首先，设置一个拦截器，拦截数据库操作，判断类型，动态选择数据源
DynamicDataSourceinterceptor.java

package com.mlr.dao.split;

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\\0020.*|.*update\\u0020.*";

  public java.lang.Object intercept(Invocation invocation) throws Throwable {
    boolean synchronizationActive = TransactionSynchronizationManager.isSynchronizationActive();
    //对于不是事务管理的操作


      Object[] objects = invocation.getArgs();
      String lookupKey =  DynamicDataSourceHolder.DB_MASTER;
      //获取操作类型
      MappedStatement mappedStatement = (MappedStatement) objects[0];
    if (synchronizationActive != true) {
      if (mappedStatement.getSqlCommandType().equals(SqlCommandType.SELECT)) {
        if (mappedStatement.getId().contains(SelectKeyGenerator.SELECT_KEY_SUFFIX)) {
          lookupKey = DynamicDataSourceHolder.DB_MASTER;
        } else {
          BoundSql boundSql = mappedStatement.getSqlSource().getBoundSql(objects[1]);
          String sql = boundSql.getSql().toLowerCase(Locale.CHINA).replaceAll("[\\t\\n\\r]", "");

          //符合正则用主库，不符合用从库
          if (sql.matches(REGEX)) {
            lookupKey = DynamicDataSourceHolder.DB_MASTER;
          } else {
            lookupKey = DynamicDataSourceHolder.DB_SLAVE;
          }
        }
      }

    }
    //对于事务管理都用主库
    else{
      lookupKey = DynamicDataSourceHolder.DB_MASTER;
    }
    logger.debug("设置方法[{}],use[{}]Strategy,SqlCommandType[{}]...",mappedStatement.getId(),lookupKey,mappedStatement.getSqlCommandType().name());
    DynamicDataSourceHolder.setDBType(lookupKey);
    return invocation.proceed();
  }

  /**
   * Executor支持增删改查操作，当操作时候拦截下来判断用哪个数据源
   */
  public java.lang.Object plugin(java.lang.Object target) {
    if (target instanceof Executor) {
      return Plugin.wrap(target, this);
    } else {
      return target;
    }
  }

  public void setProperties(Properties properties) {

  }
}

DynamicDataSourceHolder.java

package com.mlr.dao.split;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DynamicDataSourceHolder {

  private static Logger logger = LoggerFactory.getLogger(DynamicDataSourceHolder.class);

  private static ThreadLocal<String> contextHolder = new ThreadLocal<String>();

  public static final String DB_MASTER = "master";
  public static final String DB_SLAVE = "slave";

  /**
   * 获取类型
   * @return
   */
  public static String getDBType() {

    String db = contextHolder.get();

    if (db == null) {
      db = DB_MASTER;
    }
    return db;
  }

  /**
   * 设置连接类型
   * @param str
   */
  public static void setDBType(String str) {
    logger.debug("所使用的数据源为" + str);
    contextHolder.set(str);
  }

  /**
   * 清理连接类型
   * @param str
   */
  public static void clearDBType(String str) {
    contextHolder.remove();
  }


}

DynamicDataSource .java

package com.mlr.dao.split;

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

public class DynamicDataSource extends AbstractRoutingDataSource{


  protected Object determineCurrentLookupKey() {
    return DynamicDataSourceHolder.getDBType();
  }
}

然后配置mybatis-config.xml中添加拦截器

<plugins>
    <plugin interceptor="com.mlr.dao.split.DynamicDataSourceinterceptor"></plugin>
  </plugins>

在spring-dao.xml中配置数据源

<?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} -->
  <context:property-placeholder location="classpath:jdbc.properties"/>

  <!-- 2.数据库连接池 -->
  <bean id="abstractDataSource" abstract="true" destroy-method="close"
    class="com.mchange.v2.c3p0.ComboPooledDataSource">
    <!-- 配置连接池属性 -->
    <property name="driverClass" value="${jdbc.driver}"/>
    <property name="jdbcUrl" value="${jdbc.url}"/>
    <property name="user" value="${jdbc.username}"/>
    <property name="password" value="${jdbc.password}"/>


    <!-- c3p0连接池的私有属性 -->
    <property name="maxPoolSize" value="30"/>
    <property name="minPoolSize" 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>
  <!--主库数据源-->
  <bean id="master" parent="abstractDataSource">
    <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>
  <!--从库数据源-->
  <bean id="slave" parent="abstractDataSource">
    <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，这里targetDataSource就是路由数据源所对应名称-->
  <bean id="dynamicDataSource" class="com.mlr.dao.split.DynamicDataSource">
    <property name="targetDataSources">
      <map>
        <entry  value-ref="master" key="master"></entry>
        <entry key="master" value-ref="master"></entry>
    </map>
  </property>
</bean>
  <!--懒加载，程序运行后判断sql-->
<bean id="dataSource" class="org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy">
  <property name="targetDataSource">
    <ref bean="dynamicDataSource"></ref>
  </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.mlr.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.mlr.dao"/>
</bean>
  </beans>