前言

在程式設計過程中，我們總是會遇到各種各樣的一樣，受檢異常和非受檢異常，也可以對這些異常進行重寫或者擴充套件，總而言之，這就涉及到一個處理異常的問題。

好的異常處理方式既容易配置又可以保持使用端的友好互動，更為重要的是在出現問題的時候快速的幫助我們定位問題。

事實上，對程式碼的理解很總要，這樣你就知道什麼時候應該丟擲什麼異常了，比如陣列越界，檔案過大，棧越界，連線超時這些標準異常，等等。當然，在什麼時候丟擲什麼異常不是本文的重點，網上同類的文章很多，傳送門Java 基礎 積累-不斷更新：異常分類：Error,Exception，RuntimeException以及其子類，其他異常

本文主要著重於異常的丟擲方式和捕獲方式。

再一個，對於以介面對外提供服務的專案與以頁面對外提供服務的專案側重點也是不一樣的。前者需要在遇到異常時繼續返回接口出參，只不過是內容有所不同，而以頁面互動

的在出現異常時，則可能是跳轉到了不同的頁面並且給予提示資訊。

最後，異常的處理包括異常的丟擲和處理，丟擲異常是一個，捕獲異常和接下來的處理是另一個。

（1）丟擲異常——捕獲異常——跳轉頁面

（2）丟擲異常——捕獲異常——接口出參

程式碼

基礎工作

(1)自定義的異常類

package com.bestcxx.stu.fileup.exception;

/**
 * 自定義的異常類
 * @author WuJieJecket
 *
 */
@SuppressWarnings("serial")
public class MyException extends Exception {
	public MyException(String string) {
		super(string);
	}

}
 

(2)頁面等前端檔案的位置-檢視解析配置-關注頁面基礎位置WEB-INF/views

applicationContext-mvc.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:tx="http://www.springframework.org/schema/tx"  
    xmlns:aop="http://www.springframework.org/schema/aop"  
    xmlns:util="http://www.springframework.org/schema/util"  
    xmlns:orm="http://www.springframework.org/schema/orm"   
    xmlns:mvc="http://www.springframework.org/schema/mvc"  
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd  
                        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd  
                        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.3.xsd  
                        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd  
                        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.3.xsd  
                        http://www.springframework.org/schema/orm http://www.springframework.org/schema/orm/spring-orm-4.3.xsd  
                        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd  
    ">
    <!-- 配置註解驅動 -->  
    <mvc:annotation-driven/>
    
    <!-- 定義預設訪問 -->  
    <mvc:view-controller path="/" view-name="forward:home"/>
    
    <!-- 處理靜態資源 -->
	<mvc:resources location="/WEB-INF/css/" mapping="/css/**" />
	<mvc:resources location="/WEB-INF/js/" mapping="/js/**" />
	
    <!-- 配置檢視解析器 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">  
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>  
        <property name="contentType" value="text/html"/>        
        <property name="prefix" value="/WEB-INF/views/"/>  
        <property name="suffix" value=".jsp"/>  
    </bean>
    
   
</beans>
 

開始了

異常的丟擲

（1）區域性方法丟擲

	/**
	 * 異常處理測試
	 * @return
	 */
	@GetMapping("exception")
	public String exception() throws Exception{
		if(true){
			throw new MyException("報錯");			
		}
		
		return "success";
	}

（2）攔截器丟擲-類加配置檔案

MyInterceptor.java

package com.bestcxx.stu.fileup.intercepter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.servlet.ServletRequestContext;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import com.bestcxx.stu.fileup.exception.MyException;

public class MyInterceptor implements HandlerInterceptor {
	private long maxSize;

	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {
		System.out.println(this.getClass()+" preHandle開始："+System.currentTimeMillis());
		System.out.println(this.getClass()+" 自定義攔截器訪問前："+maxSize);
		 if(request!=null && ServletFileUpload.isMultipartContent(request)) {
	            ServletRequestContext ctx = new ServletRequestContext(request);
	            long requestSize = ctx.contentLength();
	            if (requestSize > maxSize) {
	            	System.out.println(this.getClass()+" preHandle結束："+System.currentTimeMillis()+" 檔案太大主動丟擲異常"); 
	            	//throw new MaxUploadSizeExceededException(maxSize);
	                throw new MyException(maxSize+"檔案太大超了");
	            }
	        }
		System.out.println(this.getClass()+" preHandle結束："+System.currentTimeMillis());
		return true;
		
	}

	@Override
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
			ModelAndView modelAndView) throws Exception {
		// TODO Auto-generated method stub
		System.out.println(this.getClass()+" postHandle開始："+System.currentTimeMillis());
		System.out.println(this.getClass()+" 自定義攔截器訪問中："+maxSize);
		System.out.println(this.getClass()+" postHandle結束："+System.currentTimeMillis());
		
	}

	@Override
	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
			throws Exception {
		// TODO Auto-generated method stub
		System.out.println(this.getClass()+" afterCompletion開始："+System.currentTimeMillis());
		System.out.println(this.getClass()+" 自定義攔截器訪問後："+maxSize);
		System.out.println(this.getClass()+" afterCompletion結束："+System.currentTimeMillis());

	}

	public void setMaxSize(long maxSize) {
		this.maxSize = maxSize;
	}
	
	

}

applicationContext-intercepter.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:tx="http://www.springframework.org/schema/tx"  
    xmlns:aop="http://www.springframework.org/schema/aop"  
    xmlns:util="http://www.springframework.org/schema/util"  
    xmlns:orm="http://www.springframework.org/schema/orm"   
    xmlns:mvc="http://www.springframework.org/schema/mvc"  
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd  
                        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd  
                        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.3.xsd  
                        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd  
                        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.3.xsd  
                        http://www.springframework.org/schema/orm http://www.springframework.org/schema/orm/spring-orm-4.3.xsd  
                        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd  
    ">
    <!-- 攔截器配置 -->
     <mvc:interceptors>
     	<mvc:interceptor>
     		<mvc:mapping path="/**"/>
     		<bean class="com.bestcxx.stu.fileup.intercepter.MyInterceptor">
     			<!-- <property name="maxSize" value="5242880"></property> --><!-- 5mb -->
     			<property name="maxSize" value="5000"></property>
     		</bean>
     	</mvc:interceptor>
     </mvc:interceptors>
    
</beans>

（3）過濾器丟擲-類加web.xml

略

(4)Spring 為檔案上傳大小限制單獨提供的異常-MaxUploadSizeExceededException

需要增加配置檔案

applicationContext-file.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:tx="http://www.springframework.org/schema/tx"  
    xmlns:aop="http://www.springframework.org/schema/aop"  
    xmlns:util="http://www.springframework.org/schema/util"  
    xmlns:orm="http://www.springframework.org/schema/orm"   
    xmlns:mvc="http://www.springframework.org/schema/mvc"  
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd  
                        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd  
                        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.3.xsd  
                        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd  
                        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.3.xsd  
                        http://www.springframework.org/schema/orm http://www.springframework.org/schema/orm/spring-orm-4.3.xsd  
                        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd  
    ">
    <!--檔案上傳-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">  
		<!-- <property name="maxUploadSize"><value>1</value></property> -->
		<!-- <property name="maxUploadSize"><value>5242880</value></property> --><!-- 設定上傳檔案的最大尺寸為 5mb=5*1024kb=5*1024*1024b -->
		<property name="maxInMemorySize"><value>1</value></property><!-- 小於該尺寸的檔案不生成臨時檔案 -->
		<property name="defaultEncoding"><value>UTF-8</value></property><!-- 預設上傳格式為utf-8 -->
		<property name="resolveLazily"><value>true</value></property><!-- 延遲處理異常-將異常交予 controller 處理 -->
	</bean> 
</beans>

異常的捕獲

（1）區域性方法捕獲-與丟擲異常的方法處於同一個controller類-可介面可頁面

這裡是捕獲異常後跳轉到一個頁面

/**
	 * 捕獲本類的異常
	 * 優先順序比全域性異常高
	 * 針對頁面請求的異常處理，預設返回error.jsp
	 * 一個類僅允許存在一個 @ExceptionHandler 標註的方法
	 * @param ex
	 * @param request
	 * @return
	 */
	@ExceptionHandler(Exception.class)
	public ModelAndView handlePageException(Exception ex, WebRequest request) {
	request.setAttribute("msg","異常捕獲:"+this.getClass()+" "+ex.getMessage(), RequestAttributes.SCOPE_REQUEST);
	ModelAndView mav = new ModelAndView("error");
	mav.addObject("ex", ex);
	return mav;
	}
	
	
	
 

	/**
	 * 異常處理測試
	 * @return
	 */
	@GetMapping("exception")
	public String exception() throws Exception{
		if(true){
			throw new MyException("報錯");			
		}
		
		return "success";
	}

WEB-INF/error.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>error.jsp</title>
</head>
<body>
	<h1> ${msg} </h1>
	<h1> ${ex} </h1>
</body>
</html>

如果是返回一個介面的話

需要注意的是，一個類只能有一個方法被 @Exceptionhandler 註釋

本文使用@ResponseBody 做實體與json轉化。其他更便捷方法請參考Spring json和物件的自動轉化

/**
	 * 捕獲本類的異常
	 * 優先順序比全域性異常高
	 * 針對介面調動的異常處理
	 * 一個類僅允許存在一個 @ExceptionHandler 標註的方法
	 * @param ex
	 * @param request
	 * @return
	 */
	@ExceptionHandler(Exception.class)
	@ResponseBody
	public Object handleRestfulException(Exception ex, WebRequest request) {
		request.setAttribute("msg","異常捕獲:"+this.getClass()+" "+ex.getMessage(), RequestAttributes.SCOPE_REQUEST);
		ModelAndView mav = new ModelAndView("error");
		mav.addObject("ex", ex);
		HashMap map=new HashMap();
		map.put("msg", "非 ModelAndView 的實體或者字串");
		return map;
	}

（2）全域性捕獲

有三種方式，以為只需要一種就可以了，所以將他們統一羅列出來

applicationContext-exception.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:tx="http://www.springframework.org/schema/tx"  
    xmlns:aop="http://www.springframework.org/schema/aop"  
    xmlns:util="http://www.springframework.org/schema/util"  
    xmlns:orm="http://www.springframework.org/schema/orm"   
    xmlns:mvc="http://www.springframework.org/schema/mvc"  
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd  
                        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd  
                        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.3.xsd  
                        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd  
                        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.3.xsd  
                        http://www.springframework.org/schema/orm http://www.springframework.org/schema/orm/spring-orm-4.3.xsd  
                        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd  
    ">
   <!-- 方式一 -->
   <!-- 全域性異常捕獲-針對頁面訪問 -->
    <!-- <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
	     定義預設的異常處理頁面
	    <property name="defaultErrorView" value="error"/>
	    定義異常處理頁面用來獲取異常資訊的變數名，也可不定義，預設名為exception 
    	<property name="exceptionAttribute" value="ex"/>
    	設定日誌輸出級別，不定義則預設不輸出警告等錯誤日誌資訊     
        <property name="warnLogCategory" value="WARN"></property> 
        預設HTTP狀態碼     
        <property name="defaultStatusCode" value="200"></property>     
         
    	對於需要特殊處理的異常
    	<property name="exceptionMappings">     
             <props>     
                 <prop key="java.lang.Exception">error</prop>     
                 <prop key="java.lang.Error">error</prop>
             </props>     
         </property>     
         <property name="statusCodes">     
             <props>     
                 <prop key="error">500</prop>/views/error.jsp
             </props>     
         </property>
	</bean> -->
    
    <!-- 方式二 -->
	<!-- Exception 類捕獲-針對頁面或者介面訪問-->
   <!-- <context:component-scan base-package="com.bestcxx.stu.fileup.exception.ExceptionResolver"/>  -->
    
    <!-- 方式三 -針對頁面或者介面訪問-->
    <!-- 全域性異常處理器只要你實現了HandlerExceptionResolver介面，這個類就是一個全域性異常處理器-->  
    <bean class="com.bestcxx.stu.fileup.exception.GlobalExceptionResolver"></bean>
    
</beans>

方式一是針對頁面訪問的

方式二和方式三可以是頁面也可以是介面(本例是頁面處理)

且方式二和方式三需要單獨提供處理類，在類內部寫如下的內容，返回為null即可，網上也有返回json型別的view

@Override
	public ModelAndView resolveException(HttpServletRequest request,
			HttpServletResponse response, Object handler, Exception ex) {
		response.setContentType("application/json;charset=UTF-8");
		response.setCharacterEncoding("UTF-8");
		if(ex instanceof NoLoginException){
			PrintWriter writer=null;
			try {
				writer = response.getWriter();
				writer.write(((NoLoginException)ex).toString());
				writer.flush();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally{
				if(writer!=null){
					writer.close();
				}
			}
				
		}
		return null;
	}

方式二ExceptionResolver.java

package com.bestcxx.stu.fileup.exception;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.servlet.ModelAndView;

/**
 * 全域性異常配置
 * @author Administrator
 *
 */
@ControllerAdvice
public class ExceptionResolver {
	
	@ExceptionHandler(RuntimeException.class)
    public ModelAndView handlerRuntimeException(RuntimeException ex){
		if(ex instanceof MaxUploadSizeExceededException){
			return new ModelAndView("error").addObject("msg", "檔案太大！");			
		}
		return new ModelAndView("error").addObject("msg", "未知錯誤："+ex);	
    }
	
	@ExceptionHandler(Exception.class)
    public ModelAndView handlerMaxUploadSizeExceededException(Exception ex){
		if(ex instanceof Exception){
			return new ModelAndView("error").addObject("msg", ex);			
		}
		
		return new ModelAndView("error").addObject("msg", "未知錯誤："+ex);	
		
    }

}

方式三GlobalExceptionResolver.java

package com.bestcxx.stu.fileup.exception;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

public class GlobalExceptionResolver implements HandlerExceptionResolver {

	@Override
	public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler,
			Exception ex) {
		ModelAndView modelAndView=new ModelAndView();  
		 System.out.println("異常資訊輸出："+ex.toString());
		//如果是檔案太大
		if (ex instanceof MaxUploadSizeExceededException) {
            long maxSize = ((MaxUploadSizeExceededException) ex).getMaxUploadSize();
            System.out.println(this.getClass()+" 上傳檔案太大，不能超過" + maxSize/1024/1024 + "mb"); // 列印錯誤資訊
            
            //將錯誤資訊傳到頁面  
            modelAndView.addObject("msg",this.getClass()+" 出現異常:"+"上傳檔案太大，不能超過" + maxSize/1024/1024 + "mb"+ex.getMessage()); 
            
            //指向到錯誤介面  
            modelAndView.setViewName("error");  
            return modelAndView;
        } 
		
		
        if(ex instanceof MyException){ //自定義異常
        	 modelAndView.addObject("msg","自定義異常:"+ex.getMessage());  
        }else{  
            //如果該 異常型別不是系統 自定義的異常，構造一個自定義的異常型別（資訊為“未知錯誤”）。  
        	modelAndView.addObject("msg","未知異常:"+ex.getMessage());  
        }  
		
        //將錯誤資訊傳到頁面  
        modelAndView.addObject("msg","出現異常:"+ex.getMessage());  
          
        //指向到錯誤介面  
        modelAndView.setViewName("error");  
          
        return modelAndView;
	}

}