org.apache.kafka.streams.kstream.internals.PrintForeachAction Maven / Gradle / Ivy

/*
 * 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.kafka.streams.kstream.internals;

import org.apache.kafka.streams.kstream.ForeachAction;
import org.apache.kafka.streams.kstream.KeyValueMapper;

import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;

public class PrintForeachAction implements ForeachAction {

    private final String label;
    private final PrintWriter printWriter;
    private final boolean closable;
    private final KeyValueMapper mapper;

    /**
     * Print customized output with given writer. The {@link OutputStream} can be {@link System#out} or the others.
     *
     * @param outputStream The output stream to write to.
     * @param mapper The mapper which can allow user to customize output will be printed.
     * @param label The given name will be printed.
     */
    PrintForeachAction(final OutputStream outputStream,
                       final KeyValueMapper mapper,
                       final String label) {
        this.printWriter = new PrintWriter(new OutputStreamWriter(outputStream, StandardCharsets.UTF_8));
        this.closable = outputStream != System.out && outputStream != System.err;
        this.mapper = mapper;
        this.label = label;
    }

    @Override
    public void apply(final K key, final V value) {
        final String data = String.format("[%s]: %s", label, mapper.apply(key, value));
        printWriter.println(data);
        if (!closable) {
            printWriter.flush();
        }
    }

    public void close() {
        if (closable) {
            printWriter.close();
        } else {
            printWriter.flush();
        }
    }

}