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前言
在applicationContext.xml中配置完bean之后，Bean的声明周期状态有哪些。生命周期的各个阶段可以做什么。在applicationContext.xml配置bean的作用域有哪些。其中各个作用域代表的是什么。适用于什么情况。这篇文章做一个记录。
生命周期
初始化
可以直接查看图片，图片来自Spring Bean Life Cycle
从上图看出，Bean初始化完成包括9个步骤。其中一些步骤包括接口的实现，其中包括BeanNameAware接口，BeanFactoryAware接口。ApplicationContextAware接口。BeanPostProcessor接口，InitializingBean接口。那么这些接口在整个生命周期阶段都起到什么作用？后面我们一一介绍。
实例化前
当Bean全部属性设置完毕后，往往需要执行一些特定的行为，Spring提供了两种方式来实现此功能:
- 使用init-mothod方法
- 实现initializingBean接口
指定初始化方法
如下:
package com.model;
public class InitBean {
public static final String NAME = "mark";
public static final int AGE = 20;
public InitBean() {
// TODO Auto-generated constructor stub
System.out.println("执行构造方法");
}
public String name;
public int age ;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void init(){
System.out.println("调用init方法进行成员变量的初始化");
this.name = NAME;
this.age = AGE;
System.out.println("初始化完成");
}
}
</div>
编写加载器
package com.model;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.service.UserServiceImpl;
public class Main {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("initbean.xml");
InitBean bean = (InitBean) context.getBean("init");
}
}
</div>
配置Bean
注意init-method参数
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="init" class="com.model.InitBean" init-method="init"/> </beans></div>
执行结果
实现InitializingBean接口
实现InitializingBean接口会实现afterPropertiesSet方法，这个方法会自动调用。但是这个方式是侵入性的。一般情况下，不建议使用。
实现afterPropertiesSet方法
package com.model;
import org.springframework.beans.factory.InitializingBean;
public class InitBean implements InitializingBean {
public static final String NAME = "mark";
public static final int AGE = 20;
public InitBean() {
// TODO Auto-generated constructor stub
System.out.println("执行构造方法");
}
public String name;
public int age ;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void init(){
System.out.println("调用init方法进行成员变量的初始化");
this.name = NAME;
this.age = AGE;
System.out.println("初始化完成");
}
@Override
public void afterPropertiesSet() throws Exception {
// TODO Auto-generated method stub
System.out.println("调用init方法进行成员变量的初始化");
this.name = NAME;
this.age = AGE;
System.out.println("初始化完成");
}
}
</div>
配置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" xmlns:p="http://www.springframework.org/schema/p" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <!-- <bean id="init" class="com.model.InitBean" init-method="init"/> --> <bean id="init" class="com.model.InitBean" init-method="init"/> </beans></div>
结果:
销毁
同样，上图中表示来Bean销毁时候的过程。包括DisposableBean接口。
使用destroy-method方法
package com.model;
import org.springframework.beans.factory.InitializingBean;
public class InitBean implements InitializingBean {
public static final String NAME = "mark";
public static final int AGE = 20;
public InitBean() {
// TODO Auto-generated constructor stub
System.out.println("执行构造方法");
}
public String name;
public int age ;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void init(){
System.out.println("调用init方法进行成员变量的初始化");
this.name = NAME;
this.age = AGE;
System.out.println("初始化完成");
}
@Override
public void afterPropertiesSet() throws Exception {
// TODO Auto-generated method stub
System.out.println("调用init方法进行成员变量的初始化");
this.name = NAME;
this.age = AGE;
System.out.println("初始化完成");
}
public void close(){
System.out.println("bean被销毁");
}
}
</div>
配置Bean
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <!-- <bean id="init" class="com.model.InitBean" init-method="init"/> --> <bean id="init" class="com.model.InitBean" destroy-method="close"/> </beans></div>
配置加载器
package com.model;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.service.UserServiceImpl;
public class Main {
public static void main(String[] args) {
AbstractApplicationContext context = new ClassPathXmlApplicationContext("initbean.xml");
context.registerShutdownHook();
InitBean bean = (InitBean) context.getBean("init");
}
}
</div>