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Spring AOP 动态多数据源的实例详解
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 Spring AOP 动态多数据源的实例详解

当项目中使用到读写分离的时候,我们就会遇到多数据源的问题。多数据源让人最头痛的,不是配置多个数据源,而是如何能灵活动态的切换数据源。例如在一个spring和Mybatis的框架的项目中,我们在spring配置中往往是配置一个dataSource来连接数据库,然后绑定给sessionFactory,在dao层代码中再指定sessionFactory来进行数据库操作。

 

正如上图所示,每一块都是指定绑死的,如果是多个数据源,也只能是下图中那种方式。

可看出在Dao层代码中写死了两个SessionFactory,这样日后如果再多一个数据源,还要改代码添加一个SessionFactory,显然这并不符合开闭原则。

那么正确的做法应该是:

具体代码与配置如下:

1、applicationContext-mgr.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:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsdhttp://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"> <!-- use annotation --> <context:annotation-config /> <context:component-scan base-package="com.carl.o2o.**.mgr"> </context:component-scan> <!-- master --> <bean id="master" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <property name="driverClass" value="${
    driverClassName_master}
    "/> <property name="user" value="${
    username_master}
    "/> <property name="password" value="${
    password_master}
    "/> <property name="jdbcUrl" value="${
    url_master}
    ?Unicode=true&characterEncoding=UTF-8&allowMultiQueries=true"/> <property name="maxPoolSize" value="150"/> <property name="minPoolSize" value="10"/> <property name="initialPoolSize" value="20"/> <property name="maxIdleTime" value="3600"/> <property name="acquireIncrement" value="10"/> <property name="idleConnectionTestPeriod" value="1800"/> </bean> <!-- slave --> <bean id="slave" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <property name="driverClass" value="${
    driverClassName_slave}
    "/> <property name="user" value="${
    username_slave}
    "/> <property name="password" value="${
    password_slave}
    "/> <property name="jdbcUrl" value="${
    url_slave}
    ?Unicode=true&characterEncoding=UTF-8"/> <property name="maxPoolSize" value="150"/> <property name="minPoolSize" value="10"/> <property name="initialPoolSize" value="20"/> <property name="maxIdleTime" value="3600"/> <property name="acquireIncrement" value="10"/> <property name="idleConnectionTestPeriod" value="1800"/> </bean> <!-- spring 动态数据源 --> <bean id="dynamicDataSource" class="com.carl.dbUtil.DynamicDataSource"> <property name="targetDataSources"> <map key-type="java.lang.String"> <entry key="slave" value-ref="slave" /> </map> </property> <property name="defaultTargetDataSource" ref="master" /> </bean> <!-- mybatis mapper config --> <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="dataSource" ref="dynamicDataSource"/> <property name="configLocation" value="classpath:o2o_mybatis_config.xml"/> <property name="mapperLocations" > <list> <value>classpath:sqlMap/*.xml</value> <value>classpath*:/com/carl/o2o/**/*.xml</value> </list> </property> </bean> <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate"> <constructor-arg index="0" ref="sqlSessionFactory"></constructor-arg> </bean> <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"> <property name="basePackage" value="com.carl.o2o.**.mgr.dao" /> </bean> <!-- 多数据源 aop --> <bean id="DataSourceAspect" class="com.carl.dbUtil.DataSourceAspect" /> <aop:config> <aop:advisor pointcut="execution(* com.carl.o2o.mgr.*.*(..))" advice-ref="DataSourceAspect" /> </aop:config> <!-- 事务 --> <bean name="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="dynamicDataSource"></property> </bean> </beans>

2、DynamicDataSource

DynamicDataSource使用Spring中的代码结合AOP实现多数据源切换.

    public class DynamicDataSource extends AbstractRoutingDataSource {
    public DynamicDataSource() {
    }
    protected Object determineCurrentLookupKey() {
    return DBContextHolder.getDbType();
    }
    public Logger getParentLogger() {
    return null;
    }
    }

3、DBContextHolder

DynamicDataSource的辅助类,用于实际的切换多数据源。

    public class DBContextHolder {
    private static ThreadLocal<String> contextHolder = new ThreadLocal();
    public static String MASTER = "master";
    public static String SLAVE = "slave";
    public DBContextHolder() {
    }
    public static String getDbType() {
    String db = (String)contextHolder.get();
    if(db == null) {
    db = MASTER;
    }
    return db;
    }
    public static void setDbType(String str) {
    contextHolder.set(str);
    }
    public static void setMaster() {
    contextHolder.set(MASTER);
    }
    public static void setSlave() {
    contextHolder.set(SLAVE);
    }
    public static void clearDBType() {
    contextHolder.remove();
    }
    }

4、DataSourceAspect

多数据源AOP切面编程实现。

    public class DataSourceAspect implements MethodBeforeAdvice, AfterReturningAdvice, ThrowsAdvice {
    private static final Logger log = LogManager.getLogger(DataSourceAspect.class);
    public DataSourceAspect() {
    }
    public void before(Method m, Object[] args, Object target) throws Throwable {
    try {
    if(m != null) {
    if((m.getName().startsWith("list") || m.getName().startsWith("select") || m.getName().startsWith("get") || m.getName().startsWith("count")) && !m.getName().contains("FromMaster")) {
    DBContextHolder.setDbType("slave");
    }
    else {
    DBContextHolder.setDbType("master");
    }
    }
    }
    catch (Exception var5) {
    log.error("data source aspect error.", var5);
    }
    }
    public void after(JoinPoint point) {
    log.info("clear db type after method.current id {
    }
    ", new Object[]{
    Long.valueOf(Thread.currentThread().getId())}
    );
    DBContextHolder.clearDBType();
    }
    public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {
    }
    public void afterThrowing(Method method, Object[] args, Object target, Exception ex) throws Throwable {
    log.info("current db type {
    }
    when exception", new Object[]{
    DBContextHolder.getDbType()}
    );
    DBContextHolder.setDbType("master");
    }
    }

以上就是 Spring AOP 动态多数据源的实例详解,如有疑问请留言或者到本站社区交流讨论,感谢阅读,希望能帮助到大家,谢谢大家对本站的支持!

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