value和ref的区别

ref和value的区别

ref即引用,

ref="dataSource"就是引用dataSource的bean

value直接设置一个值

ref,spring容器会在引用后进行验证,验证当前的xml是否存在引用的bean

value,spring会在 容器启动,实例化bean 时进行验证

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applicationContext-transaction.xml

<?xml version="1.0" encoding="utf-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
	xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
	http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
	http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
	http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">
	
	<!-- 定义事务管理器 -->
	<bean id="transactionManager"
		class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
		<property name="dataSource" ref="dataSource" />
	</bean>

	<!-- 定义事务策略 -->
	<tx:advice id="txAdvice" transaction-manager="transactionManager">
		<tx:attributes>
			<!--所有以query开头的方法都是只读的 -->
			<tx:method name="query*" read-only="true" />
			<!--其他方法使用默认事务策略 -->
			<tx:method name="*" />
		</tx:attributes>
	</tx:advice>

	<aop:config>
		<!--pointcut元素定义一个切入点，execution中的第一个星号 用以匹配方法的返回类型，
			这里星号表明匹配所有返回类型。 com.abc.dao.*.*(..)表明匹配cn.itcast.mybatis.service包下的所有类的所有 
			方法 -->
		<aop:pointcut id="myPointcut" expression="execution(* cn.itcast.mybatis.service.*.*(..))" />
		<!--将定义好的事务处理策略应用到上述的切入点 -->
		<aop:advisor advice-ref="txAdvice" pointcut-ref="myPointcut" />
	</aop:config>
	
</beans>

applicationContext.xml

?xml version="1.0" encoding="utf-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
	http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
	http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
	http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">

    <!-- 使用spring自带的占位符替换功能 -->
    <bean
            class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <!-- 允许JVM参数覆盖 -->
        <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
        <!-- 忽略没有找到的资源文件 -->
        <property name="ignoreResourceNotFound" value="true" />
        <!-- 配置资源文件 -->
        <property name="locations">
            <list>
                <value>classpath:jdbc.properties</value>
            </list>
        </property>
    </bean>

    <!-- 开启注解扫描 -->
    <context:component-scan base-package="cn.itcast.usermanage.service"/>

    <!-- 配置数据源 -->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
          init-method="init" destroy-method="close">
        <property name="driverClassName" value="${jdbc.driver}" />
        <property name="url" value="${jdbc.url}" />
        <property name="username" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
    </bean>

</beans>