https://github.com/spring-projects/spring-framework: Spring Web MVC (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2020 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
 *
 *      https://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.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.lang.Nullable;
import org.springframework.util.StringUtils;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;


Abstract base class for HandlerExceptionResolver implementations. 
Supports mapped handlers and handler classes that the resolver should be applied to and implements the Ordered interface. 
Author:Arjen Poutsma, Juergen Hoeller, Sam Brannen
Since:3.0
/**
 * Abstract base class for {@link HandlerExceptionResolver} implementations.
 *
 * <p>Supports mapped {@linkplain #setMappedHandlers handlers} and
 * {@linkplain #setMappedHandlerClasses handler classes} that the resolver
 * should be applied to and implements the {@link Ordered} interface.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @since 3.0
 */
public abstract class AbstractHandlerExceptionResolver implements HandlerExceptionResolver, Ordered {

	private static final String HEADER_CACHE_CONTROL = "Cache-Control";


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

	private int order = Ordered.LOWEST_PRECEDENCE;

	@Nullable
	private Set<?> mappedHandlers;

	@Nullable
	private Class<?>[] mappedHandlerClasses;

	@Nullable
	private Log warnLogger;

	private boolean preventResponseCaching = false;


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

	@Override
	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.

If no handlers or 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 a fallback for all exceptions; any further HandlerExceptionResolvers in the chain will be
ignored in this case.

/**
	 * Specify the set of handlers that this exception resolver should apply to.
	 * <p>The exception mappings and the default error view will only apply to the specified handlers.
	 * <p>If no handlers or 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 a 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 types; the specified types may be interfaces or superclasses of handlers as well.

If no handlers or 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 a fallback for all exceptions; any further HandlerExceptionResolvers in the chain will be
ignored in this case.

/**
	 * Specify the set of classes that this exception resolver should apply to.
	 * <p>The exception mappings and the default error view will only apply to handlers of the
	 * specified types; the specified types may be interfaces or superclasses of handlers as well.
	 * <p>If no handlers or 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 a 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 a log category according to the logger's configuration. If null or empty String is passed, warn logging is turned off. 
By default there is no warn logging although subclasses like DefaultHandlerExceptionResolver can change that default. Specify this setting to activate warn logging into a specific category. Alternatively, override the logException method for custom logging. 
See Also:
/**
	 * Set the log category for warn logging. The name will be passed to the underlying logger
	 * implementation through Commons Logging, getting interpreted as a log category according
	 * to the logger's configuration. If {@code null} or empty String is passed, warn logging
	 * is turned off.
	 * <p>By default there is no warn logging although subclasses like
	 * {@link org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver}
	 * can change that default. 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 java.util.logging.Logger#getLogger(String)
	 */
	public void setWarnLogCategory(String loggerName) {
		this.warnLogger = (StringUtils.hasLength(loggerName) ? LogFactory.getLog(loggerName) : null);
	}

	
Specify whether to prevent HTTP response caching for any view resolved
by this exception resolver.

Default is false. Switch this to true in order to automatically generate HTTP response headers that suppress response caching. 
/**
	 * Specify whether to prevent HTTP response caching for any view resolved
	 * by this exception resolver.
	 * <p>Default is {@code false}. Switch this to {@code true} in order to
	 * automatically generate HTTP response headers that suppress response caching.
	 */
	public void setPreventResponseCaching(boolean preventResponseCaching) {
		this.preventResponseCaching = preventResponseCaching;
	}


	
Check whether this resolver is supposed to apply (i.e. if the supplied handler matches any of the configured handlers or handler classes), and then delegate to the doResolveException template method. 
/**
	 * Check whether this resolver is supposed to apply (i.e. if the supplied handler
	 * matches any of the configured {@linkplain #setMappedHandlers handlers} or
	 * {@linkplain #setMappedHandlerClasses handler classes}), and then delegate
	 * to the {@link #doResolveException} template method.
	 */
	@Override
	@Nullable
	public ModelAndView resolveException(
			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) {

		if (shouldApplyTo(request, handler)) {
			prepareResponse(ex, response);
			ModelAndView result = doResolveException(request, response, handler, ex);
			if (result != null) {
				// Print debug message when warn logger is not enabled.
				if (logger.isDebugEnabled() && (this.warnLogger == null || !this.warnLogger.isWarnEnabled())) {
					logger.debug("Resolved [" + ex + "]" + (result.isEmpty() ? "" : " to " + result));
				}
				// Explicitly configured warn logger in logException method.
				logException(ex, request);
			}
			return result;
		}
		else {
			return null;
		}
	}

	
Check whether this resolver is supposed to apply to the given handler.

The default implementation checks against the configured handlers and handler classes, if any. 
Params:
  • request – current HTTP request
  • handler – the executed handler, or null if none chosen at the time of the exception (for example, if multipart resolution failed)
See Also:
Returns:whether this resolved should proceed with resolving the exception
for the given request and handler
/**
	 * Check whether this resolver is supposed to apply to the given handler.
	 * <p>The default implementation checks against the configured
	 * {@linkplain #setMappedHandlers handlers} and
	 * {@linkplain #setMappedHandlerClasses 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, @Nullable Object handler) {
		if (handler != null) {
			if (this.mappedHandlers != null && this.mappedHandlers.contains(handler)) {
				return true;
			}
			if (this.mappedHandlerClasses != null) {
				for (Class<?> handlerClass : this.mappedHandlerClasses) {
					if (handlerClass.isInstance(handler)) {
						return true;
					}
				}
			}
		}
		return !hasHandlerMappings();
	}

	
Whether there are any handler mappings registered via setMappedHandlers(Set<?>) or setMappedHandlerClasses(Class<?>[]). 
Since:5.3
/**
	 * Whether there are any handler mappings registered via
	 * {@link #setMappedHandlers(Set)} or {@link #setMappedHandlerClasses(Class[])}.
	 * @since 5.3
	 */
	protected boolean hasHandlerMappings() {
		return (this.mappedHandlers != null || this.mappedHandlerClasses != null);
	}

	
Log the given exception at warn level, provided that warn logging has been activated through the "warnLogCategory" property. 
Calls buildLogMessage in order to determine the concrete message to log. 
Params:
  • ex – the exception that got thrown during handler execution
  • request – current HTTP request (useful for obtaining metadata)
See Also:
/**
	 * 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.
	 * @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));
		}
	}

	
Build a log message for the given exception, occurred during processing the given request.

Params:
  • ex – the exception that got thrown during handler execution
  • request – current HTTP request (useful for obtaining metadata)
Returns:the log message to use
/**
	 * Build a log message for the given exception, occurred 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 "Resolved [" + ex + "]";
	}

	
Prepare the response for the exceptional case.

The default implementation prevents the response from being cached, if the "preventResponseCaching" property has been set to "true". 
Params:
  • ex – the exception that got thrown during handler execution
  • response – current HTTP response
See Also:
  • preventCaching
/**
	 * Prepare the response for the exceptional case.
	 * <p>The default implementation prevents the response from being cached,
	 * if the {@link #setPreventResponseCaching "preventResponseCaching"} property
	 * has been set to "true".
	 * @param ex the exception that got thrown during handler execution
	 * @param response current HTTP response
	 * @see #preventCaching
	 */
	protected void prepareResponse(Exception ex, HttpServletResponse response) {
		if (this.preventResponseCaching) {
			preventCaching(response);
		}
	}

	
Prevents the response from being cached, through setting corresponding HTTP Cache-Control: no-store header. 
Params:
  • response – current HTTP response
/**
	 * Prevents the response from being cached, through setting corresponding
	 * HTTP {@code Cache-Control: no-store} header.
	 * @param response current HTTP response
	 */
	protected void preventCaching(HttpServletResponse response) {
		response.addHeader(HEADER_CACHE_CONTROL, "no-store");
	}


	
Actually resolve the given exception that got thrown during handler execution, returning a ModelAndView that represents a specific error page if appropriate. 
May be overridden in subclasses, in order to apply specific exception checks.
Note that this template method will be invoked after checking whether this
resolved applies ("mappedHandlers" etc), so an implementation may simply proceed
with its actual exception handling.

Params:
  • request – current HTTP request
  • response – current HTTP response
  • handler – the executed handler, or null if none chosen at the time of the exception (for example, if multipart resolution failed)
  • ex – the exception that got thrown during handler execution
Returns:a corresponding ModelAndView to forward to, or null for default processing in the resolution chain
/**
	 * Actually resolve the given exception that got thrown during handler execution,
	 * returning a {@link 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} 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 {@code ModelAndView} to forward to,
	 * or {@code null} for default processing in the resolution chain
	 */
	@Nullable
	protected abstract ModelAndView doResolveException(
			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex);

}