Added support for array error messages (#436).

src/main/java/org/gitlab4j/api/GitLabApiException.java

@@ -101,10 +101,23 @@ public class GitLabApiException extends Exception {
 
                             if (buf.length() > 0) {
                                 this.message = "The following fields have validation errors: " + buf.toString();
-                            }    
+                            }
 
-                        } else {
+                        } else if (jsonMessage.isArray()) {
+
+                           List<String> values = new ArrayList<>();
+                           for (JsonNode value : jsonMessage) {
+                                values.add(value.asText());
+                           }
+
+                           if (values.size() > 0) {
+                               this.message = String.join("\n", values);
+                           }
+
+                        } else if (jsonMessage.isTextual()) {
                             this.message = jsonMessage.asText();
+                        } else {
+                            this.message = jsonMessage.toString();
                         }
 
                     } else {

src/test/java/org/gitlab4j/api/MockResponse.java

@@ -34,6 +34,10 @@ public class MockResponse extends Response {
     private String itemJson;
     private String listJson;
 
+    private int status = 200;
+    private Status statusInfo = Status.OK;
+    private MediaType mediaType = MediaType.APPLICATION_JSON_TYPE;
+
     public MockResponse() {
     }
 
@@ -41,6 +45,13 @@ public class MockResponse extends Response {
         init(type, itemFilename, listFilename);
     }
 
+    public <T> MockResponse(Status statusInfo, String jsonString) {
+        this.statusInfo = statusInfo;
+        this.status = statusInfo.getStatusCode();
+        this.itemJson = jsonString;
+        this.responseItem = jsonString;
+    }
+
     public <T> void init(Class<T> type, String itemFilename, String listFilename) throws Exception {
 
         if (itemFilename != null) {
@@ -110,11 +121,25 @@ public class MockResponse extends Response {
         }
     }
 
+    @Override
+    public boolean hasEntity() {
+        return (itemJson != null || listJson != null);
+    }
+
     @Override
     public int getStatus() {
-        return (200);
+        return (status);
     }
 
+    @Override
+    public StatusType getStatusInfo() {
+        return (statusInfo);
+    }
+
+    @Override
+    public MediaType getMediaType() {
+        return (mediaType);
+    }
 
     /**************************************************************************************************
      * The remaining methods are stubbed so we can create an instance of this class. They are simply
@@ -122,11 +147,6 @@ public class MockResponse extends Response {
      * on Java 11+ and did not wish to pull in the JAXB module even for testing. 
      **************************************************************************************************/
 
-    @Override
-    public StatusType getStatusInfo() {
-        return null;
-    }
-
     @Override
     public <T> T readEntity(Class<T> entityType, Annotation[] annotations) {
         return null;
@@ -137,11 +157,6 @@ public class MockResponse extends Response {
         return null;
     }
 
-    @Override
-    public boolean hasEntity() {
-        return false;
-    }
-
     @Override
     public boolean bufferEntity() {
         return false;
@@ -151,11 +166,6 @@ public class MockResponse extends Response {
     public void close() {
     }
 
-    @Override
-    public MediaType getMediaType() {
-        return null;
-    }
-
     @Override
     public Locale getLanguage() {
         return null;

src/test/java/org/gitlab4j/api/TestGitLabApiException.java

@@ -10,6 +10,8 @@ import static org.junit.Assume.assumeNotNull;
 import java.util.List;
 import java.util.Map;
 
+import javax.ws.rs.core.Response.Status;
+
 import org.gitlab4j.api.models.Project;
 import org.gitlab4j.api.models.Visibility;
 import org.junit.AfterClass;
@@ -31,6 +33,12 @@ import org.junit.experimental.categories.Category;
 public class TestGitLabApiException extends AbstractIntegrationTest {
 
     private static final String TEST_PROJECT_NAME_DUPLICATE = "test-gitlab4j-create-project-duplicate";
+    private static final String TEST_ERROR_MESSAGE = "Another open merge request already exists for this source branch: !6";
+    private static final String TEST_RESPONSE_JSON_STRING = "{\"message\": \"" + TEST_ERROR_MESSAGE + "\"}";
+    private static final String TEST_RESPONSE_JSON_ARRAY = "{\"message\": [\"" + TEST_ERROR_MESSAGE + "\"]}";
+    private static final String TEST_RESPONSE_ERROR_JSON_STRING = "{\"error\": \"" + TEST_ERROR_MESSAGE + "\"}";
+
+
     private static GitLabApi gitLabApi;
 
     public TestGitLabApiException() {
@@ -98,4 +106,28 @@ public class TestGitLabApiException extends AbstractIntegrationTest {
             assertFalse(validationErrors.isEmpty());
         }
     }
+
+    @Test
+    public void testStringMessage() throws GitLabApiException {
+        final MockResponse response = new MockResponse(Status.BAD_REQUEST, TEST_RESPONSE_JSON_STRING);
+        GitLabApiException glae = new GitLabApiException(response);
+        assertEquals(Status.BAD_REQUEST.getStatusCode(), glae.getHttpStatus());
+        assertEquals(TEST_ERROR_MESSAGE, glae.getMessage());
+    }
+
+    @Test
+    public void testArrayMessage() throws GitLabApiException {
+        final MockResponse response = new MockResponse(Status.BAD_REQUEST, TEST_RESPONSE_JSON_ARRAY);
+        GitLabApiException glae = new GitLabApiException(response);
+        assertEquals(Status.BAD_REQUEST.getStatusCode(), glae.getHttpStatus());
+        assertEquals(TEST_ERROR_MESSAGE, glae.getMessage());
+    }
+
+    @Test
+    public void testError() throws GitLabApiException {
+        final MockResponse response = new MockResponse(Status.BAD_REQUEST, TEST_RESPONSE_ERROR_JSON_STRING);
+        GitLabApiException glae = new GitLabApiException(response);
+        assertEquals(Status.BAD_REQUEST.getStatusCode(), glae.getHttpStatus());
+        assertEquals(TEST_ERROR_MESSAGE, glae.getMessage());
+    }
 }