第一步：建立一個DynamicDataSource的類，繼承AbstractRoutingDataSource並重寫determineCurrentLookupKey方法，程式碼如下：

package spring;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class DynamicDataSource extends AbstractRoutingDataSource {
   @Override
protected Object determineCurrentLookupKey() {

      return 
 
DynamicDataSourceHolder.getDataSource();
   }
}

package spring;

public class DynamicDataSourceHolder {




   private static final ThreadLocal<String> THREAD_DATA_SOURCE = new ThreadLocal<String>();

   public static String getDataSource() {
      return 
 
THREAD_DATA_SOURCE.get();
   }

   public static void setDataSource(String dataSource) {
      THREAD_DATA_SOURCE.set(dataSource);
   }

   public static void clearDataSource() {
      THREAD_DATA_SOURCE.remove();
   }


}

<bean id="readServerDataSource" 
 
class="org.apache.commons.dbcp2.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="${jdbc.mysql.driver}"/>
    <property name="url" value="${jdbc.mysql.url}"/>
    <property name="username" value="${jdbc.mysql.username}"/>
    <property name="password" value="${jdbc.mysql.password}"/>
    <property name="initialSize" value="${jdbc.initialSize}"/>
    <property name="minIdle" value="${jdbc.minIdle}"/>
    <property name="maxIdle" value="${jdbc.maxIdle}"/>
    <!--<property name="maxActive" value="${jdbc.maxActive}"/>-->
    <!--<property name="maxWait" value="${jdbc.maxWait}"/>-->
<property name="defaultAutoCommit" value="${jdbc.defaultAutoCommit}"/>
    <!--<property name="removeAbandoned" value="${jdbc.removeAbandoned}"/>-->
<property name="removeAbandonedTimeout" value="${jdbc.removeAbandonedTimeout}"/>
    <property name="testWhileIdle" value="${jdbc.testWhileIdle}"/>
    <property name="timeBetweenEvictionRunsMillis" value="${jdbc.timeBetweenEvictionRunsMillis}"/>
    <property name="numTestsPerEvictionRun" value="${jdbc.numTestsPerEvictionRun}"/>
    <property name="minEvictableIdleTimeMillis" value="${jdbc.minEvictableIdleTimeMillis}"/>
</bean>


<bean id="writeServerDataSource" class="org.apache.commons.dbcp2.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="${jdbc.mysql.driver}"/>
    <property name="url" value="${jdbc.mysql.url}"/>
    <property name="username" value="${jdbc.mysql.username}"/>
    <property name="password" value="${jdbc.mysql.password}"/>
    <property name="initialSize" value="${jdbc.initialSize}"/>
    <property name="minIdle" value="${jdbc.minIdle}"/>
    <property name="maxIdle" value="${jdbc.maxIdle}"/>
    <!--<property name="maxActive" value="${jdbc.maxActive}"/>-->
    <!--<property name="maxWait" value="${jdbc.maxWait}"/>-->
<property name="defaultAutoCommit" value="${jdbc.defaultAutoCommit}"/>
    <!--<property name="removeAbandoned" value="${jdbc.removeAbandoned}"/>-->
<property name="removeAbandonedTimeout" value="${jdbc.removeAbandonedTimeout}"/>
    <property name="testWhileIdle" value="${jdbc.testWhileIdle}"/>
    <property name="timeBetweenEvictionRunsMillis" value="${jdbc.timeBetweenEvictionRunsMillis}"/>
    <property name="numTestsPerEvictionRun" value="${jdbc.numTestsPerEvictionRun}"/>
    <property name="minEvictableIdleTimeMillis" value="${jdbc.minEvictableIdleTimeMillis}"/>
</bean>

<bean id="dataSource" class="spring.DynamicDataSource">
<property name="targetDataSources">
    <map key-type="java.lang.String">
        <!-- 指定lookupKey和與之對應的資料來源 -->
<entry key="readServerDataSource" value-ref="readServerDataSource"></entry>
        <entry key="writeServerDataSource" value-ref="writeServerDataSource"></entry>
    </map>
</property>
<!-- 這裡可以指定預設的資料來源 -->
<property name="defaultTargetDataSource" ref="readServerDataSource"/>
</bean>

<!-- MyBatis配置 -->
<bean id="sqlSessionTemplate" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <!-- 自動掃描domain目錄, 省掉Configuration.xml裡的手工配置 -->
<property name="typeAliasesPackage" value="order.dao.domain"/>
    <!-- 顯式指定Mapper檔案位置 -->
<property name="mapperLocations" value="classpath*:mybatis/*.xml"/>
    <property name="configLocation" value="classpath:mybatis-config.xml"/>
</bean>

接下來配置自定義註解用來切換資料來源，這樣操作起來更加的簡便，不用每次都去set

首先，我們得定義一個名為DataSource的註解

package spring;

import org.springframework.stereotype.Component;

import java.lang.annotation.*;

import static java.lang.annotation.RetentionPolicy.RUNTIME;

@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
 public @interface DataSource {
     String value();
}

package spring;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

@Component
@Aspect
public class DataSourceAspect {
   /**
    * 攔截目標方法，獲取由@DataSource指定的資料來源標識，設定到執行緒儲存中以便切換資料來源
*
    * @param point
* @throws Exception
*/
public void intercept(JoinPoint point) throws Exception {
      Class<?> target = point.getTarget().getClass();
      MethodSignature signature = (MethodSignature) point.getSignature();
      // 預設使用目標型別的註解，如果沒有則使用其實現介面的註解
for (Class<?> clazz : target.getInterfaces()) {
         resolveDataSource(clazz, signature.getMethod());
      }
      resolveDataSource(target, signature.getMethod());
   }

   /**
    * 提取目標物件方法註解和型別註解中的資料來源標識
*
    * @param clazz
* @param method
*/
private void resolveDataSource(Class<?> clazz, Method method) {
      try {
         Class<?>[] types = method.getParameterTypes();
         // 預設使用型別註解
if (clazz.isAnnotationPresent((Class<? extends Annotation>) DataSource.class)) {
            DataSource source = clazz.getAnnotation(DataSource.class);
            DynamicDataSourceHolder.setDataSource(source.value());
         }
         // 方法註解可以覆蓋型別註解
Method m = clazz.getMethod(method.getName(), types);
         if (m != null && m.isAnnotationPresent(DataSource.class)) {
            DataSource source = m.getAnnotation(DataSource.class);
            DynamicDataSourceHolder.setDataSource(source.value());
         }
      } catch (Exception e) {
         System.out.println(clazz + ":" + e.getMessage());
      }
   }
}

提示：註解@DataSource既可以加在方法上，也可以加在介面或者介面的實現類上，優先級別：方法>實現類>介面。也就是說如果介面、介面實現類以及方法上分別加了@DataSource註解來指定資料來源，則優先以方法上指定的為準。

例子用讀的資料來源：

@Service("ProductDAOImpl")
@DataSource("readServerDataSource")
public class ProductDAOImpl extends MyAbstractPageService<IProductDAO, Product> {

   @Autowired
private IProductDAO dao;

   @Override
public IProductDAO getDao() {
      return dao;
   }

   public IProductDAO querySum() {
      return dao;
   }

   public IProductDAO queryId(String id) {
      return dao;
   }
}