001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.wicket.core.request.handler; 018 019import org.apache.wicket.Application; 020import org.apache.wicket.request.IRequestCycle; 021import org.apache.wicket.request.IRequestHandler; 022import org.apache.wicket.request.http.WebResponse; 023 024/** 025 * The empty AJAX request target does output an empty AJAX response. 026 * <br/> 027 * May be used as a light, "do nothing" Ajax response. 028 * 029 * @author Matej Knopp 030 */ 031public final class EmptyAjaxRequestHandler implements IRequestHandler 032{ 033 /** immutable hashcode. */ 034 private static final int HASH = 17 * 1542323; 035 036 /** singleton instance. */ 037 private static final EmptyAjaxRequestHandler instance = new EmptyAjaxRequestHandler(); 038 039 /** 040 * Construct. 041 */ 042 private EmptyAjaxRequestHandler() 043 { 044 } 045 046 /** 047 * Gets the singleton instance. 048 * 049 * @return the singleton instance 050 */ 051 public static EmptyAjaxRequestHandler getInstance() 052 { 053 return instance; 054 } 055 056 /** {@inheritDoc} */ 057 @Override 058 public void respond(IRequestCycle requestCycle) 059 { 060 WebResponse response = (WebResponse)requestCycle.getResponse(); 061 final String encoding = Application.get() 062 .getRequestCycleSettings() 063 .getResponseRequestEncoding(); 064 065 // Set content type based on markup type for page 066 response.setContentType("text/xml; charset=" + encoding); 067 068 // Make sure it is not cached by a client 069 response.disableCaching(); 070 071 response.write("<?xml version=\"1.0\" encoding=\""); 072 response.write(encoding); 073 response.write("\"?><ajax-response></ajax-response>"); 074 } 075 076 @Override 077 public boolean equals(Object obj) 078 { 079 return obj instanceof EmptyAjaxRequestHandler; 080 } 081 082 @Override 083 public int hashCode() 084 { 085 return HASH; 086 } 087 088 @Override 089 public String toString() 090 { 091 return "EmptyAjaxRequestTarget"; 092 } 093}