Codeless的部落格

Bean的scope包含:singleton(default)、prototype、request、session、global-session

HelloWorld.java

package com.example ;

public class HelloWorld {
private String message ;
public void getMessage(){
 System.out.println("Your Message : " + message);
}
public void setMessage(String message) {
this.message = message;
} 
}

Main.java

package com.example ;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
public static void main(String[] args) {
ApplicationContext context = 
 new ClassPathXmlApplicationContext("Beans.xml");
 HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
 obj.setMessage("hello world");
 obj.getMessage();
 HelloWorld obj1 = (HelloWorld) context.getBean("helloWorld");
 obj1.getMessage();
}
}

Beans.xml

結果顯示如下:

Your Message : hello world
Your Message : hello world

scope改為prototype 結果顯示如下:

Your Message : hello world
Your Message : null (類似於request的概念,重新獲取一個新的Bean物件後則reset掉)

Bean的life cycle

初始化可實作介面InitializingBean中的afterPropertiesSet()

public class ExampleBean implements InitializingBean {
 public void afterPropertiesSet() {
 // do some initialization work
 }
}

同理亦可實作介面DisposableBean中的destroy()

public class ExampleBean implements DisposableBean {
 public void destroy() {
 // do some destruction work
 }
}

上述方式可透過Spring中的Bean去設定

HelloWorld.java

package com.example ;

public class HelloWorld {
private String message ;
public void init(){
System.out.println("Initialization now") ;
}
public void getMessage(){
 System.out.println("Your Message : " + message);
}
public void setMessage(String message) {
this.message = message;
}
public void destroy(){
System.out.println("Destory now") ;
}
}

透過registerShutdownHook()去呼叫destroy()

Main.java

package com.example ;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
public static void main(String[] args) {
AbstractApplicationContext context = 
 new ClassPathXmlApplicationContext("Beans.xml");
 HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
 obj.getMessage();
 context.registerShutdownHook();
}
}

Beans.xml

針對不同Bean的init-method和destroy-method不需要每次都設定,可按照下列方式default設定

Beans.xml

結果顯示如下所示:

Initialization now
Your Message : Hello World!
Destory now