spring aop 动态多数据源的实例详解
当项目中使用到读写分离的时候，我们就会遇到多数据源的问题。多数据源让人最头痛的，不是配置多个数据源，而是如何能灵活动态的切换数据源。例如在一个spring和mybatis的框架的项目中，我们在spring配置中往往是配置一个datasource来连接数据库，然后绑定给sessionfactory，在dao层代码中再指定sessionfactory来进行数据库操作。
正如上图所示，每一块都是指定绑死的，如果是多个数据源，也只能是下图中那种方式。
可看出在dao层代码中写死了两个sessionfactory，这样日后如果再多一个数据源，还要改代码添加一个sessionfactory，显然这并不符合开闭原则。
那么正确的做法应该是：
具体代码与配置如下:
1、applicationcontext-mgr.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:aop="http://www.springframework.org/schema/aop"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemalocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
<!-- use annotation -->
<context:annotation-config />
<context:component-scan base-package="com.carl.o2o.**.mgr">
</context:component-scan>
<!-- master -->
<bean id="master" class="com.mchange.v2.c3p0.combopooleddatasource">
<property name="driverclass" value="${driverclassname_master}"/>
<property name="user" value="${username_master}"/>
<property name="password" value="${password_master}"/>
<property name="jdbcurl" value="${url_master}?unicode=true&characterencoding=utf-8&allowmultiqueries=true"/>
<property name="maxpoolsize" value="150"/>
<property name="minpoolsize" value="10"/>
<property name="initialpoolsize" value="20"/>
<property name="maxidletime" value="3600"/>
<property name="acquireincrement" value="10"/>
<property name="idleconnectiontestperiod" value="1800"/>
</bean>
<!-- slave -->
<bean id="slave" class="com.mchange.v2.c3p0.combopooleddatasource">
<property name="driverclass" value="${driverclassname_slave}"/>
<property name="user" value="${username_slave}"/>
<property name="password" value="${password_slave}"/>
<property name="jdbcurl" value="${url_slave}?unicode=true&characterencoding=utf-8"/>
<property name="maxpoolsize" value="150"/>
<property name="minpoolsize" value="10"/>
<property name="initialpoolsize" value="20"/>
<property name="maxidletime" value="3600"/>
<property name="acquireincrement" value="10"/>
<property name="idleconnectiontestperiod" value="1800"/>
</bean>
<!-- spring 动态数据源 -->
<bean id="dynamicdatasource" class="com.carl.dbutil.dynamicdatasource">
<property name="targetdatasources">
<map key-type="java.lang.string">
<entry key="slave" value-ref="slave" />
</map>
</property>
<property name="defaulttargetdatasource" ref="master" />
</bean>
<!-- mybatis mapper config -->
<bean id="sqlsessionfactory" class="org.mybatis.spring.sqlsessionfactorybean">
<property name="datasource" ref="dynamicdatasource"/>
<property name="configlocation" value="classpath:o2o_mybatis_config.xml"/>
<property name="mapperlocations" >
<list>
<value>classpath:sqlmap/*.xml</value>
<value>classpath*:/com/carl/o2o/**/*.xml</value>
</list>
</property>
</bean>
<bean id="sqlsession" class="org.mybatis.spring.sqlsessiontemplate">
<constructor-arg index="0" ref="sqlsessionfactory"></constructor-arg>
</bean>
<bean class="org.mybatis.spring.mapper.mapperscannerconfigurer">
<property name="basepackage" value="com.carl.o2o.**.mgr.dao" />
</bean>
<!-- 多数据源 aop -->
<bean id="datasourceaspect" class="com.carl.dbutil.datasourceaspect" />
<aop:config>
<aop:advisor pointcut="execution(* com.carl.o2o.mgr.*.*(..))" advice-ref="datasourceaspect" />
</aop:config>
<!-- 事务 -->
<bean name="transactionmanager" class="org.springframework.jdbc.datasource.datasourcetransactionmanager">
<property name="datasource" ref="dynamicdatasource"></property>
</bean>
</beans>
2、dynamicdatasource
dynamicdatasource使用spring中的代码结合aop实现多数据源切换.
public class dynamicdatasource extends abstractroutingdatasource {
public dynamicdatasource() {
}
protected object determinecurrentlookupkey() {
return dbcontextholder.getdbtype();
}
public logger getparentlogger() {
return null;
}
}
3、dbcontextholder
dynamicdatasource的辅助类，用于实际的切换多数据源。
public class dbcontextholder {
private static threadlocal<string> contextholder = new threadlocal();
public static string master = "master";
public static string slave = "slave";
public dbcontextholder() {
}
public static string getdbtype() {
string db = (string)contextholder.get();
if(db == null) {
db = master;
}
return db;
}
public static void setdbtype(string str) {
contextholder.set(str);
}
public static void setmaster() {
contextholder.set(master);
}
public static void setslave() {
contextholder.set(slave);
}
public static void cleardbtype() {
contextholder.remove();
}
}
4、datasourceaspect
多数据源aop切面编程实现。
public class datasourceaspect implements methodbeforeadvice, afterreturningadvice, throwsadvice {
private static final logger log = logmanager.getlogger(datasourceaspect.class);
public datasourceaspect() {
}
public void before(method m, object[] args, object target) throws throwable {
try {
if(m != null) {
if((m.getname().startswith("list") || m.getname().startswith("select") || m.getname().startswith("get")
|| m.getname().startswith("count")) && !m.getname().contains("frommaster")) {
dbcontextholder.setdbtype("slave");
} else {
dbcontextholder.setdbtype("master");
}
}
} catch (exception var5) {
log.error("data source aspect error.", var5);
}
}
public void after(joinpoint point) {
log.info("clear db type after method.current id {}", new object[]{long.valueof(thread.currentthread().getid())});
dbcontextholder.cleardbtype();
}
public void afterreturning(object returnvalue, method method, object[] args, object target) throws throwable {
}
public void afterthrowing(method method, object[] args, object target, exception ex) throws throwable {
log.info("current db type {} when exception", new object[]{dbcontextholder.getdbtype()});
dbcontextholder.setdbtype("master");
}
}
以上就是 spring aop 动态多数据源的实例详解，如有疑问请留言或者到本站社区交流讨论，感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！
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