spring-spring mvc-mybatis 实现主从数据库配置

一、配置文件

1、spring-mybatis.xml

master_driverUrl=jdbc:mysql://localhost:3306/shiro?useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true
master_username=root
master_password=12345

slave_driverUrl=jdbc:mysql://localhost:3306/wechat?useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true
slave_username=root
slave_password=12345

2、spring-mybatis.xml

<!-- 多数据源aop datasource -->
    <context:component-scan base-package="com.wangzhixuan.commons.datasource" />

    <!-- base dataSource -->
    <bean name="baseDataSource" class="com.alibaba.druid.pool.DruidDataSource"
        destroy-method="close">
        <property name="initialSize" value="5" />
        <property name="maxActive" value="100" />
        <property name="minIdle" value="10" />
        <property name="maxWait" value="60000" />
        <property name="validationQuery" value="SELECT 'x'" />
        <property name="testOnBorrow" value="true" />
        <property name="testOnReturn" value="true" />
        <property name="testWhileIdle" value="true" />
        <property name="timeBetweenEvictionRunsMillis" value="60000" />
        <property name="minEvictableIdleTimeMillis" value="300000" />
        <property name="removeAbandoned" value="true" />
        <property name="removeAbandonedTimeout" value="1800" />
        <property name="logAbandoned" value="true" />
        <property name="filters" value="mergeStat" />
    </bean>

    <!-- 主库 -->
    <bean name="master-dataSource" parent="baseDataSource"
        init-method="init">
        <property name="url" value="${master_driverUrl}" />
        <property name="username" value="${master_username}" />
        <property name="password" value="${master_password}" />
    </bean>

    <!-- 从库 -->
    <bean name="slave-dataSource" parent="baseDataSource" init-method="init">
        <property name="url" value="${slave_driverUrl}" />
        <property name="username" value="${slave_username}" />
        <property name="password" value="${slave_password}" />
    </bean>
    
    <!--主从库选择 -->
    <bean id="dynamicDataSource" class="com.wangzhixuan.commons.datasource.DynamicDataSource">
        <property name="master" ref="master-dataSource" />
        <property name="slaves">
            <list>
                <ref bean="slave-dataSource" />
            </list>
        </property>
    </bean>

二、通用类

package com.wangzhixuan.commons.datasource;

import com.wangzhixuan.commons.annotation.DataSourceChange;
import com.wangzhixuan.commons.exception.DataSourceAspectException;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

/**
 * 有{@link com.wangzhixuan.commons.annotation.DataSourceChange}注解的方法，调用时会切换到指定的数据源
 *
 * @author tanghd
 */
@Aspect
@Component
public class DataSourceAspect {
    private static final Logger LOGGER = LoggerFactory.getLogger(DataSourceAspect.class);

    @Around("@annotation(dataSourceChange)")
    public Object doAround(ProceedingJoinPoint pjp, DataSourceChange dataSourceChange) {
        Object retVal = null;
        boolean selectedDataSource = false;
        try {
            if (null != dataSourceChange) {
                selectedDataSource = true;
                if (dataSourceChange.slave()) {
                    DynamicDataSource.useSlave();
                } else {
                    DynamicDataSource.useMaster();
                }
            }
            retVal = pjp.proceed();
        } catch (Throwable e) {
            LOGGER.warn("数据源切换错误", e);
            throw new DataSourceAspectException("数据源切换错误", e);
        } finally {
            if (selectedDataSource) {
                DynamicDataSource.reset();
            }
        }
        return retVal;
    }
}

package com.wangzhixuan.commons.datasource;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;

/**
 * 继承{@link org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource}
 * 配置主从数据源后，根据选择，返回对应的数据源。多个从库的情况下，会平均的分配从库，用于负载均衡。
 *
 * @author tanghd
 */
public class DynamicDataSource extends AbstractRoutingDataSource {

    private static final Logger LOGGER = LoggerFactory.getLogger(DynamicDataSource.class);

    private DataSource master; // 主库，只允许有一个
    private List<DataSource> slaves; // 从库，允许有多个
    private AtomicLong slaveCount = new AtomicLong();
    private int slaveSize = 0;

    private Map<Object, Object> dataSources = new HashMap<Object, Object>();

    private static final String DEFAULT = "master";
    private static final String SLAVE = "slave";

    private static final ThreadLocal<LinkedList<String>> datasourceHolder = new ThreadLocal<LinkedList<String>>() {

        @Override
        protected LinkedList<String> initialValue() {
            return new LinkedList<String>();
        }

    };

    /**
     * 初始化
     */
    @Override
    public void afterPropertiesSet() {
        if (null == master) {
            throw new IllegalArgumentException("Property 'master' is required");
        }
        dataSources.put(DEFAULT, master);
        if (null != slaves && slaves.size() > 0) {
            for (int i = 0; i < slaves.size(); i++) {
                dataSources.put(SLAVE + (i + 1), slaves.get(i));
            }
            slaveSize = slaves.size();
        }
        this.setDefaultTargetDataSource(master);
        this.setTargetDataSources(dataSources);
        super.afterPropertiesSet();
    }

    /**
     * 选择使用主库，并把选择放到当前ThreadLocal的栈顶
     */
    public static void useMaster() {
        if (LOGGER.isDebugEnabled()) {
            LOGGER.debug("use datasource :" + datasourceHolder.get());
        }
        LinkedList<String> m = datasourceHolder.get();
        m.offerFirst(DEFAULT);
    }

    /**
     * 选择使用从库，并把选择放到当前ThreadLocal的栈顶
     */
    public static void useSlave() {
        if (LOGGER.isDebugEnabled()) {
            LOGGER.debug("use datasource :" + datasourceHolder.get());
        }
        LinkedList<String> m = datasourceHolder.get();
        m.offerFirst(SLAVE);
    }

    /**
     * 重置当前栈
     */
    public static void reset() {
        LinkedList<String> m = datasourceHolder.get();
        if (LOGGER.isDebugEnabled()) {
            LOGGER.debug("reset datasource {}", m);
        }
        if (m.size() > 0) {
            m.poll();
        }
    }

    /**
     * 如果是选择使用从库，且从库的数量大于1，则通过取模来控制从库的负载,
     * 计算结果返回AbstractRoutingDataSource
     */
    @Override
    protected Object determineCurrentLookupKey() {
        LinkedList<String> m = datasourceHolder.get();
        String key = m.peekFirst() == null ? DEFAULT : m.peekFirst();
        if (LOGGER.isDebugEnabled()) {
            LOGGER.debug("currenty datasource :" + key);
        }
        if (null != key) {
            if (DEFAULT.equals(key)) {
                return key;
            } else if (SLAVE.equals(key)) {
                if (slaveSize > 1) {// Slave loadBalance
                    long c = slaveCount.incrementAndGet();
                    c = c % slaveSize;
                    return SLAVE + (c + 1);
                } else {
                    return SLAVE + "1";
                }
            }
            return null;
        } else {
            return null;
        }
    }

    public DataSource getMaster() {
        return master;
    }

    public List<DataSource> getSlaves() {
        return slaves;
    }

    public void setMaster(DataSource master) {
        this.master = master;
    }

    public void setSlaves(List<DataSource> slaves) {
        this.slaves = slaves;
    }

}

package com.wangzhixuan.commons.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Inherited
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DataSourceChange {
    boolean slave() default false;
}

三、在服务层调用时加入数据源标识，DataSourceChange注解，设置数据源为从库（这里只写出了接口的实现，dao和mapper，请自行添加）

package com.wangzhixuan.service.impl;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.wangzhixuan.commons.annotation.DataSourceChange;
import com.wangzhixuan.mapper.SlaveMapper;
import com.wangzhixuan.service.SlaveService;

@Service
public class SlaveServiceImpl implements SlaveService {

    @Autowired
    private SlaveMapper slaveMapper;

    @Override
    @DataSourceChange(slave = true)
    public Integer count() {
        return slaveMapper.count();
    }

    @Override
    @DataSourceChange(slave = true)
    public Integer count2() {
        return slaveMapper.count2();
    }

}

四、测试类（这里是查询从库里的一张表的记录总数），将原来的主库切换到从库。

   @Test
    public void testFindAllShop() {
        Integer count = slaveService.count();
        //Integer count2 = slaveService.count2();
        System.out.println("#######1:"+count);
    }