上次发了一篇mysql主从复制的博客，就我正在做的项目来讲，项目开始之初就是两个数据库服务器，一个master，一个slave，运维已经做好了主从复制的架构，但是基本上用的都是master数据库，从库基本都没怎么用。正好有一个关于统计的需求查询效率有点低，也比较频繁，就想着还不如查从库了。然后就去研究了一下springboot+JPA环境下的多数据源和读写分离。
一、首先要配置druid数据源
1、druid的某个配置很重要，因为数据库的每个连接是默认有一个8小时的超时时间的，如果过了8小时，连接会自动断掉，而druid此时还不知道连接已经断掉，也没有回收，一直用那个连接就会报错。此种情况一般出现于定时任务，比如某个统计需要每天统计一次，某个连接可能24小时才会使用一次，这时就会出现这个问题。
解决方案：
①、更改数据库默认的wait_outtime，改长一点，不推荐
②、可以从数据源入手，更改druid的配置，让druid每隔一段时间自动去检测连接池中每个连接是否可用，如果不可用则回收。后面需要连接时，会重新开启一个连接。这个时间间隔需要小于数据库的超时时间才对。
2、druid配置和jpa配置
①、主库配置：
# JDBC配置
spring.datasource.druid.url= jdbc:mysql://10.10.10.105:23306/xiuba_user?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=round&autoReconnect=true&useSSL=false
spring.datasource.druid.username= xiuba
spring.datasource.druid.driver-class-name= com.mysql.jdbc.Driver
spring.datasource.druid.password= xiuba123456
# 连接池配置，说明请参考Druid Wiki，DruidDataSource配置属性列表
spring.datasource.druid.initial-size=3
spring.datasource.druid.max-active=20
spring.datasource.druid.min-idle=3
spring.datasource.druid.max-wait=60000
spring.datasource.druid.time-between-eviction-runs-millis=50000
spring.datasource.druid.min-evictable-idle-time-millis=80000
spring.datasource.druid.max-evictable-idle-time-millis=100000
spring.datasource.druid.validation-query=select 'x'
spring.datasource.druid.validation-query-timeout=10
spring.datasource.druid.test-on-borrow=false
spring.datasource.druid.test-on-return=false
spring.datasource.druid.test-while-idle=true
#默认值stat，配置多个英文逗号分隔
spring.datasource.druid.filters= stat,wall,slf4j
# WebStatFilter配置，说明请参考Druid Wiki，配置_配置WebStatFilter
spring.datasource.druid.web-stat-filter.enabled=true
spring.datasource.druid.web-stat-filter.urlPattern=/*
spring.datasource.druid.web-stat-filter.exclusions=*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*
spring.datasource.druid.web-stat-filter.sessionStatMaxCount=600
spring.datasource.druid.web-stat-filter.sessionStatEnable=true
#spring.datasource.druid.web-stat-filter.principalSessionName=
#spring.datasource.druid.web-stat-filter.principalCookieName=
spring.datasource.druid.web-stat-filter.profileEnable=true
# StatViewServlet配置，说明请参考Druid Wiki，配置_StatViewServlet配置
spring.datasource.druid.stat-view-servlet.enabled=true
spring.datasource.druid.stat-view-servlet.urlPattern=/druid/*
spring.datasource.druid.stat-view-servlet.resetEnable=true
spring.datasource.druid.stat-view-servlet.loginUsername=druid
spring.datasource.druid.stat-view-servlet.loginPassword=123456
#spring.datasource.druid.stat-view-servlet.allow=
#spring.datasource.druid.stat-view-servlet.deny=②、从库配置
#从库配置
# JDBC配置
spring.datasource.druid.slave.url= jdbc:mysql://10.10.10.104:23306/xiuba_user?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=round&autoReconnect=true&useSSL=false
spring.datasource.druid.slave.username=xiuba_select
spring.datasource.druid.slave.driver-class-name= com.mysql.jdbc.Driver
spring.datasource.druid.slave.password=xiuba123456
# 连接池配置，说明请参考Druid Wiki，DruidDataSource配置属性列表
spring.datasource.druid.slave.initial-size=3
spring.datasource.druid.slave.max-active=20
spring.datasource.druid.slave.min-idle=3
spring.datasource.druid.slave.max-wait=60000
spring.datasource.druid.slave.time-between-eviction-runs-millis=50000
spring.datasource.druid.slave.min-evictable-idle-time-millis=80000
spring.datasource.druid.slave.max-evictable-idle-time-millis=100000
spring.datasource.druid.slave.validation-query=select 'x'
spring.datasource.druid.slave.validation-query-timeout=10
spring.datasource.druid.slave.test-on-borrow=false
spring.datasource.druid.slave.test-on-return=false
spring.datasource.druid.slave.test-while-idle=true
#默认值stat，配置多个英文逗号分隔
spring.datasource.druid.slave.filters= stat,wall,slf4j③、JPA配置
spring.jpa.properties.hibernate.hbm2ddl.auto= update
spring.jpa.open-in-view=true
spring.jpa.properties.hibernate.show_sql=false
spring.jpa.properties.hibernate.format_sql=false注意：
①： 因为jpa或者说hibernate是orm框架，有一个自动更新数据库的配置，可以使数据库根据项目中的实体类自动生成相应的表结构，非常方便好用。但是这也引来了一些问题，如果从库也应用这个配置，就会更改从库的表结构，而从库只要自己发生变化而不是主库复制来的，就会发生mysql错误，使主从复制停止，造成重大错误。所以此时jpa的配置应该主从分离，此操作实现在EntityManager生成配置类中。
②：为了避免上述情况在我们不经意间发生，最好给从库配置一个只能读不能写的权限的用户，我们所有操作都用这个用户来执行，避免人为错误。
二、数据源生成类：
package com.zhibi.xiuba.config.data;
import com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.env.Environment;
import javax.sql.DataSource;
/**
* Created by QinHe on 2018-07-24.
*/
@Configuration
public class DruidDataSourceConfig {
/**
* 主DataSource 配置
*/
@Primary
@ConfigurationProperties(prefix = "spring.datasource.druid")
@Bean(name = "primaryDruidDataSource")
public DataSource primaryDruidDataSource(Environment environment) {
return DruidDataSourceBuilder.create().build(environment, "spring.datasource.druid.");
}
/**
* 从DataSource 配置
*/
@ConfigurationProperties(prefix = "spring.datasource.druid.slave")
@Bean(name = "slaveDruidDataSource")
public DataSource slaveDruidDataSource(Environment environment) {
return DruidDataSourceBuilder.create().build(environment, "spring.datasource.druid.slave.");
}
}
三、EntityManager生成类
与jpa结合起来：
1、主库：
扫描二维码关注公众号，回复：
2820112 查看本文章
package com.zhibi.xiuba.config.data;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
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.annotation.Resource;
import javax.persistence.EntityManager;
import javax.sql.DataSource;
import java.util.Map;
/**
* Created by QinHe on 2018-07-24.
*/
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
entityManagerFactoryRef = "entityManagerFactoryPrimary",
transactionManagerRef = "transactionManagerPrimary",
basePackages = {"com.zhibi.xiuba.repository.primary"}) //设置Repository所在位置
public class PrimaryConfig {
@Resource(name = "primaryDruidDataSource")
private DataSource primaryDruidDataSource;
@Autowired
private JpaProperties jpaProperties;
@Primary
@Bean(name = "entityManagerFactoryPrimary")
public LocalContainerEntityManagerFactoryBean entityManagerFactoryPrimary(EntityManagerFactoryBuilder builder) {
return builder
.dataSource(primaryDruidDataSource)
.properties(getVendorProperties(primaryDruidDataSource))
.packages("com.zhibi.xiuba") //设置实体类所在位置
.persistenceUnit("primaryPersistenceUnit")
.build();
}
@Primary
@Bean(name = "entityManagerPrimary")
public EntityManager entityManagerPrimary(EntityManagerFactoryBuilder builder) {
return entityManagerFactoryPrimary(builder).getObject().createEntityManager();
}
private Map<String, String> getVendorProperties(DataSource dataSource) {
return jpaProperties.getHibernateProperties(dataSource);
}
@Primary
@Bean(name = "transactionManagerPrimary")
public PlatformTransactionManager transactionManagerPrimary(EntityManagerFactoryBuilder builder) {
return new JpaTransactionManager(entityManagerFactoryPrimary(builder).getObject());
}
}
2、从库
package com.zhibi.xiuba.config.data;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
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.annotation.Resource;
import javax.persistence.EntityManager;
import javax.sql.DataSource;
import java.util.Map;
/**
* Created by QinHe on 2018-07-24.
*/
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
entityManagerFactoryRef = "entityManagerFactorySlave",
transactionManagerRef = "transactionManagerSlave",
basePackages = {"com.zhibi.xiuba.repository.slave"}) //设置Repository所在位置
public class SlaveConfig {
@Resource(name = "slaveDruidDataSource")
private DataSource slaveDruidDataSource;
@Autowired
private JpaProperties jpaProperties;
@Bean(name = "entityManagerFactorySlave")
public LocalContainerEntityManagerFactoryBean entityManagerFactorySlave(EntityManagerFactoryBuilder builder) {
LocalContainerEntityManagerFactoryBean slavePersistenceUnit = builder
.dataSource(slaveDruidDataSource)
.properties(getVendorProperties(slaveDruidDataSource))
.packages("com.zhibi.xiuba") //设置实体类所在位置
.persistenceUnit("slavePersistenceUnit")
.build();
slavePersistenceUnit.getJpaPropertyMap().remove("hibernate.hbm2ddl.auto");
return slavePersistenceUnit;
}
@Bean(name = "entityManagerSlave")
public EntityManager entityManagerSlave(EntityManagerFactoryBuilder builder) {
return entityManagerFactorySlave(builder).getObject().createEntityManager();
}
private Map<String, String> getVendorProperties(DataSource dataSource) {
return jpaProperties.getHibernateProperties(dataSource);
}
@Bean(name = "transactionManagerSlave")
public PlatformTransactionManager transactionManagerSlave(EntityManagerFactoryBuilder builder) {
return new JpaTransactionManager(entityManagerFactorySlave(builder).getObject());
}
}