Avoid loss of body content in AbstractRequestLoggingFilter

Prior to this commit, the `ContentCachingRequestWrapper` class would
cache the response content only if the reponse would be consumed using
its InputStream. In case of a Form request, Spring MVC consumes the
response using the `getParameter*` Servlet API methods. This causes the
cached content to never be written.

This commit makes the `ContentCachingResponseWrapper` write the request
body to the cache buffer by using the `getParameter*` API, thus avoiding
those issues.

Issue: SPR-7913

spring-web/src/test/java/org/springframework/web/util/ContentCachingRequestWrapperTests.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2002-2015 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.util;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.mock.web.test.MockHttpServletRequest;
+import org.springframework.util.FileCopyUtils;
+
+/**
+ * @author Brian Clozel
+ */
+public class ContentCachingRequestWrapperTests {
+
+	protected static final String FORM_CONTENT_TYPE = "application/x-www-form-urlencoded";
+
+	protected static final String CHARSET = "UTF-8";
+
+	private MockHttpServletRequest request;
+
+	@Before
+	public void setup() throws Exception {
+		this.request = new MockHttpServletRequest();
+	}
+
+	@Test
+	public void cachedContent() throws Exception {
+		this.request.setMethod("GET");
+		this.request.setCharacterEncoding(CHARSET);
+		this.request.setContent("Hello World".getBytes(CHARSET));
+
+		ContentCachingRequestWrapper wrapper = new ContentCachingRequestWrapper(this.request);
+		byte[] response = FileCopyUtils.copyToByteArray(wrapper.getInputStream());
+		Assert.assertArrayEquals(response, wrapper.getContentAsByteArray());
+	}
+
+	@Test
+	public void requestParams() throws Exception {
+		this.request.setMethod("POST");
+		this.request.setContentType(FORM_CONTENT_TYPE);
+		this.request.setCharacterEncoding(CHARSET);
+		this.request.setParameter("first", "value");
+		this.request.setParameter("second", new String[] {"foo", "bar"});
+
+		ContentCachingRequestWrapper wrapper = new ContentCachingRequestWrapper(this.request);
+		// getting request parameters will consume the request body
+		Assert.assertFalse(wrapper.getParameterMap().isEmpty());
+		Assert.assertEquals("first=value&second=foo&second=bar", new String(wrapper.getContentAsByteArray()));
+	}
+
+}