Spring中bean的范围

Spring中bean的范围

Spring中有5种bean的范围：

5 types of bean scopes supported :

1. singleton – Return a single bean instance per Spring IoC container 这个范围也是默认的
2. prototype – Return a new bean instance each time when requested
3. request – Return a single bean instance per HTTP request. *
4. session – Return a single bean instance per HTTP session. *
5. globalSession – Return a single bean instance per global HTTP session. *

P.S * means only valid in the context of a web-aware Spring ApplicationContext

我们看个关于singleton and prototype.的例子：

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public class CustomerService  {     String message;         public String getMessage() {         return message;     }         public void setMessage(String message) {         this.message = message;     } }

1. Singleton example

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<beans xmlns="http://www./schema/beans"     xmlns:xsi="http://www./2001/XMLSchema-instance"     xsi:schemaLocation="http://www./schema/beans     http://www./schema/beans/spring-beans-2.5.xsd">            <bean id="customerService"              class="com.mkyong.customer.services.CustomerService" />     </beans>

　　运行：

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public class App  {     public static void main( String[] args )     {         ApplicationContext context =           new ClassPathXmlApplicationContext(new String[] {"Spring-Customer.xml"});             CustomerService custA = (CustomerService)context.getBean("customerService");         custA.setMessage("Message by custA");         System.out.println("Message : " + custA.getMessage());             //retrieve it again         CustomerService custB = (CustomerService)context.getBean("customerService");         System.out.println("Message : " + custB.getMessage());     } }

　　输出为：

Message : Message by custA
Message : Message by custA

2. Prototype example

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<beans xmlns="http://www./schema/beans"     xmlns:xsi="http://www./2001/XMLSchema-instance"     xsi:schemaLocation="http://www./schema/beans     http://www./schema/beans/spring-beans-2.5.xsd">        <bean id="customerService" class="com.mkyong.customer.services.CustomerService"           scope="prototype"/>     </beans>

　　运行输出为：

Message : Message by custA
Message : null

也可以使用注解来做这些事情：

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package com.mkyong.customer.services;     import org.springframework.context.annotation.Scope; import org.springframework.stereotype.Service;     @Service @Scope("prototype") public class CustomerService  {     String message;         public String getMessage() {         return message;     }         public void setMessage(String message) {         this.message = message;     } }

　　

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<beans xmlns="http://www./schema/beans"     xmlns:xsi="http://www./2001/XMLSchema-instance"     xmlns:context="http://www./schema/context"     xsi:schemaLocation="http://www./schema/beans     http://www./schema/beans/spring-beans-2.5.xsd     http://www./schema/context     http://www./schema/context/spring-context-2.5.xsd">            <context:component-scan base-package="com.mkyong.customer" />     </beans>