[java] 外部コマンド実行するクラス(スレッド安全版？)

ProcessBroker.java

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * ProcessBroker pb = new ProcessBroker("ps -ef | grep java".split(" "));
 * pb.execute();
 * System.out.println(pb.getStdout());
 * System.out.println(pb.getStderr());
 */
public class ProcessBroker {

	private List<String> command = new ArrayList<String>();
	private StringBuffer stdout = new StringBuffer();
	private StringBuffer stderr = new StringBuffer();

	public ProcessBroker(String... command) {
		this.command.addAll(Arrays.asList(command));
	}

	public int execute() throws IOException, InterruptedException {
		Process process = new ProcessBuilder(command).start();
		new StreamReaderThread(process.getInputStream(), stdout).start();
		new StreamReaderThread(process.getErrorStream(), stderr).start();
		return process.waitFor();
	}

	public String getStdout() {
		return stdout.toString();
	}

	public String getStderr() {
		return stderr.toString();
	}

	class StreamReaderThread extends Thread {

		InputStream inputStream;
		StringBuffer output;

		StreamReaderThread(final InputStream inputStream, StringBuffer output) {
			this.inputStream = inputStream;
			this.output = output;
		}

		@Override
		public void start() {
			try {
				readStream(inputStream, output);
			} catch (IOException e) {
				output.append(e.getMessage());
			}
		}

		private void readStream(InputStream inputStream, StringBuffer sb)
				throws IOException {
			try (Reader reader = new InputStreamReader(inputStream)) {
				char[] buf = new char[1 << 20]; // 1MiB buffer
				int n;
				while ((n = reader.read(buf, 0, buf.length)) > -1) {
					sb.append(buf, 0, n);
				}
			}
		}
	}
}