java - Java Process hangs during stdInput reading

Question

I got some problem trying to launch a process that executes an EXPDP command to make the backup of a Oracle DB.

This is the method that launches the process, the problem is when I try to read from stInput and stdError. The process hangs forever, and if I stop the debug to see where the runtime execution is, the line I get is:

FileInputStream.readBytes(byte[], int, int) line: not available [native method] 

At the method entrypoint the value of the cmdCommand parameter is:

"EXPDP system/syspwd@orcl DIRECTORY=DATA_PUMP_DIR SCHEMAS=fabro DUMPFILE=backupFabro.dmp LOGFILE=backupFabro.log"

The method is the following, and it hangs on the first while loop.

 public Boolean cmdCommand(String cmdCommand) throws IOException{
            logger.info("**************************************");
            logger.info("Esecuzione comando:");
            logger.info(cmdCommand);
            logger.info("**************************************");
            final Process p = Runtime.getRuntime().exec(cmdCommand);
            Boolean end = false;
            BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));
            BufferedReader stdError = new BufferedReader(new InputStreamReader(p.getErrorStream()));
            String line = null; 
            try {
                while ((line = stdInput.readLine()) != null) {
                    logger.info(line);
                }
                while((line= stdError.readLine()) != null){
                    logger.error(line);
                }
            } catch (IOException e) {
                logger.error(e.getMessage(), e);
            }
            finally{
                stdError.close();
                stdInput.close();
            }
            try {
                if(p.waitFor() != 0){                       
                    logger.error("error etc etc");
                }
                else{
                    end = true;
                    logger.info("success ecc ecc");
                }
            } catch (Exception e) {
                logger.error(e.getMessage(), e);
                p.destroy();
            }
            return end;
        }

Answer 1

尝试使用 .ready() 函数。

try {
      if (stdError.ready()) 
      {
            while((line= stdError.readLine()) != null){
                logger.error(line);
            }
      }
}

对标准输出做同样的事情。

它对我来说就像一个魅力。