examples/src/main/java/org/apache/james/mime4j/samples/mbox/IterateOverMbox.java

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package org.apache.james.mime4j.samples.mbox;

import org.apache.james.mime4j.MimeException;
import org.apache.james.mime4j.dom.Message;
import org.apache.james.mime4j.dom.MessageBuilder;
import org.apache.james.mime4j.mboxiterator.CharBufferWrapper;
import org.apache.james.mime4j.mboxiterator.MboxIterator;
import org.apache.james.mime4j.message.DefaultMessageBuilder;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.StandardCharsets;

/**
 * Simple example of how to use Apache Mime4j Mbox Iterator. We split one mbox file file into
 * individual email messages.
 */
public class IterateOverMbox {

    private final static CharsetEncoder ENCODER = StandardCharsets.UTF_8.newEncoder();

    // simple example of how to split an mbox into individual files
    public static void main(String[] args) throws Exception {
        final String fileName = retrieveMBoxFileName(args);
        System.out.println(fileName);
        final File mbox = new File(fileName);
        long start = System.currentTimeMillis();
        int count = 0;

        for (CharBufferWrapper message : MboxIterator.fromFile(mbox).charset(ENCODER.charset()).build()) {
            // saveMessageToFile(count, buf);
            System.out.println(messageSummary(message.asInputStream(ENCODER.charset())));
            count++;
        }
        System.out.println("Found " + count + " messages");
        long end = System.currentTimeMillis();
        System.out.println("Done in: " + (end - start) + " milis");
    }

    private static String retrieveMBoxFileName(String[] args) {
        if (args.length < 1) {
            return ClassLoader.getSystemResource("test-1/mbox.rlug").getFile();
        }
        return args[0];
    }

    private static void saveMessageToFile(int count, CharBuffer buf) throws IOException {
        FileOutputStream fout = new FileOutputStream(new File("target/messages/msg-" + count));
        FileChannel fileChannel = fout.getChannel();
        ByteBuffer buf2 = ENCODER.encode(buf);
        fileChannel.write(buf2);
        fileChannel.close();
        fout.close();
    }

    /**
     * Parse a message and return a simple {@link String} representation of some important fields.
     *
     * @param messageBytes the message as {@link java.io.InputStream}
     * @return String
     */
    private static String messageSummary(InputStream messageBytes) throws IOException, MimeException {
        MessageBuilder builder = new DefaultMessageBuilder();
        Message message = builder.parseMessage(messageBytes);
        return String.format("\nMessage %s \n" +
                "Sent by:\t%s\n" +
                "To:\t%s\n",
                message.getSubject(),
                message.getSender(),
                message.getTo());
    }
}