java读写分离实现 javadao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"/>
        <!-- 自动扫描mapping.xml文件-->
        <!--
        <property name="mapperLocations" value="classpath:com/ifeng/auto/we_provider/mapping/*.xml" />
         -->
        <property name="mapperLocations" value="classpath:mapping1/*.xml"/>
    </bean>
    <bean id="sqlSessionFactory_r" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource_r"/>
        <!-- 自动扫描mapping.xml文件-->
        <!--
        <property name="mapperLocations" value="classpath:com/ifeng/auto/we_provider/mapping2/*.xml" />
         -->
        <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

		<!-- https://mvnrepository.com/artifact/org.aspectj/aspectjrt -->
		<dependency>
			<groupId>org.aspectj</groupId>
			<artifactId>aspectjrt</artifactId>
			<version>1.7.4</version>
		</dependency>
				<dependency>
					<groupId>org.aspectj</groupId>
					<artifactId>aspectjweaver</artifactId>
					<version>1.7.4</version>
				</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<String> holder = new ThreadLocal<String>();

    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

<?xml version="1.0" encoding="UTF-8"?>
<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">
    <!-- 引入配置文件 -->
    <context:property-placeholder location="classpath:db.properties" ignore-unresolvable="true"/>

    <!-- 数据源配置 -->
    <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>

        <!-- 配置初始化大小、最小、最大 -->
        <property name="initialSize" value="1"/>
        <property name="minIdle" value="1"/>
        <property name="maxActive" value="20"/>

        <!-- 配置获取连接等待超时的时间 -->
        <property name="maxWait" value="60000"/>

        <!-- 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 -->
        <property name="timeBetweenEvictionRunsMillis" value="60000"/>

        <!-- 配置一个连接在池中最小生存的时间，单位是毫秒 -->
        <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>

        <!-- 配置初始化大小、最小、最大 -->
        <property name="initialSize" value="1"/>
        <property name="minIdle" value="1"/>
        <property name="maxActive" value="20"/>

        <!-- 配置获取连接等待超时的时间 -->
        <property name="maxWait" value="60000"/>

        <!-- 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 -->
        <property name="timeBetweenEvictionRunsMillis" value="60000"/>

        <!-- 配置一个连接在池中最小生存的时间，单位是毫秒 -->
        <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">
                <!-- write -->
                <entry key="write" value-ref="dataSource_wr"/>
                <!-- read -->
                <entry key="read" value-ref="dataSource_r"/>
            </map>

        </property>
        <property name="defaultTargetDataSource" ref="dataSource_wr"/>
    </bean>

    <!-- spring和MyBatis完美整合，不需要mybatis的配置映射文件-->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- 自动扫描mapping.xml文件-->
        <!--
        <property name="mapperLocations" value="classpath:com/ifeng/auto/we_provider/mapping/*.xml" />
         -->
        <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>

    <!-- DAO接口所在包名，Spring会自动查找其下的类 -->
    <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