SpringBoot的异常处理机制

小伙伴们是不是刚接触Spring Boot做网页开发的时候，如果代码发生异常，会返回一个错误信息页面，如下图

springboot中是如何处理异常的呢？

这里就要接触到一个Spring Boot类BasicErrorController，如下图

注释信息也说明了，这是一个基础全局错误controller,Spring Boot自带的，看到这个RequestMapping地址，这是一个相当于三元写法，如果你在配置文件配置了server.error.path的话，就会使用你配置的异常处理地址，如果没有就会使用你配置的error.path路径地址，如果还是没有，默认使用/error来作为发生异常的处理地址，如下图

那么这个类是如何处理异常的呢，如下图

它提供了两个接口处理方法，源码中produces = MediaType.TEXT_HTML_VALUE，这其实是把常量抽取出来了，produces其实是text/html，当你是网页请求的时候返回的网页数据，下面的接口是当你的请求为其他的时候，返回的是ResponseEntity对象（json数据或者其他，取决与你的返回数据类型配置）。

我们看到第一个接口返回了一个error页面，如果你的项目静态页面下刚好存在一个error所对应的页面，那么Spring Boot会得到你本地的页面，如下图

application.yml 添加配置

#配置视图版块位置
freemarker:
  template-loader-path: classpath:/templates

#mvc配置前缀和后缀
mvc:
  view:
    prefix: /
    suffix: .html

那么这个BasicErrorController默认返回的信息是哪一些呢，如下图

那么，我们该如何抛弃掉或者覆盖掉Spring Boot默认异常处理呢，Spring Boot开发指南上提供了以下四种方法：

1、自定义一个bean，实现ErrorController接口，那么默认的错误处理机制将不再生效。
2、自定义一个bean，继承BasicErrorController类，使用一部分现成的功能，自己也可以添加新的public方法，使用@RequestMapping及其produces属性指定新的地址映射。
3、自定义一个ErrorAttribute类型的bean，那么还是默认的两种响应方式，只不过改变了内容项而已。
4、继承AbstractErrorController

那还来介绍一种方法：统一异常处理

package com.riemann.springbootdemo.exception;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;

/**
 * @author riemann
 * @date 2019/06/08 11:59
 */
@ControllerAdvice
public class GlobalExceptionHandle extends RuntimeException{

    private static final Logger logger = LoggerFactory.getLogger(GlobalExceptionHandle.class);

    @ExceptionHandler(value = Exception.class)
    public ModelAndView exceptionHandle(HttpServletRequest request, Exception exception) {
        String url = request.getRequestURL().toString();
        logger.error("URL: " + url);
        logger.error("Excption: ", exception);
        ModelAndView mv = new ModelAndView();
        mv.addObject("exception", exception);
        mv.addObject("url", url);
        mv.setViewName("error");
        return mv;
    }

}

统一处理Exception异常，只需要在类上标注ControllerAdvice这个注解，然后在类方法上标注好对应的ExceptionHandler及异常类。如下图

日志error级别打印

2019-06-08 12:37:15.565 ERROR 6456 --- [nio-8080-exec-1] c.r.s.exception.GlobalExceptionHandle    : URL: http://localhost:8080/user/add
2019-06-08 12:37:15.569 ERROR 6456 --- [nio-8080-exec-1] c.r.s.exception.GlobalExceptionHandle    : Excption: 

org.springframework.web.HttpRequestMethodNotSupportedException: Request method 'GET' not supported
	at org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping.handleNoMatch(RequestMappingInfoHandlerMapping.java:200) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.lookupHandlerMethod(AbstractHandlerMethodMapping.java:419) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:365) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:65) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMapping.getHandler(AbstractHandlerMapping.java:401) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.getHandler(DispatcherServlet.java:1231) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1014) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) [spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) [spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) [spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_91]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_91]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.17.jar:9.0.17]
	at java.lang.Thread.run(Thread.java:745) [na:1.8.0_91]

自定义异常界面成功