JFileChooserFactory.java

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/*
 * Autopsy Forensic Browser
 *
 * Copyright 2021 Basis Technology Corp.
 * Contact: carrier <at> sleuthkit <dot> org
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.sleuthkit.autopsy.guiutils;

import com.google.common.util.concurrent.ThreadFactoryBuilder;
import java.awt.Cursor;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFileChooser;
import org.openide.windows.WindowManager;
import org.sleuthkit.autopsy.coreutils.ThreadConfined;

public final class JFileChooserFactory {

    private static final Logger logger = Logger.getLogger(JFileChooserFactory.class.getName());

    private final FutureTask<JFileChooser> futureFileChooser;
    private JFileChooser chooser;
    private final ExecutorService executor;

    public JFileChooserFactory() {
        this(null);
    }

    public JFileChooserFactory(Class<? extends JFileChooser> cls) {
        if (cls == null) {
            futureFileChooser = new FutureTask<>(JFileChooser::new);
        } else {
            futureFileChooser = new FutureTask<>(new ChooserCallable(cls));
        }
        
        // Append the caller class name to the thread name to add information to thread dumps.
        String threadName = "JFileChooser-background-thread";
        String callerName = getCallerClassName();
        if (callerName != null) {
            threadName += "-" + callerName;
        }

        executor = Executors.newSingleThreadExecutor(new ThreadFactoryBuilder().setNameFormat(threadName).build());
        executor.execute(futureFileChooser);
    }
    
    private static String getCallerClassName() { 
        StackTraceElement[] stElements = Thread.currentThread().getStackTrace();
        for (int i=1; i<stElements.length; i++) {
            StackTraceElement ste = stElements[i];
            
            // Look for the first class that is not this one.
            if (!ste.getClassName().equals(JFileChooserFactory.class.getName())&& ste.getClassName().indexOf("java.lang.Thread")!=0) {
                String resultClassName = ste.getClassName();
                if (resultClassName.contains(".")) {
                    // For brevity, omit the package name
                    int index = resultClassName.lastIndexOf(".") + 1;
                    if (index < resultClassName.length()) {
                        resultClassName = resultClassName.substring(index);
                    }
                }
                return resultClassName;
            }
        }
        return null;
     }

    @ThreadConfined(type = ThreadConfined.ThreadType.AWT)
    public JFileChooser getChooser() {
        if (chooser == null) {
            // In case this takes a moment show the wait cursor.
            try {
                WindowManager.getDefault().getMainWindow().setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
                try {
                    // get() will only return when the initilization of the 
                    // JFileChooser has completed.
                    chooser = futureFileChooser.get();
                } catch (InterruptedException | ExecutionException ex) {
                    // An exception is generally not expected. On the off chance
                    // one does occur save the situation by created a new
                    // instance in the EDT.
                    logger.log(Level.WARNING, "Failed to initialize JFileChooser in background thread.");
                    chooser = new JFileChooser();
                }
            } finally {
                WindowManager.getDefault().getMainWindow().setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
                executor.shutdown();
            }
        }

        return chooser;
    }

    private class ChooserCallable implements Callable<JFileChooser> {

        private final Class<? extends JFileChooser> type;

        ChooserCallable(Class<? extends JFileChooser> type) {
            this.type = type;
        }

        @Override
        public JFileChooser call() throws Exception {
            return type.newInstance();
        }
    }
}