1.概述

项目中经常会遇到一个应用需要访问多个数据源的情况，本文介绍在SpringBoot项目中利用SpringDataJpa技术如何支持多个数据库的数据源。

具体的代码参照该 示例项目

2.建立实体类（Entity）

首先，我们创建两个简单的实体类，分别属于两个不同的数据源，用于演示多数据源数据的保存和查询。

Test实体类：

package com.example.demo.test.data;  import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table;  @Entity @Table(name = "test") public class Test {      @Id     private Integer id;      public Test(){      }      public Integer getId() {         return this.id;     }      public void setId(Integer id){         this.id = id;     } } 

Other实体类：

package com.example.demo.other.data;  import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table;  @Entity @Table(name = "other") public class Other {      @Id     private Integer id;      public Integer getId() {         return this.id;     }      public void setId(Integer id){         this.id = id;     } } 

需要注意的是，这两个实体类分属于不同的package，这一点极为重要，spring会根据实体类所属的package来决定用那一个数据源进行操作。

3.建立Repository

分别建立两个实体类对应的Repository，用于进行数据操作。

TestRepository:

package com.example.demo.test.data;  import org.springframework.data.jpa.repository.JpaRepository;  public interface TestRepository extends JpaRepository<Test, Integer> { } 

OtherRepository:

package com.example.demo.other.data;  import org.springframework.data.jpa.repository.JpaRepository;  public interface OtherRepository extends JpaRepository<Other, Integer> { } 

得益于spring-data-jpa优秀的封装，我们只需创建一个接口，就拥有了对实体类的操作能力。

3.对多数据源进行配置

分别对Test和Other两个实体类配置对应的数据源。配置的内容主要包含三个要素：

1. dataSource，数据源的连接信息
2. entityManagerFactory，数据处理
3. transactionManager，事务管理

Test实体类的数据源配置 TestDataConfig：

package com.example.demo.config;  import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder; import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties; 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 org.springframework.transaction.annotation.EnableTransactionManagement;  import javax.persistence.EntityManagerFactory; import javax.sql.DataSource;  @Configuration @EnableTransactionManagement @EnableJpaRepositories(         entityManagerFactoryRef = "entityManagerFactory",         basePackages = {"com.example.demo.test.data"} ) public class TestDataConfig {      @Autowired     private JpaProperties jpaProperties;      @Primary     @Bean(name = "dataSource")     @ConfigurationProperties(prefix = "spring.datasource")     public DataSource dataSource() {         return DataSourceBuilder.create().build();     }      @Primary     @Bean(name = "entityManagerFactory")     public LocalContainerEntityManagerFactoryBean entityManagerFactory(             EntityManagerFactoryBuilder builder,             @Qualifier("dataSource") DataSource dataSource) {         return builder                 .dataSource(dataSource)                 .packages("com.example.demo.test.data")                 .properties(jpaProperties.getHibernateProperties(dataSource))                 .persistenceUnit("test")                 .build();     }      @Primary     @Bean(name = "transactionManager")     public PlatformTransactionManager transactionManager(             @Qualifier("entityManagerFactory") EntityManagerFactory entityManagerFactory) {         return new JpaTransactionManager(entityManagerFactory);     }  }  

代码中的Primary注解表示这是默认数据源。

Other实体类的数据源配置 OtherDataConfig：

package com.example.demo.config;  import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder; import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties; 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.data.jpa.repository.config.EnableJpaRepositories; import org.springframework.orm.jpa.JpaTransactionManager; import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean; import org.springframework.transaction.PlatformTransactionManager; import org.springframework.transaction.annotation.EnableTransactionManagement;  import javax.persistence.EntityManagerFactory; import javax.sql.DataSource;  @Configuration @EnableTransactionManagement @EnableJpaRepositories(         entityManagerFactoryRef = "otherEntityManagerFactory",         transactionManagerRef = "otherTransactionManager",         basePackages = {"com.example.demo.other.data"} ) public class OtherDataConfig {      @Autowired     private JpaProperties jpaProperties;      @Bean(name = "otherDataSource")     @ConfigurationProperties(prefix = "other.datasource")     public DataSource otherDataSource() {         return DataSourceBuilder.create().build();     }      @Bean(name = "otherEntityManagerFactory")     public LocalContainerEntityManagerFactoryBean otherEntityManagerFactory(             EntityManagerFactoryBuilder builder,             @Qualifier("otherDataSource") DataSource otherDataSource) {         return builder                 .dataSource(otherDataSource)                 .packages("com.example.demo.other.data")                 .properties(jpaProperties.getHibernateProperties(otherDataSource))                 .persistenceUnit("other")                 .build();     }      @Bean(name = "otherTransactionManager")     public PlatformTransactionManager otherTransactionManager(             @Qualifier("otherEntityManagerFactory") EntityManagerFactory otherEntityManagerFactory) {         return new JpaTransactionManager(otherEntityManagerFactory);     }  }  

3.数据操作

我们创建一个Service类TestService来分别对两个数据源进行数据的操作。

package com.example.demo.service;  import com.example.demo.other.data.Other; import com.example.demo.other.data.OtherRepository; import com.example.demo.test.data.Test; import com.example.demo.test.data.TestRepository; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component;  @Component public class TestService {      @Autowired     private TestRepository testRepository;      @Autowired     private OtherRepository otherRepository;      @Value("${name:World}")     private String name;      public String getHelloMessage() {         Test test = new Test();         test.setId(1);         test = testRepository.save(test);          Other other = new Other();         other.setId(2);         other = otherRepository.save(other);          return "Hello " + this.name + " : test's value = " + test.getId() + " , other's value = " + other.getId();      }  }  

对Test和Other分别进行数据插入和读取操作，程序运行后会打印出两个数据源各自的数据。 数据库采用的mysql，连接信息在application.yml进行配置。

spring:   datasource:     url: jdbc:mysql://localhost:3306/test?characterEncoding=utf-8&useSSL=false     testWhileIdle: true     validationQuery: SELECT 1 from dual     username: test     password: 11111111     driverClassName: com.mysql.jdbc.Driver   jpa:     database: MYSQL     show-sql: true     hibernate:       show-sql: true       ddl-auto: create       naming-strategy: org.hibernate.cfg.ImprovedNamingStrategy     properties:       hibernate.dialect: org.hibernate.dialect.MySQL5Dialect other:   datasource:     url: jdbc:mysql://localhost:3306/other?characterEncoding=utf-8&useSSL=false     testWhileIdle: true     validationQuery: SELECT 1     username: other     password: 11111111     driverClassName: com.mysql.jdbc.Driver   jpa:     database: MYSQL     show-sql: true     hibernate:       show-sql: true       ddl-auto: create       naming-strategy: org.hibernate.cfg.ImprovedNamingStrategy     properties:       hibernate.dialect: org.hibernate.dialect.MySQL5Dialect 

Test实体对应的是主数据源，采用了spring-boot的默认数据源配置项，Other实体单独配置数据源连接。具体应该读取哪一段配置内容，是在配置类OtherDataConfig中这行代码指定的。

@ConfigurationProperties(prefix = "other.datasource") 

本示例需要建立的数据库用户和库可以通过以下命令处理：

CREATE USER 'test'@'localhost' IDENTIFIED BY '11111111'; GRANT ALL PRIVILEGES ON *.* TO 'test'@'localhost'; CREATE USER 'other'@'localhost' IDENTIFIED BY '11111111'; GRANT ALL PRIVILEGES ON *.* TO 'other'@'localhost'; create database test; create database other; 

4.总结

spring-data-jpa极大的简化了数据库操作，对于多数据源的支持，也只是需要增加一下配置文件和配置类而已。其中的关键内容有3点：

1. 配置文件中数据源的配置

2. 配置类的编写

3. 实体类所在的package必须与配置类中指定的package一致，如OtherDataConfig中指定的basePackages = {"com.example.demo.other.data"}