SpringMVC4+MyBatis+SQL Server2014实现读写分离

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本文介绍如何使用MyBatis的AbstractRoutingDataSource和Interceptor实现读写分离，通过配置pom.xml依赖、jdbc.properties数据库信息及springmvc-servlet.xml等文件完成开发环境搭建。

前言

基于mybatis的AbstractRoutingDataSource和Interceptor用拦截器的方式实现读写分离，根据MappedStatement的boundsql，查询sql的select、insert、update、delete，根据起判断使用读写连接串。

开发环境

SpringMVC4、mybatis3

项目结构

读写分离实现

1、pom.xml

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.10</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>4.3.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-beans</artifactId>
      <version>4.3.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>4.3.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>4.3.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context-support</artifactId>
      <version>4.3.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>4.3.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>4.3.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.apache.velocity</groupId>
      <artifactId>velocity</artifactId>
      <version>1.6.2</version>
    </dependency>
    <dependency>
      <groupId>org.apache.velocity</groupId>
      <artifactId>velocity-tools</artifactId>
      <version>2.0</version>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.4.2</version>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis-spring</artifactId>
      <version>1.3.0</version>
    </dependency>
    <dependency>
      <groupId>com.microsoft.sqlserver</groupId>
      <artifactId>sqljdbc4</artifactId>
      <version>4.0</version>
    </dependency>
    <dependency>
      <groupId>commons-dbcp</groupId>
      <artifactId>commons-dbcp</artifactId>
      <version>1.4</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
    </dependency>

  
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.25</version>
    </dependency>
  </dependencies>

2、jdbc.properties

sqlserver.driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
sqlserver.url=jdbc:sqlserver://127.0.0.1:1433;databaseName=test

sqlserver.read.username=sa
sqlserver.read.password=000000

sqlserver.writer.username=sa
sqlserver.writer.password=000000

3、springmvc-serlvet.xml，主要配置都在这里

<?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:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       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
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd
       http://www.springframework.org/schema/aop
       http://www.springframework.org/schema/aop/spring-aop.xsd
       ">

    <!--从配置文件加载数据库信息-->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations" value="classpath:config/jdbc.properties"/>
        <property name="fileEncoding" value="UTF-8"/>
    </bean>

    <!--配置数据源，这里使用Spring默认-->
    <bean id="abstractDataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${sqlserver.driver}"/>
        <property name="url" value="${sqlserver.url}"/>
    </bean>

    <!--读-->
    <bean id="shawnTimeDataSourceRead" parent="abstractDataSource">
        <property name="username" value="${sqlserver.read.username}"/>
        <property name="password" value="${sqlserver.read.password}"/>
    </bean>

    <!--写-->
    <bean id="shawnTimeDataSourceWiter" parent="abstractDataSource">
        <property name="username" value="${sqlserver.writer.username}"/>
        <property name="password" value="${sqlserver.writer.password}"/>
    </bean>

    <bean id="shawnTimeDataSource" class="com.autohome.rwdb.DynamicDataSource">
        <property name="readDataSource" ref="shawnTimeDataSourceRead"/>
        <property name="writeDataSource" ref="shawnTimeDataSourceRead"/>
    </bean>

    <bean id="shawnTimeTransactionManager" class="com.autohome.rwdb.DynamicDataSourceTransactionManager">
        <property name="dataSource" ref="shawnTimeDataSource"/>
    </bean>

    <!--配置sqlSessionFactory-->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="configLocation" value="classpath:springmvc-mybatis.xml"/>
        <property name="dataSource" ref="shawnTimeDataSource"/>
        <property name="plugins">
            <array>
                <bean class="com.autohome.rwdb.DynamicPlugin"/>
            </array>
        </property>
    </bean>

    <!--扫描Mapper-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.autohome.dao"/>
    </bean>

    <!--启用最新的注解器、映射器-->
    <mvc:annotation-driven/>

    <context:component-scan base-package="com.autohome.*"/>

    <!--jsp视图解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

</beans>

4、DynamicDataSource。实现AbstractRoutingDataSource

package com.autohome.rwdb;

import java.util.HashMap;
import java.util.Map;

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

public class DynamicDataSource extends AbstractRoutingDataSource {

    private Object writeDataSource; //写数据源

    private Object readDataSource; //读数据源

    @Override
    public void afterPropertiesSet() {
        if (this.writeDataSource == null) {
            throw new IllegalArgumentException("Property 'writeDataSource' is required");
        }
        setDefaultTargetDataSource(writeDataSource);
        Map<Object, Object> targetDataSources = new HashMap<Object, Object>();
        targetDataSources.put(DynamicDataSourceGlobal.WRITE.name(), writeDataSource);
        if(readDataSource != null) {
            targetDataSources.put(DynamicDataSourceGlobal.READ.name(), readDataSource);
        }
        setTargetDataSources(targetDataSources);
        super.afterPropertiesSet();
    }

    @Override
    protected Object determineCurrentLookupKey() {

        DynamicDataSourceGlobal dynamicDataSourceGlobal = DynamicDataSourceHolder.getDataSource();

        if(dynamicDataSourceGlobal == null
                || dynamicDataSourceGlobal == DynamicDataSourceGlobal.WRITE) {
            return DynamicDataSourceGlobal.WRITE.name();
        }

        return DynamicDataSourceGlobal.READ.name();
    }

    public void setWriteDataSource(Object writeDataSource) {
        this.writeDataSource = writeDataSource;
    }

    public Object getWriteDataSource() {
        return writeDataSource;
    }

    public Object getReadDataSource() {
        return readDataSource;
    }

    public void setReadDataSource(Object readDataSource) {
        this.readDataSource = readDataSource;
    }
}

5、DynamicDataSourceGlobal

package com.autohome.rwdb;


public enum DynamicDataSourceGlobal {
    READ, WRITE;
}

6、DynamicDataSourceHolder

package com.autohome.rwdb;

public final class DynamicDataSourceHolder {

    private static final ThreadLocal<DynamicDataSourceGlobal> holder = new ThreadLocal<DynamicDataSourceGlobal>();

    private DynamicDataSourceHolder() {
        //
    }

    public static void putDataSource(DynamicDataSourceGlobal dataSource){
        holder.set(dataSource);
    }

    public static DynamicDataSourceGlobal getDataSource(){
        return holder.get();
    }

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

}

7、DynamicDataSourceTransactionManager

package com.autohome.rwdb;

import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.TransactionDefinition;


public class DynamicDataSourceTransactionManager extends DataSourceTransactionManager {

    /**
     * 只读事务到读库，读写事务到写库
     * @param transaction
     * @param definition
     */
    @Override
    protected void doBegin(Object transaction, TransactionDefinition definition) {

        //设置数据源
        boolean readOnly = definition.isReadOnly();
        if(readOnly) {
            DynamicDataSourceHolder.putDataSource(DynamicDataSourceGlobal.READ);
        } else {
            DynamicDataSourceHolder.putDataSource(DynamicDataSourceGlobal.WRITE);
        }
        super.doBegin(transaction, definition);
    }

    /**
     * 清理本地线程的数据源
     * @param transaction
     */
    @Override
    protected void doCleanupAfterCompletion(Object transaction) {
        super.doCleanupAfterCompletion(transaction);
        DynamicDataSourceHolder.clearDataSource();
    }
}

8、DynamicPlugin

package com.autohome.rwdb;

import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
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.*;
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 DynamicPlugin implements Interceptor {

    protected static final Logger logger = LoggerFactory.getLogger(DynamicPlugin.class);

    private static final String REGEX = ".*insert\\u0020.*|.*delete\\u0020.*|.*update\\u0020.*";

    private static final Map<String, DynamicDataSourceGlobal> cacheMap = new ConcurrentHashMap<String, DynamicDataSourceGlobal>();

    @Override
    public Object intercept(Invocation invocation) throws Throwable {

        boolean synchronizationActive = TransactionSynchronizationManager.isSynchronizationActive();
        if(!synchronizationActive) {
            Object[] objects = invocation.getArgs();
            MappedStatement ms = (MappedStatement) objects[0];

            DynamicDataSourceGlobal dynamicDataSourceGlobal = null;

            if((dynamicDataSourceGlobal = cacheMap.get(ms.getId())) == null) {
                //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)) {
                        dynamicDataSourceGlobal = DynamicDataSourceGlobal.WRITE;
                    } else {
                        BoundSql boundSql = ms.getSqlSource().getBoundSql(objects[1]);
                        //获取MappedStatement 的sql语句，select update delete insert
                        String sql = boundSql.getSql().toLowerCase(Locale.CHINA).replaceAll("[\\t\\n\\r]", " ");

                        if(sql.matches(REGEX)) {
                            dynamicDataSourceGlobal = DynamicDataSourceGlobal.WRITE;
                        } else {
                            dynamicDataSourceGlobal = DynamicDataSourceGlobal.READ;
                        }
                    }
                }else{
                    dynamicDataSourceGlobal = DynamicDataSourceGlobal.WRITE;
                }
                System.out.println("设置方法["+ms.getId()+"] use ["+ dynamicDataSourceGlobal.name()+"] Strategy, SqlCommandType ["+ms.getSqlCommandType().name()+"]..");
                cacheMap.put(ms.getId(), dynamicDataSourceGlobal);
            }
            DynamicDataSourceHolder.putDataSource(dynamicDataSourceGlobal);
        }

        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        if (target instanceof Executor) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
    }

    @Override
    public void setProperties(Properties properties) {

    }
}