Java读写分离实现
1、查看源码
AbstractRoutingDataSource类中有个determineTargetDataSource方法
protected DataSource determineTargetDataSource() { Assert.notNull(this.resolvedDataSources, "DataSource router not initialized"); Object lookupKey = this.determineCurrentLookupKey(); DataSource dataSource = (DataSource)this.resolvedDataSources.get(lookupKey); if (dataSource == null && (this.lenientFallback || lookupKey == null)) { dataSource = this.resolvedDefaultDataSource; } if (dataSource == null) { throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]"); } else { return dataSource; } }
determineTargetDataSource会调用抽象方法determineCurrentLookupKey
@Nullable protected abstract Object determineCurrentLookupKey();
2、创建类继承AbstractRoutingDataSource
1 import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource; 2 3 public class DynamicDataSource extends AbstractRoutingDataSource{ 4 5 @Override 6 protected Object determineCurrentLookupKey() { 7 return DynamicDataSourceHolder.getDbType(); 8 } 9 10 }
1 import org.slf4j.Logger; 2 import org.slf4j.LoggerFactory; 3 4 public class DynamicDataSourceHolder { 5 private static Logger logger = LoggerFactory.getLogger(DynamicDataSourceHolder.class); 6 private static ThreadLocal<String> contextHolder = new ThreadLocal<String>(); 7 public static final String DB_MASTER = "master"; 8 public static final String DB_SLAVE = "slave"; 9 10 public static String getDbType() { 11 String db = contextHolder.get(); 12 if (db == null) { 13 14 db = DB_MASTER; 15 } 16 return db; 17 } 18 19 /** 20 * 设置线程的dbType 21 * 22 * @param str 23 */ 24 public static void setDbType(String str) { 25 logger.debug("所使用的数据源为:" + str); 26 contextHolder.set(str); 27 } 28 29 /** 30 * 清理连接类型 31 */ 32 public static void clearDBType() { 33 contextHolder.remove(); 34 } 35 36 }
3、设置Mybatis拦截器
import java.util.Locale; import java.util.Properties; import org.apache.ibatis.executor.Executor; import org.apache.ibatis.executor.keygen.SelectKeyGenerator; import org.apache.ibatis.mapping.BoundSql; import org.apache.ibatis.mapping.MappedStatement; import org.apache.ibatis.mapping.SqlCommandType; import org.apache.ibatis.plugin.Interceptor; import org.apache.ibatis.plugin.Intercepts; import org.apache.ibatis.plugin.Invocation; import org.apache.ibatis.plugin.Plugin; import org.apache.ibatis.plugin.Signature; import org.apache.ibatis.session.ResultHandler; import org.apache.ibatis.session.RowBounds; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.transaction.support.TransactionSynchronizationManager; @Intercepts({ @Signature(type = Executor.class, method = "update", args = { MappedStatement.class, Object.class }), @Signature(type = Executor.class, method = "query", args = { MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class }) }) public class DynamicDataSourceInterceptor implements Interceptor { private static Logger logger = LoggerFactory.getLogger(DynamicDataSourceInterceptor.class); private static final String REGEX = ".*insert\\u0020.*|.*delete\\u0020.*|.*update\\u0020.*"; @Override public Object intercept(Invocation invocation) throws Throwable { //判断当前是不是事务 boolean synchronizationActive = TransactionSynchronizationManager.isActualTransactionActive(); //获取crud操作的参数 Object[] objects = invocation.getArgs(); //获取第一个参数可以知道,具体是crud哪个操作 MappedStatement ms = (MappedStatement) objects[0]; String lookupKey = DynamicDataSourceHolder.DB_MASTER; if (synchronizationActive != true) { // 读方法 if (ms.getSqlCommandType().equals(SqlCommandType.SELECT)) { // selectKey 为自增id查询主键(SELECT LAST_INSERT_ID())方法,使用主库 if (ms.getId().contains(SelectKeyGenerator.SELECT_KEY_SUFFIX)) { lookupKey = DynamicDataSourceHolder.DB_MASTER; } else { //获取第二个参数,即sql BoundSql boundSql = ms.getSqlSource().getBoundSql(objects[1]); String sql = boundSql.getSql().toLowerCase(Locale.CHINA).replaceAll("[\\t\\n\\r]", " "); //查看是不是增删改,若是则用主库,查则用从库 if (sql.matches(REGEX)) { lookupKey = DynamicDataSourceHolder.DB_MASTER; } else { lookupKey = DynamicDataSourceHolder.DB_SLAVE; } } } } else { //若为事务,一般就是写等操作,用主库 lookupKey = DynamicDataSourceHolder.DB_MASTER; } logger.debug("设置方法[{}] use [{}] Strategy, SqlCommanType [{}]..", ms.getId(), lookupKey, ms.getSqlCommandType().name()); //最终决定要哪个数据库 DynamicDataSourceHolder.setDbType(lookupKey); return invocation.proceed(); } //若是Excutor就拦截下来 @Override public Object plugin(Object target) { //拦截Executor是因为,Execuror支持一系列增删改查 if (target instanceof Executor) { return Plugin.wrap(target, this); } else { return target; } } @Override public void setProperties(Properties arg0) { // TODO Auto-generated method stub } }
4、修改Mybatis-conf.xml文件
5、修改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:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- 配置整合mybatis过程 --> <!-- 1.配置数据库相关参数properties的属性:${url} --> <bean class="com.imooc.o2o.util.EncryptPropertyPlaceholderConfigurer"> <property name="locations"> <list> <value>classpath:jdbc.properties</value> <value>classpath:redis.properties</value> </list> </property> <property name="fileEncoding" value="UTF-8" /> </bean> <!-- 2.数据库连接池 --> <bean id="abstractDataSource" abstract="true" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <!-- c3p0连接池的私有属性 --> <property name="maxPoolSize" value="30" /> <property name="minPoolSize" value="10" /> <property name="initialPoolSize" value="10"/> <!-- 关闭连接后不自动commit --> <property name="autoCommitOnClose" value="false" /> <!-- 获取连接超时时间 --> <property name="checkoutTimeout" value="10000" /> <!-- 当获取连接失败重试次数 --> <property name="acquireRetryAttempts" value="2" /> </bean> <bean id="master" parent="abstractDataSource"> <!-- 配置连接池属性 --> <property name="driverClass" value="${jdbc.driver}" /> <property name="jdbcUrl" value="${jdbc.master.url}" /> <property name="user" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> </bean> <bean id="slave" parent="abstractDataSource"> <!-- 配置连接池属性 --> <property name="driverClass" value="${jdbc.driver}" /> <property name="jdbcUrl" value="${jdbc.slave.url}" /> <property name="user" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> </bean> <!-- 配置动态数据源,这儿targetDataSources就是路由数据源所对应的名称 --> <bean id="dynamicDataSource" class="com.imooc.o2o.dao.split.DynamicDataSource"> <property name="targetDataSources"> <map> <entry value-ref="master" key="master"></entry> <entry value-ref="slave" key="slave"></entry> </map> </property> </bean> <bean id="dataSource" class="org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy"> <property name="targetDataSource"> <ref bean="dynamicDataSource" /> </property> </bean> <!-- 3.配置SqlSessionFactory对象 --> <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <!-- 注入数据库连接池 --> <property name="dataSource" ref="dataSource" /> <!-- 配置MyBaties全局配置文件:mybatis-config.xml --> <property name="configLocation" value="classpath:mybatis-config.xml" /> <!-- 扫描entity包 使用别名 --> <property name="typeAliasesPackage" value="com.imooc.entity" /> <!-- 扫描sql配置文件:mapper需要的xml文件 --> <property name="mapperLocations" value="classpath:mapper/*.xml" /> </bean> <!-- 4.配置扫描Dao接口包,动态实现Dao接口,注入到spring容器中 --> <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"> <!-- 注入sqlSessionFactory --> <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" /> <!-- 给出需要扫描Dao接口包 --> <property name="basePackage" value="com.imooc.o2o.dao" /> </bean> </beans>
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