagerFactoryBean(EntityManagerFactoryBuilder builder) {
        return builder.dataSource(dataSource)
                .properties(getVendorProperties())
                .packages("com.ztemap.datasource")
                .build();
    }


    @Bean("entityManagerSlave")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return localContainerEntityManagerFactoryBean(builder).getObject().createEntityManager();
    }

    @Bean("transactionManagerSlave")
    public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(localContainerEntityManagerFactoryBean(builder).getObject());
    }

    private Map getVendorProperties() {
        HibernateSettings hibernateSettings = new HibernateSettings();
//        hibernateSettings.ddlAuto(ddlAuto);
        return jpaProperties.getHibernateProperties(hibernateSettings);
    }
}

entityManagerFactoryRef映射LocalContainerEntityManagerFactoryBean对应的bean名称，表示配置连接工厂
同理transactionManagerMaster也是一样，表示的是事务管理器
basePackages扫描的是继承JpaRepository等类所在的包，packages扫描的是实体类所在的包。

编写数据访问层接口

首先写两个实体类
Message，Student

@Data
@Entity
@AllArgsConstructor
public class Student {
    @Id
    @GeneratedValue
    private Integer id;
    private String name;
    public Student(String name) {
        this.name = name;
    }
}

@Entity
@Data
public class Message {
    @Id
    @GeneratedValue
    private Long id;
    @Column(nullable = false)
    private String name;
    @Column(nullable = false)
    private String content;
    public Message(){}
    public Message(String name, String content) {
        this.name = name;
        this.content = content;
    }
}

数据访问层

public interface MessageRepository extends JpaRepository<Message, Long> {
}

@Repository
public interface StudentRepository extends JpaRepository<Student,Integer> {
}

注意： 需要将两个结构放置在不同的包下。