improve efficiency of SendResponseFilter#addResponseHeaders() (#1622)

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/post/SendResponseFilter.java

@@ -199,30 +199,28 @@ public class SendResponseFilter extends ZuulFilter {
 	private void addResponseHeaders() {
 		RequestContext context = RequestContext.getCurrentContext();
 		HttpServletResponse servletResponse = context.getResponse();
-		List<Pair<String, String>> zuulResponseHeaders = context.getZuulResponseHeaders();
-		@SuppressWarnings("unchecked")
-		List<String> rd = (List<String>) RequestContext.getCurrentContext()
-				.get("routingDebug");
-		if (rd != null) {
-			StringBuilder debugHeader = new StringBuilder();
-			for (String it : rd) {
-				debugHeader.append("[[[" + it + "]]]");
-			}
-			if (INCLUDE_DEBUG_HEADER.get()) {
+		if (INCLUDE_DEBUG_HEADER.get()) {
+			@SuppressWarnings("unchecked")
+			List<String> rd = (List<String>) context.get("routingDebug");
+			if (rd != null) {
+				StringBuilder debugHeader = new StringBuilder();
+				for (String it : rd) {
+					debugHeader.append("[[[" + it + "]]]");
+				}
 				servletResponse.addHeader("X-Zuul-Debug-Header", debugHeader.toString());
 			}
 		}
+		List<Pair<String, String>> zuulResponseHeaders = context.getZuulResponseHeaders();
 		if (zuulResponseHeaders != null) {
 			for (Pair<String, String> it : zuulResponseHeaders) {
 				servletResponse.addHeader(it.first(), it.second());
 			}
 		}
-		RequestContext ctx = RequestContext.getCurrentContext();
-		Long contentLength = ctx.getOriginContentLength();
 		// Only inserts Content-Length if origin provides it and origin response is not
 		// gzipped
 		if (SET_CONTENT_LENGTH.get()) {
-			if ( contentLength != null && !ctx.getResponseGZipped()) {
+			Long contentLength = context.getOriginContentLength();
+			if ( contentLength != null && !context.getResponseGZipped()) {
 				if(useServlet31) {
 					servletResponse.setContentLengthLong(contentLength);
 				} else {

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/zuul/filters/post/SendResponseFilterTests.java

@@ -19,6 +19,9 @@ package org.springframework.cloud.netflix.zuul.filters.post;
 import java.io.ByteArrayInputStream;
 import javax.servlet.http.HttpServletRequest;
 
+import com.netflix.config.ConfigurationManager;
+import com.netflix.zuul.constants.ZuulConstants;
+import com.netflix.zuul.context.Debug;
 import com.netflix.zuul.context.RequestContext;
 
 import org.junit.After;
@@ -64,6 +67,33 @@ public class SendResponseFilterTests {
 		runFilter(characterEncoding, content, true);
 	}
 
+	@Test
+	public void runWithDebugHeader() throws Exception {
+		ConfigurationManager.getConfigInstance().setProperty(ZuulConstants.ZUUL_INCLUDE_DEBUG_HEADER, true);
+
+		SendResponseFilter filter = createFilter("hello", null, new MockHttpServletResponse(), false);
+		Debug.addRoutingDebug("test");
+		filter.run();
+
+		String debugHeader = RequestContext.getCurrentContext().getResponse()
+				.getHeader("X-Zuul-Debug-Header");
+		assertThat("wrong debug header", debugHeader, equalTo("[[[test]]]"));
+	}
+
+	@Test
+	public void runWithOriginContentLength() throws Exception {
+		ConfigurationManager.getConfigInstance().setProperty(ZuulConstants.ZUUL_SET_CONTENT_LENGTH, true);
+
+		SendResponseFilter filter = createFilter("hello", null, new MockHttpServletResponse(), false);
+		RequestContext.getCurrentContext().setOriginContentLength(6L); // for test
+		RequestContext.getCurrentContext().setResponseGZipped(false);
+		filter.run();
+
+		String contentLength = RequestContext.getCurrentContext().getResponse()
+				.getHeader("Content-Length");
+		assertThat("wrong origin content length", contentLength, equalTo("6"));
+	}
+
 	private void runFilter(String characterEncoding, String content, boolean streamContent) throws Exception {
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		SendResponseFilter filter = createFilter(content, characterEncoding, response, streamContent);