动态数据源2之分库解析（固定N数据源，切换多数据源）

港控/mmm° 2022-09-23 05:57 14阅读 0赞

匆匆忙忙整理了 这篇文章http://blog.csdn.net/rainyspring4540/article/details/51828573

回头看这篇文章的代码来学习原理还是够呛的，由于涉及建库后生成的新数据源需要动态加入原有数据源列表中，使得代码里要通过重新构造AbstractRoutingDataSource类，即通过extends AbstractDataSource抽象类,implements InitializingBean接口，实现增强型的MyAbstractRoutingDataSource，来达到动态数据源的新增和切换并存，整个过程有点复杂，不便于自己入门，呵呵。。。

不过直接下载上篇文章里现成的代码，还是可以快速搭建起包含一整套分库逻辑（备份主库、建子库、为子库动态创建数据源、使用和切换数据源），所以上篇文章就作为快速搭建的案例吧。

下面的文章主要是上篇文章的简化版本，目的在于仅仅抽离出单纯的切换多数据源，便于更好的理解通过单纯的继承AbstractRoutingDataSource来自定义真正的动态数据源DynamicDataSource类，简单好理解，入门更快。

这篇文章主要讲比较常见的《固定N数据源，切换多数据源》

代码地址：http://download.csdn.net/detail/rainyspring4540/9569066

代码很简单，代码包中未包含库文件，我简单说下：

环境：mysql5.6 ，win7，eclipse kepler ，jQuery v13 ,springmvc4+hibernate4

根据配置文件：你需要创建库名为db，a，b的三个库，再分别创建表create table msg(name varchar(255) primary key, note varchar(255));就ok了。

关注2个文件：

package util.db;
    
    import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
    
    public class DynamicDataSource extends AbstractRoutingDataSource {
    	private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();
    
    	public static String getCurrentLookupKey() {
    		return (String) contextHolder.get();
    	}
    
    	public static void setCurrentLookupKey(String currentLookupKey) {
    		contextHolder.set(currentLookupKey);
    	}
    	
    	@Override
    	public Object determineCurrentLookupKey() {
    		return getCurrentLookupKey();
    	}
    
    }

和配置文件：

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
    	xmlns:context="http://www.springframework.org/schema/context"
    	xmlns:aop="http://www.springframework.org/schema/aop" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xmlns:tx="http://www.springframework.org/schema/tx"
    	xsi:schemaLocation="
    	        http://www.springframework.org/schema/beans
    			http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
    			http://www.springframework.org/schema/context 
    			http://www.springframework.org/schema/context/spring-context-3.2.xsd
    			http://www.springframework.org/schema/aop
    			http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
    			http://www.springframework.org/schema/tx
    			http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">
    	<context:component-scan base-package="controller"/>
    	<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    		
    		
    		
    		<property name="locations">
    		 	<list>
                    
                    <value>classpath*:/config/config.properties</value>
                    
                    
                    
                    
                </list>
    		</property>
    	</bean>
    	
    	<bean id="defaultDataSource" class="org.apache.commons.dbcp.BasicDataSource"
    		destroy-method="close">
    		<property name="driverClassName" value="${main.driver}" />
    		<property name="url" value="${main.url}" />
    		<property name="username" value="${main.username}" />
    		<property name="password" value="${main.password}" />
    	</bean>
    	<bean id="ds_a" class="org.apache.commons.dbcp.BasicDataSource"
    		destroy-method="close">
    		<property name="driverClassName" value="${a.driver}" />
    		<property name="url" value="${a.url}" />
    		<property name="username" value="${a.username}" />
    		<property name="password" value="${a.password}" />
    	</bean>
    	<bean id="ds_b" class="org.apache.commons.dbcp.BasicDataSource"
    		destroy-method="close">
    		<property name="driverClassName" value="${b.driver}" />
    		<property name="url" value="${b.url}" />
    		<property name="username" value="${b.username}" />
    		<property name="password" value="${b.password}" />
    	</bean>
    	<bean id="dynamicDataSource" class="util.db.DynamicDataSource">
    		<property name="targetDataSources">
    			<map key-type="java.lang.String">
    				 <entry key="defaultDataSource" value-ref="defaultDataSource" /> 
    				 <entry key="ds_a" value-ref="ds_a" /> 
    				 <entry key="ds_b" value-ref="ds_b" />
    			</map>
    		</property>
    		<property name="defaultTargetDataSource" ref="defaultDataSource" />
    	</bean>
    
    	
    	<bean id="defaultLobHandler" class="org.springframework.jdbc.support.lob.DefaultLobHandler" 
    		lazy-init="true" />
    
    	
    	<bean id="sessionFactory"  class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
            <property name="dataSource" ref="dynamicDataSource" />
            <property name="packagesToScan">
                <list>
                    
                    <value>entity</value>
                </list>
            </property>
            <property name="hibernateProperties">
                <props>
                    <prop key="hibernate.hbm2ddl.auto" >${hibernate.hbm2ddl.auto}</prop>
                    <prop key="hibernate.dialect">${hibernate.dialect}</prop>
                    <prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
                   
                </props>
            </property>
        </bean>
        <bean id="hibernateTemplate" class="org.springframework.orm.hibernate4.HibernateTemplate">
    		<property name="sessionFactory" ref="sessionFactory"></property>
    	</bean>
        
        <bean id="transactionManager"
            class="org.springframework.orm.hibernate4.HibernateTransactionManager">
          
          <property name="sessionFactory" ref="sessionFactory" />
          
         
       </bean>
       
       
       <bean id="persistenceExceptionTranslationPostProcessor" 
           class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />
    	
    	
    
    	
    	<context:annotation-config />
    	
    	<tx:annotation-driven transaction-manager="transactionManager" />
    	
    	
    	
    	<bean id="internalResourceViewResolver"
    		class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    		<property name="viewClass"
    			value="org.springframework.web.servlet.view.JstlView" />
    		
    		<property name="suffix" value=".jsp" />
    		
    		<property name="order" value="0" />
    	</bean>
    </beans>