Changes done to handle empty tables.

Author: vikasrathee-cs

src/main/java/io/cdap/plugin/servicenow/apiclient/ServiceNowTableAPIClientImpl.java

@@ -533,6 +533,7 @@ public Map<String, String> getRecordFromServiceNowTable(String tableName, String
    * @param tableName       The name of the table for which the schema is being constructed.
    *
    * @return A {@link Schema} object representing the table structure as interpreted from the Schema API.
+   * Return null if table has no  records
    *
    * @throws RuntimeException if the schema response is null or contains no result.
    */
@@ -544,8 +545,9 @@ private Schema prepareStringBasedSchema(RestAPIResponse restAPIResponse, List<Se
       for (String key : firstRecord.keySet()) {
         columns.add(new ServiceNowColumn(key, "string"));
       }
+      return SchemaBuilder.constructSchema(tableName, columns);
     }
-    return SchemaBuilder.constructSchema(tableName, columns);
+    return null;
   }
 
 

src/main/java/io/cdap/plugin/servicenow/source/ServiceNowInputFormat.java

@@ -108,6 +108,9 @@ private static ServiceNowTableInfo getTableMetaData(String tableName,
     int recordCount = 0;
     try {
       schema = restApi.fetchTableSchema(tableName, valueType);
+      if (schema == null) {
+        return null;
+      }
       recordCount = restApi.getTableRecordCount(tableName);
     } catch (ServiceNowAPIException e) {
       throw new RuntimeException(String.format("Error in fetching table metadata due to reason: %s", e.getMessage()),

src/main/java/io/cdap/plugin/servicenow/source/ServiceNowMultiInputFormat.java

@@ -104,6 +104,9 @@ private static ServiceNowTableInfo getTableMetaData(String tableName, ServiceNow
       // This is used for ServiceNowMultiSource and provides structure of the table and being dependent on
       // connector config, makes it a read only function
       schema = restApi.fetchTableSchema(tableName, SourceValueType.SHOW_ACTUAL_VALUE);
+      if (schema == null) {
+        return null;
+      }
       recordCount = restApi.getTableRecordCount(tableName);
     } catch (ServiceNowAPIException e) {
       throw new RuntimeException(e);

src/main/java/io/cdap/plugin/servicenow/source/ServiceNowMultiRecordReader.java

@@ -105,6 +105,9 @@ private void fetchSchema(ServiceNowTableAPIClientImpl restApi) {
     // Fetch the schema
     try {
       Schema tempSchema = restApi.fetchTableSchema(tableName, multiSourcePluginConf.getValueType());
+      if (tempSchema == null) {
+        return;
+      }
       tableFields = tempSchema.getFields();
       List<Schema.Field> schemaFields = new ArrayList<>(tableFields);
       schemaFields.add(Schema.Field.of(tableNameField, Schema.of(Schema.Type.STRING)));

src/test/java/io/cdap/plugin/servicenow/source/ServiceNowInputFormatTest.java

@@ -17,13 +17,13 @@
 
 package io.cdap.plugin.servicenow.source;
 
+import io.cdap.cdap.api.data.schema.Schema;
 import io.cdap.plugin.servicenow.apiclient.ServiceNowTableAPIClientImpl;
 import io.cdap.plugin.servicenow.connector.ServiceNowConnectorConfig;
 import io.cdap.plugin.servicenow.restapi.RestAPIResponse;
 import io.cdap.plugin.servicenow.util.SourceApplication;
 import io.cdap.plugin.servicenow.util.SourceQueryMode;
 import io.cdap.plugin.servicenow.util.SourceValueType;
-import org.apache.http.HttpStatus;
 import org.apache.http.client.methods.CloseableHttpResponse;
 import org.apache.http.impl.client.CloseableHttpClient;
 import org.apache.http.impl.client.HttpClientBuilder;
@@ -138,9 +138,14 @@ public void testFetchTableInfo() throws Exception {
       "        }\n" +
       "    ]\n" +
       "}";
+    String schemaString = "{\"type\":\"record\",\"name\":\"ServiceNowColumnMetaData\",\"fields\":[{\"name\":" +
+      "\"backgroundElementId\",\"type\":\"long\"},{\"name\":\"bgOrderPos\",\"type\":\"long\"},{\"name\":" +
+      "\"description\",\"type\":[\"string\",\"null\"]},{\"name\":\"userId\",\"type\":\"string\"}]}";
+    Schema schema = Schema.parseJson(schemaString);
     RestAPIResponse restAPIResponse = new RestAPIResponse(headers, responseBody, null);
     Mockito.when(restApi.executeGetWithRetries(Mockito.any())).thenReturn(restAPIResponse);
     Mockito.when(restApi.parseResponseToResultListOfMap(restAPIResponse.getResponseBody())).thenReturn(result);
+    Mockito.when(restApi.fetchTableSchema("table", SourceValueType.SHOW_ACTUAL_VALUE)).thenReturn(schema);
     OAuthClient oAuthClient = Mockito.mock(OAuthClient.class);
     PowerMockito.whenNew(OAuthClient.class).
       withArguments(Mockito.any(URLConnectionClient.class)).thenReturn(oAuthClient);
@@ -237,9 +242,18 @@ public void testFetchTableInfoReportingMode() throws Exception {
       "        }\n" +
       "    ]\n" +
       "}";
+    String schemaString = "{\"type\":\"record\",\"name\":\"ServiceNowColumnMetaData\",\"fields\":[{\"name\":" +
+      "\"backgroundElementId\",\"type\":\"long\"},{\"name\":\"bgOrderPos\",\"type\":\"long\"},{\"name\":" +
+      "\"description\",\"type\":[\"string\",\"null\"]},{\"name\":\"userId\",\"type\":\"string\"}]}";
+    Schema schema = Schema.parseJson(schemaString);
     RestAPIResponse restAPIResponse = new RestAPIResponse(headers, responseBody, null);
     Mockito.when(restApi.executeGetWithRetries(Mockito.any())).thenReturn(restAPIResponse);
     Mockito.when(restApi.parseResponseToResultListOfMap(restAPIResponse.getResponseBody())).thenReturn(result);
+    Mockito.when(restApi.fetchTableSchema("proc_po", SourceValueType.SHOW_ACTUAL_VALUE)).thenReturn(schema);
+    Mockito.when(restApi.fetchTableSchema("proc_po_item",
+                                          SourceValueType.SHOW_ACTUAL_VALUE)).thenReturn(schema);
+    Mockito.when(restApi.fetchTableSchema("proc_rec_slip",
+                                          SourceValueType.SHOW_ACTUAL_VALUE)).thenReturn(schema);
     OAuthClient oAuthClient = Mockito.mock(OAuthClient.class);
     PowerMockito.whenNew(OAuthClient.class).
       withArguments(Mockito.any(URLConnectionClient.class)).thenReturn(oAuthClient);
@@ -260,7 +274,7 @@ public void testFetchTableInfoReportingMode() throws Exception {
       thenReturn(response);
     SourceApplication application = SourceApplication.PROCUREMENT;
     SourceValueType valueType = SourceValueType.SHOW_ACTUAL_VALUE;
-    Assert.assertEquals(4, ServiceNowInputFormat.fetchTableInfo(mode, connectorConfig, "table",
+    Assert.assertEquals(3, ServiceNowInputFormat.fetchTableInfo(mode, connectorConfig, "table",
                                                                 application, valueType, true).size());
   }