第二章 创建bean及bean的范围
一：实例化bean
??? 构造方法实例化???
package com.spring.chapter2.service;public interface Fruit {public void eat();}?
package com.spring.chapter2.service.impl;import com.spring.chapter2.service.Fruit;public class Apple implements Fruit {public void eat() {System.out.println("吃苹果！");}}?
package com.spring.chapter2.service.impl;import com.spring.chapter2.service.Fruit;public class Orange implements Fruit {private String name;public Orange() {super();}public Orange(String name) {super();this.name = name;}@Overridepublic void eat() {System.out.println("吃桔子");}public String getName() {return name;}public void setName(String name) {this.name = name;}}?????配置文件：?//chapter2.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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><bean id="fruit" /></beans>
???测试类：??
public class Test {public static void main(String[] args) {ApplicationContext acx = new ClassPathXmlApplicationContext("chapter2.xml");Fruit fruit =(Fruit)acx.getBean("fruit");fruit.eat();}}?? spring容器在实例化对象的时候,需要用到无参的构造方法.记住,提供一个无参的构造.
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二：使用静态工厂方法实例化??
public class FruitFactory {public static Fruit getInstanceApple() {return new Apple();}public static Fruit getInstanceOrange() {return new Orange();}public static Fruit getInstance(int type) {if(type == 1){return new Apple();}else if (type == 2){return new Orange();}else{return null;}}}?? 配置文件：?//chapter2.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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><bean id="apple" factory-method="getInstanceApple" /><bean id="orange" factory-method="getInstanceOrange" /><bean id="fruit" factory-method="getInstance"><constructor-arg type="int" value="2" /></bean></beans>
?? 测试类：??
public class Test {public static void main(String[] args) {ApplicationContext acx = new ClassPathXmlApplicationContext("chapter2.xml");Apple apple =(Apple)acx.getBean("apple");apple.eat();Orange orange =(Orange)acx.getBean("orange");orange.eat();Fruit fruit =(Fruit)acx.getBean("fruit");fruit.eat();}}?
三：Bean的作用域??
作用域描述singleton在每个Spring IoC容器中一个bean定义对应一个对象实例。prototype一个bean定义对应多个对象实例。request在一次HTTP请求中，一个bean定义对应一个实例；即每次HTTP请求将会有各自的bean实例， 它们依据某个bean定义创建而成。该作用域仅在基于web的Spring ApplicationContext情形下有效。session 在一个HTTP Session中，一个bean定义对应一个实例。该作用域仅在基于web的Spring ApplicationContext情形下有效。global session在一个全局的HTTP Session中，一个bean定义对应一个实例。典型情况下，仅在使用portlet context的时候有效。该作用域仅在基于web的Spring ApplicationContext情形下有效。??singleton单例示例
???? <bean id="fruit" scope="singleton"/>
???? scope="singleton"是默认值,设于不设都可以,每次容器都会给同一个对象给你
? prototype非单例示例
???? <bean id="fruit" scope="prototype"/>
???? 配置此范围后,每次向容器索取对象时,容器会创建一个新的对象给你.
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四：延迟初始化bean
??? lazy-init="true"
??? lazy-init="false"
??? <bean id="fruit" lazy-init="false" />
??? 不要和scope属性一起使用.
????true:延时,不立即创建
????false:不延时,立即创建
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五：类初始化和销毁自动调用的方法
??? <bean id="fruit" init-method="init"
??destroy-method="destroy" />
????init-method="init":指定方法名,在对象实例化以后,自动调用
??? destroy-method="destroy":指定方法名,在容器关闭以后,自动调用