lazy 翻译过来是"懒惰的"
@Lazy（懒加载）：该注解用于惰性加载初始化标注的类、方法和参数。
在Spring中常用于单实例Bean对象的创建和使用；
单实例Bean懒加载：容器启动后不创建对象，而是在第一次获取Bean创建对象时，初始化。
可标注在类、方法、构造方法、参数、字段上
@Target({ElementType.TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.PARAMETER, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Lazy {
/**
* Whether lazy initialization should occur.
*/
boolean value() default true;
}
package com.dashu.bean;
public class Persion {
public Persion(String name, int age) {
this.name = name;
this.age = age;
}
private String name;
private 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;
}
@Override
public String toString() {
return "Persion{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
package com.dashu.config;
import com.dashu.bean.Persion;
import org.springframework.context.annotation.*;
/**
* @Configuration 注解：告诉Spring这是一个配置类
*
* 配置类 == 配置文件（beans.xml文件）
*
*/
@Configuration
public class BeanConfig {
@Lazy
@Bean
public Persion persion(){
System.out.println("初始化Persion...");
return new Persion("张三",20);
}
}
package com.dashu;
import com.dashu.bean.Persion;
import com.dashu.config.BeanConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {
public static void main(String[] args) {
AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(BeanConfig.class);
/**
* 只在第一次获取Bean时，初始化。之后的获取都是同一个对象
*/
Persion persion1 = (Persion) annotationConfigApplicationContext.getBean("persion");
Persion persion2 = annotationConfigApplicationContext.getBean(Persion.class);
System.out.println(persion1 == persion2);
}
}
