/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.wicket.response.filter;
import org.apache.wicket.util.string.AppendingStringBuffer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The EmptySrcAttributeFilter checks if an empty src attribute is found in the response.
*
* Empty src attribute is problematic as it makes some browsers, i.e. firefox, request an URL twice.
* Two issues arise:
*
* 1. Unnecessary server load.
*
* 2. If the browser only renders the first response, some links in the page might be broken as
* wicket rerendered them in the second request and dropped the ones rendered in the first request.
*/
public class EmptySrcAttributeCheckFilter implements IResponseFilter
{
private static final Logger log = LoggerFactory.getLogger(EmptySrcAttributeCheckFilter.class);
/**
* Indicates that an empty src attribute is found in the response.
*/
public static final EmptySrcAttributeCheckFilter INSTANCE = new EmptySrcAttributeCheckFilter();
/**
* @see org.apache.wicket.IResponseFilter#filter(AppendingStringBuffer)
*/
@Override
public AppendingStringBuffer filter(final AppendingStringBuffer responseBuffer)
{
int pos = responseBuffer.indexOf("src=\"\"");
if (pos < 0)
{
pos = responseBuffer.indexOf("src=''");
if (pos < 0)
{
pos = responseBuffer.indexOf("src=\"#\"");
if (pos < 0)
{
pos = responseBuffer.indexOf("src='#'");
}
}
}
if (pos >= 0)
{
log.warn("Empty src attribute found in response:");
int from = Math.max(0, pos - 32);
int to = Math.min(pos + 32, responseBuffer.length());
log.warn("[...]" + responseBuffer.substring(from, to) + "[...]");
}
return responseBuffer;
}
}