【spring学习】bean的三种实例化方法

你的名字 2022-09-01 09:25 138阅读 0赞

1.  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);
        }
    }

输出：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMzU4NTc0_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMzU4NTc0_size_16_color_FFFFFF_t_70]: /images/20220829/523eae16e6cb449b839e00a8452f415e.png