org.springframework.web.servlet.handler.SimpleMappingExceptionResolver.java Source code

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/*
 * Copyright 2002-2018 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.Collections;
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.lang.Nullable;
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
 * @author Rossen Stoyanchev
 * @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";

    @Nullable
    private Properties exceptionMappings;

    @Nullable
    private Class<?>[] excludedExceptions;

    @Nullable
    private String defaultErrorView;

    @Nullable
    private Integer defaultStatusCode;

    private Map<String, Integer> statusCodes = new HashMap<>();

    @Nullable
    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}
     * 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 one or more exceptions to be excluded from the exception mappings.
     * Excluded exceptions are checked first and if one of them equals the actual
     * exception, the exception will remain unresolved.
     * @param excludedExceptions one or more excluded exception types
     */
    public void setExcludedExceptions(Class<?>... excludedExceptions) {
        this.excludedExceptions = excludedExceptions;
    }

    /**
     * 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 = Integer.valueOf(statusCodes.getProperty(viewName));
            this.statusCodes.put(viewName, statusCode);
        }
    }

    /**
     * An alternative to {@link #setStatusCodes(Properties)} for use with
     * Java-based configuration.
     */
    public void addStatusCode(String viewName, int statusCode) {
        this.statusCodes.put(viewName, statusCode);
    }

    /**
     * Returns the HTTP status codes provided via {@link #setStatusCodes(Properties)}.
     * Keys are view names; values are status codes.
     */
    public Map<String, Integer> getStatusCodesAsMap() {
        return Collections.unmodifiableMap(this.statusCodes);
    }

    /**
     * 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 the 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}
     * for not exposing an exception attribute at all.
     * @see #DEFAULT_EXCEPTION_ATTRIBUTE
     */
    public void setExceptionAttribute(@Nullable 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} 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
     */
    @Override
    @Nullable
    protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response,
            @Nullable 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, first checking against the
     * {@link #setExcludedExceptions(Class[]) "excludedExecptions"}, then searching the
     * {@link #setExceptionMappings "exceptionMappings"}, and finally using the
     * {@link #setDefaultErrorView "defaultErrorView"} as a 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 excluded or none found
     */
    @Nullable
    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 + "'");
            }
            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
     */
    @Nullable
    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 + "' based on 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 == 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} for the servlet container's default
     * (200 in case of a standard error view)
     * @see #setDefaultStatusCode
     * @see #applyStatusCodeIfPossible
     */
    @Nullable
    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 " + 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) {
            mv.addObject(this.exceptionAttribute, ex);
        }
        return mv;
    }

}