當前SpringMVC非常流行，在大多數情況，我們都需要自定義一些錯誤頁面（例如：401， 402， 403， 500...），以便更友好的提示。對於spring mvc，這些當然是支持自定義的，spring是怎麼做的？ 還是去看看spring的源碼吧：
眾所周知，springmvc的入口是DispatcherServlet, 在DispatcherServlet的源碼中，不知你是否注意到了以下方法：
protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response,
Object handler, Exception ex) throws Exception {
// Check registered HandlerExceptionResolvers...
ModelAndView exMv = null;
for (HandlerExceptionResolver handlerExceptionResolver : this.handlerExceptionResolvers) {
exMv = handlerExceptionResolver.resolveException(request, response, handler, ex);
if (exMv != null) {
break;
}
}
if (exMv != null) {
if (exMv.isEmpty()) {
request.setAttribute(EXCEPTION_ATTRIBUTE, ex);
return null;
}
// We might still need view name translation for a plain error model...
if (!exMv.hasView()) {
exMv.setViewName(getDefaultViewName(request));
}
if (logger.isDebugEnabled()) {
logger.debug("Handler execution resulted in exception - forwarding to resolved error view: " + exMv, ex);
}
WebUtils.exposeErrorRequestAttributes(request, ex, getServletName());
return exMv;
}
throw ex;
}這個方法就是springmvc對於異常的處理，其調用了HandlerExceptionResolver的resolveException方法。HandlerExceptionResolver有眾多實現類，其中，重點看看
SimpleMappingExceptionResolver（我們就是要通過它來配置自定義錯誤頁面）。
public class SimpleMappingExceptionResolver extends AbstractHandlerExceptionResolver {
...
private Properties exceptionMappings;
private Class<?>[] excludedExceptions;
private Map<String, Integer> statusCodes = new HashMap<String, Integer>();
...
public void setExceptionMappings(Properties mappings) {
this.exceptionMappings = mappings;
}
public void setStatusCodes(Properties statusCodes) {
for (Enumeration<?> enumeration = statusCodes.propertyNames(); enumeration.hasMoreElements();) {
String viewName = (String) enumeration.nextElement();
Integer statusCode = new Integer(statusCodes.getProperty(viewName));
this.statusCodes.put(viewName, statusCode);
}
}
}
@Override
protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response,
Object handler, Exception ex) {
// Expose ModelAndView for chosen error view.
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);
}
return getModelAndView(viewName, ex, request);
}
else {
return null;
}
}
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;
}
}
}
// Check for specific exception mappings.
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;
}
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;
}
protected Integer determineStatusCode(HttpServletRequest request, String viewName) {
if (this.statusCodes.containsKey(viewName)) {
return this.statusCodes.get(viewName);
}
return this.defaultStatusCode;
}由此可見：
SimpleMappingExceptionResolver通過 exceptionMappings和statusCodes來確立Exception、http狀態碼以及view之間的映射關系。明白這個就很簡單了，我們可以通過設置exceptionMappings、statusCodes的值來實現我們自定義的映射關系。
我們在WEB-INF/views/commons/error（目錄自己定）新建我們自定義的錯誤頁面，404.html, 500.html等等。
SimpleMappingExceptionResolver只實現映射關系，我們還需要通過配置web.xml來實現。
<error-page>
<error-code>404</error-code>
<location>/error/404.html</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>/error/500.html</location>
</error-page>在spring-mvc配置文件中將404.html、500.html等設置為資源文件，避免被springmvc再次攔截。
<mvc:resources mapping="/error/**" location="/WEB-INF/views/commons/error/" />配置SimpleMappingExceptionResolver。
<bean class="org.springframework.web.servlet.handler. SimpleMappingExceptionResolver">
<property name="exceptionMappings">
<map>
<entry key="ResourceNotFoundException" value="common/error/resourceNotFoundError" />
<entry key=".DataAccessException" value="common/error/dataAccessError" />
</map>
</property>
<property name="statusCodes">
<map>
<entry key="common/error/resourceNotFoundError" value="404" />
<entry key="common/error/dataAccessError" value="500" />
</map>
</property>
</bean> 到此，就實現我們需要的配置了。
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