简介

微服务推崇单服务单数据库；但是还是免不了存在一个微服务连接多个数据库的情况，今天介绍一下如何使用 JPA 的多数据源。主要采用将不同数据库的 Repository 接口分别存放到不同的 package，Spring 去扫描不同的包，注入不同的数据源来实现多数据源。

创建 jpa-multip-datasource 项目
分别创建db01和db02数据库

学生表 t_student

CREATE TABLE `t_student` (
`id`  int(11) NOT NULL AUTO_INCREMENT ,
`user_name`  varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
`sex`  int(1) NULL DEFAULT NULL ,
`grade`  varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
PRIMARY KEY (`id`)
)
ENGINE=InnoDB
DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci
AUTO_INCREMENT=1 ROW_FORMAT=DYNAMIC;

教师表 t_teacher

CREATE TABLE `t_teacher` (
`id`  int(11) NOT NULL AUTO_INCREMENT ,
`user_name`  varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
`sex`  int(1) NULL DEFAULT NULL ,
`office`  varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
PRIMARY KEY (`id`)
)
ENGINE=InnoDB
DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci
AUTO_INCREMENT=1 ROW_FORMAT=DYNAMIC;
pom.xml文件引入如下依赖
<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>4.0.0</modelVersion>

 <groupId>com.olive</groupId>
 <artifactId>jpa-multip-datasource</artifactId>
 <version>0.0.1-SNAPSHOT</version>
 <packaging>jar</packaging>

 <name>jpa-multip-datasource</name>
 <url>http://maven.apache.org</url>

 <parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.5.14</version>
  <relativePath /> <!-- lookup parent from repository -->
 </parent>

 <properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <maven.compiler.source>8</maven.compiler.source>
  <maven.compiler.target>8</maven.compiler.target>
 </properties>

 <dependencies>
  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-test</artifactId>
   <scope>test</scope>
  </dependency>
  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-jpa</artifactId>
  </dependency>
  <dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
  </dependency>

  <dependency>
   <groupId>org.projectlombok</groupId>
   <artifactId>lombok</artifactId>
  </dependency>
 </dependencies>
</project>
配置两个数据源

分别为第一个主数据源(primary)，第二数据源(second)，具体配置如下：

# 基本配置
server:
  port: 8080

# 数据库
spring:
  jpa:
    show-sql: true
    database-platform: org.hibernate.dialect.MySQL5InnoDBDialect
    hibernate:
      ddl-auto: update
  datasource:
    primary:
      driver-class-name: com.mysql.jdbc.Driver
      jdbc-url: jdbc:mysql://127.0.0.1:3306/db01?characterEncoding=utf-8&allowMultiQueries=true&autoReconnect=true
      username: root
      password: root
    sencond:
      driver-class-name: com.mysql.cj.jdbc.Driver
      jdbc-url: jdbc:mysql://127.0.0.1:3306/db02?characterEncoding=utf-8&allowMultiQueries=true&autoReconnect=true
      username: root
      password: root

  jackson:
    serialization:
      indent-output: true
配置数据源

DataSourceConfig 配置

/**
 * @Description: 数据源配置
 */
@Configuration
public class DataSourceConfig {

    @Bean(name = "primaryDataSource")
    @Qualifier("primaryDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    @Primary
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "secondDataSource")
    @Qualifier("secondDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.sencond")
    public DataSource secondDataSource() {
        return DataSourceBuilder.create().build();
    }
}

PrimaryConfig数据源

/**
 * @Description: 主数据源配置
 * @date
 */
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactoryPrimary",
                        transactionManagerRef = "transactionManagerPrimary",
                        basePackages = {"com.olive.repository.primary"})
public class PrimaryConfig {

    @Autowired
    @Qualifier("primaryDataSource")
    private DataSource primaryDataSource;

    @Autowired
    private HibernateProperties hibernateProperties;

    @Autowired
    private JpaProperties jpaProperties;

    @Primary
    @Bean(name = "entityManagerPrimary")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactoryPrimary(builder).getObject().createEntityManager();
    }

    @Primary
    @Bean(name = "entityManagerFactoryPrimary")    //primary实体工厂
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryPrimary (EntityManagerFactoryBuilder builder) {
        return builder.dataSource(primaryDataSource)
                .properties(getHibernateProperties())
                .packages("com.olive.entity.primary")     //换成你自己的实体类所在位置
                .persistenceUnit("primaryPersistenceUnit")
                .build();
    }

    @Primary
    @Bean(name = "transactionManagerPrimary")
    public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactoryPrimary(builder).getObject());
    }

    private Map<String, Object> getHibernateProperties() {
        return hibernateProperties.determineHibernateProperties(jpaProperties.getProperties(), new HibernateSettings());
    }

}

SecondConfig 数据源源

/**
 * @Description: 第二个数据源配置
 */
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactorySecond",
                        transactionManagerRef = "transactionManagerSecond",
                        basePackages = {"com.olive.repository.second"})
public class SecondConfig {

    @Autowired
    @Qualifier("secondDataSource")
    private DataSource secondDataSource;

    @Resource
    private JpaProperties jpaProperties;

    @Resource
    private HibernateProperties hibernateProperties;

    @Bean(name = "entityManagerSecond")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactorySecond(builder).getObject().createEntityManager();
    }

    @Bean(name = "entityManagerFactorySecond")    //primary实体工厂
    public LocalContainerEntityManagerFactoryBean entityManagerFactorySecond (EntityManagerFactoryBuilder builder) {

        return builder.dataSource(secondDataSource)
                .properties(getHibernateProperties())
                .packages("com.olive.entity.second")     //换成你自己的实体类所在位置
                .persistenceUnit("secondaryPersistenceUnit")
                .build();
    }

    @Bean(name = "transactionManagerSecond")
    public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactorySecond(builder).getObject());
    }

    private Map<String, Object> getHibernateProperties() {
        return hibernateProperties.determineHibernateProperties(jpaProperties.getProperties(), new HibernateSettings());
    }

}
创建学生与老师实体类

Student实体类

package com.olive.entity.primary;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

import lombok.Data;

@Data
@Entity(name="t_student")
public class StudentDO implements Serializable{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "user_name") // 若实体属性和表字段名称一致时，可以不用加@Column注解
    private String name;

    @Column(name = "sex")
    private int sex;
    
    @Column(name = "grade")
    private String grade;
}

Teacher实体类

package com.olive.entity.second;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

import lombok.Data;

@Data
@Entity(name="t_teacher")
public class TeacherDO implements Serializable {

 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Long id;

 @Column(name = "user_name") // 若实体属性和表字段名称一致时，可以不用加@Column注解
 private String name;

 @Column(name = "sex")
 private int sex;
 
 @Column(name = "office")
 private String office;
}
数据库持久类

StudentRepository类

package com.olive.repository.primary;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.olive.entity.primary.StudentDO;

@Repository
public interface StudentRepository extends JpaRepository<StudentDO, Long> {

}

TeacherRepository类

package com.olive.repository.second;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.olive.entity.second.TeacherDO;

@Repository
public interface TeacherRepository extends JpaRepository<TeacherDO, Long> {


}
创建springboot引导类
package com.olive;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class);
    }

}
测试
package com.olive;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import com.olive.entity.primary.StudentDO;
import com.olive.entity.second.TeacherDO;
import com.olive.repository.primary.StudentRepository;
import com.olive.repository.second.TeacherRepository;

@SpringBootTest
public class JpaTest {

 @Autowired
 StudentRepository studentRepository;

 @Autowired
 TeacherRepository teacherRepository;

 @Test
 public void userSave() {
  StudentDO studentDO = new StudentDO();
  studentDO.setName("BUG弄潮儿");
  studentDO.setSex(1);
  studentDO.setGrade("一年级");
  studentRepository.save(studentDO);

  TeacherDO teacherDO = new TeacherDO();
  teacherDO.setName("Java乐园");
  teacherDO.setSex(2);
  teacherDO.setOffice("语文");
  teacherRepository.save(teacherDO);
 }
}

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