java实现数据库读写分离
**数据库配置为一个主库 多个从库 主库用于写操作 从库只读操作
读写分离实现即为配置两个数据源，一个用于读写 连接主库 假设为ds_wr，一个用于只读 连接从库 假设为ds_r。
对数据库读操作时，操作ds_r数据源。
对数据源写操作时，操作ds_wr数据源。
读写分离可以有两种实现方式
第一种为写两套mappper
mapper写两套 一套用于读写 一套用于只读 **
<bean id="sqlSessionFactory_wr" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource_wr"/>
<property name="mapperLocations" value="classpath:mapping1/*.xml"/>
bean>
<bean id="sqlSessionFactory_r" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource_r"/>
<property name="mapperLocations" value="classpath:mapping/*.xml"/>
bean>
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.ifeng.auto.we_provider.dao1"/>
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory_wr"/>
bean>
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.ifeng.auto.we_provider.dao2"/>
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory_r"/>
bean> dao1包中mapper是读写方法 对应xml文件在mapping1文件夹中
dao2包中mapper是只读方法 对应xml文件在mapping2文件夹中
User user = userMapper2.get(1);
user.setName("Susan")
userMapper1.update(user); 第二种为通过实现AbstractRoutingDataSource类来动态管理数据源，本篇博客主要讲这部分内容
利用面向切面思维，每一次进入service方法前，选择数据源
首先pom.xml中添加依赖
<dependency>
<groupId>org.aspectjgroupId>
<artifactId>aspectjrtartifactId>
<version>1.7.4version>
dependency>
<dependency>
<groupId>org.aspectjgroupId>
<artifactId>aspectjweaverartifactId>
<version>1.7.4version>
dependency> 实现AbstractRoutingDataSource类 作为数据源
package com.ifeng.auto.we_provider.common.db;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
/**
* Created by Terry on 2016/7/23.
*/
public class DynamicDataSource extends AbstractRoutingDataSource {
@Override
protected Object determineCurrentLookupKey() {
return DynamicDataSourceHolder.getDataSouce();
}
}
用ThreadLcoal管理当前数据源
package com.ifeng.auto.we_provider.common.db;
public class DynamicDataSourceHolder {
public static final ThreadLocal holder = new ThreadLocal();
public static void putDataSource(String name) {
holder.set(name);
}
public static String getDataSouce() {
return holder.get();
}
} 用注解的形式实现AOP管理数据源
package com.ifeng.auto.we_provider.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface DataSource {
String value();
} 切面类
package com.ifeng.auto.we_provider.common.proxy;
import com.ifeng.auto.we_provider.annotation.DataSource;
import com.ifeng.auto.we_provider.common.db.DynamicDataSourceHolder;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.reflect.MethodSignature;
import java.lang.reflect.Method;
/**
* Created by Terry on 2016/7/23.
*/
public class DataSourceAspect {
public void before(JoinPoint point)
{
Object target = point.getTarget();
System.out.println(target.toString());
String method = point.getSignature().getName();
System.out.println(method);
Class classz = target.getClass();
Class[] parameterTypes = ((MethodSignature) point.getSignature())
.getMethod().getParameterTypes();
try {
Method m = classz.getMethod(method, parameterTypes);
System.out.println(m.getName());
if (m != null && m.isAnnotationPresent(DataSource.class)) {
DataSource data = m.getAnnotation(DataSource.class);
DynamicDataSourceHolder.putDataSource(data.value());
}
} catch (Exception e) {
e.printStackTrace();
}
}
} 将注解放在service实现类的方法前，自动设置当前数据源为注解中数据源。
接下来配置aop以及数据源。
mybatis.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.1.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
<context:property-placeholder location="classpath:db.properties" ignore-unresolvable="true"/>
<bean id="dataSource_wr" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
<property name="url" value="${db.url}"/>
<property name="username" value="${db.username}"/>
<property name="password" value="${db.password}"/>
<property name="connectionProperties" value="${db.driver}">property>
<property name="initialSize" value="1"/>
<property name="minIdle" value="1"/>
<property name="maxActive" value="20"/>
<property name="maxWait" value="60000"/>
<property name="timeBetweenEvictionRunsMillis" value="60000"/>
<property name="minEvictableIdleTimeMillis" value="300000"/>
<property name="validationQuery" value="SELECT 'x'"/>
<property name="testWhileIdle" value="true"/>
<property name="testOnBorrow" value="true"/>
<property name="testOnReturn" value="false"/>
bean>
<bean id="dataSource_r" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
<property name="url" value="${db1.url}"/>
<property name="username" value="${db1.username}"/>
<property name="password" value="${db1.password}"/>
<property name="connectionProperties" value="${db.driver}">property>
<property name="initialSize" value="1"/>
<property name="minIdle" value="1"/>
<property name="maxActive" value="20"/>
<property name="maxWait" value="60000"/>
<property name="timeBetweenEvictionRunsMillis" value="60000"/>
<property name="minEvictableIdleTimeMillis" value="300000"/>
<property name="validationQuery" value="SELECT 'x'"/>
<property name="testWhileIdle" value="true"/>
<property name="testOnBorrow" value="true"/>
<property name="testOnReturn" value="false"/>
bean>
<bean id="dataSource" class="com.ifeng.auto.we_provider.common.db.DynamicDataSource">
<property name="targetDataSources">
<map key-type="java.lang.String">
<entry key="write" value-ref="dataSource_wr"/>
<entry key="read" value-ref="dataSource_r"/>
map>
property>
<property name="defaultTargetDataSource" ref="dataSource_wr"/>
bean>
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="mapperLocations" value="classpath:mapping/*.xml"/>
bean>
<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource" />
bean>
<aop:aspectj-autoproxy proxy-target-class="true"/>
<bean id="dataSourceAspect" class="com.ifeng.auto.we_provider.common.proxy.DataSourceAspect"/>
<aop:config>
<aop:aspect id="c" ref="dataSourceAspect">
<aop:pointcut id="tx" expression="execution(* com.ifeng.auto.we_provider.service..*.*(..))"/>
<aop:before pointcut-ref="tx" method="before"/>
aop:aspect>
aop:config>
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.ifeng.auto.we_provider.dao"/>
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
bean>
beans> 在service实现类中
@DataSource("write")
public void savetag(UserTag userTag) {
userTagMapper.addUserTag(userTag);
} @DataSource("read")
public UserTag getUserTagByUUID(String uuid) {
return userTagMapper.getUserTagByUUID(uuid);
} 至此 读写分离实现