Spring中有5种bean的范围:
5 types of bean scopes supported :
- singleton – Return a single bean instance per Spring IoC container 这个范围也是默认的
- prototype – Return a new bean instance each time when requested
- request – Return a single bean instance per HTTP request. *
- session – Return a single bean instance per HTTP session. *
- 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:
public class CustomerService { String message; public String getMessage() { return message; } public void setMessage(String message) { this.message = message; } }
1. Singleton example
<beans xmlns="http://www.springframework.org/schema/beans" 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-2.5.xsd"> <bean id="customerService" class="com.mkyong.customer.services.CustomerService" /> </beans>
运行:
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
<beans xmlns="http://www.springframework.org/schema/beans" 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-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:
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; } }
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd"> <context:component-scan base-package="com.mkyong.customer" /> </beans>