/*
* JBoss, Home of Professional Open Source
* Copyright 2012, Red Hat, Inc., and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* 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 ${package}.util;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.regex.Pattern;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
/**
* <p>This filter wraps qualified requests for JSON content with that standard JSONP padding. This makes these calls accessible
* cross-domain using standard JSONP approaches.
* </p>
* <p>To qualify for wrapping the request must be made to the <i>/rest/*</i> path, and contain a query parameter call
* <i>jsoncallback</> that defines the JSONP callback method to use with the response.
* </p>
* @author balunasj
*
*/
@WebFilter("/rest/*")
public class JSONPRequestFilter implements Filter {
//The callback method to use
private static final String CALLBACK_METHOD = "jsonpcallback";
//This is a simple safe pattern check for the callback method
public static final Pattern SAFE_PRN = Pattern.compile("[a-zA-Z0-9_\\.]+");
public static final String CONTENT_TYPE= "application/javascript";
@Override
public void init(FilterConfig config) throws ServletException {
//Nothing needed
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
ServletException {
if (!(request instanceof HttpServletRequest)) {
throw new ServletException("Only HttpServletRequest requests are supported");
}
final HttpServletRequest httpRequest = (HttpServletRequest) request;
final HttpServletResponse httpResponse = (HttpServletResponse) response;
//extract the callback method from the request query parameters
String callback = getCallbackMethod(httpRequest);
if (!isJSONPRequest(callback)) {
//Request is not a JSONP request move on
chain.doFilter(request, response);
}else{
//Need to check if the callback method is safe
if (!SAFE_PRN.matcher(callback).matches()) {
throw new ServletException("JSONP Callback method '" + CALLBACK_METHOD + "' parameter not valid function");
}
//Will stream updated response
final ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
//Create a custom response wrapper to adding in the padding
HttpServletResponseWrapper responseWrapper = new HttpServletResponseWrapper(httpResponse) {
@Override
public ServletOutputStream getOutputStream() throws IOException {
return new ServletOutputStream() {
@Override
public void write(int b) throws IOException {
byteStream.write(b);
}
};
}
@Override
public PrintWriter getWriter() throws IOException {
return new PrintWriter(byteStream);
}
};
//Process the rest of the filter chain, including the JAX-RS request
chain.doFilter(request, responseWrapper);
//Override response content and encoding
response.setContentType(CONTENT_TYPE);
response.setCharacterEncoding("UTF-8");
//Write the padded updates to the output stream.
response.getOutputStream().write((callback + "(").getBytes());
response.getOutputStream().write(byteStream.toByteArray());
response.getOutputStream().write(");".getBytes());
}
}
private String getCallbackMethod(HttpServletRequest httpRequest) {
return httpRequest.getParameter(CALLBACK_METHOD);
}
private boolean isJSONPRequest(String callbackMethod) {
//A simple check to see if the query parameter has been set.
return (callbackMethod != null && callbackMethod.length() > 0);
}
@Override
public void destroy() {
//Nothing to do
}
}