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Spring–循环依赖导致启动失败

简介

说明

本文介绍Spring的循环依赖什么时候会出现以及如何解决循环依赖。

循环依赖场景

  1. 单例field的循环依赖       (采用三级缓存+提前暴露对象的方法解决)
  2. 构造器的循环依赖          (无法解决循环依赖问题)
  3. 多例field的循环依赖       (无法解决循环依赖问题)
    1. 对于多例的bean,Spring不缓存”prototype”作用域的bean,不提前暴露一个创建中的bean。

启动失败问题复现

公共代码

package com.example.controller;

import com.example.tmp.A;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {
    @Autowired
    private A a;

    @GetMapping("/test1")
    public String test1() {
        return a.getTest();
    }
}

1.构造器注入

代码

package com.example.tmp;
 
import org.springframework.stereotype.Component;
 
@Component
public class A {
    // @Autowired
    private B b;

    public A(B b){
        this.b = b;
    }
 
    private String name = "Tony";
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public String getTest() {
        return b.getAge().toString() + name;
    }
}
package com.example.tmp;
 
import org.springframework.stereotype.Component;
 
@Component
public class B {
    // @Autowired
    private A a;

    public B(A a) {
        this.a = a;
    }
 
    private Integer age = 20;
 
    public Integer getAge() {
        return age;
    }
 
    public void setAge(Integer age) {
        this.age = age;
    }
}

测试

启动结果

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.0.RELEASE)

2021-04-03 10:40:18.732  INFO 5872 --- [           main] com.example.DemoApplication              : Starting DemoApplication on DESKTOP-QI6B9ME with PID 5872 (E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes started by Liu in E:\work\Idea_proj\demo_JAVA\demo_SpringBoot)
2021-04-03 10:40:18.748  INFO 5872 --- [           main] com.example.DemoApplication              : No active profile set, falling back to default profiles: default
2021-04-03 10:40:20.904  INFO 5872 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2021-04-03 10:40:20.920  INFO 5872 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2021-04-03 10:40:20.920  INFO 5872 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.35]
2021-04-03 10:40:20.998  INFO 5872 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2021-04-03 10:40:20.998  INFO 5872 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2219 ms
2021-04-03 10:40:24.436  WARN 5872 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'helloController': Unsatisfied dependency expressed through field 'a'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'a' defined in file [E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes\com\example\tmp\A.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'b' defined in file [E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes\com\example\tmp\B.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'a': Requested bean is currently in creation: Is there an unresolvable circular reference?
2021-04-03 10:40:24.451  INFO 5872 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2021-04-03 10:40:24.451  INFO 5872 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-04-03 10:40:24.467 ERROR 5872 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

The dependencies of some of the beans in the application context form a cycle:

   helloController (field com.example.tmp.A com.example.controller.HelloController.a)
┌─────┐
|  a defined in file [E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes\com\example\tmp\A.class]
↑     ↓
|  b defined in file [E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes\com\example\tmp\B.class]
└─────┘


2021-04-03 10:40:24.467  WARN 5872 --- [           main] o.s.boot.SpringApplication               : Unable to close ApplicationContext

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'springApplicationAdminRegistrar' defined in class path resource [org/springframework/boot/autoconfigure/admin/SpringApplicationAdminJmxAutoConfiguration.class]: Unsatisfied dependency expressed through method 'springApplicationAdminRegistrar' parameter 1; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.core.env.Environment' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:798) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:539) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.AbstractApplicationEventMulticaster.retrieveApplicationListeners(AbstractApplicationEventMulticaster.java:245) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.AbstractApplicationEventMulticaster.getApplicationListeners(AbstractApplicationEventMulticaster.java:197) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:134) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:403) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:360) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.boot.availability.AvailabilityChangeEvent.publish(AvailabilityChangeEvent.java:81) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.availability.AvailabilityChangeEvent.publish(AvailabilityChangeEvent.java:67) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.doClose(ServletWebServerApplicationContext.java:167) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.close(AbstractApplicationContext.java:978) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:814) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:325) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at com.example.DemoApplication.main(DemoApplication.java:10) [classes/:na]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.core.env.Environment' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1716) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1272) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	... 23 common frames omitted

2.Feild注入多例(@AutoWired) 

本处将A类设置为多例,将B类设置为单例。(其实,都设为多例或者A类设置为单例,B类设置为多例都是一样的,都会报循环依赖错误)

代码

package com.example.tmp;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
 
@Component
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class A {
    @Autowired
    private B b;
 
    private String name = "Tony";
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public String getTest() {
        return b.getAge().toString() + name;
    }
}
package com.example.tmp;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
 
@Component
public class B {
    @Autowired
    private A a;
 
    private Integer age = 20;
 
    public Integer getAge() {
        return age;
    }
 
    public void setAge(Integer age) {
        this.age = age;
    }
}

测试

启动结果

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.0.RELEASE)

2021-04-03 11:09:09.781  INFO 12048 --- [           main] com.example.DemoApplication              : Starting DemoApplication on DESKTOP-QI6B9ME with PID 12048 (E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes started by Liu in E:\work\Idea_proj\demo_JAVA\demo_SpringBoot)
2021-04-03 11:09:09.783  INFO 12048 --- [           main] com.example.DemoApplication              : No active profile set, falling back to default profiles: default
2021-04-03 11:09:10.555  INFO 12048 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2021-04-03 11:09:10.562  INFO 12048 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2021-04-03 11:09:10.562  INFO 12048 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.35]
2021-04-03 11:09:10.650  INFO 12048 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2021-04-03 11:09:10.650  INFO 12048 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 822 ms
2021-04-03 11:09:10.698  WARN 12048 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'helloController': Unsatisfied dependency expressed through field 'a'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'a': Unsatisfied dependency expressed through field 'b'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'b': Unsatisfied dependency expressed through field 'a'; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'a': Requested bean is currently in creation: Is there an unresolvable circular reference?
2021-04-03 11:09:10.700  INFO 12048 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2021-04-03 11:09:10.710  INFO 12048 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-04-03 11:09:10.712 ERROR 12048 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

The dependencies of some of the beans in the application context form a cycle:

   helloController (field com.example.tmp.A com.example.controller.HelloController.a)
┌─────┐
|  a (field com.example.tmp.B com.example.tmp.A.b)
↑     ↓
|  b (field com.example.tmp.A com.example.tmp.B.a)
└─────┘


2021-04-03 11:09:10.717  WARN 12048 --- [           main] o.s.boot.SpringApplication               : Unable to close ApplicationContext

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'springApplicationAdminRegistrar' defined in class path resource [org/springframework/boot/autoconfigure/admin/SpringApplicationAdminJmxAutoConfiguration.class]: Unsatisfied dependency expressed through method 'springApplicationAdminRegistrar' parameter 1; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.core.env.Environment' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:798) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:539) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.AbstractApplicationEventMulticaster.retrieveApplicationListeners(AbstractApplicationEventMulticaster.java:245) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.AbstractApplicationEventMulticaster.getApplicationListeners(AbstractApplicationEventMulticaster.java:197) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:134) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:403) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:360) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.boot.availability.AvailabilityChangeEvent.publish(AvailabilityChangeEvent.java:81) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.availability.AvailabilityChangeEvent.publish(AvailabilityChangeEvent.java:67) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.doClose(ServletWebServerApplicationContext.java:167) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.close(AbstractApplicationContext.java:978) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:814) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:325) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at com.example.DemoApplication.main(DemoApplication.java:10) [classes/:na]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.core.env.Environment' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1716) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1272) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	... 23 common frames omitted

3.Setter注入多例(@AutoWired) 

本处将A类设置为多例,将B类设置为单例。(其实,都设为多例或者A类设置为单例,B类设置为多例都是一样的,都会报循环依赖错误)

代码

package com.example.tmp;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
 
@Component
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class A {
    B b;
 
    private String name = "Tony";
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public String getTest() {
        return b.getAge().toString() + name;
    }

    public B getB() {
        return b;
    }

    @Autowired
    public void setB(B b) {
        this.b = b;
    }
}
package com.example.tmp;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
 
@Component
public class B {
    private A a;
 
    private Integer age = 20;
 
    public Integer getAge() {
        return age;
    }
 
    public void setAge(Integer age) {
        this.age = age;
    }

    public A getA() {
        return a;
    }

    @Autowired
    public void setA(A a) {
        this.a = a;
    }
}

测试

启动结果

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.0.RELEASE)

2021-04-03 11:11:45.352  INFO 5928 --- [           main] com.example.DemoApplication              : Starting DemoApplication on DESKTOP-QI6B9ME with PID 5928 (E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes started by Liu in E:\work\Idea_proj\demo_JAVA\demo_SpringBoot)
2021-04-03 11:11:45.354  INFO 5928 --- [           main] com.example.DemoApplication              : No active profile set, falling back to default profiles: default
2021-04-03 11:11:46.169  INFO 5928 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2021-04-03 11:11:46.176  INFO 5928 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2021-04-03 11:11:46.176  INFO 5928 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.35]
2021-04-03 11:11:46.255  INFO 5928 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2021-04-03 11:11:46.255  INFO 5928 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 860 ms
2021-04-03 11:11:46.298  WARN 5928 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'helloController': Unsatisfied dependency expressed through field 'a'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'a': Unsatisfied dependency expressed through method 'setB' parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'b': Unsatisfied dependency expressed through method 'setA' parameter 0; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'a': Requested bean is currently in creation: Is there an unresolvable circular reference?
2021-04-03 11:11:46.300  INFO 5928 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2021-04-03 11:11:46.316  INFO 5928 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-04-03 11:11:46.318 ERROR 5928 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

The dependencies of some of the beans in the application context form a cycle:

   helloController (field com.example.tmp.A com.example.controller.HelloController.a)
┌─────┐
|  a
↑     ↓
|  b
└─────┘


2021-04-03 11:11:46.326  WARN 5928 --- [           main] o.s.boot.SpringApplication               : Unable to close ApplicationContext

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'springApplicationAdminRegistrar' defined in class path resource [org/springframework/boot/autoconfigure/admin/SpringApplicationAdminJmxAutoConfiguration.class]: Unsatisfied dependency expressed through method 'springApplicationAdminRegistrar' parameter 1; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.core.env.Environment' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:798) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:539) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.AbstractApplicationEventMulticaster.retrieveApplicationListeners(AbstractApplicationEventMulticaster.java:245) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.AbstractApplicationEventMulticaster.getApplicationListeners(AbstractApplicationEventMulticaster.java:197) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:134) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:403) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:360) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.boot.availability.AvailabilityChangeEvent.publish(AvailabilityChangeEvent.java:81) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.availability.AvailabilityChangeEvent.publish(AvailabilityChangeEvent.java:67) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.doClose(ServletWebServerApplicationContext.java:167) ~[spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.close(AbstractApplicationContext.java:978) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:814) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:325) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.3.0.RELEASE.jar:2.3.0.RELEASE]
	at com.example.DemoApplication.main(DemoApplication.java:10) [classes/:na]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.core.env.Environment' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1716) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1272) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
	... 23 common frames omitted

解决方案

见:Spring–循环依赖的解决方案–实例 – 自学精灵

1

评论7

请先

  1. 对象A/B分别被@Component修饰纳入spring管理,且对象A中包含成员变量B,对象B中包含成员变量A;对象A/B均为单构造器且构造参数为B/A对象---此时我使用@Autowired修饰各自成员变量A/B,还是会报错;并没有出现spring自动解决依赖循环的情况,只能通过@Lazy解决。您给的spring解决依赖循环的文字结论我理解了,但是因为缺少对应代码层面举例,不太好理解。麻烦您能举一个 spring依赖循环方案前后的差异例子
    秋风扫落叶 2023-08-12 0
    • 短时间很难彻底理解,可以再结合这个文章看一下,https://learn.skyofit.com/archives/925:如果用了构造器注入,还没到@Autowired起作用,就直接报循环依赖的错了。
      自学精灵 2023-08-12 0
  2. 看了您所有的依赖循环文章以及bean的生命周期,自己也查了部分资料,依赖循环这块还是有点懵。总结如下:A/B之前存在双向依赖--1、A对象初始化时优先获取缓存,缓存中不存在手动创建对象,并以bean名称为键,ObjectFactory为值存入三级缓存;A初始化完成,执行属性填充时发现依赖B对象。2、B对象不存在,也进行手动创建,同上,也将其ObjectFactory等信息存入三级缓存;B对象初始化完成,执行属性填充发现依赖A对象;在三级缓存中获取到A对象对应ObjectFactory,通过ObjectFactory获取到代理对象A并存入二级缓存,同时删除三级缓存中的A对象信息;B对象属性填充完成,将B对象放入一级缓存,并删除B对象相关二级、三级缓存。3、A对象获取到B对象一级缓存,同时将A对象本身放入一级缓存,同样的,删除其二级、三级缓存。问题如下:1、您举例的对象依赖例子不够清晰,多例循环依赖很好理解,而构造器单例造成循环依赖和@Async造成循环依赖好像原理不一致,我的理解,构造器单例是因为初始化对象没法完成,而@Async是因为检测到@Async时生成代理对象发现对象中已存在普通对象进而导致问题。@Async引发循环依赖更符合您的结论,用您的结论去套用单例构造器循环依赖反而很难理解。@Async网址:https://www.cnblogs.com/yangxiaohui227/p/10523025.html
    秋风扫落叶 2023-08-12 0
  3. 构造器依赖循环条件:双方对象单构造器且构造参数为双方对象。1、如构造器中包含无参构造器则优先使用无参构造器,从而避免依赖循环。2、构造器中包含多个参数(第一个参数为对象B,第二个参数为String),我给第一个参数加上@Lazy,为何会报错:No qualifying bean of type 'java.lang.String' available... @Lazy会修饰构造器中所有参数吗?我明明加在第一个参数前
    秋风扫落叶 2023-08-12 0
    • @Lazy只修饰对应的参数的,报错应该是因为只在两个对象中的其中一个的构造函数加了@Lazy。两个对象都加才行。
      自学精灵 2023-08-12 0
      • 我确认2个都加了,具体报错如下: factory.UnsatisfiedDependencyException: Error creating bean with name 'a' defined in file [C:\work\ide\workSpace\*\A.class]: Unsatisfied dependency expressed through constructor parameter 1; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'java.lang.String' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}或 NoSuchBeanDefinitionException: No qualifying bean of type 'java.lang.String' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
        秋风扫落叶 2023-08-12 0
        • 这个的原因不是@Lazy了,@Lazy是修饰对应的参数,不是所有参数。这个报错的原因是:Bean的构造函数的参数必须都是Bean,Spring会从容器中找到对应的Bean去注入。而Spring中没有JDK的String这个类型的Bean,所以报错。
          自学精灵 2023-08-12 1
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