SpringMVC 全局异常处理

旧城等待， 2021-12-01 14:38 404阅读 0赞

## SpringMVC 全局异常处理 ##

#### 1. SimpleMappingExceptionResolver ####

1.  SimpleMappingExceptionResolver继承树

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我们可以看到AbstractHandlerExceptionResolver实现了HandlerExceptionResolver中的resolveException, 其具体实现如下:

public ModelAndView resolveException(
    			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) { 
    		 //判断该resolver是否支持handler
    		if (shouldApplyTo(request, handler)) { 
                //清除response缓存
    			prepareResponse(ex, response);
                //调用doResolverException, 该方法是抽象方法, 由SimpleMappingExceptionResolver实现
    			ModelAndView result = doResolveException(request, response, handler, ex);
    		    //省略部分代码
    			return result;
    		}
    		else { 
    			return null;
    		}
    	}

SimpleMappingExceptionResolver实现了上面AbstractHandlerExceptionResolver留下来的抽象方法doResolveException来处理异常的方法, 实现如下:

protected ModelAndView doResolveException(
    			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) { 
            //根据异常类型决定viewName
    		String viewName = determineViewName(ex, request);
    		if (viewName != null) { 
                //根据viewName决定statusCode
    			Integer statusCode = determineStatusCode(request, viewName);
    			if (statusCode != null) { 
    				applyStatusCodeIfPossible(request, response, statusCode);
    			}
                //根据viewName, ex, request生成ModelAndView
    			return getModelAndView(viewName, ex, request);
    		}
    		else { 
    			return null;
    		}
    	}

上面我们可以看到通过determineViewName来决定什么类型的异常对应什么样的viewName, 调用determineStatusCode根据viewName来确定statusCode, 我们看看这两个方法是怎么决定的:

protected String determineViewName(Exception ex, HttpServletRequest request) { 
    		String viewName = null;
            //如果该ex的类型是我们排除掉的异常, 直接return null;
    		if (this.excludedExceptions != null) { 
    			for (Class<?> excludedEx : this.excludedExceptions) { 
    				if (excludedEx.equals(ex.getClass())) { 
    					return null;
    				}
    			}
    		}
    		// 匹配该异常对应的viewName
    		if (this.exceptionMappings != null) { 
                //传入了this.exceptionMappings
                //类型为private Properties exceptionMappings;
                //所以我们只需要通过该properties来设置viewName和ex类型的对应关系
    			viewName = findMatchingViewName(this.exceptionMappings, ex);
    		}
    		// 如果viewName为null,并且设置了默认的错误页面
    		if (viewName == null && this.defaultErrorView != null) { 
    			//省略部分代码
                //返回默认错误页面
    			viewName = this.defaultErrorView;
    		}
    		return viewName;
    	}
    
    //根据viewName 获取 statusCode
    	protected Integer determineStatusCode(HttpServletRequest request, String viewName) { 
    		if (this.statusCodes.containsKey(viewName)) { 
    			return this.statusCodes.get(viewName);
    		}
    		return this.defaultStatusCode;
    	}

上述代码我们发现, 只需要通过一个Properties类型来设置异常类型和viewName的对应关系

@Bean
        public SimpleMappingExceptionResolver simpleMappingExceptionResolver(){ 
            SimpleMappingExceptionResolver resolver = new SimpleMappingExceptionResolver();
            //表示这个处理器不处理空指针异常和数组越界
            resolver.setExcludedExceptions(NullPointerException.class, ArrayIndexOutOfBoundsException.class);
            //设置我们想要处理的异常和对应的异常页面viewName
            Properties properties = new Properties();
            properties.setProperty("org.apache.shiro.authz.AuthorizationException", "unauthorized");
            resolver.setExceptionMappings(properties);
            //设置默认的异常处理页面
            resolver.setDefaultErrorView("error");
            //设置默认的异常状态码
            resolver.setDefaultStatusCode(503);
            //设置不同错误页面对应的状态码
            Properties properties1 = new Properties();
            properties1.setProperty("unauthorized", "300");
            resolver.setStatusCodes(properties1);
            return resolver;
        }

#### 2. 实现HandlerExceptionResolver ####

实现该方法

ModelAndView resolveException(
    			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex);

#### 3. 使用@ExceptionHandler ####

@RestController
    public class UserInfoController { 
    
        @Autowired
        UserInfoService service;
    
        @RequestMapping("test")
        public String test(){ 
            throw new RuntimeException("baocuola");
        }
        
        @ExceptionHandler(RuntimeException.class)
    	@ResponseStatus(HttpStatus.BAD_REQUEST)
        public String exception(RuntimeException ex){ 
            Map<String, String> map = new HashMap<>();
            map.put("code", "400");
            map.put("message", ex.getMessage());
            return new Gson().toJson(map);
        }
    }

当我们访问"/test"的时候, test方法抛出RuntimeException, 因为exception方法声明拦截RuntimeException, 所以将会调用exception方法.

你也可以指定多个需要处理的异常类型，比如这样@ExceptionHandler(value = \{MissingServletRequestParameterException.class,BindException.class\})，这样就会处理多个异常了。

因为UserInfoController被@RestController修饰, 所以返回的是json数据, 当只是使用普通的@Controller修饰的时候, 返回值会被解析成错误页面, 这就跟普通的Controller中的方法一样.

但是这样只是在当前Controller里面起作用, 对于其他Controller抛出的异常是不会进行处理的.

如果想在所有的Controller里面统一处理异常的话，可以用@ControllerAdvice来创建一个专门处理的类

@ControllerAdvice
    public class AdviceController { 
    
        @ResponseBody
        @@ResponseStatus(HttpStatus.BAD_REQUEST)
        @ExceptionHandler(RuntimeException.class)
        public String exception(RuntimeException ex){ 
            Map<String, String> map = new HashMap<>();
            map.put("code", "300");
            map.put("message", ex.getMessage());
            return new Gson().toJson(map);
        }
    }

这样不管是哪个Controller抛出异常都可以被该exception所拦截

参考: [https://blog.csdn.net/liujia120103/article/details/75126124][https_blog.csdn.net_liujia120103_article_details_75126124]

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[https_blog.csdn.net_liujia120103_article_details_75126124]: https://blog.csdn.net/liujia120103/article/details/75126124