Springboot JPA实现多数据源配置

1. 需求

要实现一个MES系统的web-API接口，MES系统是购买的商业软件，厂商的接口报价过高，因此由内部IT团队开发实现这个接口。考虑到系统的追溯性，因此设计一个中间库，第三方报工系统传过来的数据同时存放在中间库和MES系统里。

2. 设计实现

搜索查阅了很多博文及实验后，终于实现了多数据库的访问，调试时遇到了几个问题，在搜索后也找到了解决方案并修正。

实现思路是采用JavaConfig配合项目目录的方式，通过@EnableJpaRepositories注解的basePackages来指定对应的数据源

2 1. 项目目录结构如下

--src\项目基础目录
----JPA (对应数据库的Entities与Repositories)
------config
------DB1 (数据源1)
--------config
--------entities
--------repositories
------DB2 (数据源2)
--------config
--------entities
--------repositories

2.2. application.yml 或 application.properties

Spring:
	datasource:
		db1:
			jdbc-url: <数据源url>
			user: <数据库用户>
			password: <数据库密码>
			driver-class-name: <数据库驱动类名>
		db2:
			jdbc-url: <数据源url>
			user: <数据库用户>
			password: <数据库密码>
			driver-class-name: <数据库驱动类名>

2.3. 在jpa\config目录下新建一个配置类，用于配置多数据源映射，用@Configuration声明

@Configuration
public class DataSourceConfig {

    @Bean(name = "DataSource1")
    @Qualifier("DataSource1")
    @ConfigurationProperties(prefix = "spring.datasource.db1")
    @Primary
    public DataSource DataSource1() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "DataSource2")
    @Qualifier("DataSource2")
    @ConfigurationProperties(prefix = "spring.datasource.db2")
    public DataSource DataSource2() {
        return DataSourceBuilder.create().build();
    }
}

2.4. 在jpa\db1\config目录创建一个JavaConfig类，用于配置db1

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactoryDb1",
        transactionManagerRef = "transactionManagerDb1",
        basePackages = {"<basePackageUrl>.jpa.db1"})
public class Db1DBConfig {

    @Autowired
    @Qualifier("db1DataSource")
    private DataSource db1DataSource;

    @Autowired
    private HibernateProperties hibernateProperties;

    @Autowired
    private JpaProperties jpaProperties;

    @Primary
    @Bean(name = "entityManagerDb1")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactoryDb1(builder).getObject().createEntityManager();
    }

    @Primary
    @Bean(name = "entityManagerFactoryDb1")
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryNM (EntityManagerFactoryBuilder builder) {
        return builder.dataSource(db1DataSource)
                .properties(getHibernateProperties())
                .packages("<basePackageUrl>.jpa.db1.repositories")     //换成你自己的实体类所在位置
                .persistenceUnit("db1PersistenceUnit")
                .build();
    }

    @Primary
    @Bean(name = "transactionManagerDb1")
    public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactoryDb1(builder).getObject());
    }

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

2.5. 在jpa\db2\config目录创建一个JavaConfig类，用于配置db2

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactoryDb2",
        transactionManagerRef = "transactionManagerDb2",
        basePackages = {"<basePackageUrl>.jpa.db2"})
public class Db2DBConfig {
    @Autowired
    @Qualifier("db2DataSource")
    private DataSource db2DataSource;

    @Autowired
    private HibernateProperties hibernateProperties;

    @Autowired
    private JpaProperties jpaProperties;

    @Bean(name = "entityManagerDb2")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactoryDb2(builder).getObject().createEntityManager();
    }

    @Bean(name = "entityManagerFactoryDb2")    //primary实体工厂
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryMes (EntityManagerFactoryBuilder builder) {
        return builder.dataSource(mesDataSource)
                .properties(getHibernateProperties())
                .packages("<basePackageUrl>.jpa.db2")     //换成你自己的实体类所在位置
                .persistenceUnit("db2PersistenceUnit")
                .build();
    }

    @Bean(name = "transactionManagerDb2")
    public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactoryDb2(builder).getObject());
    }

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

这样就完成了多数据源的配置，以后在相应的db目录下创建相关的entity和repository。

service与controller就不必放在jpa目录下，service的代码与单数据源的代码一样，就不再赘述。