JAVA高级面试进阶训练营视频教程

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前言

　　前段时间使用spring jpa做了一个项目，由于涉及到了多个数据库，因此需要进行多数据源的配置。网上找了很多的资料，尝试着配置，都以失败告终。之后通过断点最终完成了多数据源的配置。这篇博客主要为了记录下，使用SimpleJpaRepository如何配置多数据源。也希望可以帮助到更多的人。

 

环境

java版本：8

框架： spring boot(2.0.4.RELEASE)、jpa

数据库：mysql

 

配置步骤

• 目录结果

 

• pom文件

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.4.RELEASE</version>
    <relativePath/>
  </parent>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
    </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>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>${mysql.driver.version}</version>
      <scope>runtime</scope>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.0.19</version>
    </dependency>
  </dependencies>

 

• application.yml

spring:
  application:
    name: multi-database
  datasource:
    main:
      url: jdbc:mysql://localhost:3306/test_main?useUnicode=true&characterEncoding=utf-8&useSSL=false
      username: root
      password: ***
    slave:
      url: jdbc:mysql://localhost:3306/test_slave?useUnicode=true&characterEncoding=utf-8&useSSL=false
      username: root
      password: ***
  jpa:
    properties:
      hibernate:
        ddl-auto: update
        naming:
          physical-strategy: org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy
    generate-ddl: true
    show-sql: true
    database: mysql
    database-platform: org.hibernate.dialect.MySQL5InnoDBDialect

配置文件中我配置了两个数据源，一个是 main ，一个是 slave 。

 

• 数据连接池配置

DruidDBConfig.java:

@Configuration
public class DruidDBConfig {

    @Value("${spring.datasource.main.url}")
    private String mainDBUrl;

    @Value("${spring.datasource.main.username}")
    private String mainUsername;

    @Value("${spring.datasource.main.password}")
    private String mainPassword;

    @Value("${spring.datasource.slave.url}")
    private String slaveDBUrl;

    @Value("${spring.datasource.slave.username}")
    private String slaveUsername;

    @Value("${spring.datasource.slave.password}")
    private String slavePassword;

    @Value("com.mysql.jdbc.Driver")
    private String driverClassName;

    @Value("5")
    private int initialSize;

    @Value("5")
    private int minIdle;

    @Value("20")
    private int maxActive;

    @Value("60000")
    private int maxWait;

    /**
     * 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒
     */
    @Value("60000")
    private int timeBetweenEvictionRunsMillis;
    /**
     * 配置一个连接在池中最小生存的时间，单位是毫秒
     */
    @Value("300000")
    private int minEvictableIdleTimeMillis;

    @Value("SELECT 1 FROM DUAL")
    private String validationQuery;

    @Value("true")
    private boolean testWhileIdle;

    @Value("false")
    private boolean testOnBorrow;

    @Value("false")
    private boolean testOnReturn;

    /**
     * 打开PSCache，并且指定每个连接上PSCache的大小
     */
    @Value("true")
    private boolean poolPreparedStatements;

    @Value("20")
    private int maxPoolPreparedStatementPerConnectionSize;

    @Value("druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500")
    private String connectionProperties;

    @Bean(name = "mainDataSource")
    @Qualifier("mainDataSource")
    @Primary // 主数据源，如果有两个数据源，没有指定数据源则默认为该数据源
    public DataSource mainDataSource() {
        return getDruidDataSource(mainUsername, mainPassword, mainDBUrl);
    }

    @Bean(name = "slaveDataSource")
    @Qualifier("slaveDataSource")
    public DataSource slaveDataSource() {
        return getDruidDataSource(slaveUsername, slavePassword, slaveDBUrl);
    }

    private DruidDataSource getDruidDataSource(String username, String password, String url) {
        DruidDataSource datasource = new DruidDataSource();

        datasource.setUrl(url);
        datasource.setUsername(username);
        datasource.setPassword(password);
        datasource.setDriverClassName(driverClassName);

        //configuration
        datasource.setInitialSize(initialSize);
        datasource.setMinIdle(minIdle);
        datasource.setMaxActive(maxActive);
        datasource.setMaxWait(maxWait);
        datasource.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
        datasource.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
        datasource.setValidationQuery(validationQuery);
        datasource.setTestWhileIdle(testWhileIdle);
        datasource.setTestOnBorrow(testOnBorrow);
        datasource.setTestOnReturn(testOnReturn);
        datasource.setPoolPreparedStatements(poolPreparedStatements);
        datasource.setMaxPoolPreparedStatementPerConnectionSize(maxPoolPreparedStatementPerConnectionSize);
        datasource.setConnectionProperties(connectionProperties);

        return datasource;
    }
}

在这里统一管理两个数据源。

 

• 主数据源的配置

MainDataSourceConfig.java:

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactoryMain"
        , transactionManagerRef = "transactionManagerMain"
        , basePackages = {"com.yun.demo.dao.main"})// dao所在的位置
public class MainDataSourceConfig {
    @Autowired
    @Qualifier("mainDataSource")
    private DataSource mainDataSource;

    @Autowired
    private JpaProperties jpaProperties;


    @Primary
    @Bean(name = "entityManagerMain")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return SharedEntityManagerCreator.createSharedEntityManager(entityManagerFactoryMain(builder).getObject()); // 这里比较关键，这里我们要创建一个SharedEntityManager，不然无法在SimpleJpa上使用多个数据源
    }
    @Primary
    @Bean(name = "entityManagerFactoryMain")
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryMain (EntityManagerFactoryBuilder builder) {
        return builder
                .dataSource(mainDataSource)
                .properties(getVendorProperties())
                .packages("com.yun.demo.entity.main") //设置实体类所在位置
                .persistenceUnit("mainPersistenceUnit")
                .build();
    }

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


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

由于 SimpleJpaRepository 使用的是 SharedEntityManager 去管理的，而网上大部分帖子都不是使用它，因此如果你的类继承了 SimpleJpaRepository ，而没有有配置 SimpleJpaRepository ，就会报错 no transaction is in progress 。下面就是报错信息：

Caused by: javax.persistence.TransactionRequiredException: no transaction is in progress
    at org.hibernate.internal.SessionImpl.checkTransactionNeeded(SessionImpl.java:3505)
    at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1427)
    at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1423)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:350)
    at com.sun.proxy.$Proxy71.flush(Unknown Source)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.flush(SimpleJpaRepository.java:534)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.saveAndFlush(SimpleJpaRepository.java:505)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository$$FastClassBySpringCGLIB$$31f56960.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:746)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
    ... 37 more

 

• 从数据源的配置

SlaveDataSourceConfig.java:

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactorySlave"
        , transactionManagerRef = "transactionManagerSlave"
        , basePackages = {"com.yun.demo.dao.slave"})
public class SlaveDataSourceConfig {
    @Autowired
    @Qualifier("slaveDataSource")
    private DataSource slaveDataSource;

    @Autowired
    private JpaProperties jpaProperties;


    @Bean(name = "entityManagerSlave")
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return SharedEntityManagerCreator.createSharedEntityManager(entityManagerFactorySlave(builder).getObject());
    }
    @Bean(name = "entityManagerFactorySlave")
    public LocalContainerEntityManagerFactoryBean entityManagerFactorySlave (EntityManagerFactoryBuilder builder) {
        return builder
                .dataSource(slaveDataSource)
                .properties(getVendorProperties())
                .packages("com.yun.demo.entity.slave") //设置实体类所在位置
                .persistenceUnit("slavePersistenceUnit")
                .build();
    }

    @Bean(name = "transactionManagerSlave")
    public PlatformTransactionManager transactionManagerSlave(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactorySlave(builder).getObject());
    }


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

从库的配置跟主库的配置差不多。

 

• 告诉dao这里我们需要使用从库的数据源

SlaveDao.java:

package com.yun.demo.dao.slave;  //这里是配置从库的数据源的basePackages地址

import com.yun.demo.entity.slave.Address;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.data.jpa.repository.support.JpaEntityInformationSupport;
import org.springframework.stereotype.Repository;

import javax.persistence.EntityManager;

@Repository
public class AddressDao extends MySimpleJpaRepository<Address, Long> {

    @Autowired //这里需要使用@Qualifier("entityManagerSlave")将数据源配置到从库
    public AddressDao(@Qualifier("entityManagerSlave") EntityManager entityManager) {
        super(JpaEntityInformationSupport.getEntityInformation(Address.class, entityManager), entityManager);
    }

}

 

• 修改从库 SimpleJpaRepository 的事务管理器

由于 SimpleJpaRepository  的事务管理器是默认没有使用从库的事务，因此从库如果使用 SimpleJpaRepository ，就会报以下错误：

Caused by: javax.persistence.TransactionRequiredException: no transaction is in progress
    at org.hibernate.internal.SessionImpl.checkTransactionNeeded(SessionImpl.java:3505)
    at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1427)
    at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1423)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:350)
    at com.sun.proxy.$Proxy71.flush(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:305)
    at com.sun.proxy.$Proxy71.flush(Unknown Source)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.flush(SimpleJpaRepository.java:534)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.saveAndFlush(SimpleJpaRepository.java:505)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository$$FastClassBySpringCGLIB$$31f56960.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:746)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
    ... 37 more

解决上面的问题，需要重写 SimpleJpaRepository 类。不多说，上代码：

package com.yun.demo.dao.slave;

import org.springframework.data.jpa.repository.support.JpaEntityInformation;
import org.springframework.data.jpa.repository.support.SimpleJpaRepository;
import org.springframework.transaction.annotation.Transactional;

import javax.persistence.EntityManager;

public class MySimpleJpaRepository<T, ID> extends SimpleJpaRepository<T, ID> {
    public MySimpleJpaRepository(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {
        super(entityInformation, entityManager);
    }

    @Override
    @Transactional(transactionManager = "transactionManagerSlave") // 在这里我们告诉这个方法，我们需要使用从库的事务管理器
    public <S extends T> S saveAndFlush(S entity) {
        S result = this.save(entity);
        this.flush();
        return result;
    }
}

上面的类中我只举了一个方法的例子，如果你有更多的增、删、改方法需要用，那么都需要重写。

 

至此我们应该就可以解决上面的问题了。