SpringBoot--解决注入实现类导致的启动失败问题

左手的ㄟ右手 2023-09-29 17:24 38阅读 0赞

原文网址：[SpringBoot--解决注入实现类导致的启动失败问题\_IT利刃出鞘的博客-CSDN博客][SpringBoot--_IT_-CSDN]

## 简介 ##

**说明**

本文介绍SpringBoot注入实现类导致的启动失败的解决方案。

**问题描述**

*  注册bean时，返回值类型是接口，方法里创建了一个实现类。
 *  通过@Autowired注入实现类，结果报错了，应用启动失败。
 *  通过@Autowired注入接口，启动成功。
 *  通过@Autowired注入接口，通过@Autowired注入实现类，启动成功。

## 问题复现 ##

### 注入实现类启动失败 ###

package com.knife;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @SpringBootApplication
    public class DemoApplication {
        @Autowired
        private DistributeLock distributeLock;
    
        public static void main(String[] args) {
            SpringApplication.run(DemoApplication.class, args);
        }
    
    }
    
    @Configuration
    class LockConfig{
        @Bean
        public Lock lock() {
            return new DistributeLock();
        }
    }
    
    interface Lock{}
    
    class DistributeLock implements Lock{}

**报错信息（无法找到com.knife.DistributeLock这个bean）**

2022-09-10 16:37:43.419  INFO 142692 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1013 ms
    2022-09-10 16:41:28.518  WARN 142692 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoApplication': Unsatisfied dependency expressed through field 'distributeLock'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.knife.DistributeLock' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    2022-09-10 16:41:28.521  INFO 142692 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
    2022-09-10 16:41:28.533  INFO 142692 --- [           main] ConditionEvaluationReportLoggingListener : 
    
    Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
    2022-09-10 16:41:28.601 ERROR 142692 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 
    
    ***************************
    APPLICATION FAILED TO START
    ***************************
    
    Description:
    
    Field distributeLock in com.knife.DemoApplication required a bean of type 'com.knife.DistributeLock' that could not be found.
    
    The injection point has the following annotations:
    	- @org.springframework.beans.factory.annotation.Autowired(required=true)
    
    
    Action:
    
    Consider defining a bean of type 'com.knife.DistributeLock' in your configuration.
    
    2022-09-10 16:41:28.607  WARN 142692 --- [           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.

### 注入接口启动成功 ###

package com.knife;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @SpringBootApplication
    public class DemoApplication {
        @Autowired
        private Lock lock;
    
        public static void main(String[] args) {
            SpringApplication.run(DemoApplication.class, args);
        }
    
    }
    
    @Configuration
    class LockConfig{
        @Bean
        public Lock lock() {
            return new DistributeLock();
        }
    }
    
    interface Lock{}
    
    class DistributeLock implements Lock{}

结果（启动成功）

### 注入接口和实现类启动成功 ###

package com.knife;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @SpringBootApplication
    public class DemoApplication {
        @Autowired
        private Lock lock;
    
        @Autowired
        private DistributeLock distributeLock;
    
        public static void main(String[] args) {
            SpringApplication.run(DemoApplication.class, args);
        }
    
    }
    
    @Configuration
    class LockConfig{
        @Bean
        public Lock lock() {
            return new DistributeLock();
        }
    }
    
    interface Lock{}
    
    class DistributeLock implements Lock{}

## 原因分析 ##

**报错原因概述**

Spring是通过类型来匹配bean的，DemoApplication需要的是DistributeLock类型的bean，但找不到（只有Lock类型的bean），于是报错。

**源码追踪**

## 解决方案 ##

[SpringBoot--_IT_-CSDN]: https://knife.blog.csdn.net/article/details/127454094