How to use

ThreadLocalPrintStream

in

org.apache.brooklyn.util.stream

/** installs a thread local print stream to System.out if one is not already set;
 * caller may then #capture and #captureTee on it.
 * @return the ThreadLocalPrintStream which System.out is using */
public synchronized static ThreadLocalPrintStream stdout() {
  PrintStream oldOut = System.out;
  if (oldOut instanceof ThreadLocalPrintStream) return (ThreadLocalPrintStream)oldOut;
  ThreadLocalPrintStream newOut = new ThreadLocalPrintStream(System.out);
  System.setOut(newOut);
  return newOut;
}

public String end() {
  if (streamToRestore!=null)
    stream.setThreadLocalPrintStream(streamToRestore);
  else
    stream.clearThreadLocalPrintStream();
  finished = true;
  return out.toString();
}
public boolean isActive() {

/** creates a capturing context which sees the output to this stream, without interrupting the original target */
public OutputCapturingContext captureTee() {
  ByteArrayOutputStream out = new ByteArrayOutputStream();
  PrintStream toRestore = setThreadLocalPrintStream(new TeeOutputStream(getDelegate(), out));
  return new OutputCapturingContext(this, out, toRestore);
}

OutputCapturingContext stdout = ThreadLocalPrintStream.stdout().captureTee();
OutputCapturingContext stderr = ThreadLocalPrintStream.stderr().captureTee();

/** simple example showing how a capture to stdout can be set up */
@Test
public void testStdoutCapture() {
  OutputCapturingContext capture = ThreadLocalPrintStream.stdout().captureTee();
  System.out.println("hello");
  String out = capture.end();
  Assert.assertEquals("hello", out.trim());
  
  System.out.println("goodbye - not captured, restored normal output");
  Assert.assertEquals("hello", out.trim());
}

@Test
public void testStdoutCaptureDetail() {
  ThreadLocalPrintStream.stdout();
  System.out.println("1 - not captured, but next goes to capture only");
  OutputCapturingContext capture = ThreadLocalPrintStream.stdout().capture();
  final String TWO = "2 - captured";
  System.out.println(TWO);
  Assert.assertEquals(TWO, capture.getOutputSoFar().trim());
  String out = capture.end();
  Assert.assertEquals(TWO, out.trim());
  System.out.println("3 - not captured, restored normal output");
  Assert.assertEquals(TWO, capture.getOutputSoFar().trim());
}

@Test
public void testStderrCaptureDetail() {
  ThreadLocalPrintStream.stderr();
  System.err.println("1 - not captured, but next goes to capture only");
  OutputCapturingContext capture = ThreadLocalPrintStream.stderr().capture();
  final String TWO = "2 - captured";
  System.err.println(TWO);
  Assert.assertEquals(TWO, capture.getOutputSoFar().trim());
  String out = capture.end();
  Assert.assertEquals(TWO, out.trim());
  System.err.println("3 - not captured, restored normal output");
  Assert.assertEquals(TWO, capture.getOutputSoFar().trim());
}

/** constructor which installs a ByteArrayOutputStream to this stream */
public OutputCapturingContext(ThreadLocalPrintStream stream) {
  this.stream = stream;
  this.out = new ByteArrayOutputStream();
  this.streamToRestore = stream.setThreadLocalPrintStream(out);
}
/** constructor for a capturing context which is already installed */

@Test
public void testStdoutCaptureTeeDetail() {
  ThreadLocalPrintStream.stdout();
  System.out.println("1 - not captured, but next go to capture and stdout");
  OutputCapturingContext capture1 = ThreadLocalPrintStream.stdout().captureTee();
  OutputCapturingContext capture2 = ThreadLocalPrintStream.stdout().captureTee();
  final String TWO = "2 - captured";
  System.out.println(TWO);
  Assert.assertEquals(TWO, capture1.getOutputSoFar().trim());
  Assert.assertEquals(TWO, capture2.getOutputSoFar().trim());
  String out2 = capture2.end();
  
  final String THREE = "3 - captured by 1";
  System.out.println(THREE);
  String out1 = capture1.end();
  
  System.out.println("4 - not captured, restored normal output");
  Assert.assertEquals(TWO, out2.trim());
  Assert.assertEquals(TWO+Os.LINE_SEPARATOR+THREE, out1.trim());
}

/** installs a thread local print stream to System.err if one is not already set;
 * caller may then #capture and #captureTee on it.
 * @return the ThreadLocalPrintStream which System.err is using */
public synchronized static ThreadLocalPrintStream stderr() {
  PrintStream oldErr = System.err;
  if (oldErr instanceof ThreadLocalPrintStream) return (ThreadLocalPrintStream)oldErr;
  ThreadLocalPrintStream newErr = new ThreadLocalPrintStream(System.err);
  System.setErr(newErr);
  return newErr;
}