[test](example) add example for datagen source (#589)

Author: JNSimba

flink-doris-connector/src/test/java/org/apache/doris/flink/example/DataGen2DorisExample.java

@@ -0,0 +1,62 @@
+// 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.doris.flink.example;
+
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
+
+/** This is an example of using Doris sink with DataGen. */
+public class DataGen2DorisExample {
+    public static void main(String[] args) {
+        final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
+        env.setParallelism(1);
+        env.enableCheckpointing(30000);
+        final StreamTableEnvironment tEnv = StreamTableEnvironment.create(env);
+
+        tEnv.executeSql(
+                "CREATE TABLE student_source ("
+                        + "    id INT,"
+                        + "    name STRING,"
+                        + "    age INT"
+                        + ") WITH ("
+                        + "  'connector' = 'datagen',"
+                        + "  'rows-per-second' = '1',"
+                        + "  'fields.name.length' = '20',"
+                        + "  'fields.id.min' = '1',"
+                        + "  'fields.id.max' = '100000',"
+                        + "  'fields.age.min' = '3',"
+                        + "  'fields.age.max' = '30'"
+                        + ");");
+
+        tEnv.executeSql(
+                "CREATE TABLE student_sink ("
+                        + "    id INT,"
+                        + "    name STRING,"
+                        + "    age INT"
+                        + "    ) "
+                        + "    WITH ("
+                        + "      'connector' = 'doris',"
+                        + "      'fenodes' = '127.0.0.1:8030',"
+                        + "      'table.identifier' = 'test.student',"
+                        + "      'username' = 'root',"
+                        + "      'password' = '',"
+                        + "      'sink.label-prefix' = 'doris_label'"
+                        + ")");
+        tEnv.executeSql("INSERT INTO student_sink select * from student_source");
+    }
+}