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：

dataSource，数据源的连接信息

entityManagerFactory，数据处理

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;@Componentpublic 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.MySQL5Dialectother: 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：

配置文件中数据源的配置

配置类的编写

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"}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。