java日誌記錄，並將該記錄輸出到自定義的窗口中（二）

package logger;

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.logging.*;

import javax.swing.*;

public class LoggingImageViewer {
 public static void main(String[] args) {
  if(System.getProperty("java.util.logging.config.class") == null
    && System.getProperty("java.util.logging.config.file") == null) {
   try {
    Logger.getLogger("logger").setLevel(Level.ALL);
    final int LOG_ROTATION_COUNT = 10;
    Handler handler = new FileHandler("%h/LoggingImageViewer.log", 0, LOG_ROTATION_COUNT);
    Logger.getLogger("logger").addHandler(handler);
   } catch (IOException e) {
    Logger.getLogger("logger").log(Level.SEVERE, "Can't create log file handler.", e);
   }
  }
  
  EventQueue.invokeLater(new Runnable() {
   @Override
   public void run() {
    Handler windowHandler = new WindowHandler();
    windowHandler.setLevel(Level.ALL);
    Logger.getLogger("logger").addHandler(windowHandler);
    
    JFrame frame = new ImageViewerFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
    Logger.getLogger("logger").fine("Showing frame");
    frame.setVisible(true);
   }
  });
 }
}

class WindowHandler extends StreamHandler {
 public WindowHandler() {
  frame = new JFrame();
  final JTextArea output = new JTextArea();
  output.setEditable(false);
  frame.setSize(200, 200);
  frame.add(new JScrollPane(output));
  frame.setFocusableWindowState(false);
  frame.setVisible(true);
  //安裝一個流，該流的write方法將流顯示輸出到output
  setOutputStream(new OutputStream() {
   @Override
   public void write(int b) throws IOException {
    
   }
   
   @Override
   public void write(byte[] b, int off, int len) {
    output.append(new String(b, off, len));
   }
  });
 }
 
 //強制刷新
 @Override
 public void publish(LogRecord record) {
  if(!frame.isVisible()) {
   return;
  }
  super.publish(record);
  flush();
 }
 
 private JFrame frame;
}