[ZEPPELIN-3014] NPE bug fix and Error message enhancement with Kylin Interpreter

kylin/src/main/java/org/apache/zeppelin/kylin/KylinErrorResponse.java

@@ -0,0 +1,66 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.zeppelin.kylin;
+
+
+import static org.apache.zeppelin.interpreter.Interpreter.logger;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonSyntaxException;
+import org.apache.zeppelin.common.JsonSerializable;
+
+/**
+ * class for Kylin Error Response.
+ */
+class KylinErrorResponse implements JsonSerializable {
+  private static final Gson gson = new Gson();
+
+  private String stacktrace;
+  private String exception;
+  private String url;
+  private String code;
+  private Object data;
+  private String msg;
+
+  public KylinErrorResponse(String stacktrace, String exception, String url,
+      String code, Object data, String msg) {
+    this.stacktrace = stacktrace;
+    this.exception = exception;
+    this.url = url;
+    this.code = code;
+    this.data = data;
+    this.msg = msg;
+  }
+
+  public String getException() {
+    return exception;
+  }
+
+  public String toJson() {
+    return gson.toJson(this);
+  }
+
+  public static KylinErrorResponse fromJson(String json) {
+    try {
+      return gson.fromJson(json, KylinErrorResponse.class);
+    } catch (JsonSyntaxException ex) {
+      return null;
+    }
+  }
+
+}

kylin/src/main/java/org/apache/zeppelin/kylin/KylinInterpreter.java

@@ -18,6 +18,7 @@
 package org.apache.zeppelin.kylin;
 
 import org.apache.commons.codec.binary.Base64;
+import org.apache.commons.io.IOUtils;
 import org.apache.http.HttpResponse;
 import org.apache.http.client.HttpClient;
 import org.apache.http.client.methods.HttpPost;
@@ -30,9 +31,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.io.BufferedReader;
 import java.io.IOException;
-import java.io.InputStreamReader;
 import java.util.List;
 import java.util.Properties;
 import java.util.regex.Matcher;
@@ -168,26 +167,41 @@ public String getSQL(String cmd) {
   private InterpreterResult executeQuery(String sql) throws IOException {
 
     HttpResponse response = prepareRequest(sql);
+    String result;
 
-    if (response.getStatusLine().getStatusCode() != 200) {
-      logger.error("failed to execute query: " + response.getEntity().getContent().toString());
-      return new InterpreterResult(InterpreterResult.Code.ERROR,
-          "Failed : HTTP error code " + response.getStatusLine().getStatusCode());
-    }
-
-    BufferedReader br = new BufferedReader(
-        new InputStreamReader((response.getEntity().getContent())));
-    StringBuilder sb = new StringBuilder();
+    try {
+      int code = response.getStatusLine().getStatusCode();
+      result = IOUtils.toString(response.getEntity().getContent(), "UTF-8");
+
+      if (code != 200) {
+        StringBuilder errorMessage = new StringBuilder("Failed : HTTP error code " + code);
+        logger.error("Failed to execute query: " + result);
+
+        KylinErrorResponse kylinErrorResponse = KylinErrorResponse.fromJson(result);
+        if (kylinErrorResponse == null) {
+          logger.error("Cannot get json from string: " + result);
+          // when code is 401, the response is html, not json
+          if (code == 401) {
+            errorMessage.append(". Error message: Unauthorized. This request requires "
+                + "HTTP authentication. Please make sure your have set your credentials"
+                + " correctly.");
+          } else {
+            errorMessage.append(". Error message: " + result);
+          }
+        } else {
+          String exception = kylinErrorResponse.getException();
+          logger.error("The exception is " + exception);
+          errorMessage.append(". Error message: " + exception);
+        }
 
-    String output;
-    logger.info("Output from Server .... \n");
-    while ((output = br.readLine()) != null) {
-      logger.info(output);
-      sb.append(output).append('\n');
+        return new InterpreterResult(InterpreterResult.Code.ERROR, errorMessage.toString());
+      }
+    } catch (NullPointerException | IOException e) {
+      throw new IOException(e);
     }
-    InterpreterResult rett = new InterpreterResult(InterpreterResult.Code.SUCCESS, 
-        formatResult(sb.toString()));
-    return rett;
+
+    return new InterpreterResult(InterpreterResult.Code.SUCCESS,
+        formatResult(result));
   }
 
   String formatResult(String msg) {
@@ -205,17 +219,20 @@ String formatResult(String msg) {
       table = mr.group(1);
     }
 
-    String[] row = table.split("],\\[");
-    for (int i = 0; i < row.length; i++) {
-      String[] col = row[i].split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)", -1);
-      for (int j = 0; j < col.length; j++) {
-        if (col[j] != null) {
-          col[j] = col[j].replaceAll("^\"|\"$", "");
+    if (table != null && !table.isEmpty()) {
+      String[] row = table.split("],\\[");
+      for (int i = 0; i < row.length; i++) {
+        String[] col = row[i].split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)", -1);
+        for (int j = 0; j < col.length; j++) {
+          if (col[j] != null) {
+            col[j] = col[j].replaceAll("^\"|\"$", "");
+          }
+          res.append(col[j] + " \t");
         }
-        res.append(col[j] + " \t");
+        res.append(" \n");
       }
-      res.append(" \n");
     }
+
     return res.toString();
   }