详解Spring全局异常处理的三种方式

在J2EE项目的开发中，不管是对底层的数据库操作过程，还是业务层的处理过程，还是控制层的处理过程，都不可避免会遇到各种可预知的、不可预知的异常需要处理。每个过程都单独处理异常，系统的代码耦合度高，工作量大且不好统一，维护的工作量也很大。 那么，能不能将所有类型的异常处理从各处理过程解耦出来，这样既保证了相关处理过程的功能较单一，也实现了异常信息的统一处理和维护？答案是肯定的。下面将介绍使用Spring MVC统一处理异常的解决和实现过程

• 使用Spring MVC提供的SimpleMappingExceptionResolver
• 实现Spring的异常处理接口HandlerExceptionResolver 自定义自己的异常处理器
• 使用@ExceptionHandler注解实现异常处理

(一) SimpleMappingExceptionResolver

使用这种方式具有集成简单、有良好的扩展性、对已有代码没有入侵性等优点，但该方法仅能获取到异常信息，若在出现异常时，对需要获取除异常以外的数据的情况不适用。

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = {"com.balbala.mvc.web"})
public class WebMVCConfig extends WebMvcConfigurerAdapter{
 @Bean
  public SimpleMappingExceptionResolver simpleMappingExceptionResolver()
  {
    SimpleMappingExceptionResolver b = new SimpleMappingExceptionResolver();
    Properties mappings = new Properties();
    mappings.put("org.springframework.web.servlet.PageNotFound", "page-404");
    mappings.put("org.springframework.dao.DataAccessException", "data-access");
    mappings.put("org.springframework.transaction.TransactionException", "transaction-Failure");
    b.setExceptionMappings(mappings);
    return b;
  }
}

(二) HandlerExceptionResolver

相比第一种来说,HandlerExceptionResolver能准确显示定义的异常处理页面,达到了统一异常处理的目标

1.定义一个类实现HandlerExceptionResolver接口,这次贴一个自己以前的代码

package com.athena.common.handler;
import com.athena.common.constants.ResponseCode;
import com.athena.common.exception.AthenaException;
import com.athena.common.http.RspMsg;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
/**
 * Created by sam on 15/4/14.
 */
public class GlobalHandlerExceptionResolver implements HandlerExceptionResolver {
 private static final Logger LOG = LoggerFactory.getLogger(GlobalHandlerExceptionResolver.class);
  /**
  * 在这里处理所有得异常信息
  */
  @Override
  public ModelAndView resolveException(HttpServletRequest req,                     HttpServletResponse resp, Object o, Exception ex) {
    ex.printStackTrace();
    if (ex instanceof AthenaException) {
      //AthenaException为一个自定义异常
      ex.printStackTrace();
      printWrite(ex.toString(), resp);
      return new ModelAndView();
    }
    //RspMsg为一个自定义处理异常信息的类
    //ResponseCode为一个自定义错误码的接口
    RspMsg unknownException = null;
    if (ex instanceof NullPointerException) {
      unknownException = new RspMsg(ResponseCode.CODE_UNKNOWN, "业务判空异常", null);
    } else {
      unknownException = new RspMsg(ResponseCode.CODE_UNKNOWN, ex.getMessage(), null);    }
      printWrite(unknownException.toString(), resp);
      return new ModelAndView();
  } 

  /**
  * 将错误信息添加到response中
  *
  * @param msg
  * @param response
  * @throws IOException
  */
  public static void printWrite(String msg, HttpServletResponse response) {
     try {
       PrintWriter pw = response.getWriter();
       pw.write(msg);
       pw.flush();
       pw.close();
     } catch (Exception e) {
       e.printStackTrace();
     }
  }
}

2.加入spring的配置中,这里只贴出了相关部分

import com.athena.common.handler.GlobalHandlerExceptionResolver;
import org.springframework.context.annotation.Bean;
import com.athena.common.handler.GlobalHandlerExceptionResolver;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
/**
 * Created by sam on 15/4/14.
 */
public class WebSpringMvcConfig extends WebMvcConfigurerAdapter {

  @Bean
  public GlobalHandlerExceptionResolver globalHandlerExceptionResolver() {
   return new GlobalHandlerExceptionResolver();
  }
}

(三)@ExceptionHandler

这是笔者现在项目的使用方式,这里也仅贴出了相关部分

1.首先定义一个父类,实现一些基础的方法

package com.balabala.poet.base.spring;
import com.google.common.base.Throwables;
import com.raiyee.poet.base.exception.MessageException;
import com.raiyee.poet.base.utils.Ajax;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;

public class BaseGlobalExceptionHandler {
   protected static final Logger logger = null;
   protected static final String DEFAULT_ERROR_MESSAGE = "系统忙，请稍后再试"; 

   protected ModelAndView handleError(HttpServletRequest req, HttpServletResponse rsp, Exception e, String viewName, HttpStatus status) throws Exception {
     if (AnnotationUtils.findAnnotation(e.getClass(), ResponseStatus.class) != null)
     throw e;
     String errorMsg = e instanceof MessageException ? e.getMessage() : DEFAULT_ERROR_MESSAGE;
     String errorStack = Throwables.getStackTraceAsString(e);  

     getLogger().error("Request: {} raised {}", req.getRequestURI(), errorStack);
     if (Ajax.isAjax(req)) {
       return handleAjaxError(rsp, errorMsg, status);
     }
     return handleViewError(req.getRequestURL().toString(), errorStack, errorMsg, viewName);
   }  

   protected ModelAndView handleViewError(String url, String errorStack, String errorMessage, String viewName) {
     ModelAndView mav = new ModelAndView();
     mav.addObject("exception", errorStack);
     mav.addObject("url", url);
     mav.addObject("message", errorMessage);
     mav.addObject("timestamp", new Date());
     mav.setViewName(viewName);
     return mav;
    }  

   protected ModelAndView handleAjaxError(HttpServletResponse rsp, String errorMessage, HttpStatus status) throws IOException {
      rsp.setCharacterEncoding("UTF-8");
      rsp.setStatus(status.value());
      PrintWriter writer = rsp.getWriter();
      writer.write(errorMessage);
      writer.flush();
      return null;
   }  

   public Logger getLogger() {
      return LoggerFactory.getLogger(BaseGlobalExceptionHandler.class);
   }
}

2.针对你需要捕捉的异常实现相对应的处理方式

package com.balabala.poet.base.spring;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.NoHandlerFoundException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@ControllerAdvice
public class GlobalExceptionHandler extends BaseGlobalExceptionHandler {  

   //比如404的异常就会被这个方法捕获
   @ExceptionHandler(NoHandlerFoundException.class)
   @ResponseStatus(HttpStatus.NOT_FOUND)
    public ModelAndView handle404Error(HttpServletRequest req, HttpServletResponse rsp, Exception e) throws Exception {
       return handleError(req, rsp, e, "error-front", HttpStatus.NOT_FOUND);
    }  

   //500的异常会被这个方法捕获
   @ExceptionHandler(Exception.class)
   @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
   public ModelAndView handleError(HttpServletRequest req, HttpServletResponse rsp, Exception e) throws Exception {
       return handleError(req, rsp, e, "error-front", HttpStatus.INTERNAL_SERVER_ERROR);
   }  

   //TODO 你也可以再写一个方法来捕获你的自定义异常
   //TRY NOW!!!

   @Override
   public Logger getLogger() {
      return LoggerFactory.getLogger(GlobalExceptionHandler.class);
   }

 }

以上就三种处理方式，希望对大家的学习有所帮助，也希望大家多多支持我们。