flink-sql-udf

package flinkdemo.flinksql.sqlJoin;

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.java.BatchTableEnvironment;
import org.apache.flink.table.functions.ScalarFunction;
import org.apache.flink.types.Row;

import java.util.ArrayList;
import java.util.List;

/**
 * @author zhangkai
 * @create 2019/12/23
 */
public class UdfSql {
    /**
     * 繼承 ScalarFunction 類
     * 重寫 eval方法
     * tableEnv註冊 udf 函數
     * sql使用函數
     * */
    public static void main(String[] args) throws Exception{
        ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
        BatchTableEnvironment tableEnv = BatchTableEnvironment.create(env);

        tableEnv.registerFunction("stringConcat",new StringConcat("study_","_good"));
        String[] strArr = "hadoop,flink,hadoop,spark,kafka,hadoop,flink".split(",");

        List list = new ArrayList<>();
        for(String ele : strArr){
            list.add(new WordCount(ele,1));
        }
        DataSet<WordCount> dataSource = env.fromCollection(list);

        tableEnv.registerDataSet("wordCCount",dataSource,"word,frequency");

        Table table = tableEnv.sqlQuery("select stringConcat(word)as word ,sum(frequency) as frequency from wordCCount group by word");

        DataSet<Row> rowDataSet = tableEnv.toDataSet(table, Row.class);
        rowDataSet.print();

    }

    public static class StringConcat extends ScalarFunction {
        String pre;
        String last;

        public StringConcat() {
        }

        public StringConcat(String pre, String last) {
            this.pre = pre;
            this.last = last;
        }

        public String eval(String value){
            return pre + value + last;
        }

    }

    public static class WordCount{
        public String word;
        public long frequency;

        public WordCount() {
        }

        public WordCount(String word, long frequency) {
            this.word = word;
            this.frequency = frequency;
        }

        @Override
        public String toString() {
            return "WordCount{" +
                    "word='" + word + '\'' +
                    ", frequency=" + frequency +
                    '}';
        }
    }

}