为什么我在Spring启动应用程序中遇到异常？

Question

我的Spring启动应用程序，

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

在获得Whitelabel错误页面后，我在我的一个控制器中映射了/error，

@RestController
public class ResourceController {

    @RequestMapping("/home")
    String home() {
        return "Hello, Welcome!";
    }

    @RequestMapping("/error")
    String error() {
        return "Error occurred!";
    }
}

我映射了一个/error，出现以下异常：，

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'requestMappingHandlerMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'basicErrorController' method 
org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#error(HttpServletRequest)
to { /error}: There is already 'resourceController' bean method
com.example.demo.controller.ResourceController#error() mapped.
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1796) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:595) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:879) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
    at com.example.demo.DemoApplication.main(DemoApplication.java:10) [classes/:na]
Caused by: java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'basicErrorController' method 
org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#error(HttpServletRequest)
to { /error}: There is already 'resourceController' bean method

遵循User9123的解决方案，但是，我仍然得到下面的页面，

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Tue Mar 03 03:27:22 BDT 2020
There was an unexpected error (type=None, status=999).
No message available

Answer 1

Spring告诉您存在一个不明确的映射。因为两者都com。实例演示。控制器。ResourceController和组织。springframework。靴子自动配置。网状物servlet。错误BasicErrorController具有相同的请求映射/error。

因此，您不能在ResourceController类中保留/error。

您可以在特定API上添加基本请求映射路径，也可以更改请求映射路径，这会导致不明确的情况。

例子：

第一种方法：在控制器上添加基本映射路径，以消除不明确的情况。

@RestController
@RequestMapping("/resource")
public class ResourceController {

    @RequestMapping("/home")
    String home() {
        return "Hello, Welcome!";
    }

    @RequestMapping("/error")
    String error() {
        return "Error occurred!";
    }
}

注意：在这种情况下，所有API的路径都以：

或

第二种方法：更改特定API上的请求映射路径，这会导致不明确的情况。

例如：

@RestController
public class ResourceController {

    @RequestMapping("/home")
    String home() {
        return "Hello, Welcome!";
    }

    @RequestMapping("/resource/error")
    String error() {
        return "Error occurred!";
    }
}

注意：在这种情况下，您必须使用

在我看来，我建议你采用第一种方法。

Answer 2

/error处理程序已经在Spring Boot应用程序中定义。您可以禁用它：

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration;

@SpringBootApplication(exclude = {ErrorMvcAutoConfiguration.class})
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

或者改变你的 /error

Answer 3

错误背后的原因是您的ResourceController中有绑定URL“/error”，Spring Boot BasicErrorController已在内部使用该绑定URL“/error”来显示白标签错误页面。

您可以将requestMapping从URL“/error”更改为其他内容以消除错误。如果您对使用URL或自定义SpringREST错误处理的默认行为感兴趣，您可以在这里阅读更多内容。

https://mkyong.com/spring-boot/spring-rest-error-handling-example/