Fix InputStream caching in ContentCachingReqWrapper

Prior to this commit, the ContentCachingRequestWrapper would immediately
consume the wrapped request's InputStream when asked for the cached
content; that caused several issues:

* the request body was read in memory even if it wasn't yet consumed by
the application, leading to inefficiencies.
* when requesting the InputStream, an empty InputStream was returned
since the original was already read.

This case only happened for form POSTs requests.

This commit makes sure that the wrapper does not alter the request
expected behavior:

* when getting the inputstream, it is wrapped in order to cache its
content
* when getting request parameters, the request body is cached and its
inputstream is consumed, as expected

Issue: SPR-12810

spring-web/src/main/java/org/springframework/web/util/ContentCachingRequestWrapper.java

@@ -20,7 +20,6 @@
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;
 import java.util.Arrays;
 import java.util.Enumeration;
@@ -88,14 +87,36 @@ public BufferedReader getReader() throws IOException {
 		return this.reader;
 	}
 
-	/**
-	 * Return the cached request content as a byte array.
-	 */
-	public byte[] getContentAsByteArray() {
+	@Override
+	public String getParameter(String name) {
 		if(this.cachedContent.size() == 0 && isFormPost()) {
 			writeRequestParamsToContent();
 		}
-		return this.cachedContent.toByteArray();
+		return super.getParameter(name);
+	}
+
+	@Override
+	public Map<String, String[]> getParameterMap() {
+		if(this.cachedContent.size() == 0 && isFormPost()) {
+			writeRequestParamsToContent();
+		}
+		return super.getParameterMap();
+	}
+
+	@Override
+	public Enumeration<String> getParameterNames() {
+		if(this.cachedContent.size() == 0 && isFormPost()) {
+			writeRequestParamsToContent();
+		}
+		return super.getParameterNames();
+	}
+
+	@Override
+	public String[] getParameterValues(String name) {
+		if(this.cachedContent.size() == 0 && isFormPost()) {
+			writeRequestParamsToContent();
+		}
+		return super.getParameterValues(name);
 	}
 
 	private boolean isFormPost() {
@@ -107,7 +128,7 @@ private void writeRequestParamsToContent() {
 		try {
 			if (this.cachedContent.size() == 0) {
 				String requestEncoding = getCharacterEncoding();
-				Map<String, String[]> form = getParameterMap();
+				Map<String, String[]> form = super.getParameterMap();
 				for (Iterator<String> nameIterator = form.keySet().iterator(); nameIterator.hasNext(); ) {
 					String name = nameIterator.next();
 					List<String> values = Arrays.asList(form.get(name));
@@ -133,6 +154,13 @@ private void writeRequestParamsToContent() {
 		}
 	}
 
+	/**
+	 * Return the cached request content as a byte array.
+	 */
+	public byte[] getContentAsByteArray() {
+		return this.cachedContent.toByteArray();
+	}
+
 	private class ContentCachingInputStream extends ServletInputStream {
 
 		private final ServletInputStream is;
@@ -150,5 +178,4 @@ public int read() throws IOException {
 			return ch;
 		}
 	}
-
 }

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

@@ -61,6 +61,23 @@ public void requestParams() throws Exception {
 		// 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()));
+		// SPR-12810 : inputstream body should be consumed
+		Assert.assertEquals("", new String(FileCopyUtils.copyToByteArray(wrapper.getInputStream())));
+	}
+
+	// SPR-12810
+	@Test
+	public void inputStreamFormPostRequest() 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);
+
+		byte[] response = FileCopyUtils.copyToByteArray(wrapper.getInputStream());
+		Assert.assertArrayEquals(response, wrapper.getContentAsByteArray());
 	}
 
 }