http://www.jboss.org/undertow-parent/undertow-servlet: Undertow (JBoss by Red Hat) 
/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * 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 io.undertow.servlet.api;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import io.undertow.server.HttpServerExchange;


An exception handler allows you to perform custom actions when an exception propagates out of the servlet
handler chain. The default handler will simply log the exception, however it is possible to write custom
handlers to handle the error however you want. A common use for this would be to change the log format for
exceptions, or possibly suppress the logging for certain exceptions types.


Implementations of this interface may also choose to suppress error page handler, and handle error page generation
internally by returning true

Author:Stuart Douglas
/**
 * An exception handler allows you to perform custom actions when an exception propagates out of the servlet
 * handler chain. The default handler will simply log the exception, however it is possible to write custom
 * handlers to handle the error however you want. A common use for this would be to change the log format for
 * exceptions, or possibly suppress the logging for certain exceptions types.
 * <p>
 * Implementations of this interface may also choose to suppress error page handler, and handle error page generation
 * internally by returning <code>true</code>
 *
 * @author Stuart Douglas
 */
public interface ExceptionHandler {

    
Handles an exception. If this method returns true then the request/response cycle is considered to be finished,
and no further action will take place, if this returns false then standard error page redirect will take place.
The default implementation of this simply logs the exception and returns false, allowing error page and async context
error handling to proceed as normal.

Params:
  • exchange –        The exchange
  • request –         The request
  • response –        The response
  • throwable –       The exception
Returns:true true if the error was handled by this method
/**
     * Handles an exception. If this method returns true then the request/response cycle is considered to be finished,
     * and no further action will take place, if this returns false then standard error page redirect will take place.
     *
     * The default implementation of this simply logs the exception and returns false, allowing error page and async context
     * error handling to proceed as normal.
     *
     * @param exchange        The exchange
     * @param request         The request
     * @param response        The response
     * @param throwable       The exception
     * @return <code>true</code> true if the error was handled by this method
     */
    boolean handleThrowable(final HttpServerExchange exchange, ServletRequest request, ServletResponse response, Throwable throwable);
}