Spring Bean的作用域和XML配置

来源：互联网发布：软件项目管理论文编辑：程序博客网时间：2024/06/14 23:11

所有的Spring Bean默认都是单例的。当容器分配一个bean时（不论是通过装配，还是调用容器的getBean() 方法），它总是返回一个同一个bean对象。当需要多个实例时(比如票对象，电影票每个人都是不一样的)，需要额外的配置

<bean id="ticket" class="com.ticket" scope="prototype"></bean>

可以对scope进行参数配置满足开发需要，有一下几种情况：

作用域定义 singleton 在每个spring容器中，一个Bean定义只有一个对象的实例（默认） prototype 允许Bean定义可以被实力化任意次 request 在一次HTTP请求中，每个bean定义对应一个实例。该作用域仅在基于Web的spring上下文（Spring MVC）中才有效 session 在一个HTTP Session 中，每一个Bean定义对应一个实例。该作用域仅在基于Web的spring上下文（Spring MVC）中才有效 global-session 在一个全局HTTP Session中，每个Bean定义对应的一个实例，该作用域仅在Portlet上下文中才有效

bean配置
这里写图片描述

package bean;public interface Performer {     void perform();}

package bean;/** * 杂技师 *  * @author SJ-PC * */public class Juggler implements Performer {    private int beanBags = 3;    public Juggler() {    }    public Juggler(int beanBags){        this.beanBags=beanBags;    }    @Override    public void perform() {        System.out.println("表演杂技"+" "+beanBags);    }}

package bean;public interface Poem {    void recite();}

package bean;public class Sonnet29 implements Poem {    @Override    public void recite() {        System.out.println("Sonnet29 recite");    }}

package bean;public class PoeticJuggler extends Juggler {    Poem poem;    public PoeticJuggler(Poem poem) {        this.poem = poem;    }    public PoeticJuggler(Poem poem, int beanbags) {        super(beanbags);        this.poem = poem;    }    @Override    public void perform() {        super.perform();        System.out.println("while reciting");        poem.recite();    }}

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:context="http://www.springframework.org/schema/context"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"    xmlns:tx="http://www.springframework.org/schema/tx" xmlns:p="http://www.springframework.org/schema/p"    xmlns:util="http://www.springframework.org/schema/util" xmlns:jdbc="http://www.springframework.org/schema/jdbc"    xmlns:cache="http://www.springframework.org/schema/cache"    xsi:schemaLocation="      http://www.springframework.org/schema/context      http://www.springframework.org/schema/context/spring-context.xsd      http://www.springframework.org/schema/beans      http://www.springframework.org/schema/beans/spring-beans.xsd      http://www.springframework.org/schema/tx      http://www.springframework.org/schema/tx/spring-tx.xsd      http://www.springframework.org/schema/jdbc      http://www.springframework.org/schema/jdbc/spring-jdbc-3.1.xsd      http://www.springframework.org/schema/cache      http://www.springframework.org/schema/cache/spring-cache-3.1.xsd      http://www.springframework.org/schema/aop      http://www.springframework.org/schema/aop/spring-aop.xsd      http://www.springframework.org/schema/util      http://www.springframework.org/schema/util/spring-util.xsd">    <bean id="duke" class="bean.Juggler">        <constructor-arg value="15" />    </bean>    <bean id="sonnet29" class="bean.Sonnet29">    </bean>    <bean id="poeticjuggler" class="bean.PoeticJuggler">        <constructor-arg value="15"/>        <constructor-arg ref="sonnet29" />    </bean></beans>

import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import bean.Performer;public class Main {    public static void main(String[] args) {        ApplicationContext context = new ClassPathXmlApplicationContext("spring-idol.xml");        Performer performer = (Performer)context.getBean("poeticjuggler");        performer.perform();    }}

阅读全文

0 0