I'm having trouble using standard input inside JDB

Question

Hello Java(R) community
The problem is:
I cannot read a stream of characters from the keyboard inside JDB. Just to set context I'm using:
jdk 1.3.1_01 with jdb version 99/06/11 under RedHat(R) Linux(R) 7.1
I've written the following code:
1:import java.io.*;
2:
3:public class Test {
4:
5: Reader reader = new InputStreamReader(System.in);
6: char[] buffer = new char[256];
7:
8: public void myRead() {
9:
10: System.out.print("Insert some text: ");
11: try {
12: reader.read(buffer);
13: }
14: catch (IOException e) {
15: System.out.println(e.getMessage());
16: }
17: System.out.println("You've inserted the following text: " + new String(buffer));
18: }
19:
20: public static void main(String[] args) {
21:
22: Test ref = new Test();
23: ref.myRead();
24: }
25:}
The above is compiled with javac -g Test.java
At the shell you run ' java Test ' and it just echoes the input you give to it
Inside jdb you set a breakpoint with ' stop in Test.myRead()'. When there, it stops at line 10; you invoke the 'next' command and it just don't print the message (just becuse it's not a println it just don't flush I suppose); after that the next line to execute is 12; so you invoke 'next' again and the real problem happens! Nothing can be read from the standard input. If you try to run the 'list' command jdb says "Current thread isn't suspended".
Does anyone knows what's going on?
Thanks in advance for a reply.

Answer 1

If you use the launching connector to start the debugee,
(this is the default used when you start jdb)
then jdb cannot tell the difference between jdb commands
that you are typing, and other text you want sent to the
debugee program. You will have the same problem with
output going the other way. The debugee program output
will be mixed in with any jdb output that comes along.
This is because the controlling window has only one stdin,
stdout, stderr that both processes (as well as anything else
you are running in that window) are forced to share.
You need to separate the debugger and debugee, as follows:
1) Start the debugee program (HelloWorld in this example)
in one command window:
% java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=4571 HelloWorld
2) In another window, attach your debugger (jdb in this example)
to the debugee via a socket:
% jdb -connect com.sun.jdi.SocketAttach:hostname=localhost,port=4571
You may also use the shared memory transport if you are
on a win32 platform, as follows:
1) In one command window:
% java -Xdebug -Xrunjdwp:transport=dt_shmem,server=y,address=mine HelloWorld
2) In a second command window (again using jdb as an example):
% jdb -connect com.sun.jdi.SharedMemoryAttach:name=mine
For more information, refer to "Connection and Invocation Details"
at this URL:
http://java.sun.com/j2se/1.4/docs/guide/jpda/conninv.html