/*
* 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.flink.table.examples.java;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.TableEnvironment;
import org.apache.flink.table.api.java.BatchTableEnvironment;
/**
* Simple example that shows how the Batch SQL API is used in Java.
*
* This example shows how to:
* - Convert DataSets to Tables
* - Register a Table under a name
* - Run a SQL query on the registered Table
*
*/
public class WordCountSQL {
// *************************************************************************
// PROGRAM
// *************************************************************************
public static void main(String[] args) throws Exception {
// set up execution environment
ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
BatchTableEnvironment tEnv = TableEnvironment.getTableEnvironment(env);
DataSet<WC> input = env.fromElements(
new WC("Hello", 1),
new WC("Ciao", 1),
new WC("Hello", 1));
// register the DataSet as table "WordCount"
tEnv.registerDataSet("WordCount", input, "word, frequency");
// run a SQL query on the Table and retrieve the result as a new Table
Table table = tEnv.sql(
"SELECT word, SUM(frequency) as frequency FROM WordCount GROUP BY word");
DataSet<WC> result = tEnv.toDataSet(table, WC.class);
result.print();
}
// *************************************************************************
// USER DATA TYPES
// *************************************************************************
public static class WC {
public String word;
public long frequency;
// public constructor to make it a Flink POJO
public WC() {
}
public WC(String word, long frequency) {
this.word = word;
this.frequency = frequency;
}
@Override
public String toString() {
return "WC " + word + " " + frequency;
}
}
}