【spring data jpa】数据的增删改查(CRUD)

一、添加依赖

在pom文件中添加spring data jpa依赖

    org.springframework.data
    spring-data-jpa
    3.1.4


    org.hibernate
    hibernate-core
    6.3.1.Final


    org.apache.derby
    derby
    10.14.2.0
    test


    junit
    junit
    4.13.1
    test

这里使用的是spring data jpa的3.1.4版本，另外引入了hibernate、derby、junit等包

二、创建实体

在src/test/java的cn.horse.chapter01.entity包下创建User实体类

package cn.horse.chapter01.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.Id;

@Entity(name = "T_USER")
public class User {

    @Id
    private String id;
    private String username;

    public void setId(String id) {
        this.id = id;
    }

    public String getId() {
        return id;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getUsername() {
        return username;
    }
}

@Entity：实体表映射，name用于指定表名称

@Id：指定主键

三、创建持久化类

在src/test/java的cn.horse.chapter01.repository包下创建UserRepository持久化类

package cn.horse.chapter01.repository;

import cn.horse.chapter01.entity.User;
import org.springframework.data.repository.CrudRepository;

public interface UserRepository extends CrudRepository {
}

UserRepository继承CrudRepository类，这样UserRepository类将可以使用父类中提供的CRUD方法；另外继承CrudRepository类需要指定泛型，第一个泛型类型是持久化实体类型，第二个泛型类型是持久化主键类型

四、应用配置

在src/test/java的cn.horse.chapter01.config包下创建ApplicationConfig配置类

package cn.horse.chapter01.config;

import jakarta.persistence.EntityManagerFactory;
import org.hibernate.cfg.AvailableSettings;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import javax.sql.DataSource;
import java.util.Properties;

@Configuration
@EnableJpaRepositories(basePackages = "cn.horse.chapter01.repository")
@EnableTransactionManagement
class ApplicationConfig {

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource driverManagerDataSource = new DriverManagerDataSource();
        driverManagerDataSource.setDriverClassName("org.apache.derby.jdbc.EmbeddedDriver");
        driverManagerDataSource.setUrl("jdbc:derby:demo;create=true");
        driverManagerDataSource.setUsername("");
        driverManagerDataSource.setPassword("");
        return driverManagerDataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {

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

        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(vendorAdapter);
        factory.setPackagesToScan("cn.horse.chapter01.entity");
        factory.setDataSource(dataSource());

        Properties jpaProperties = new Properties();
        jpaProperties.put(AvailableSettings.HBM2DDL_AUTO, "create");
        factory.setJpaProperties(jpaProperties);
        return factory;
    }

    @Bean
    public PlatformTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {

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

@EnableJpaRepositories：配置可用持久化类，另外我们还配置了持久化类扫描的包路径（cn.horse.chapter01.repository）
@EnableTransactionManagement：配置可用事务管理

另外还将数据源（DataSource）、实体管理工厂（EntityManagerFactory）、Jpa事务管理（PlatformTransactionManager）实例注册到Spring容器中。

其中实体管理工厂（EntityManagerFactory）实例的创建由LocalContainerEntityManagerFactoryBean对象完成，LocalContainerEntityManagerFactoryBean对象创建的过程中设置了实体类扫描的包路径（cn.horse.chapter01.entity），属性中还设置了DDL方式（create），此方式会先删除表后再创建新表。

五、启动程序

1、准备数据

在src/test/resources的cn/horse/chapter01目录下创建data.sql脚本

INSERT INTO T_USER(id, username) VALUES('1', '张三'),('2', '李四'),('3', '王五');

2、单元测试

在src/test/java的cn.horse.chapter01包下创建SpringDataJpaTest测试类

package cn.horse.chapter01;

import cn.horse.chapter01.entity.User;
import cn.horse.chapter01.repository.UserRepository;
import org.junit.Assert;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.jdbc.datasource.init.ScriptUtils;

import javax.sql.DataSource;
import java.sql.SQLException;
import java.util.Iterator;

public class SpringDataJpaTest {

    static final ApplicationContext applicationContext;
    static final UserRepository userRepository;
    static {
        applicationContext = new AnnotationConfigApplicationContext("cn.horse.chapter01.config");
        userRepository = applicationContext.getBean(UserRepository.class);
        try {
            ScriptUtils.executeSqlScript(applicationContext.getBean(DataSource.class).getConnection(), new ClassPathResource("cn/horse/chapter01/data.sql"));
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

    @Test
    public void testFindAll() {
        Iterator iterator = userRepository.findAll().iterator();
        Assert.assertEquals("1", iterator.next().getId());
        Assert.assertEquals("2", iterator.next().getId());
        Assert.assertEquals("3", iterator.next().getId());
        Assert.assertEquals(false, iterator.hasNext());
    }

    @Test
    public void testCount() {
        Assert.assertEquals(3, userRepository.count());
    }

    @Test
    public void testInsert() {
        long historyCount = userRepository.count();
        User user = new User();
        user.setId("4");
        user.setUsername("赵六");
        userRepository.save(user);
        Assert.assertEquals(historyCount + 1, userRepository.count());
        Assert.assertNotNull(userRepository.findById("4").orElse(null));
        Assert.assertEquals("赵六", userRepository.findById("4").map(User::getUsername).orElse(null));
    }

    @Test
    public void testUpdate() {
        long historyCount = userRepository.count();
        User user = new User();
        user.setId("1");
        user.setUsername("张三2");
        userRepository.save(user);
        Assert.assertEquals(historyCount, userRepository.count());
        Assert.assertNotNull(userRepository.findById("1").orElse(null));
        Assert.assertEquals("张三2", userRepository.findById("1").map(User::getUsername).orElse(null));
    }

    @Test
    public void testDelete() {
        long historyCount = userRepository.count();
        userRepository.deleteById("3");
        Assert.assertEquals(historyCount - 1, userRepository.count());
        Assert.assertNull(userRepository.findById("3").orElse(null));
    }
}

执行单元测试通过