Java知识点梳理——读写分离
1、读写分离：可以通过Spring提供的AbstractRoutingDataSource类，重写determineCurrentLookupKey方法，实现动态切换数据源的功能；读写分离可以有效减轻写库的压力，又可以把查询数据的请求分发到不同读库；MySql主从同步传送门
2、写数据库：当调用insert、update、delete及一些实时数据用到的库；
3、读数据库：当调用select查询数据用到的库；
4、JaveWeb工程通过AbstractRoutingDataSource类实现读写分离；
a、jdbc.properties文件配置读写数据源
datasource.type=mysql datasource.driverClassName=com.mysql.jdbc.Driver datasource.username=root #写库 w.datasource.url=jdbc\:mysql\://127.0.0.1\:3306/ddt?characterEncoding\=utf-8 w.datasource.password=write123 #读库 r.datasource.url=jdbc\:mysql\://IP\:3306/ddt?characterEncoding\=utf-8 r.datasource.password=read123 #连接池配置 c3p0.acquireIncrement=3 c3p0.acquireRetryAttempts=10 c3p0.acquireRetryDelay=1000 c3p0.initialPoolSize=20 c3p0.idleConnectionTestPeriod=3600 c3p0.testConnectionOnCheckout=true c3p0.minPoolSize=10 c3p0.maxPoolSize=80 c3p0.maxStatements=100 c3p0.numHelperThreads=10 c3p0.maxIdleTime=10800
b、application.xml文件
<?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:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.0.xsd"> <!-- 使用annotation 自动注册bean,并保证@Required,@Autowired的属性被注入 --> <context:component-scan base-package="com.eb3"> <context:include-filter type="annotation" expression="org.springframework.stereotype.Service" /> <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller" /> </context:component-scan> <bean class="org.springframework.beans.factory.config.PreferencesPlaceholderConfigurer" > <property name="ignoreResourceNotFound" value="true" /> <property name="properties" ref="configProperties" /> </bean> <bean id="configProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean"> <property name="locations"> <list> <value>classpath*:jdbc.properties</value> </list> </property> </bean> <context:property-placeholder location="classpath:jdbc.properties"/> <!-- 定义Hibernate读数据源 --> <bean id="dataSourceRead" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <property name="driverClass"> <value>${datasource.driverClassName}</value> </property> <property name="jdbcUrl"> <value>${r.datasource.url}</value> </property> <property name="user"> <value>${datasource.username}</value> </property> <property name="password"> <value>${r.datasource.password}</value> </property> <!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。--> <property name="acquireIncrement"> <value>${c3p0.acquireIncrement}</value> </property> <!--定义在从数据库获取新连接失败后重复尝试的次数。--> <property name="acquireRetryAttempts"> <value>${c3p0.acquireRetryAttempts}</value> </property> <!--两次连接中间隔时间，单位毫秒。--> <property name="acquireRetryDelay"> <value>${c3p0.acquireRetryDelay}</value> </property> <property name="initialPoolSize"> <value>${c3p0.initialPoolSize}</value> </property> <property name="testConnectionOnCheckout"> <value>${c3p0.testConnectionOnCheckout}</value> </property> <property name="minPoolSize"> <value>${c3p0.minPoolSize}</value> </property> <property name="maxPoolSize"> <value>${c3p0.maxPoolSize}</value> </property> <property name="maxIdleTime"> <value>${c3p0.maxIdleTime}</value> </property> <property name="idleConnectionTestPeriod"> <value>${c3p0.idleConnectionTestPeriod}</value> </property> <property name="maxStatements"> <value>${c3p0.maxStatements}</value> </property> <property name="numHelperThreads"> <value>${c3p0.numHelperThreads}</value> </property> </bean> <!-- 定义Hibernate写数据源 --> <bean id="dataSourceWrite" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <property name="driverClass"> <value>${datasource.driverClassName}</value> </property> <property name="jdbcUrl"> <value>${w.datasource.url}</value> </property> <property name="user"> <value>${datasource.username}</value> </property> <property name="password"> <value>${w.datasource.password}</value> </property> <!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。--> <property name="acquireIncrement"> <value>${c3p0.acquireIncrement}</value> </property> <!--定义在从数据库获取新连接失败后重复尝试的次数。--> <property name="acquireRetryAttempts"> <value>${c3p0.acquireRetryAttempts}</value> </property> <!--两次连接中间隔时间，单位毫秒。--> <property name="acquireRetryDelay"> <value>${c3p0.acquireRetryDelay}</value> </property> <property name="initialPoolSize"> <value>${c3p0.initialPoolSize}</value> </property> <property name="testConnectionOnCheckout"> <value>${c3p0.testConnectionOnCheckout}</value> </property> <property name="minPoolSize"> <value>${c3p0.minPoolSize}</value> </property> <property name="maxPoolSize"> <value>${c3p0.maxPoolSize}</value> </property> <property name="maxIdleTime"> <value>${c3p0.maxIdleTime}</value> </property> <property name="idleConnectionTestPeriod"> <value>${c3p0.idleConnectionTestPeriod}</value> </property> <property name="maxStatements"> <value>${c3p0.maxStatements}</value> </property> <property name="numHelperThreads"> <value>${c3p0.numHelperThreads}</value> </property> </bean> <!-- 动态数据源 --> <bean id="dynamicDataSource" class="com.eb3.ddt.DynamicDataSource"> <!-- 通过key-value关联数据源 --> <property name="targetDataSources"> <map> <entry value-ref="dataSourceWrite" key="dataSourceWrite"></entry> <entry value-ref="dataSourceRead" key="dataSourceRead"></entry> </map> </property> <property name="defaultTargetDataSource" ref="dataSourceWrite" /> </bean> <!-- 设置sessionFactory --> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"> <!-- 依赖注入数据源，注入正是上文定义的dataSource --> <property name="dataSource" ref="dynamicDataSource" /> <property name="packagesToScan" value="com.eb3.ddt.pojo,com.eb3.loan.pojo"/> <!--定义Hibernate的SessionFactory的属性 --> <property name="hibernateProperties"> <props> <!-- 指定Hibernate的连接方言--> <prop key="hibernate.dialect"> ${hibernate.dialect} </prop> <prop key="hibernate.connection.autocommit">${hibernate.connection.autocommit}</prop> <!-- 制定Hibernate是否打印SQL语句 --> <prop key="hibernate.show_sql">${hibernate.show_sql}</prop> <prop key="hibernate.format_sql">${hibernate.format_sql}</prop> <!-- 设create(启动创建),create-drop(启动创建,退出删除),update(启动更新),validate(启动验证) --> <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}</prop> <prop key="connection.characterEncoding">utf-8</prop> <!-- 设置二级缓存 --> <prop key="hibernate.cache.user_query_cache">${hibernate.cache.user_query_cache}</prop> <prop key="hibernate.user_second_level_cache">${hibernate.user_second_level_cache}</prop> <prop key="hibernate.cache.provider_class">${hibernate.cache.class}</prop> <prop key="hibernate.cache.provider_configuration_file_resource_path">${hibernate.ehcache_config_file}</prop> </props> </property> </bean> <!-- 事务管理器配置,单数据源事务 --> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory" ref="sessionFactory"/> </bean>
<tx:advice id="txAdvice" transaction-manager="transactionManager"> <tx:attributes> <tx:method name="save*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="add*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="delete*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="update*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="merge*" isolation="READ_COMMITTED" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="get*" read-only="true"/> <tx:method name="find*" read-only="true"/> <tx:method name="list*" read-only="true"/> <tx:method name="select*" read-only="true"/> <tx:method name="*" propagation="REQUIRED" /> </tx:attributes> </tx:advice> <aop:config> <aop:pointcut id="interceptorPointCuts" expression="execution(* com.eb3.*.service.*.*(..))" /> <aop:advisor advice-ref="txAdvice" pointcut-ref="interceptorPointCuts" /> </aop:config> <aop:aspectj-autoproxy proxy-target-class="true" /> <!-- 定时器配置 task:scheduler@pool-size调度线程池的大小，调度线程在被调度任务完成前不会空闲 task:executor/@pool-size：可以指定执行线程池的初始大小、最大大小 task:executor/@queue-capacity：等待执行的任务队列的容量 task:executor/@rejection-policy：当等待队已满时的策略，分为丢弃、由任务执行器直接运行等方式 @Async 异步任务时 task任务执行线程数 task:scheduler 和 task:executor 两个线程池同样起作用 没有异步注解时 task任务执行线程数只受task:scheduler的线程池大小影响 --> <!-- 声明一个具有10个线程的池，每一个对象将获取同样的运行机会 --> <task:scheduler id="scheduler" pool-size="10" /> <task:executor id="executor" keep-alive="3600" pool-size="100-300" queue-capacity="500" rejection-policy="CALLER_RUNS" /> <task:annotation-driven executor="executor" scheduler="scheduler" /> </beans>
c、继承AbstractRoutingDataSource类的动态数据源类DynamicDataSource
package com.eb3.ddt; import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource; public class DynamicDataSource extends AbstractRoutingDataSource { /** * 重写determineCurrentLookupKey方法 */ @Override protected Object determineCurrentLookupKey() { Object obj = DBHelper.getDbType(); return obj; } }
d、DBHelper工具类
package com.eb3.ddt; import org.apache.commons.lang.StringUtils; public class DBHelper { private static ThreadLocal<String> dbContext = new ThreadLocal<String>(); // 写数据源标识 public final static String DB_WRITE = "dataSourceWrite"; // 读数据源标识 public final static String DB_READ = "dataSourceRead"; /** * 获取数据源类型，即是写数据源，还是读数据源 * * @return */ public static String getDbType() { String db_type = dbContext.get(); if (StringUtils.isEmpty(db_type)) { // 默认是写数据源 db_type = DB_WRITE; } return db_type; } /** * 设置该线程的数据源类型 * * @param str */ public static void setDbType(String str) { dbContext.set(str); } }
e、服务层调用
/*@Aspect 此注解会影响数据源切换，运行代码得知不加的话会先执行DynamicDataSource里的determineCurrentLookupKey方法，后执行Service层里DBHelper.setDbType()方法，导致数据源切换失败！ */ @Aspect @Component("userService") public class UserServiceImpl extends BaseServiceImpl<User, User, Integer> implements UserService { @Resource private UserDao userDao; @Override protected BaseDao<User, Integer> getDao() { return this.userDao; } @Override public void save(User user) { DBHelper.setDbType(DBHelper.DB_WRITE); // 写库 this.userDao.save(user); } @Override public User findByUserName(String username) { DBHelper.setDbType(DBHelper.DB_READ); // 读库 List<User> userList = this.userDao.findBy("username", username); return CollectionUtils.isNotEmpty(userList) ? userList.get(0) : null; } }
