org.springframework.integration.stream.CharacterStreamReadingMessageSource.java Source code

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Here is the source code for org.springframework.integration.stream.CharacterStreamReadingMessageSource.java

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/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.integration.stream;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;

import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.integration.endpoint.AbstractMessageSource;
import org.springframework.messaging.MessagingException;
import org.springframework.util.Assert;

/**
 * A pollable source for {@link Reader Readers}.
 *
 * @author Mark Fisher
 * @author Gary Russell
 * @author Artem Bilan
 */
public class CharacterStreamReadingMessageSource extends AbstractMessageSource<String>
        implements ApplicationEventPublisherAware {

    private final BufferedReader reader;

    private final boolean blockToDetectEOF;

    private ApplicationEventPublisher applicationEventPublisher;

    /**
     * Construct an instance with the provider reader.
     * {@link #receive()} will return {@code null} when the reader is not ready.
     * @param reader the reader.
     */
    public CharacterStreamReadingMessageSource(Reader reader) {
        this(reader, -1, false);
    }

    /**
     * Construct an instance with the provider reader and buffer size.
     * {@link #receive()} will return {@code null} when the reader is not ready.
     * @param reader the reader.
     * @param bufferSize the buffer size.
     */
    public CharacterStreamReadingMessageSource(Reader reader, int bufferSize) {
        this(reader, bufferSize, false);
    }

    /**
     * Construct an instance with the provided reader and buffer size.
     * When {@code blockToDetectEOF} is {@code false},
     * {@link #receive()} will return {@code null} when the reader is not ready.
     * When it is {@code true}, the thread will block until data is available; when the
     * underlying stream is closed, a {@link StreamClosedEvent} is published to inform
     * the application via an {@link org.springframework.context.ApplicationListener}.
     * This can be useful, for example, when piping stdin
     * <pre class="code">
     *     cat foo.txt | java -jar my.jar
     * </pre>
     * or
     * <pre class="code">
     *     java -jar my.jar &lt; foo.txt
     * </pre>
     * @param reader the reader.
     * @param bufferSize the buffer size; if negative use the default in
     * {@link BufferedReader}.
     * @param blockToDetectEOF true to block the thread until data is available and
     * publish a {@link StreamClosedEvent} at EOF.
     * @since 5.0
     */
    public CharacterStreamReadingMessageSource(Reader reader, int bufferSize, boolean blockToDetectEOF) {
        Assert.notNull(reader, "reader must not be null");
        if (reader instanceof BufferedReader) {
            this.reader = (BufferedReader) reader;
        } else if (bufferSize > 0) {
            this.reader = new BufferedReader(reader, bufferSize);
        } else {
            this.reader = new BufferedReader(reader);
        }
        this.blockToDetectEOF = blockToDetectEOF;
    }

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.applicationEventPublisher = applicationEventPublisher;
    }

    @Override
    public String getComponentType() {
        return "stream:stdin-channel-adapter(character)";
    }

    @Override
    public String doReceive() {
        try {
            synchronized (this.reader) {
                if (!this.blockToDetectEOF && !this.reader.ready()) {
                    return null;
                }
                String line = this.reader.readLine();
                if (line == null && this.applicationEventPublisher != null) {
                    this.applicationEventPublisher.publishEvent(new StreamClosedEvent(this));
                }
                return line;
            }
        } catch (IOException e) {
            throw new MessagingException("IO failure occurred in adapter", e);
        }
    }

    /**
     * Create a source that reads from {@link System#in}. EOF will not be detected.
     * @return the stream.
     */
    public static final CharacterStreamReadingMessageSource stdin() {
        return new CharacterStreamReadingMessageSource(new InputStreamReader(System.in));
    }

    /**
     * Create a source that reads from {@link System#in}. EOF will not be detected.
     * @param charsetName the charset to use when converting bytes to String.
     * @return the stream.
     */
    public static final CharacterStreamReadingMessageSource stdin(String charsetName) {
        try {
            return new CharacterStreamReadingMessageSource(new InputStreamReader(System.in, charsetName));
        } catch (UnsupportedEncodingException e) {
            throw new IllegalArgumentException("unsupported encoding: " + charsetName, e);
        }
    }

    /**
     * Create a source that reads from {@link System#in}. EOF will be detected and the application
     * context closed.
     * @return the stream.
     * @see CharacterStreamReadingMessageSource#CharacterStreamReadingMessageSource(Reader, int, boolean)
     * @since 5.0
     */
    public static final CharacterStreamReadingMessageSource stdinPipe() {
        return new CharacterStreamReadingMessageSource(new InputStreamReader(System.in), -1, true);
    }

    /**
     * Create a source that reads from {@link System#in}. EOF will be detected and the application
     * context closed.
     * @param charsetName the charset to use when converting bytes to String.
     * @return the stream.
     * @see CharacterStreamReadingMessageSource#CharacterStreamReadingMessageSource(Reader, int, boolean)
     * @since 5.0
     */
    public static final CharacterStreamReadingMessageSource stdinPipe(String charsetName) {
        try {
            return new CharacterStreamReadingMessageSource(new InputStreamReader(System.in, charsetName), -1, true);
        } catch (UnsupportedEncodingException e) {
            throw new IllegalArgumentException("unsupported encoding: " + charsetName, e);
        }
    }

}