目錄

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基本概念

演示

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基本概念

singleton作用域就是單例模式；用spring容器實現單例模式

而prototype作用域可以理解為多例模式！

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Singleton作用域例子：

左側的ref就是右側bean的id，這里就是把右邊的bean通過spring注入到左側的bean中；

而Singleton是如下的情況：

而Prototype是這樣的

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演示

如下的文件結構：

Bean1.java

package singleandprodemo.demo;public class Bean1 {private Bean2 bean2;public Bean2 getBean2() {return bean2;}public void setBean2(Bean2 bean2) {this.bean2 = bean2;}@Overridepublic String toString() {return "Bean1{" +"bean2=" + bean2 +'}';} }

Bean2.java

package singleandprodemo.demo;public class Bean2 { }

spring.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.xsd"><bean class="singleandprodemo.demo.Bean2" id="bean2" scope="singleton"/><bean class="singleandprodemo.demo.Bean1" id="bean1"><property name="bean2" ref="bean2"/></bean> </beans>

這里要注意bean1沒有填寫scope，這里沒填的默認是scope為singleton

這里編寫如下的運行代碼：

public void contextLoads() {ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");Bean2 bean2_1 = context.getBean("bean2", Bean2.class);System.out.println("bean2_1 = " + bean2_1);Bean2 bean2_2 = context.getBean("bean2", Bean2.class);System.out.println("bean2_2 = " + bean2_2);Bean1 bean1 = context.getBean("bean1", Bean1.class);System.out.println("bean1 = " + bean1);}

運行截圖如下：

從這里可以知道，單例模式在一個spring上下文環境中，被單例化；

修改如下運行代碼：

public void contextLoads() {ApplicationContext context1 = new ClassPathXmlApplicationContext("spring.xml");Bean2 bean2_1 = context1.getBean("bean2", Bean2.class);System.out.println("bean2_1 = " + bean2_1);Bean2 bean2_2 = context1.getBean("bean2", Bean2.class);System.out.println("bean2_2 = " + bean2_2);Bean1 bean1 = context1.getBean("bean1", Bean1.class);System.out.println("bean1 = " + bean1);System.out.println("---------------華麗的分割線---------------");ApplicationContext context2 = new ClassPathXmlApplicationContext("spring.xml");Bean2 bean2_3 = context2.getBean("bean2", Bean2.class);System.out.println("bean2_1 = " + bean2_3);Bean2 bean2_4 = context2.getBean("bean2", Bean2.class);System.out.println("bean2_2 = " + bean2_4);Bean1 bean2 = context2.getBean("bean1", Bean1.class);System.out.println("bean1 = " + bean2);}

運行截圖如下：

可見不同的spring上下文環境中實例的Bean是不一樣的；

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修改spring.xml文件如下：

<?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.xsd"><bean class="singleandprodemo.demo.Bean2" id="bean2" scope="singleton"/><bean class="singleandprodemo.demo.Bean1" id="bean1" scope="prototype"><property name="bean2" ref="bean2"/></bean> </beans>

運行代碼如下：

public void contextLoads() {ApplicationContext context1 = new ClassPathXmlApplicationContext("spring.xml");Bean2 bean2_1 = context1.getBean("bean2", Bean2.class);System.out.println("bean2_1 = " + bean2_1);Bean2 bean2_2 = context1.getBean("bean2", Bean2.class);System.out.println("bean2_2 = " + bean2_2);Bean1 bean1 = context1.getBean("bean1", Bean1.class);Bean1 bean11 = context1.getBean("bean1", Bean1.class);System.out.println("bean1 = " + bean1);System.out.println("bean11 = " + bean11);System.out.println(bean1 == bean11);}

運行截圖如下：

從這里可以知道，但bean1為prototye的時候，實例化的bean1是不同的，（因為上面的false）

下面給出一張表：

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這里如果有這樣的一個應用場景：

Bean1是singleton，Bean2是prototype，Bean1依賴Bean2，希望每次調用Bean1的某個方法時，該方法拿到的Bean2都是一個新的實例；

這里使用到了方法注入！！！！！！！！！！！！！！

修改Bean1.java

package singleandprodemo.demo;public abstract class Bean1 {protected abstract Bean2 createBean2();public void printBean2(){System.out.println("bean2 = " + createBean2());} }

spring.xml
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<?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.xsd"><bean class="singleandprodemo.demo.Bean2" id="bean2" scope="prototype"/><bean class="singleandprodemo.demo.Bean1" id="bean1" scope="prototype"><!-- <property name="bean2" ref="bean2"/> --><lookup-method name="createBean2" bean="bean2"></lookup-method></bean> </beans>

測試代碼如下：

public void contextLoads() {ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");Bean1 bean1 = context.getBean("bean1", Bean1.class);bean1.printBean2();bean1.printBean2();bean1.printBean2();bean1.printBean2();}

運行截圖如下：

總結

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