Read the error stream when server response is 400 or above

build.gradle

@@ -49,6 +49,7 @@ dependencies {
 	testCompile "org.mockito:mockito-all:1.8.5"
 	testCompile "org.powermock:powermock-module-junit4:1.4.11"
 	testCompile "org.powermock:powermock-api-mockito:1.4.11"
+	testImplementation "org.mock-server:mockserver-netty:5.10.0"
 
 	testImplementation "com.google.truth:truth:1.0.1"
 }

src/main/java/com/pusher/client/util/HttpAuthorizer.java

@@ -14,6 +14,8 @@
 import java.util.Map;
 import javax.net.ssl.HttpsURLConnection;
 
+import static java.net.HttpURLConnection.HTTP_BAD_REQUEST;
+
 /**
  * Used to authenticate a {@link com.pusher.client.channel.PrivateChannel
  * private} or {@link com.pusher.client.channel.PresenceChannel presence}
@@ -110,7 +112,7 @@ public String authorize(final String channelName, final String socketId) throws
             defaultHeaders.putAll(mHeaders);
             // Add in the Content-Length, so it can't be overwritten by mHeaders
             defaultHeaders.put("Content-Length","" + Integer.toString(body.getBytes().length));
-            
+
             for (final String headerName : defaultHeaders.keySet()) {
                 final String headerValue = defaultHeaders.get(headerName);
                 connection.setRequestProperty(headerName, headerValue);
@@ -125,7 +127,7 @@ public String authorize(final String channelName, final String socketId) throws
             wr.close();
 
             // Read response
-            final InputStream is = connection.getInputStream();
+            final InputStream is = getResponseInputStream(connection);
             final BufferedReader rd = new BufferedReader(new InputStreamReader(is));
             String line;
             final StringBuffer response = new StringBuffer();
@@ -146,4 +148,11 @@ public String authorize(final String channelName, final String socketId) throws
             throw new AuthorizationFailureException(e);
         }
     }
+
+    private InputStream getResponseInputStream(HttpURLConnection connection) throws IOException {
+        if (connection.getResponseCode() >= HTTP_BAD_REQUEST) {
+            return connection.getErrorStream();
+        }
+        return connection.getInputStream();
+    }
 }

src/test/java/com/pusher/client/util/HttpAuthorizerTest.java

@@ -1,13 +1,28 @@
 package com.pusher.client.util;
 
+import com.pusher.client.AuthorizationFailureException;
 import junit.framework.Assert;
-
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
 import org.junit.Test;
+import org.mockserver.integration.ClientAndServer;
 
-import com.pusher.client.AuthorizationFailureException;
+import static com.google.common.truth.Truth.assertThat;
+import static java.net.HttpURLConnection.HTTP_FORBIDDEN;
+import static java.net.HttpURLConnection.HTTP_OK;
+import static org.mockserver.integration.ClientAndServer.startClientAndServer;
+import static org.mockserver.model.HttpRequest.request;
+import static org.mockserver.model.HttpResponse.response;
 
 public class HttpAuthorizerTest {
 
+    private static ClientAndServer mockServer;
+
+    @BeforeClass
+    public static void startMockServer() {
+        mockServer = startClientAndServer(1080);
+    }
+
     @Test(expected = IllegalArgumentException.class)
     public void testConstructWithMalformedURLThrowsRuntimeException() {
         new HttpAuthorizer("bad url");
@@ -30,4 +45,40 @@ public void testNon200ResponseThrowsAuthorizationFailureException() {
         final HttpAuthorizer auth = new HttpAuthorizer("https://127.0.0.1/no-way-this-is-a-valid-url");
         auth.authorize("private-fish", "some socket id");
     }
+
+    @Test
+    public void testResponseStatusHttpBadRequestOrAboveThrowsAuthorizationExceptionWithDetailedErrorMessage() {
+        String errorResponseMessage = "No cats allowed";
+        mockServer.when(request().withPath("/no-way-this-is-a-valid-url/wanna-bet"))
+                .respond(response()
+                        .withStatusCode(HTTP_FORBIDDEN)
+                        .withBody(errorResponseMessage)
+                );
+        final HttpAuthorizer auth = new HttpAuthorizer("http://127.0.0.1:1080/no-way-this-is-a-valid-url/wanna-bet");
+
+        try {
+            auth.authorize("private-dog", "barking");
+        } catch (AuthorizationFailureException e) {
+                assertThat(e).hasMessageThat().isEqualTo(errorResponseMessage);
+        }
+    }
+
+    @Test
+    public void testResponseStatusLowerThanHttpBadRequestReturnsSuccessResponse() {
+        String expectedResponseMessage = "Keep on purring";
+        mockServer.when(request().withPath("/no-way-this-is-a-valid-url/wanna-bet"))
+                .respond(response()
+                        .withStatusCode(HTTP_OK)
+                        .withBody(expectedResponseMessage)
+                );
+        final HttpAuthorizer auth = new HttpAuthorizer("http://127.0.0.1:1080/no-way-this-is-a-valid-url/wanna-bet");
+
+        String responseMessage = auth.authorize("private-cat", "purring");
+        assertThat(responseMessage).isEqualTo(expectedResponseMessage);
+    }
+
+    @AfterClass
+    public static void stopMockServer() {
+        mockServer.stop();
+    }
 }