【Java】Bean的生命周期——print大法带你了解Bean的生命周期（初探）
、定义一个Student类#
为了方便看到生命周期过程，我直接使用print大法;
另外，将类交给Spring容器管理可以通过xml文件形式和注解形式，接下来我都实现一下
1、xml形式#
package com.goahead.bean;
public class Student1 {
private String name;
public Student1() {
System.out.println("1、实例化");
}
public Student1(String name) {
this.name = name;
}
public void setName(String name) {
System.out.println("2、依赖注入");
this.name = name;
}
public void myInit() {
System.out.println("3、初始化");
}
public void myDestroy() {
System.out.println("5、销毁");
}
}
2、注解形式#
package com.goahead.bean;
import org.springframework.stereotype.Component;
import org.springframework.beans.factory.annotation.Value;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
@Component
public class Student2 {
private String name;
public Student2() {
System.out.println("1、实例化");
}
public Student2(String name) {
this.name = name;
}
@Value("goahead")
public void setName(String name) {
System.out.println("2、依赖注入");
this.name = name;
}
@PostConstruct
public void myInit() {
System.out.println("3、初始化");
}
@PreDestroy
public void myDestroy() {
System.out.println("5、销毁");
}
}
二、将Student类交给Spring容器#
1、xml文件形式#
需要在resource文件夹下定义一个xml文件
<?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 id="student" class="com.goahead.bean.Student" init-method="myInit" destroy-method="myDestroy">
<property name="name" value="goahead"/>
</bean>
</beans>
2、注解形式（推荐）#
注解形式我们只需在Student2类上加相应的注解，然后加一个配置类
在config目录下创建一个 AppConfig类
package com.goahead.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan("com.goahead.bean") // 扫描包路径
public class AppConfig {
}
三、测试#
由于我们第二步实现了两种方式，所以测试也对应两种方式
1、对应xml形式#
import com.goahead.bean.Student1;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class AppTest1 {
@Test
public void test1() {
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
Student1 student1 = context.getBean(Student1.class);
System.out.println("4、使用Bean");
((ClassPathXmlApplicationContext)context).close();
}
}
2、注解形式#
import com.goahead.bean.Student2;
import com.goahead.config.AppConfig;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class AppTest2 {
@Test
public void test2() {
// 使用AnnotationConfigApplicationContext替代ClassPathXmlApplicationContext
AnnotationConfigApplicationContext context =
new AnnotationConfigApplicationContext(AppConfig.class);
Student2 student = context.getBean(Student2.class);
System.out.println("4、使用Bean");
context.close(); // 触发销毁方法
}
}
四、测试结果#
1、xml形式#
image
2、注解形式#
image