/*
* Copyright 2002-2009 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.servlet.handler;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.util.WebUtils;
/**
* {@link org.springframework.web.servlet.HandlerExceptionResolver} implementation that allows for mapping exception
* class names to view names, either for a set of given handlers or for all handlers in the DispatcherServlet.
*
* <p>Error views are analogous to error page JSPs, but can be used with any kind of exception including any checked
* one, with fine-granular mappings for specific handlers.
*
* @author Juergen Hoeller
* @author Arjen Poutsma
* @since 22.11.2003
* @see org.springframework.web.servlet.DispatcherServlet
*/
public class SimpleMappingExceptionResolver extends AbstractHandlerExceptionResolver {
/** The default name of the exception attribute: "exception". */
public static final String DEFAULT_EXCEPTION_ATTRIBUTE = "exception";
private Properties exceptionMappings;
private String defaultErrorView;
private Integer defaultStatusCode;
private Map<String, Integer> statusCodes = new HashMap<String, Integer>();
private String exceptionAttribute = DEFAULT_EXCEPTION_ATTRIBUTE;
/**
* Set the mappings between exception class names and error view names.
* The exception class name can be a substring, with no wildcard support at present.
* A value of "ServletException" would match <code>javax.servlet.ServletException</code>
* and subclasses, for example.
* <p><b>NB:</b> Consider carefully how
* specific the pattern is, and whether to include package information (which isn't mandatory).
* For example, "Exception" will match nearly anything, and will probably hide other rules.
* "java.lang.Exception" would be correct if "Exception" was meant to define a rule for all
* checked exceptions. With more unusual exception names such as "BaseBusinessException"
* there's no need to use a FQN.
* @param mappings exception patterns (can also be fully qualified class names) as keys,
* and error view names as values
*/
public void setExceptionMappings(Properties mappings) {
this.exceptionMappings = mappings;
}
/**
* Set the name of the default error view. This view will be returned if no specific mapping was found. <p>Default is
* none.
*/
public void setDefaultErrorView(String defaultErrorView) {
this.defaultErrorView = defaultErrorView;
}
/**
* Set the HTTP status code that this exception resolver will apply for a given resolved error view. Keys are
* view names; values are status codes.
* <p>Note that this error code will only get applied in case of a top-level request. It will not be set for an include
* request, since the HTTP status cannot be modified from within an include.
* <p>If not specified, the default status code will be applied.
* @see #setDefaultStatusCode(int)
*/
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);
}
}
/**
* Set the default HTTP status code that this exception resolver will apply if it resolves an error view and if there
* is no status code mapping defined.
* <p>Note that this error code will only get applied in case of a top-level request. It will not be set for an
* include request, since the HTTP status cannot be modified from within an include.
* <p>If not specified, no status code will be applied, either leaving this to the controller or view, or keeping
* the servlet engine's default of 200 (OK).
* @param defaultStatusCode HTTP status code value, for example 500
* ({@link HttpServletResponse#SC_INTERNAL_SERVER_ERROR}) or 404 ({@link HttpServletResponse#SC_NOT_FOUND})
* @see #setStatusCodes(Properties)
*/
public void setDefaultStatusCode(int defaultStatusCode) {
this.defaultStatusCode = defaultStatusCode;
}
/**
* Set the name of the model attribute as which the exception should be exposed. Default is "exception". <p>This can be
* either set to a different attribute name or to <code>null</code> for not exposing an exception attribute at all.
* @see #DEFAULT_EXCEPTION_ATTRIBUTE
*/
public void setExceptionAttribute(String exceptionAttribute) {
this.exceptionAttribute = exceptionAttribute;
}
/**
* Actually resolve the given exception that got thrown during on handler execution, returning a ModelAndView that
* represents a specific error page if appropriate. <p>May be overridden in subclasses, in order to apply specific
* exception checks. Note that this template method will be invoked <i>after</i> checking whether this resolved applies
* ("mappedHandlers" etc), so an implementation may simply proceed with its actual exception handling.
* @param request current HTTP request
* @param response current HTTP response
* @param handler the executed handler, or <code>null</code> if none chosen at the time of the exception (for example,
* if multipart resolution failed)
* @param ex the exception that got thrown during handler execution
* @return a corresponding ModelAndView to forward to, or <code>null</code> for default processing
*/
@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;
}
}
/**
* Determine the view name for the given exception, searching the {@link #setExceptionMappings "exceptionMappings"},
* using the {@link #setDefaultErrorView "defaultErrorView"} as fallback.
* @param ex the exception that got thrown during handler execution
* @param request current HTTP request (useful for obtaining metadata)
* @return the resolved view name, or <code>null</code> if none found
*/
protected String determineViewName(Exception ex, HttpServletRequest request) {
String viewName = 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;
}
/**
* Find a matching view name in the given exception mappings.
* @param exceptionMappings mappings between exception class names and error view names
* @param ex the exception that got thrown during handler execution
* @return the view name, or <code>null</code> if none found
* @see #setExceptionMappings
*/
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) {
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;
}
/**
* Return the depth to the superclass matching.
* <p>0 means ex matches exactly. Returns -1 if there's no match.
* Otherwise, returns depth. Lowest depth wins.
*/
protected int getDepth(String exceptionMapping, Exception ex) {
return getDepth(exceptionMapping, ex.getClass(), 0);
}
private int getDepth(String exceptionMapping, Class exceptionClass, int depth) {
if (exceptionClass.getName().contains(exceptionMapping)) {
// Found it!
return depth;
}
// If we've gone as far as we can go and haven't found it...
if (exceptionClass.equals(Throwable.class)) {
return -1;
}
return getDepth(exceptionMapping, exceptionClass.getSuperclass(), depth + 1);
}
/**
* Determine the HTTP status code to apply for the given error view.
* <p>The default implementation returns the status code for the given view name (specified through the
* {@link #setStatusCodes(Properties) statusCodes} property), or falls back to the
* {@link #setDefaultStatusCode defaultStatusCode} if there is no match.
* <p>Override this in a custom subclass to customize this behavior.
* @param request current HTTP request
* @param viewName the name of the error view
* @return the HTTP status code to use, or <code>null</code> for the servlet container's default
* (200 in case of a standard error view)
* @see #setDefaultStatusCode
* @see #applyStatusCodeIfPossible
*/
protected Integer determineStatusCode(HttpServletRequest request, String viewName) {
if (this.statusCodes.containsKey(viewName)) {
return this.statusCodes.get(viewName);
}
return this.defaultStatusCode;
}
/**
* Apply the specified HTTP status code to the given response, if possible (that is,
* if not executing within an include request).
* @param request current HTTP request
* @param response current HTTP response
* @param statusCode the status code to apply
* @see #determineStatusCode
* @see #setDefaultStatusCode
* @see HttpServletResponse#setStatus
*/
protected void applyStatusCodeIfPossible(HttpServletRequest request, HttpServletResponse response, int statusCode) {
if (!WebUtils.isIncludeRequest(request)) {
if (logger.isDebugEnabled()) {
logger.debug("Applying HTTP status code " + statusCode);
}
response.setStatus(statusCode);
request.setAttribute(WebUtils.ERROR_STATUS_CODE_ATTRIBUTE, statusCode);
}
}
/**
* Return a ModelAndView for the given request, view name and exception.
* <p>The default implementation delegates to {@link #getModelAndView(String, Exception)}.
* @param viewName the name of the error view
* @param ex the exception that got thrown during handler execution
* @param request current HTTP request (useful for obtaining metadata)
* @return the ModelAndView instance
*/
protected ModelAndView getModelAndView(String viewName, Exception ex, HttpServletRequest request) {
return getModelAndView(viewName, ex);
}
/**
* Return a ModelAndView for the given view name and exception.
* <p>The default implementation adds the specified exception attribute.
* Can be overridden in subclasses.
* @param viewName the name of the error view
* @param ex the exception that got thrown during handler execution
* @return the ModelAndView instance
* @see #setExceptionAttribute
*/
protected ModelAndView getModelAndView(String viewName, Exception ex) {
ModelAndView mv = new ModelAndView(viewName);
if (this.exceptionAttribute != null) {
if (logger.isDebugEnabled()) {
logger.debug("Exposing Exception as model attribute '" + this.exceptionAttribute + "'");
}
mv.addObject(this.exceptionAttribute, ex);
}
return mv;
}
}
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