/*
* Copyright 2002-2010 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
*
* 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.springframework.web.filter;
import java.io.IOException;
import java.util.Locale;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
/**
* {@link javax.servlet.Filter} that converts posted method parameters into HTTP methods,
* retrievable via {@link HttpServletRequest#getMethod()}. Since browsers currently only
* support GET and POST, a common technique - used by the Prototype library, for instance -
* is to use a normal POST with an additional hidden form field (<code>_method</code>)
* to pass the "real" HTTP method along. This filter reads that parameter and changes
* the {@link HttpServletRequestWrapper#getMethod()} return value accordingly.
*
* <p>The name of the request parameter defaults to <code>_method</code>, but can be
* adapted via the {@link #setMethodParam(String) methodParam} property.
*
* <p><b>NOTE: This filter needs to run after multipart processing in case of a multipart
* POST request, due to its inherent need for checking a POST body parameter.</b>
* So typically, put a Spring {@link org.springframework.web.multipart.support.MultipartFilter}
* <i>before</i> this HiddenHttpMethodFilter in your <code>web.xml</code> filter chain.
*
* @author Arjen Poutsma
* @since 3.0
*/
public class HiddenHttpMethodFilter extends OncePerRequestFilter {
/** Default method parameter: <code>_method</code> */
public static final String DEFAULT_METHOD_PARAM = "_method";
private String methodParam = DEFAULT_METHOD_PARAM;
/**
* Set the parameter name to look for HTTP methods.
* @see #DEFAULT_METHOD_PARAM
*/
public void setMethodParam(String methodParam) {
Assert.hasText(methodParam, "'methodParam' must not be empty");
this.methodParam = methodParam;
}
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
String paramValue = request.getParameter(this.methodParam);
if ("POST".equals(request.getMethod()) && StringUtils.hasLength(paramValue)) {
String method = paramValue.toUpperCase(Locale.ENGLISH);
HttpServletRequest wrapper = new HttpMethodRequestWrapper(request, method);
filterChain.doFilter(wrapper, response);
}
else {
filterChain.doFilter(request, response);
}
}
/**
* Simple {@link HttpServletRequest} wrapper that returns the supplied method for
* {@link HttpServletRequest#getMethod()}.
*/
private static class HttpMethodRequestWrapper extends HttpServletRequestWrapper {
private final String method;
public HttpMethodRequestWrapper(HttpServletRequest request, String method) {
super(request);
this.method = method;
}
@Override
public String getMethod() {
return this.method;
}
}
}
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