springmvc 之HandlerExceptionResolver

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接着上一篇
配置文件

<bean id="exceptionResolver" class="com.eroadsf.netdisk.core.MySimpleMappingExceptionResolver">        <property name="defaultErrorView" value="common_error" />        <property name="exceptionAttribute" value="exception" />        <property name="exceptionMappings">            <props>                <prop key="java.lang.ArithmeticException">common_error</prop>                <prop key="java.lang.IllegalAccessException">no_access</prop>            </props>        </property>    </bean>

MySimpleMappingExceptionResolver

public class MySimpleMappingExceptionResolver extends SimpleMappingExceptionResolver {    private static final Logger logger = Logger.getLogger(MySimpleMappingExceptionResolver.class);    @Override    protected ModelAndView getModelAndView(String viewName, Exception ex, HttpServletRequest request) {        logger.error("exception",ex);        request.setAttribute("exception", ex);          return super.getModelAndView(viewName, ex, request);    }}

2个错误页面
common_error.jsp

<%@ page contentType="text/html;charset=UTF-8"%><html lang="en"><head></head><body>    <div id="wrapper">        <div id="page-wrapper">            <div class="row">                <div class="col-lg-12">                    <h3 class="page-header">错误异常</h3>                </div>            </div>            <!-- /.row -->            <div class="row">                <section>                    <div class="col-lg-8 col-lg-offset-2">${exception}</div>                </section>            </div>        </div>    </div></body></html>

no_access.jsp

<%@ page contentType="text/html;charset=UTF-8"%><html lang="en"><head><meta charset="utf-8"></head><body>    <div id="wrapper">        <div id="page-wrapper">            <div class="row">                <div class="col-lg-12">                    <h3 class="page-header">无法访问</h3>                </div>            </div>            <div class="row">                <section>                    <div class="col-lg-8 col-lg-offset-2">${exception}</div>                </section>            </div>        </div>    </div></body></html>

@RequestMapping(value = "/roleList")    public String  role() {        int i=1/0;        return "manager/role";    }    @RequestMapping(value = "/test")    @ResponseBody    public void  test() throws  IllegalAccessException {        throw new java.lang.IllegalAccessException();    }

当访问到/roleList
错误页面跳转到common_error.jsp
这里写图片描述
当访问/test
错误页面跳转到no_access.jsp

在实际项目中就可以根据Controller层的异常跳转到不同的错误页面。
看看是怎么实现的。我这里自定义的异常处理是继承SimpleMappingExceptionResolver

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,            HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception {    //省略    //如果自己配置了自定义的HandlerExceptionResolver将会在这个方法里处理                mv = processHandlerException(request, response, handler, exception);          //省略                      }

protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response,            Object handler, Exception ex) throws Exception {        //遍历异常处理类        for (HandlerExceptionResolver handlerExceptionResolver : this.handlerExceptionResolvers) {            exMv = handlerExceptionResolver.resolveException(request, response, handler, ex);            if (exMv != null) {                break;            }        }        //省略    }

我这里自定义的异常处理是继承SimpleMappingExceptionResolver，
间接继承AbstractHandlerExceptionResolver
AbstractHandlerExceptionResolver

@Override    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response,            Object handler, Exception ex) {        //省略            ModelAndView mav = doResolveException(request, response, handler, ex);        //省略    }

SimpleMappingExceptionResolver

@Override    protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response,            Object handler, Exception ex) {        // 根据异常选择异常要跳转的页面        String viewName = determineViewName(ex, request);        if (viewName != null) {            // Apply HTTP status code for error views, if specified.            // Only apply it if we're processing a top-level request.            Integer statusCode = determineStatusCode(request, viewName);            if (statusCode != null) {                applyStatusCodeIfPossible(request, response, statusCode);            }            //子类覆盖，可以增加对异常的处理比如记录异常日志            return getModelAndView(viewName, ex, request);        }        else {            return null;        }    }

根据配置参数exceptionMappings的列表和异常进行匹配,将匹配到的错误页面返回，没有匹配上返回默认错误页面

protected String determineViewName(Exception ex, HttpServletRequest request) {        String viewName = null;        if (this.excludedExceptions != null) {            for (Class<?> excludedEx : this.excludedExceptions) {                if (excludedEx.equals(ex.getClass())) {                    return null;                }            }        }        //检查特定的异常映射        if (this.exceptionMappings != null) {            viewName = findMatchingViewName(this.exceptionMappings, ex);        }        // Return default error view else, if defined.        if (viewName == null && this.defaultErrorView != null) {            if (logger.isDebugEnabled()) {                logger.debug("Resolving to default view '" + this.defaultErrorView + "' for exception of type [" +                        ex.getClass().getName() + "]");            }            viewName = this.defaultErrorView;        }        return viewName;    }

根据配置参数exceptionMappings的列表和异常进行匹配

protected String findMatchingViewName(Properties exceptionMappings, Exception ex) {        String viewName = null;        String dominantMapping = null;        int deepest = Integer.MAX_VALUE;        for (Enumeration<?> names = exceptionMappings.propertyNames(); names.hasMoreElements();) {            String exceptionMapping = (String) names.nextElement();            int depth = getDepth(exceptionMapping, ex);            if (depth >= 0 && (depth < deepest || (depth == deepest &&                    dominantMapping != null && exceptionMapping.length() > dominantMapping.length()))) {                deepest = depth;                dominantMapping = exceptionMapping;                viewName = exceptionMappings.getProperty(exceptionMapping);            }        }        if (viewName != null && logger.isDebugEnabled()) {            logger.debug("Resolving to view '" + viewName + "' for exception of type [" + ex.getClass().getName() +                    "], based on exception mapping [" + dominantMapping + "]");        }        return viewName;    }

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