SpringBoot 2.x 整合 jpa实现多数据源

「爱情、让人受尽委屈。」 2022-05-12 15:16 236阅读 0赞

> SpringBoot 2.x 在jpa中配置多数据源，与1.x还是存在稍许差别的，本示例基于`SpringBoot2.0.6`

### 1. 下载依赖 ###

<dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <optional>true</optional>
                <scope>provided</scope>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>

`lombok`是一款插件，可以自动生成`setter`，`getter`等方法，适应起来十分方便可有减少编码量。

### 2. 配置多数据源配置信息 ###

#### application.properties ####

#主
    spring.datasource.jdbc-url=jdbc:mysql://192.168.2.222:3306/test1?useSSL=false&useUnicode=true&characterEncoding=utf-8
    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.datasource.username=root
    spring.datasource.password=Haloo2018@
    #从
    spring.slave.datasource.jdbc-url=jdbc:mysql://192.168.2.222:3306/test1?useSSL=false&useUnicode=true&characterEncoding=utf-8
    spring.slave.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.slave.datasource.username=root
    spring.slave.datasource.password=Haloo2018@
    
    spring.jpa.database-platform=org.hibernate.dialect.MySQL5Dialect
    spring.jpa.show-sql=true
    spring.jpa.hibernate.ddl-auto=create

`spring.jpa.hibernate.ddl-auto=create-drop`是`hibernate.hbm2ddl.auto`的简称，`create-drop`代表创建的时候自动生成表，会话结束删除表.  
`注意:`SpringBoot2.x默认使用的数据源是`HikariCP`，它使用的连接参数是`jdbc-url`而不是`url`.

#### 编写数据源配置类 ####

@Configuration
    public class DataSourceConfig { 
        @Bean("master")
        @Primary
        @ConfigurationProperties(prefix = "spring.datasource")
        public DataSource dataSource(){ 
            return DataSourceBuilder.create().build();
        }
        @Bean("slave")
        @ConfigurationProperties(prefix = "spring.slave.datasource")
        public DataSource dataSourceSlave(){ 
            return DataSourceBuilder.create().build();
        }
    }

必须有一个`@Primary`作为主数据源，生成的`@Bean`都将交给`Spring`容器进行管理，所以在同类型有多个注册的情况下需要在`@Bean`上定义别名，到时候注入的时候可以通过名称来进行注册，`以免报错无法注入bean`。

#### 配置数据源的JPA信息 ####

前面的数据源仅仅配置的是一些连接参数，现在我们的JPA需要使用`datasource`,所以需要对不同的数据源配置不同的JPA属性。

**主：**

@Configuration
    @EnableTransactionManagement
    @EnableJpaRepositories(
            entityManagerFactoryRef = "entityManagerFactoryMaster",//配置连接工厂 entityManagerFactory
            transactionManagerRef = "transactionManagerMaster", //配置 事物管理器 transactionManager
            basePackages = { "com.ztemap.datasource.repository"}
    )
    public class MasterDataSourceConfig { 
        @Autowired
        @Qualifier("master")
        private DataSource dataSourceMaster;
        @Autowired
        private JpaProperties jpaProperties;
    
        @Bean("entityManagerMaster")
        @Primary
        public EntityManager entityManager(EntityManagerFactoryBuilder builder) { 
            return entityManagerFactoryBean(builder).getObject().createEntityManager();
        }
        @Bean("entityManagerFactoryMaster")
        @Primary
        public LocalContainerEntityManagerFactoryBean entityManagerFactoryBean(EntityManagerFactoryBuilder builder) { 
            return builder.dataSource(dataSourceMaster)
                    .properties(getVendorProperties())
                    .packages("com.ztemap.datasource")
                    //持久化单元名称，当存在多个EntityManagerFactory时，需要制定此名称
                    .persistenceUnit("masterPersistenceUnit")
                    .build();
    
        }
        private Map getVendorProperties() { 
            HibernateSettings hibernateSettings = new HibernateSettings();
          // hibernateSettings.ddlAuto(ddlAuto);
            return jpaProperties.getHibernateProperties(hibernateSettings);
        }
        @Bean("transactionManagerMaster")
        @Primary
        public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) { 
            return new JpaTransactionManager(entityManagerFactoryBean(builder).getObject());
        }
    }

**从：**

@Configuration
    @EnableTransactionManagement
    @EnableJpaRepositories(
            entityManagerFactoryRef="entityManagerFactorySlave",
            transactionManagerRef = "transactionManagerSlave",
            basePackages = { "com.ztemap.datasource.slave"}
    )
    public class SlaveDataSourceConfig { 
        @Autowired
        @Qualifier("slave")
        private DataSource dataSource;
        @Autowired
        private JpaProperties jpaProperties;
        @Bean("entityManagerFactorySlave")
        public LocalContainerEntityManagerFactoryBean localContainerEntityManagerFactoryBean(EntityManagerFactoryBuilder builder) { 
            return builder.dataSource(dataSource)
                    .properties(getVendorProperties())
                    .packages("com.ztemap.datasource")
                    .build();
        }
    
    
        @Bean("entityManagerSlave")
        public EntityManager entityManager(EntityManagerFactoryBuilder builder) { 
            return localContainerEntityManagerFactoryBean(builder).getObject().createEntityManager();
        }
    
        @Bean("transactionManagerSlave")
        public PlatformTransactionManager transactionManager(EntityManagerFactoryBuilder builder) { 
            return new JpaTransactionManager(localContainerEntityManagerFactoryBean(builder).getObject());
        }
    
        private Map getVendorProperties() { 
            HibernateSettings hibernateSettings = new HibernateSettings();
    // hibernateSettings.ddlAuto(ddlAuto);
            return jpaProperties.getHibernateProperties(hibernateSettings);
        }
    }

`entityManagerFactoryRef`映射`LocalContainerEntityManagerFactoryBean`对应的`bean`名称，表示配置连接工厂  
同理`transactionManagerMaster`也是一样，表示的是事务管理器  
`basePackages`扫描的是继承`JpaRepository<Student,Integer>`等类所在的包，`packages`扫描的是实体类所在的包。

#### 编写数据访问层接口 ####

首先写两个实体类  
**Message**，**Student**

@Data
    @Entity
    @AllArgsConstructor
    public class Student { 
        @Id
        @GeneratedValue
        private Integer id;
        private String name;
        public Student(String name) { 
            this.name = name;
        }
    }

@Entity
    @Data
    public class Message { 
        @Id
        @GeneratedValue
        private Long id;
        @Column(nullable = false)
        private String name;
        @Column(nullable = false)
        private String content;
        public Message(){ }
        public Message(String name, String content) { 
            this.name = name;
            this.content = content;
        }
    }

**数据访问层**

public interface MessageRepository extends JpaRepository<Message, Long> { 
    }

@Repository
    public interface StudentRepository extends JpaRepository<Student,Integer> { 
    }

**注意：** 需要将两个结构放置在不同的包下。