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Spring Framework example source code file (SimpleMappingExceptionResolver.java)

This example Spring Framework source code file (SimpleMappingExceptionResolver.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

class, default_exception_attribute, exception, exception, http, httpservletrequest, httpservletrequest, httpservletresponse, integer, modelandview, modelandview, object, request, resolving, response, servlet, string, string, util

The Spring Framework SimpleMappingExceptionResolver.java source code

/*
 * Copyright 2002-2007 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.Properties;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.Ordered;
import org.springframework.web.servlet.HandlerExceptionResolver;
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
 * @since 22.11.2003
 * @see org.springframework.web.servlet.DispatcherServlet
 */
public class SimpleMappingExceptionResolver implements HandlerExceptionResolver, Ordered {

	/**
	 * The default name of the exception attribute: "exception".
	 */
	public static final String DEFAULT_EXCEPTION_ATTRIBUTE = "exception";


	/** Logger available to subclasses */
	protected final Log logger = LogFactory.getLog(getClass());

	private int order = Integer.MAX_VALUE;  // default: same as non-Ordered

	private Set mappedHandlers;

	private Class[] mappedHandlerClasses;

	private Log warnLogger;

	private Properties exceptionMappings;

	private String defaultErrorView;

	private Integer defaultStatusCode;

	private String exceptionAttribute = DEFAULT_EXCEPTION_ATTRIBUTE;


	public void setOrder(int order) {
	  this.order = order;
	}

	public int getOrder() {
	  return this.order;
	}

	/**
	 * Specify the set of handlers that this exception resolver should apply to.
	 * The exception mappings and the default error view will only apply
	 * to the specified handlers.
	 * <p>If no handlers and handler classes are set, the exception mappings
	 * and the default error view will apply to all handlers. This means that
	 * a specified default error view will be used as fallback for all exceptions;
	 * any further HandlerExceptionResolvers in the chain will be ignored in
	 * this case.
	 */
	public void setMappedHandlers(Set mappedHandlers) {
		this.mappedHandlers = mappedHandlers;
	}

	/**
	 * Specify the set of classes that this exception resolver should apply to.
	 * The exception mappings and the default error view will only apply
	 * to handlers of the specified type; the specified types may be interfaces
	 * and superclasses of handlers as well.
	 * <p>If no handlers and handler classes are set, the exception mappings
	 * and the default error view will apply to all handlers. This means that
	 * a specified default error view will be used as fallback for all exceptions;
	 * any further HandlerExceptionResolvers in the chain will be ignored in
	 * this case.
	 */
	public void setMappedHandlerClasses(Class[] mappedHandlerClasses) {
		this.mappedHandlerClasses = mappedHandlerClasses;
	}

	/**
	 * Set the log category for warn logging. The name will be passed to the
	 * underlying logger implementation through Commons Logging, getting
	 * interpreted as log category according to the logger's configuration.
	 * <p>Default is no warn logging. Specify this setting to activate
	 * warn logging into a specific category. Alternatively, override
	 * the {@link #logException} method for custom logging.
	 * @see org.apache.commons.logging.LogFactory#getLog(String)
	 * @see org.apache.log4j.Logger#getLogger(String)
	 * @see java.util.logging.Logger#getLogger(String)
	 */
	public void setWarnLogCategory(String loggerName) {
		this.warnLogger = LogFactory.getLog(loggerName);
	}

	/**
	 * 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 and subclasses, for example.
	 * <p>NB: 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.
	 * <p>Follows the same matching algorithm as RuleBasedTransactionAttribute
	 * and RollbackRuleAttribute.
	 * @param mappings exception patterns (can also be fully qualified class names)
	 * as keys, and error view names as values
	 * @see org.springframework.transaction.interceptor.RuleBasedTransactionAttribute
	 * @see org.springframework.transaction.interceptor.RollbackRuleAttribute
	 */
	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 default HTTP status code that this exception resolver will apply
	 * if it resolves an error view.
	 * <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 (SC_INTERNAL_SERVER_ERROR) or 404 (SC_NOT_FOUND)
	 * @see javax.servlet.http.HttpServletResponse#SC_INTERNAL_SERVER_ERROR
	 * @see javax.servlet.http.HttpServletResponse#SC_NOT_FOUND
	 */
	public void setDefaultStatusCode(int defaultStatusCode) {
		this.defaultStatusCode = new Integer(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 for not exposing an exception attribute at all.
	 * @see #DEFAULT_EXCEPTION_ATTRIBUTE
	 */
	public void setExceptionAttribute(String exceptionAttribute) {
		this.exceptionAttribute = exceptionAttribute;
	}


	/**
	 * Checks whether this resolver is supposed to apply (i.e. the handler
	 * matches in case of "mappedHandlers" having been specified), then
	 * delegates to the {@link #doResolveException} template method.
	 */
	public ModelAndView resolveException(
	    HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {

		if (shouldApplyTo(request, handler)) {
			return doResolveException(request, response, handler, ex);
		}
		else {
			return null;
		}
	}

	/**
	 * Check whether this resolver is supposed to apply to the given handler.
	 * <p>The default implementation checks against the specified mapped handlers
	 * and handler classes, if any.
	 * @param request current HTTP request
	 * @param handler the executed handler, or <code>null if none chosen at the
	 * time of the exception (for example, if multipart resolution failed)
	 * @return whether this resolved should proceed with resolving the exception
	 * for the given request and handler
	 * @see #setMappedHandlers
	 * @see #setMappedHandlerClasses
	 */
	protected boolean shouldApplyTo(HttpServletRequest request, Object handler) {
		if (handler != null) {
			if (this.mappedHandlers != null && this.mappedHandlers.contains(handler)) {
				return true;
			}
			if (this.mappedHandlerClasses != null) {
				for (int i = 0; i < this.mappedHandlerClasses.length; i++) {
					if (this.mappedHandlerClasses[i].isInstance(handler)) {
						return true;
					}
				}
			}
		}
		// Else only apply if there are no explicit handler mappings.
		return (this.mappedHandlers == null && this.mappedHandlerClasses == null);
	}

	/**
	 * 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 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 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 for default processing
	 */
	protected ModelAndView doResolveException(
			HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {

		// Log exception, both at debug log level and at warn level, if desired.
		if (logger.isDebugEnabled()) {
			logger.debug("Resolving exception from handler [" + handler + "]: " + ex);
		}
		logException(ex, request);

		// 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.intValue());
			}
			return getModelAndView(viewName, ex, request);
		}
		else {
			return null;
		}
	}


	/**
	 * Log the given exception at warn level, provided that warn logging has been
	 * activated through the {@link #setWarnLogCategory "warnLogCategory"} property.
	 * <p>Calls {@link #buildLogMessage} in order to determine the concrete message
	 * to log. Always passes the full exception to the logger.
	 * @param ex the exception that got thrown during handler execution
	 * @param request current HTTP request (useful for obtaining metadata)
	 * @see #setWarnLogCategory
	 * @see #buildLogMessage
	 * @see org.apache.commons.logging.Log#warn(Object, Throwable)
	 */
	protected void logException(Exception ex, HttpServletRequest request) {
		if (this.warnLogger != null && this.warnLogger.isWarnEnabled()) {
			this.warnLogger.warn(buildLogMessage(ex, request), ex);
		}
	}

	/**
	 * Build a log message for the given exception, occured during processing
	 * the given request.
	 * @param ex the exception that got thrown during handler execution
	 * @param request current HTTP request (useful for obtaining metadata)
	 * @return the log message to use
	 */
	protected String buildLogMessage(Exception ex, HttpServletRequest request) {
		return "Handler execution resulted in exception";
	}


	/**
	 * 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 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 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.
	 * <p>Follows the same algorithm as
	 * {@link org.springframework.transaction.interceptor.RollbackRuleAttribute}.
	 */
	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().indexOf(exceptionMapping) != -1) {
			// 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 always returns the specified
	 * {@link #setDefaultStatusCode "defaultStatusCode"}, as a common
	 * status code for all error views. Override this in a custom subclass
	 * to determine a specific status code for the given view.
	 * @param request current HTTP request
	 * @param viewName the name of the error view
	 * @return the HTTP status code to use, or <code>null 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) {
		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 javax.servlet.http.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);
		}
	}

	/**
	 * 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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