Fix empty response body when using Spring RestTemplate with LogbookCl…

…ientHttpRequestInterceptor (#948)

* Add test which ensures that response body is not empty. This test is currently failing.

* Adapt tests to ensure the support of empty and non-empty GET responses.

* Fixed null response body by resetting response body stream when copying for caching.

Co-authored-by: Thomas Wimmer <thomas.wimmer@netcetera.com>

logbook-spring/src/main/java/org/zalando/logbook/spring/RemoteResponse.java

@@ -9,6 +9,7 @@
 
 import javax.annotation.Nullable;
 import java.io.IOException;
+import java.io.InputStream;
 import java.nio.charset.Charset;
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicReference;
@@ -60,8 +61,9 @@ public State without() {
 
         @Override
         public State buffer(final ClientHttpResponse response) throws IOException {
-            response.getBody();
-            byte[] data = ByteStreams.toByteArray(response.getBody());
+            InputStream responseBodyStream = response.getBody();
+            byte[] data = ByteStreams.toByteArray(responseBodyStream);
+            responseBodyStream.reset();
             return new Buffering(data);
         }
 

logbook-spring/src/test/java/org/zalando/logbook/spring/LogbookClientHttpRequestInterceptorTest.java

@@ -25,6 +25,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 import static org.springframework.test.web.client.ExpectedCount.once;
@@ -79,7 +80,7 @@ void mockHttpVerify() {
     void get200() throws IOException {
         serviceServer.expect(once(), requestTo("/test/get")).andExpect(method(HttpMethod.GET))
                 .andRespond(withSuccess().body("response"));
-        restTemplate.getForObject("/test/get", Void.class);
+        restTemplate.getForObject("/test/get", String.class);
 
         verify(writer).write(precorrelationCaptor.capture(), requestCaptor.capture());
         verify(writer).write(correlationCaptor.capture(), responseCaptor.capture());
@@ -95,6 +96,26 @@ void get200() throws IOException {
         assertTrue(responseCaptor.getValue().contains("response"));
     }
 
+    @Test
+    void get200WithEmptyResponseBody(){
+        serviceServer.expect(once(), requestTo("/test/get")).andExpect(method(HttpMethod.GET))
+                .andRespond(withSuccess());
+
+        restTemplate.getForObject("/test/get", Void.class);
+    }
+
+    @Test
+    void get200WithNonEmptyResponseBody() {
+        String expectedResponseBody = "response";
+        serviceServer.expect(once(), requestTo("/test/get")).andExpect(method(HttpMethod.GET))
+                .andRespond(withSuccess().body(expectedResponseBody));
+
+        String actualResponseBody = restTemplate.getForObject("/test/get", String.class);
+
+        assertNotNull(actualResponseBody);
+        assertEquals(expectedResponseBody, actualResponseBody);
+    }
+
     @Test
     void post400() throws IOException {
         serviceServer.expect(once(), requestTo("/test/post")).andExpect(method(HttpMethod.POST))