<bean id="masterDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" >        <property name="driverClass" value="com.mysql.jdbc.Driver"></property>        <property name="jdbcUrl" value="${database.master.jdbcUrl}"></property>        <property name="user" value="${database.master.user}" />        <property name="password" value="${database.master.password}" />        <property name="maxPoolSize" value="${database.master.maxPoolSize}"></property>          <property name="minPoolSize" value="${database.master.minPoolSize}"></property>        <property name="maxIdleTime" value="${database.master.maxIdleTime}"></property>        <property name="idleConnectionTestPeriod" value="${database.master.idleConnectionTestPeriod}"></property>    </bean>        <bean id="slaveDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" >        <property name="driverClass" value="com.mysql.jdbc.Driver"></property>        <property name="jdbcUrl" value="${database.slave.jdbcUrl}"></property>        <property name="user" value="${database.slave.user}" />        <property name="password" value="${database.slave.password}" />        <property name="maxPoolSize" value="${database.slave.maxPoolSize}"></property>          <property name="minPoolSize" value="${database.slave.minPoolSize}"></property>        <property name="maxIdleTime" value="${database.slave.maxIdleTime}"></property>        <property name="idleConnectionTestPeriod" value="${database.slave.idleConnectionTestPeriod}"></property>    </bean>

<-- 此类继承了AbstractRoutingDataSource 类，且 AbstractRoutingDataSource类 为Spring jdbc中提供的类，需要重写其中的determineCurrentLookupKey()方法，获取当前切换到的数据库源名称-->    <bean id="dataSource" class="com.imzhitu.admin.common.dataSourceMasterSlave.DynamicDataSource">        <property name="targetDataSources"><-- 将数据源置入到类中，通过之后的aop拦截到的数据库名称，匹配到指定的数据源进而链接 -->            <map key-type="java.lang.String">                <entry key="master" value-ref="masterDataSource"/>                <entry key="slave" value-ref="slaveDataSource"/>            </map>        </property>        <property name="defaultTargetDataSource" ref="masterDataSource"/>    </bean>

package com.imzhitu.admin.common.dataSourceMasterSlave;import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;/** * 动态数据源，动态获取数据源的实现 * */public class DynamicDataSource extends AbstractRoutingDataSource{        /**     * 用户返回当且切换到的数据库     */    @Override    protected Object determineCurrentLookupKey() {        return DynamicDataSourceHolder.getDataSource();//DynamicDataSourceHolder有获取和设置当前数据库的方法get & put    }}

package com.imzhitu.admin.common.dataSourceMasterSlave;/** * 动态数据源holder * */public class DynamicDataSourceHolder {    public static final ThreadLocal<String> holder = new ThreadLocal<String>();        public static void putDataSource(String name) {        holder.set(name);    }        public static String getDataSource() {        return holder.get();    }}

/* * Copyright 2002-2012 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package org.springframework.jdbc.datasource.lookup;import java.sql.Connection;import java.sql.SQLException;import java.util.HashMap;import java.util.Map;import javax.sql.DataSource;import org.springframework.beans.factory.InitializingBean;import org.springframework.jdbc.datasource.AbstractDataSource;import org.springframework.util.Assert;/** * Abstract {@link javax.sql.DataSource} implementation that routes {@link #getConnection()} * calls to one of various target DataSources based on a lookup key. The latter is usually * (but not necessarily) determined through some thread-bound transaction context. * * @author Juergen Hoeller * @since 2.0.1 * @see #setTargetDataSources * @see #setDefaultTargetDataSource * @see #determineCurrentLookupKey() */public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {    private Map<Object, Object> targetDataSources;//所有数据源，在xml中有相应的配置    private Object defaultTargetDataSource;//默认数据源，在xml中有相应的配置private Map<Object, DataSource> resolvedDataSources;//将targetDataSources值传入其中，做值的传递    private DataSource resolvedDefaultDataSource;//同targetDataSources    /**     * Specify the map of target DataSources, with the lookup key as key.     * The mapped value can either be a corresponding {@link javax.sql.DataSource}     * instance or a data source name String (to be resolved via a     * {@link #setDataSourceLookup DataSourceLookup}).     * <p>The key can be of arbitrary type; this class implements the     * generic lookup process only. The concrete key representation will     * be handled by {@link #resolveSpecifiedLookupKey(Object)} and     * {@link #determineCurrentLookupKey()}.     */    public void setTargetDataSources(Map<Object, Object> targetDataSources) {        this.targetDataSources = targetDataSources;    }    /**     * Specify the default target DataSource, if any.     * <p>The mapped value can either be a corresponding {@link javax.sql.DataSource}     * instance or a data source name String (to be resolved via a     * {@link #setDataSourceLookup DataSourceLookup}).     * <p>This DataSource will be used as target if none of the keyed     * {@link #setTargetDataSources targetDataSources} match the     * {@link #determineCurrentLookupKey()} current lookup key.     */    public void setDefaultTargetDataSource(Object defaultTargetDataSource) {        this.defaultTargetDataSource = defaultTargetDataSource;    }    /**     * Specify whether to apply a lenient fallback to the default DataSource     * if no specific DataSource could be found for the current lookup key.     * <p>Default is "true", accepting lookup keys without a corresponding entry     * in the target DataSource map - simply falling back to the default DataSource     * in that case.     * <p>Switch this flag to "false" if you would prefer the fallback to only apply     * if the lookup key was {@code null}. Lookup keys without a DataSource     * entry will then lead to an IllegalStateException.     * @see #setTargetDataSources     * @see #setDefaultTargetDataSource     * @see #determineCurrentLookupKey()     */    public void setLenientFallback(boolean lenientFallback) {        this.lenientFallback = lenientFallback;    }    /**     * Set the DataSourceLookup implementation to use for resolving data source     * name Strings in the {@link #setTargetDataSources targetDataSources} map.     * <p>Default is a {@link JndiDataSourceLookup}, allowing the JNDI names     * of application server DataSources to be specified directly.     */    public void setDataSourceLookup(DataSourceLookup dataSourceLookup) {        this.dataSourceLookup = (dataSourceLookup != null ? dataSourceLookup : new JndiDataSourceLookup());    }    @Override    public void afterPropertiesSet() {        if (this.targetDataSources == null) {            throw new IllegalArgumentException("Property ‘targetDataSources‘ is required");        }
　　　　　//*** 将targetDataSources的值传递给resolvedDataSources        this.resolvedDataSources = new HashMap<Object, DataSource>(this.targetDataSources.size());        for (Map.Entry<Object, Object> entry : this.targetDataSources.entrySet()) {            Object lookupKey = resolveSpecifiedLookupKey(entry.getKey());            DataSource dataSource = resolveSpecifiedDataSource(entry.getValue());            this.resolvedDataSources.put(lookupKey, dataSource);        }if (this.defaultTargetDataSource != null) {            this.resolvedDefaultDataSource = resolveSpecifiedDataSource(this.defaultTargetDataSource);        }
　　　　　//***    }    /**     * Resolve the given lookup key object, as specified in the     * {@link #setTargetDataSources targetDataSources} map, into     * the actual lookup key to be used for matching with the     * {@link #determineCurrentLookupKey() current lookup key}.     * <p>The default implementation simply returns the given key as-is.     * @param lookupKey the lookup key object as specified by the user     * @return the lookup key as needed for matching     */    protected Object resolveSpecifiedLookupKey(Object lookupKey) {        return lookupKey;    }    /**     * Resolve the specified data source object into a DataSource instance.     * <p>The default implementation handles DataSource instances and data source     * names (to be resolved via a {@link #setDataSourceLookup DataSourceLookup}).     * @param dataSource the data source value object as specified in the     * {@link #setTargetDataSources targetDataSources} map     * @return the resolved DataSource (never {@code null})     * @throws IllegalArgumentException in case of an unsupported value type     */    protected DataSource resolveSpecifiedDataSource(Object dataSource) throws IllegalArgumentException {        if (dataSource instanceof DataSource) {            return (DataSource) dataSource;        }        else if (dataSource instanceof String) {            return this.dataSourceLookup.getDataSource((String) dataSource);        }        else {            throw new IllegalArgumentException(                    "Illegal data source value - only [javax.sql.DataSource] and String supported: " + dataSource);        }    }

    /**     * Retrieve the current target DataSource. Determines the     * {@link #determineCurrentLookupKey() current lookup key}, performs     * a lookup in the {@link #setTargetDataSources targetDataSources} map,     * falls back to the specified     * {@link #setDefaultTargetDataSource default target DataSource} if necessary.     * @see #determineCurrentLookupKey()     */

　　//通过调用determineCurrentLookupKey()获取当前数据源名称，并匹配到相应的数据源返回；
　　//此方法在本类的 getConnection() 方法中调用，获取当前数据源的连接Connection，从而进行数据库操作    protected DataSource determineTargetDataSource() {        Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");        Object lookupKey = determineCurrentLookupKey();        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 + "]");        }        return dataSource;    }    /**     * Determine the current lookup key. This will typically be     * implemented to check a thread-bound transaction context.     * <p>Allows for arbitrary keys. The returned key needs     * to match the stored lookup key type, as resolved by the     * {@link #resolveSpecifiedLookupKey} method.     */

　　//获取当前数据源的名称；在本类的子类中需要重写此方法    protected abstract Object determineCurrentLookupKey();}

    <!-- 配置数据库注解aop -->    <aop:aspectj-autoproxy></aop:aspectj-autoproxy>    <bean id="manyDataSourceAspect" class="com.imzhitu.admin.common.dataSourceMasterSlave.DataSourceAspect"/>    <aop:config>        <aop:aspect id="dataSourceCut" ref="manyDataSourceAspect"><-- 切面类 -->            <aop:pointcut expression="execution(* com.imzhitu.admin..*.mapper.*.*(..))" id="dataSourceCutPoint"/><-- 配置切点 -->            <aop:before pointcut-ref="dataSourceCutPoint" method="before"/><-- 切面执行方法 -->        </aop:aspect>    </aop:config>

package com.imzhitu.admin.common.dataSourceMasterSlave;import java.lang.reflect.Method;import org.apache.log4j.Logger;import org.aspectj.lang.JoinPoint;import org.aspectj.lang.reflect.MethodSignature;/** * 数据源动态选择切面 * */public class DataSourceAspect {    private Logger log = Logger.getLogger(DataSourceAspect.class);    public void before(JoinPoint point){        Object target = point.getTarget();        String method = point.getSignature().getName();        Class<?>[] classz = target.getClass().getInterfaces();        Class<?>[] parameterTypes = ((MethodSignature) point.getSignature()).getMethod().getParameterTypes();        try {            Method m = classz[0].getMethod(method, parameterTypes);            if ( m != null && m.isAnnotationPresent(DataSource.class)) {                DataSource data = m.getAnnotation(DataSource.class);//获取访问mapper中的注释                DynamicDataSourceHolder.putDataSource(data.value());//获取注释中的value值，确定访问的数据源                if(log.isDebugEnabled()){                    log.debug("DataSourceAspect:======================="+data.value());                }            }        } catch (Exception e) {            // handle exception            e.printStackTrace();        }    }}

package com.imzhitu.admin.common.dataSourceMasterSlave;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * 数据库annotation定义 * @DataSource(‘master‘) / @DataSource(‘slave‘) * */@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.METHOD)public @interface DataSource {    String value();//唯一值，所以注释中没有写@DataSource(value = http://www.mamicode.com/‘master‘);也可以写成 String value() defalut"master";即默认访问主数据库
　　}

package com.imzhitu.admin.ztworld.mapper;import java.util.List;import org.apache.ibatis.annotations.Param;import com.hts.web.common.pojo.HTWorldSubtitleDto;import com.imzhitu.admin.common.dataSourceMasterSlave.DataSource;import com.imzhitu.admin.common.pojo.ZTWorldSubtitle;public interface SubtitleMapper {    @DataSource("slave")    public List<HTWorldSubtitleDto> queryCacheSubtitle(@Param("transTo")String transTo,            @Param("limit")Integer limit);        @DataSource("slave")    public List<ZTWorldSubtitle> queryTitles(ZTWorldSubtitle title);        @DataSource("slave")    public long queryTotal(ZTWorldSubtitle title);        @DataSource("master")    public void saveSubtitle(ZTWorldSubtitle title);        @DataSource("master")    public void update(ZTWorldSubtitle title);    @DataSource("master")    public void deleteByIds(Integer[] ids);        @DataSource("master")    public void updateSerialById(@Param("id")Integer id,             @Param("serial")Integer serial);}