02_Spring Bean Scope

概述： Spring 中bean的作用域有4种，默认为singleton.

类型	作用域范围
singleton	默认类型单例，通过Spring容器获取的该对象是唯一的
prototype	通过Spring容器获取对象时都会new一个新的对象出来
request	表示在一个请求内有效
session	表示在一个会话内有效

Sample：

Entity类：

 1 package com.test.entity;
 2 
 3 public class Students {
 4     private int id;
 5 
 6     private String name;
 7 
 8     private int age;
 9 
10     private Classes classes;
11 
12     public Classes getClasses() {
13         return classes;
14     }
15 
16     public void setClasses(Classes classes) {
17         this.classes = classes;
18     }
19 
20     public Students(int id, String name, int age) {
21         this.id = id;
22         this.name = name;
23         this.age = age;
24     }
25 
26     public Students(int id, String name, int age, Classes classes) {
27         this.id = id;
28         this.name = name;
29         this.age = age;
30         this.classes = classes;
31     }
32 
33     public Students(){
34 
35     }
36 
37     public int getId() {
38         return id;
39     }
40 
41     public void setId(int id) {
42         this.id = id;
43     }
44 
45     public String getName() {
46         return name;
47     }
48 
49     public void setName(String name) {
50         this.name = name;
51     }
52 
53     public int getAge() {
54         return age;
55     }
56 
57     public void setAge(int age) {
58         this.age = age;
59     }
60 
61     @Override
62     public String toString() {
63         return "Students{" +
64                 "id=" + id +
65                 ", name='" + name + '\'' +
66                 ", age=" + age +
67                 ", classes=" + classes +
68                 '}';
69     }
70 }

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Spring配置：

1 <bean id="stu1" class="com.test.entity.Students"></bean>
2 
3 <bean id="stu2" class="com.test.entity.Students" scope="prototype"></bean>

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测试类：

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 1 public static void main(String[] args) {
 2         ApplicationContext applicationContext = new ClassPathXmlApplicationContext("Spring.xml");
 3 
 4         //bean scope test --- default
 5         Students stuSingleton1 = (Students) applicationContext.getBean("stu1");
 6 
 7         Students stuSingleton2 = (Students) applicationContext.getBean("stu1");
 8 
 9         System.out.println(stuSingleton1 == stuSingleton2);
10 
11         //bean scope test --- prototype
12         Students stuPrototype1 = (Students) applicationContext.getBean("stu2");
13 
14         Students stuPrototype2 = (Students) applicationContext.getBean("stu2");
15 
16         System.out.println(stuPrototype1 == stuPrototype2);
17 }

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测试结果：

1 true
2 false

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depends-on：

 1 <bean id="car" class="com.test.entity.Car">
 2         <property name="id" value="1"></property>
 3         <property name="name" value="car"></property>
 4     </bean>
 5 
 6     <bean id="dependsStu" class="com.test.entity.Students" depends-on="car">
 7         <property name="id" value="55"></property>
 8         <property name="name" value="testDepends"></property>
 9         <property name="age" value="25"></property>
10     </bean>

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