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

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

 public class DynamicDataSource extends AbstractRoutingDataSource{

     @Override

     protected Object determineCurrentLookupKey() {

         return DynamicDataSourceHolder.getDbType();

     }

 }

DynamicDataSource

 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";

     public static String getDbType() {

         String db = contextHolder.get();

         if (db == null) {

             db = DB_MASTER;

         }

         return db;

     }

     /**

      * 设置线程的dbType

      *

      * @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

      */

     public static void clearDBType() {

         contextHolder.remove();

     }

 }

DynamicDataSourceHolder

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>

巴特西

Java读写分离实现

1、查看源码

2、创建类继承AbstractRoutingDataSource

3、设置Mybatis拦截器

4、修改Mybatis-conf.xml文件

5、修改Spring-dao.xml

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