spring源码循环依赖测试

╰+攻爆jí腚メ 2022-12-08 15:36 246阅读 0赞

**1.测试主类**

package java_config;
    import org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    public class Bootrap { 
        public static void main(String[] args) { 
            AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
            context.register(StudentConfig.class);
            AbstractAutowireCapableBeanFactory beanFactory = (AbstractAutowireCapableBeanFactory) context.getBeanFactory();
            beanFactory.setAllowCircularReferences(true);
            context.refresh();
            Student simpleBean = (Student) context.getBean("student");
            System.out.println(simpleBean.toString());
        }
    }

**2.StudentConfig类**

package java_config;
    
    import org.springframework.context.annotation.ComponentScan;
    
    @ComponentScan(value = "java_config")
    public class StudentConfig{ 
    
    }

**3.student类**

package java_config;
    
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    
    @Component
    public class Student{ 
    
    	@Autowired
    	Teacher teacher;
    	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;
    	}
    
        public Student(String name, int age) { 
            this.age = age;
            this.name = name;
        }
    
        public Student() { 
    		System.out.println("student");
        }
    
        @Override
    	public String toString() { 
    		return "Student [name=" + name + ", age=" + age + "]";
    	}
    	
    }

**4.teacher类**

package java_config;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    
    /**
     * @author: zhaoxu
     * @date: 2020/9/20 16:00
     */
    @Component
    public class Teacher { 
        @Autowired
        Student student;
        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;
        }
    
        public Teacher(String name, int age) { 
            this.age = age;
            this.name = name;
        }
    
        public Teacher() { 
            System.out.println("Teacher");
        }
    
        @Override
        public String toString() { 
            return "Teacher [name=" + name + ", age=" + age + "]";
        }
    }

`AbstractAutowireCapableBeanFactory`类中存在属性`allowCircularReferences`，默认为true，支持循环依赖  
只要在创建bean实例之前修改spring默认属性即可取消循环依赖

AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
            context.register(StudentConfig.class);
            AbstractAutowireCapableBeanFactory beanFactory = (AbstractAutowireCapableBeanFactory) context.getBeanFactory();
            beanFactory.setAllowCircularReferences(true);
            context.refresh();
            Student simpleBean = (Student) context.getBean("student");
            System.out.println(simpleBean.toString());

**5.结果：**  
`beanFactory.setAllowCircularReferences(true);`设置为true时，循环依赖成功运行  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk4MTkx_size_16_color_FFFFFF_t_70_pic_center]  
`beanFactory.setAllowCircularReferences(false);`设置为false时，循环依赖不可运行，构造方法成功创建，但是去查找属性依赖的时候，由于没有三级缓存的支持，陷入死循环，报错  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk4MTkx_size_16_color_FFFFFF_t_70_pic_center 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk4MTkx_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/08c4d6dea95a4ba1a48b354b1be92f0f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk4MTkx_size_16_color_FFFFFF_t_70_pic_center 1]: /images/20221123/d895382778234dddb2ffebe80ae0bea3.png