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,希望对大家有点帮助~
