CODEWITHSUNDEEP
javacommand-linedb2
vaisakh
vaisakh

Reputation: 1031

How to retrieve db2 command output from within Java program

I am unable to retrieve the output of "db2 list db directory" command in my Java program. Basically, what I am trying to do is this:-

  1. A combo box is populated with db2 instances in the local system
  2. User selects a particular instance from the combo box
  3. A new Process is run to list the database for that instance
  4. Display the database as another combo box

This is the piece of code I have done:-

// dbinstances is a Combo box (Eclipse SWT widget)

this.dbInstances.addSelectionListener(new SelectionListener() {

    @Override
    public void widgetSelected(SelectionEvent arg0) {

        // get selected instance name 
        String instance = dbInstances.getText();

        // command invokes db2 command window, sets current instance and issues list db command
        String command = "db2cmd /c \"set DB2INSTANCE="+instance+" & db2 list db directory\""; 

        // execute command and read output
        try{
            Process p = Runtime.getRuntime().exec(command);
            BufferedReader br= new BufferedReader(new InputStreamReader(p.getInputStream()));
            String op = null;
            while((op=br.readLine())!=null){
                System.out.println(op);
            }
        }
        catch(IOException ioe){
             ioe.printStackTrace();
         }
     }

      public void widgetDefaultSelected(SelectionEvent arg0) {}
});

The problem is that the command executes, I am unable to retrieve the output. The window just opens and closes.

One solution I tried was to redirect the output to a temporary file and read it. It works, but is quite inefficient, since this piece of code runs each time the user selects an instance.

I am running DB2 9.7 Enterprise edition on Windows XP SP3 machine.

Any thoughts on how to retrieve the output in the Java program?

Thanks a lot in advance.

Upvotes: 0

Views: 2538

Answers (2)

vaisakh
vaisakh

Reputation: 1031

Ok, figured this one out. The required solution is to add /w and /i switches to the command :-

 // command invokes db2 command window, sets current instance and issues list db command
 String command = "db2cmd /c /w /i \"set DB2INSTANCE="+instance+" & db2 list db directory\"";

According to IBM developerWorks 

//  Additional information about db2cmd Options
-c  Execute the DB2 command window and terminate.
-w  Wait until the DB2 command window terminates.
-i  Inherit the environment from the invoking shell.
-t  Inherit the title from the invoking shell

Upvotes: 1

AngocA
AngocA

Reputation: 7693

You can also use the DB2 API via JNI in order to retrieve the database list directory. You have to start the scan, get the entries, and then close the scan.

By doing this, you can control the db list in a better way that parsing an output that could variate by many reasons (HADR, the authentication mechanism, local or remote, with or without alias, ip address or server name, service name or port number, in linux (home dir) or in Windows (drive letter), and other things) The DB2 API is the same in all platforms, so it is almost platform independent, you just have to know which library load (.so or .dll), but the rest is the same.

For more information take a look at: db2DbDirOpenScan http://publib.boulder.ibm.com/infocenter/db2luw/v9r7/topic/com.ibm.db2.luw.apdv.api.doc/doc/r0001509.html db2DbDirGetNextEntry http://publib.boulder.ibm.com/infocenter/db2luw/v9r7/topic/com.ibm.db2.luw.apdv.api.doc/doc/r0001492.html db2DbDirCloseScan http://publib.boulder.ibm.com/infocenter/db2luw/v9r7/topic/com.ibm.db2.luw.apdv.api.doc/doc/r0001437.html

Upvotes: 1

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