Spring 动态数据源和AOP实现数据库读写分离

来源：互联网发布：dts音效软件编辑：程序博客网时间：2024/04/30 12:42

互联网架构演进中数据库优化是不可或缺的一环，数据库层面优化分为两个阶段：读写分离、分库分表。

今天要说的是数据库读写分离技术，其原理就是一个Master数据库，多个Slave数据库。Master库负责数据更新和实时数据查询，Slave库当然负责非实时数据查询。因为在实际的应用中，数据库都是读多写少（读取数据的频率高，更新数据的频率相对较少），而读取数据通常耗时比较长，占用数据库服务器的CPU较多，从而影响用户体验。

我们通常的做法就是把查询从主库中抽取出来，分发到多个从库上，减轻主库的压力。
采用读写分离技术的目标：有效减轻Master库的压力，又可以把用户查询数据的请求分发到不同的Slave库，从而保证系统的健壮性。

实现原理

在DAO实现类的方法加上@RoutingDataSource注解，然后通过Spring AOP技术在运行时拦截DAO的方法，获取方法上的@RoutingDataSource注解值动态切换数据源。

代码实现

1、Spring动态数据源

1、spring-dao.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:tx="http://www.springframework.org/schema/tx"       xmlns:context="http://www.springframework.org/schema/context"       xmlns:util="http://www.springframework.org/schema/util"       xsi:schemaLocation="       http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd       http://www.springframework.org/schema/tx       http://www.springframework.org/schema/tx/spring-tx.xsd       http://www.springframework.org/schema/util       http://www.springframework.org/schema/util/spring-util.xsd       http://www.springframework.org/schema/context       http://www.springframework.org/schema/context/spring-context.xsd"       default-lazy-init="false">    <bean id="parentDataSource" class="com.alibaba.druid.pool.DruidDataSource"           destroy-method="close"  abstract="true" init-method="init" >        <!-- 初始化连接大小 -->        <property name="initialSize" value="2" />        <!-- 连接池最大使用连接数量 -->        <property name="maxActive" value="10" />        <!-- 连接池最小空闲 -->        <property name="minIdle" value="5" />        <!-- 获取连接最大等待时间 -->        <property name="maxWait" value="30000" />        <!-- <property name="poolPreparedStatements" value="true" /> -->        <!-- <property name="maxPoolPreparedStatementPerConnectionSize" value="33" /> -->        <property name="validationQuery" value="SELECT 1" />        <property name="testOnBorrow" value="false" />        <property name="testOnReturn" value="false" />        <property name="testWhileIdle" value="true" />        <!-- 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="25200000" />        <!-- 打开removeAbandoned功能 -->        <property name="removeAbandoned" value="true" />        <!-- 1800秒，也就是30分钟 -->        <property name="removeAbandonedTimeout" value="1800" />        <!-- 关闭abanded连接时输出错误日志 -->        <property name="logAbandoned" value="true" />        <!-- 监控数据库 -->        <!-- <property name="filters" value="stat" /> -->        <property name="filters" value="mergeStat" />    </bean>    <!-- 配置数据源-->    <bean id="masterDataSource" parent="parentDataSource">        <property name="url" value="#{jdbc['master.jdbc.url']}" />        <property name="username" value="#{jdbc['master.jdbc.username']}" />        <property name="password" value="#{jdbc['master.jdbc.password']}" />        <property name="driverClassName" value="#{jdbc['master.jdbc.driver']}" />        <property name="maxActive" value="15" />    </bean>    <bean id="slaveDataSource" parent="parentDataSource">        <property name="url" value="#{jdbc['slave1.jdbc.url']}" />        <property name="username" value="#{jdbc['slave1.jdbc.username']}" />        <property name="password" value="#{jdbc['slave1.jdbc.password']}" />        <property name="driverClassName" value="#{jdbc['slave1.jdbc.driver']}" />    </bean>    <!--动态数据源-->    <bean id="dataSource" class="com.bytebeats.spring4.sample.ds.DynamicRoutingDataSource">        <property name="targetDataSources">            <map key-type="com.bytebeats.spring4.sample.ds.RoutingStrategy">                <entry key="WRITE" value-ref="masterDataSource"/>                <entry key="READ" value-ref="slaveDataSource"/>            </map>        </property>        <!-- 默认目标数据源为主库数据源 -->        <property name="defaultTargetDataSource" ref="masterDataSource"/>    </bean>    <!--Spring JdbcTemplate-->    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">        <property name="dataSource" ref="dataSource"/>    </bean>    <!-- 注解方式配置事物 -->    <tx:annotation-driven transaction-manager="transactionManager" />    <!-- 配置事务管理器 -->    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">        <property name="dataSource" ref="masterDataSource" />    </bean></beans>

2、动态数据源实现
DynamicRoutingDataSource.java

package com.bytebeats.spring4.sample.ds;import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;/** * 动态数据源 * * @author Ricky Fung * @create 2016-12-30 11:12 */public class DynamicRoutingDataSource extends AbstractRoutingDataSource {    @Override    protected Object determineCurrentLookupKey() {        return DynamicRoutingContextHolder.getRouteStrategy();    }}

DynamicRoutingContextHolder.java

package com.bytebeats.spring4.sample.ds;import org.springframework.util.Assert;/** * ${DESCRIPTION} * * @author Ricky Fung * @create 2016-12-30 11:14 */public class DynamicRoutingContextHolder {    private static final ThreadLocal<RoutingStrategy> contextHolder =            new ThreadLocal<>();    public static void setRouteStrategy(RoutingStrategy customerType) {        Assert.notNull(customerType, "customerType cannot be null");        contextHolder.set(customerType);    }    public static RoutingStrategy getRouteStrategy() {        return (RoutingStrategy) contextHolder.get();    }    public static void clearRouteStrategy() {        contextHolder.remove();    }}

RoutingStrategy.java

package com.bytebeats.spring4.sample.ds;/** * 读写策略 * * @author Ricky Fung * @create 2016-12-30 11:14 */public enum RoutingStrategy {    WRITE, READ;}

数据源注解

package com.bytebeats.spring4.sample.annotation;import com.bytebeats.spring4.sample.ds.RoutingStrategy;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * ${DESCRIPTION} * * @author Ricky Fung * @date 2016-12-30 15:26 */@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.METHOD)public @interface RoutingDataSource {    RoutingStrategy value();}

Spring AOP

1、spring-aop.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.xsd        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">    <!-- 配置AOP -->    <aop:aspectj-autoproxy />    <bean id="readWriteSeparateAspect" class="com.bytebeats.spring4.sample.aop.DBReadWriteSeparateAspect" />    <aop:config>        <aop:aspect ref="readWriteSeparateAspect">            <aop:pointcut id="rw" expression="execution(* com.bytebeats.spring4.sample.dao.*.*(..))" />            <aop:before pointcut-ref="rw" method="before" />        </aop:aspect>    </aop:config></beans>

2、切面类

package com.bytebeats.spring4.sample.aop;import com.bytebeats.spring4.sample.annotation.RoutingDataSource;import com.bytebeats.spring4.sample.ds.DynamicRoutingContextHolder;import org.aspectj.lang.JoinPoint;import org.aspectj.lang.reflect.MethodSignature;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.lang.reflect.Method;/** * ${DESCRIPTION} * * @author Ricky Fung * @date 2016-12-30 16:59 */public class DBReadWriteSeparateAspect {    private final Logger logger = LoggerFactory.getLogger(getClass());    public void before(JoinPoint point) {        Object target = point.getTarget();        String methodName = point.getSignature().getName();        Class<?> clazz = target.getClass();        logger.info("before class:{} method:{} execute", clazz.getName(), methodName);        Class<?>[] parameterTypes = ((MethodSignature) point.getSignature()).getMethod().getParameterTypes();        try {            Method method = clazz.getMethod(methodName, parameterTypes);            if (method != null && method.isAnnotationPresent(RoutingDataSource.class)) {                RoutingDataSource data = method.getAnnotation(RoutingDataSource.class);                DynamicRoutingContextHolder.setRouteStrategy(data.value());                logger.info("class:{} method:{} 切换数据源:{} 成功", clazz.getName(), methodName, data.value());            }        } catch (Exception e) {            logger.error("数据源切换切面异常", e);        }    }}

如何使用

假设有一个订单库，现在要实现订单表的插入和查询，IOrderDao接口定义如下：

package com.bytebeats.spring4.sample.dao;import com.bytebeats.spring4.sample.domain.Order;import java.util.List;/** * ${DESCRIPTION} * * @author Ricky Fung * @create 2016-12-30 11:15 */public interface IOrderDao {    long insert(Order order);    List<Order> queryOrders();}

我们期望insert路由到主库上，queryOrders路由到从库上，那么我们只需要在这两个方法上增加@RoutingDataSource注解即可，OrderDaoImpl 代码如下：

package com.bytebeats.spring4.sample.dao.impl;import com.bytebeats.spring4.sample.annotation.RoutingDataSource;import com.bytebeats.spring4.sample.dao.IOrderDao;import com.bytebeats.spring4.sample.domain.Order;import com.bytebeats.spring4.sample.ds.RoutingStrategy;import org.springframework.jdbc.core.JdbcTemplate;import org.springframework.jdbc.core.RowMapper;import org.springframework.stereotype.Repository;import javax.annotation.Resource;import java.sql.ResultSet;import java.sql.SQLException;import java.util.List;/** * ${DESCRIPTION} * * @author Ricky Fung * @create 2016-12-30 11:16 */@Repository("orderDao")public class OrderDaoImpl implements IOrderDao {    @Resource(name = "jdbcTemplate")    private JdbcTemplate jdbcTemplate;    @RoutingDataSource(RoutingStrategy.WRITE)    @Override    public long insert(Order order) {        String sql = "INSERT INTO tb_order(customer_name,total_price,amount,address) VALUES (?,?,?,?)";        return jdbcTemplate.update(sql, order.getCustomerName(),                order.getTotalPrice(), order.getAmount(), order.getAddress());    }    @RoutingDataSource(RoutingStrategy.READ)    @Override    public List<Order> queryOrders(){        return jdbcTemplate.query("SELECT * FROM tb_order", new RowMapper<Order>() {            @Override            public Order mapRow(ResultSet rs, int i) throws SQLException {                Order order = new Order();                order.setId(rs.getLong("id"));                order.setCustomerName(rs.getString("customer_name"));                order.setTotalPrice(rs.getDouble("total_price"));                order.setAmount(rs.getInt("amount"));                order.setAddress(rs.getString("address"));                return order;            }        });    }}

源码下载

点此下载源码：https://github.com/TiFG/spring4-in-action/tree/master/spring-ch5-rw

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