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文章来源:http://blog.csdn.net/xtj332/article/details/43953699
场景:一个读数据源一个读写数据源。
原理:借助spring的【org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource】这个抽象类实现,看名字可以了解到是一个路由数据源的东西,这个类中有一个方法
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- protected abstract Object determineCurrentLookupKey();
每次去连数据库的时候,spring会调用这个方法去找对应的数据源。返回值即对应的数据源的LookUpKey.那么这个LookUpKey在哪定义的呢?看下面的dataBase.xml的配置
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- <bean id="dataSourceRW" class="org.logicalcobwebs.proxool.ProxoolDataSource">
- <property name="alias" value="ihotelRW"></property>
- <property name="delegateProperties">
- <value>user=${jdbc.username},password=${jdbc.password}
- </value>
- </property>
- <property name="user" value="${jdbc.username}" />
- <property name="password" value="${jdbc.password}" />
- <property name="driver" value="${jdbc.driverClassName}" />
- <property name="driverUrl" value="${jdbc.url}" />
- <property name="maximumConnectionCount" value="${jdbc.maximumConnectionCount}"></property>
- <property name="maximumActiveTime" value="${jdbc.maximumActiveTime}"></property>
- <property name="maximumConnectionLifetime" value="${jdbc.maximumConnectionLifetime}"></property>
- <property name="prototypeCount" value="${jdbc.prototypeCount}"></property>
- <property name="houseKeepingSleepTime" value="${jdbc.houseKeepingSleepTime}"></property>
- <property name="simultaneousBuildThrottle" value="${jdbc.simultaneousBuildThrottle}"></property>
- <property name="houseKeepingTestSql" value="${jdbc.houseKeepingTestSql}"></property>
- <property name="verbose" value="${jdbc.verbose}"></property>
- <property name="statistics" value="${jdbc.statistics}"></property>
- <property name="statisticsLogLevel" value="${jdbc.statisticsLogLevel}"></property>
- </bean>
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- <bean id="dataSourceR" class="org.logicalcobwebs.proxool.ProxoolDataSource">
- <property name="alias" value="ihotelR"></property>
- <property name="delegateProperties">
- <value>user=${jdbc.r.username},password=${jdbc.r.password}
- </value>
- </property>
- <property name="user" value="${jdbc.r.username}" />
- <property name="password" value="${jdbc.r.password}" />
- <property name="driver" value="${jdbc.r.driverClassName}" />
- <property name="driverUrl" value="${jdbc.r.url}" />
- <property name="maximumConnectionCount" value="${jdbc.maximumConnectionCount}"></property>
- <property name="maximumActiveTime" value="${jdbc.maximumActiveTime}"></property>
- <property name="maximumConnectionLifetime" value="${jdbc.maximumConnectionLifetime}"></property>
- <property name="prototypeCount" value="${jdbc.prototypeCount}"></property>
- <property name="houseKeepingSleepTime" value="${jdbc.houseKeepingSleepTime}"></property>
- <property name="simultaneousBuildThrottle" value="${jdbc.simultaneousBuildThrottle}"></property>
- <property name="houseKeepingTestSql" value="${jdbc.houseKeepingTestSql}"></property>
- <property name="verbose" value="${jdbc.verbose}"></property>
- <property name="statistics" value="${jdbc.statistics}"></property>
- <property name="statisticsLogLevel" value="${jdbc.statisticsLogLevel}"></property>
- </bean>
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- <bean id="dynamicDataSource" class="com.dao.datasource.DynamicDataSource">
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- <property name="targetDataSources">
- <map>
- <entry value-ref="dataSourceRW" key="dataSourceKeyRW"></entry>
- <entry value-ref="dataSourceR" key="dataSourceKeyR"></entry>
- </map>
- </property>
- <property name="defaultTargetDataSource" ref="dataSourceRW" />
- </bean>
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- <bean id="sqlSessionFactory" name="sqlSessionFactory"
- class="org.mybatis.spring.SqlSessionFactoryBean">
- <property name="configLocation" value="classpath:conf/core/sqlMapConfig.xml" />
- <property name="dataSource" ref="dynamicDataSource" />
- </bean>
动态数据源dynamicDataSource中的dataSourceKeyRW、dataSourceKeyR就是
- protected abstract Object determineCurrentLookupKey();
这个方法要返回的值。那么如何设置,让这个方法的返回值是根据我们的需要返回dataSourceKeyRW、dataSourceKeyR呢?由于这个方法没有入参,并且是spring自动调用的,因此考虑使用静态变量存储dataSource的key,在调用sql语句前设置静态变量的值,然后在这个方法中得到静态变量的值,返回。又考虑到多线程,同时可能会有很多请求,为避免线程之间相互干扰,考虑使用threadLocal。
先看存储dataSourceKey的容器类。
- public class DBContextHolder {
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- private static ThreadLocal<String> contextHolder = new ThreadLocal<>();
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- private String DB_TYPE_RW = "dataSourceKeyRW";
- private String DB_TYPE_R = "dataSourceKeyR";
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- public String getDbType() {
- String db = contextHolder.get();
- if (db == null) {
- db = DB_TYPE_RW;
- }
- return db;
- }
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- public void setDbType(String str) {
- contextHolder.set(str);
- }
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- public static void clearDBType() {
- contextHolder.remove();
- }
- }
动态数据源的实现类。
- public class DynamicDataSource extends AbstractRoutingDataSource {
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- @Override
- public Logger getParentLogger() throws SQLFeatureNotSupportedException {
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- return null;
- }
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- @Override
- protected Object determineCurrentLookupKey() {
- return DBContextHolder.getDbType();
- }
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- }
在DAO层中设置数据库类型。
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- public boolean insertEmail(Email email) {
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- DBContextHolder.setDbType(DBContextHolder.DB_TYPE_RW);
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- int result = this.getSqlSession().insert(STATEMENT + ".addEntity",
- email);
- return result == 1;
- }
在本例中,我们是在DAO中指定数据库,我们也可以根据需要在service或者controller中指定DB类型,需要记住的是setDbType是针对线程维度的。要考虑多线程的问题。