【spring学习】bean的三种实例化方法-蒲公英云

【spring学习】bean的三种实例化方法

你的名字 2022-09-01 09:25 240阅读 0赞

先创建三个类

public class BeanClass {
public String message;
public BeanClass(){
```
  message="构造方法实例化";
```
}
public BeanClass(String s)
{
```
  message = s;
```
}
}

public class BeanInstanceFactory { 
    public BeanClass createBeanClassFactory(){ 
        return new BeanClass("实例工厂实例化");
    }
}
public class BeanStaticFactory { 
    public static BeanClass beanClass = new BeanClass("静态工厂实例化bean");
    public static BeanClass createInstance(){ 
        return beanClass;
    }
}

2.编写config类

public class BeanConfig { 
    //使用@Bean定义三个bean
    @Bean(value= "beanclass")
    public BeanClass getBeanClass(){ 
        return new BeanClass();
    }
    @Bean(value = "beanStaticFactory")
    public BeanClass getBeanStaticFactory(){ 
        return BeanStaticFactory.createInstance();
    }
    @Bean(value = "beanInstanceFactory")
    public BeanClass getBeanInstanceFactory(){ 
        BeanInstanceFactory beanInstanceFactory = new BeanInstanceFactory();
        return beanInstanceFactory.createBeanClassFactory();
    }
}

3.测试：

public class TestBean { 
    public static void main(String[] args) { 
        //初始化spring容器ApplicationContext
        AnnotationConfigApplicationContext app = new AnnotationConfigApplicationContext(BeanConfig.class);
      //对应config中的 @Bean(value= "beanclass")
        BeanClass bi = (BeanClass) app.getBean("beanclass");
        System.out.println(bi+bi.message);
        BeanClass b2 = (BeanClass) app.getBean("beanStaticFactory");
        System.out.println(b2+b2.message);
        BeanClass b3 = (BeanClass) app.getBean("beanInstanceFactory");
        System.out.println(b3+b3.message);
    }
}