Update content length after rebuilding form body

spring-cloud-gateway-server-webmvc/src/main/java/org/springframework/cloud/gateway/server/mvc/filter/FormFilter.java

@@ -44,6 +44,7 @@
 
 import org.springframework.cloud.gateway.server.mvc.common.MvcUtils;
 import org.springframework.core.Ordered;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
 import org.springframework.lang.Nullable;
@@ -55,6 +56,7 @@
  * parameters and form parameters the same, but a proxy should not care.
  *
  * @author Spencer Gibb
+ * @author Hutiefang Hu
  */
 @SuppressWarnings("unchecked")
 public class FormFilter implements Filter, Ordered {
@@ -141,9 +143,10 @@ static HttpServletRequest getRequestWithBodyFromRequestParameters(HttpServletReq
 		}
 		writer.flush();
 
+		byte[] body = bos.toByteArray();
 		ByteArrayServletInputStream servletInputStream = new ByteArrayServletInputStream(
-				new ByteArrayInputStream(bos.toByteArray()));
-		return new FormContentRequestWrapper(request, queryParams) {
+				new ByteArrayInputStream(body));
+		return new FormContentRequestWrapper(request, queryParams, body.length) {
 			@Override
 			public ServletInputStream getInputStream() throws IOException {
 				return servletInputStream;
@@ -186,9 +189,50 @@ private static class FormContentRequestWrapper extends HttpServletRequestWrapper
 
 		private final MultiValueMap<String, String> queryParams;
 
-		FormContentRequestWrapper(HttpServletRequest request, MultiValueMap<String, String> params) {
+		private final int contentLength;
+
+		private final boolean contentLengthHeaderPresent;
+
+		FormContentRequestWrapper(HttpServletRequest request, MultiValueMap<String, String> params, int contentLength) {
 			super(request);
 			this.queryParams = params;
+			this.contentLength = contentLength;
+			this.contentLengthHeaderPresent = request.getHeader(HttpHeaders.CONTENT_LENGTH) != null;
+		}
+
+		@Override
+		public int getContentLength() {
+			return this.contentLength;
+		}
+
+		@Override
+		public long getContentLengthLong() {
+			return this.contentLength;
+		}
+
+		@Override
+		@Nullable
+		public String getHeader(String name) {
+			if (this.contentLengthHeaderPresent && HttpHeaders.CONTENT_LENGTH.equalsIgnoreCase(name)) {
+				return String.valueOf(this.contentLength);
+			}
+			return super.getHeader(name);
+		}
+
+		@Override
+		public Enumeration<String> getHeaders(String name) {
+			if (this.contentLengthHeaderPresent && HttpHeaders.CONTENT_LENGTH.equalsIgnoreCase(name)) {
+				return Collections.enumeration(List.of(String.valueOf(this.contentLength)));
+			}
+			return super.getHeaders(name);
+		}
+
+		@Override
+		public int getIntHeader(String name) {
+			if (this.contentLengthHeaderPresent && HttpHeaders.CONTENT_LENGTH.equalsIgnoreCase(name)) {
+				return this.contentLength;
+			}
+			return super.getIntHeader(name);
 		}
 
 		@Override

spring-cloud-gateway-server-webmvc/src/test/java/org/springframework/cloud/gateway/server/mvc/filter/FormFilterTests.java

@@ -21,6 +21,7 @@
 import java.net.URLDecoder;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Enumeration;
 import java.util.List;
 
@@ -33,6 +34,7 @@
 import org.mockito.ArgumentCaptor;
 import org.mockito.Mockito;
 
+import org.springframework.http.HttpHeaders;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
 import org.springframework.util.LinkedMultiValueMap;
@@ -45,9 +47,61 @@
 
 /**
  * @author shawyeok
+ * @author Hutiefang Hu
  */
 class FormFilterTests {
 
+	@Test
+	void updateContentLengthAfterRebuildingFormBody() throws ServletException, IOException {
+		byte[] originalBody = "formArg=!".getBytes(StandardCharsets.UTF_8);
+		MockHttpServletRequest request = MockMvcRequestBuilders.post(URI.create("http://localhost/test"))
+			.contentType("application/x-www-form-urlencoded")
+			.header(HttpHeaders.CONTENT_LENGTH, originalBody.length)
+			.content(originalBody)
+			.buildRequest(null);
+		HttpServletResponse response = Mockito.mock(HttpServletResponse.class);
+		FilterChain chain = Mockito.mock(FilterChain.class);
+
+		new FormFilter().doFilter(request, response, chain);
+
+		ArgumentCaptor<ServletRequest> captor = ArgumentCaptor.forClass(ServletRequest.class);
+		verify(chain).doFilter(captor.capture(), Mockito.eq(response));
+		HttpServletRequest wrappedRequest = (HttpServletRequest) captor.getValue();
+		byte[] rebuiltBody = "formArg=%21".getBytes(StandardCharsets.UTF_8);
+		assertThat(StreamUtils.copyToByteArray(wrappedRequest.getInputStream())).isEqualTo(rebuiltBody);
+		assertThat(wrappedRequest.getContentLength()).isEqualTo(rebuiltBody.length);
+		assertThat(wrappedRequest.getContentLengthLong()).isEqualTo(rebuiltBody.length);
+		assertThat(wrappedRequest.getHeader(HttpHeaders.CONTENT_LENGTH)).isEqualTo(String.valueOf(rebuiltBody.length));
+		assertThat(Collections.list(wrappedRequest.getHeaders(HttpHeaders.CONTENT_LENGTH)))
+			.containsExactly(String.valueOf(rebuiltBody.length));
+		assertThat(wrappedRequest.getIntHeader("content-length")).isEqualTo(rebuiltBody.length);
+		assertThat(Collections.list(wrappedRequest.getHeaderNames())).contains(HttpHeaders.CONTENT_LENGTH);
+	}
+
+	@Test
+	void preserveMissingContentLengthHeaderAfterRebuildingFormBody() throws ServletException, IOException {
+		MockHttpServletRequest request = MockMvcRequestBuilders.post(URI.create("http://localhost/test"))
+			.contentType("application/x-www-form-urlencoded")
+			.content("formArg=!")
+			.buildRequest(null);
+		request.removeHeader(HttpHeaders.CONTENT_LENGTH);
+		HttpServletResponse response = Mockito.mock(HttpServletResponse.class);
+		FilterChain chain = Mockito.mock(FilterChain.class);
+
+		new FormFilter().doFilter(request, response, chain);
+
+		ArgumentCaptor<ServletRequest> captor = ArgumentCaptor.forClass(ServletRequest.class);
+		verify(chain).doFilter(captor.capture(), Mockito.eq(response));
+		HttpServletRequest wrappedRequest = (HttpServletRequest) captor.getValue();
+		int rebuiltContentLength = "formArg=%21".getBytes(StandardCharsets.UTF_8).length;
+		assertThat(wrappedRequest.getContentLength()).isEqualTo(rebuiltContentLength);
+		assertThat(wrappedRequest.getContentLengthLong()).isEqualTo(rebuiltContentLength);
+		assertThat(wrappedRequest.getHeader("content-length")).isNull();
+		assertThat(Collections.list(wrappedRequest.getHeaders("content-length"))).isEmpty();
+		assertThat(wrappedRequest.getIntHeader("content-length")).isEqualTo(-1);
+		assertThat(Collections.list(wrappedRequest.getHeaderNames())).doesNotContain(HttpHeaders.CONTENT_LENGTH);
+	}
+
 	@Test
 	void hideFormParameterFromParameterMap() throws ServletException, IOException {
 		FormFilter filter = new FormFilter();