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前言

随着业务量发展，我们通常会进行数据库拆分或是引入其他数据库，从而我们需要配置多个数据源，如：user一个库，business一个库。那么接下来我们就要考虑怎么去在spring boot中实现多个数据源的配置。

实现

建表首先是建表语句，我们要建立两个数据库，并各库内新建一张表user表

mysql> use `user`；mysql> select * from `user`;+----+-------+----------+| id | name | password |+----+-------+----------+| 1 | 用户A | ****** |+----+-------+----------+1 row in set

business表

mysql> use `business`；mysql> select * from `business`;+----+-------+-------------+| id | name | description |+----+-------+-------------+| 1 | 业务A | 业务A描述 |+----+-------+-------------+1 row in set

接下来我们通过代码实现对两个库内的多张表进行查询。配置首先，创建一个Spring配置类，定义两个DataSource用来读取application.yml中的不同配置。本文中，我们user做为主数据源，主数据源配置为spring.datasource.user开头的配置，business数据源配置为spring.datasource.business开头的配置。

@Configurationpublic class DataSourceConfig {@Primary@Bean(name = "userDataSource")@Qualifier("userDataSource")@ConfigurationProperties(prefix = "spring.datasource.user")public DataSource userDataSource() {return DataSourceBuilder.create().build();}@Bean(name = "businessDataSource")@Qualifier("businessDataSource")@ConfigurationProperties(prefix = "spring.datasource.business")public DataSource businessDataSource() {return DataSourceBuilder.create().build();}}

对应的配置文件application.yml如下：

spring:datasource:user:driver-class-name: com.mysql.jdbc.Driverjdbc-url: jdbc:mysql://localhost:3306/userusername: rootpassword: 123456business:driver-class-name: com.mysql.jdbc.Driverjdbc-url: jdbc:mysql://localhost:3306/businessusername: rootpassword: 123456

接下来我们对各数据源进行jpa的配置主数据源User

@Configuration@EnableTransactionManagement@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactoryUser",transactionManagerRef = "transactionManagerUser",//设置Repository所在位置basePackages = {"com.ppc.spring.example.jpamultidatasource.repository.user"})public class UserConfig {@Autowired@Qualifier("userDataSource")private DataSource userDataSource;@Autowiredprivate JpaProperties jpaProperties;@Autowiredprivate HibernateProperties hibernateProperties;@Primary@Bean(name = "entityManagerUser")public EntityManager entityManager(EntityManagerFactoryBuilder builder) {return entityManagerFactoryUser(builder).getObject().createEntityManager();}@Primary@Bean(name = "entityManagerFactoryUser")public LocalContainerEntityManagerFactoryBean entityManagerFactoryUser(EntityManagerFactoryBuilder builder) {return builder.dataSource(userDataSource)//设置entity所在位置.packages("com.ppc.spring.example.jpamultidatasource.entity.user").persistenceUnit("userPersistenceUnit").properties(getVendorProperties()).build();}private Map<String, Object> getVendorProperties() {return hibernateProperties.determineHibernateProperties(jpaProperties.getProperties(), new HibernateSettings());}@Primary@Bean(name = "transactionManagerUser")public PlatformTransactionManager transactionManagerUser(EntityManagerFactoryBuilder builder) {return new JpaTransactionManager(entityManagerFactoryUser(builder).getObject());}}

其他数据源business

@Configuration@EnableTransactionManagement@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactoryBusiness",transactionManagerRef = "transactionManagerBusiness",//设置repository所在位置basePackages = {"com.ppc.spring.example.jpamultidatasource.repository.business"})public class BusinessConfig {@Autowired@Qualifier("businessDataSource")private DataSource businessDataSource;@Autowiredprivate JpaProperties jpaProperties;@Autowiredprivate HibernateProperties hibernateProperties;@Bean(name = "entityManagerBusiness")public EntityManager entityManager(EntityManagerFactoryBuilder builder) {return entityManagerFactoryBusiness(builder).getObject().createEntityManager();}@Bean(name = "entityManagerFactoryBusiness")public LocalContainerEntityManagerFactoryBean entityManagerFactoryBusiness(EntityManagerFactoryBuilder builder) {return builder.dataSource(businessDataSource).properties(getVendorProperties())//设置实体类所在位置.packages("com.ppc.spring.example.jpamultidatasource.entity.business").persistenceUnit("businessPersistenceUnit").build();}private Map<String, Object> getVendorProperties() {return hibernateProperties.determineHibernateProperties(jpaProperties.getProperties(), new HibernateSettings());}@Bean(name = "transactionManagerBusiness")PlatformTransactionManager transactionManagerBusiness(EntityManagerFactoryBuilder builder) {return new JpaTransactionManager(entityManagerFactoryBusiness(builder).getObject());}}

配置中需要注意以下几点：Spring Boot 1.5.x

private Map<String, String> getVendorProperties() {return jpaProperties.getHibernateProperties(userDataSource);}

Spring Boot 2.0.x

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

Spring Boot 2.1.0参见上文代码，引进了HibernateProperties。同时，在Spring Boot 2.1.0中默认的mysql-connector-java版本为8.0.13，连接低版本mysql配置上比较繁琐，建议在配置文件中手动指定相应版本，如本文中指定5.1.46这个版本。

runtimeOnly('mysql:mysql-connector-java:5.1.46')

repository、entity的所在位置，要和实际保存的位置一致。主数据源的一些配置需要添加@Primary作为spring默认的首选项，其他数据源无需添加该注解。通过查看相关源码我们看到Spring Boot中JpaProperties的代码一直在调整，这里我们将properties相关代码单独提取出作为一个单独的方法getVendorProperties展示版本间的区别。其中：查询完成了所有的配置，接下来我们就可以开始写个简单代码验证我们配置了

@RestController@SpringBootApplicationpublic class JpaMultiDatasourceApplication {@AutowiredUserRepository userRepository;@AutowiredBusinessRepository businessRepository;public static void main(String[] args) {SpringApplication.run(JpaMultiDatasourceApplication.class, args);}@GetMapping("/user/{id}")public User getUser(@PathVariable Long id) {return userRepository.findById(id).orElse(null);}@GetMapping("/business/{id}")public Business getBusiness(@PathVariable Long id) {return businessRepository.findById(id).orElse(null);}}

我们对外暴露了两个接口，分别访问user表、business表确认可以正常获取数据。查询结果如下：

请求：http://localhost:8080/user/1结果：{"id":1,"name":"用户A","password":"******"}请求：http://localhost:8080/business/1结果：{"id":1,"name":"业务A","description":"业务A描述"}

就此，我们双数据源的配置和验证工作就完成了。