Support for Servlet request params with HTTP DELETE

This commit adds FormContentFilter, which is the same as the
HttpPutFormContentFilter but also supports DELETE.

The HttpPutFormContentFilter is now deprecated.

Issue: SPR-16874

spring-web/src/main/java/org/springframework/web/filter/FormContentFilter.java

@@ -0,0 +1,188 @@
+/*
+ * Copyright 2002-2018 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.io.InputStream;
+import java.nio.charset.Charset;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+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.http.HttpInputMessage;
+import org.springframework.http.MediaType;
+import org.springframework.http.converter.FormHttpMessageConverter;
+import org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter;
+import org.springframework.http.server.ServletServerHttpRequest;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.MultiValueMap;
+import org.springframework.util.StringUtils;
+
+/**
+ * {@code Filter} that parses form data for HTTP PUT, PATCH, and DELETE requests
+ * and exposes it as Servlet request parameters. By default the Servlet spec
+ * only requires this for HTTP POST.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.1
+ */
+public class FormContentFilter extends OncePerRequestFilter {
+
+	private static final List<String> HTTP_METHODS = Arrays.asList("PUT", "PATCH", "DELETE");
+
+
+	private FormHttpMessageConverter formConverter = new AllEncompassingFormHttpMessageConverter();
+
+
+	/**
+	 * Set the converter to use for parsing form content.
+	 * <p>By default this is an instance of {@link AllEncompassingFormHttpMessageConverter}.
+	 */
+	public void setFormConverter(FormHttpMessageConverter converter) {
+		Assert.notNull(converter, "FormHttpMessageConverter is required.");
+		this.formConverter = converter;
+	}
+
+	public FormHttpMessageConverter getFormConverter() {
+		return this.formConverter;
+	}
+
+	/**
+	 * The default character set to use for reading form data.
+	 * This is a shortcut for:<br>
+	 * {@code getFormConverter.setCharset(charset)}.
+	 */
+	public void setCharset(Charset charset) {
+		this.formConverter.setCharset(charset);
+	}
+
+
+	@Override
+	protected void doFilterInternal(final HttpServletRequest request, HttpServletResponse response,
+			FilterChain filterChain) throws ServletException, IOException {
+
+		MultiValueMap<String, String> params = parseIfNecessary(request);
+
+		if (params != null && !params.isEmpty()) {
+			filterChain.doFilter(new FormContentRequestWrapper(request, params), response);
+		}
+		else {
+			filterChain.doFilter(request, response);
+		}
+	}
+
+	@Nullable
+	private MultiValueMap<String, String> parseIfNecessary(HttpServletRequest request) throws IOException {
+
+		if (!shouldParse(request)) {
+			return null;
+		}
+
+		HttpInputMessage inputMessage = new ServletServerHttpRequest(request) {
+
+			@Override
+			public InputStream getBody() throws IOException {
+				return request.getInputStream();
+			}
+		};
+
+		return this.formConverter.read(null, inputMessage);
+	}
+
+	private boolean shouldParse(HttpServletRequest request) {
+		if (!HTTP_METHODS.contains(request.getMethod())) {
+			return false;
+		}
+		try {
+			MediaType mediaType = MediaType.parseMediaType(request.getContentType());
+			return MediaType.APPLICATION_FORM_URLENCODED.includes(mediaType);
+		}
+		catch (IllegalArgumentException ex) {
+			return false;
+		}
+	}
+
+
+	private static class FormContentRequestWrapper extends HttpServletRequestWrapper {
+
+		private MultiValueMap<String, String> formParams;
+
+		public FormContentRequestWrapper(HttpServletRequest request, MultiValueMap<String, String> params) {
+			super(request);
+			this.formParams = params;
+		}
+
+		@Override
+		@Nullable
+		public String getParameter(String name) {
+			String queryStringValue = super.getParameter(name);
+			String formValue = this.formParams.getFirst(name);
+			return (queryStringValue != null ? queryStringValue : formValue);
+		}
+
+		@Override
+		public Map<String, String[]> getParameterMap() {
+			Map<String, String[]> result = new LinkedHashMap<>();
+			Enumeration<String> names = getParameterNames();
+			while (names.hasMoreElements()) {
+				String name = names.nextElement();
+				result.put(name, getParameterValues(name));
+			}
+			return result;
+		}
+
+		@Override
+		public Enumeration<String> getParameterNames() {
+			Set<String> names = new LinkedHashSet<>();
+			names.addAll(Collections.list(super.getParameterNames()));
+			names.addAll(this.formParams.keySet());
+			return Collections.enumeration(names);
+		}
+
+		@Override
+		@Nullable
+		public String[] getParameterValues(String name) {
+			String[] parameterValues = super.getParameterValues(name);
+			List<String> formParam = this.formParams.get(name);
+			if (formParam == null) {
+				return parameterValues;
+			}
+			if (parameterValues == null || getQueryString() == null) {
+				return StringUtils.toStringArray(formParam);
+			}
+			else {
+				List<String> result = new ArrayList<>(parameterValues.length + formParam.size());
+				result.addAll(Arrays.asList(parameterValues));
+				result.addAll(formParam);
+				return StringUtils.toStringArray(result);
+			}
+		}
+	}
+
+}

spring-web/src/main/java/org/springframework/web/filter/HttpPutFormContentFilter.java

@@ -58,7 +58,10 @@ import org.springframework.util.StringUtils;
  *
  * @author Rossen Stoyanchev
  * @since 3.1
+ * @deprecated as of 5.1 in favor of {@link FormContentFilter} which is the same
+ * but also handles DELETE.
  */
+@Deprecated
 public class HttpPutFormContentFilter extends OncePerRequestFilter {
 
 	private FormHttpMessageConverter formConverter = new AllEncompassingFormHttpMessageConverter();
@@ -66,7 +69,7 @@ public class HttpPutFormContentFilter extends OncePerRequestFilter {
 
 	/**
 	 * Set the converter to use for parsing form content.
-	 * <p>By default this is an instnace of {@link AllEncompassingFormHttpMessageConverter}.
+	 * <p>By default this is an instance of {@link AllEncompassingFormHttpMessageConverter}.
 	 */
 	public void setFormConverter(FormHttpMessageConverter converter) {
 		Assert.notNull(converter, "FormHttpMessageConverter is required.");