IOHelper类

activeMQ-fileserver中操作File类的工具类。
源代码：

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.activemq.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * 
 */
public final class IOHelper {
    protected static final int MAX_DIR_NAME_LENGTH;
    protected static final int MAX_FILE_NAME_LENGTH;
    private static final int DEFAULT_BUFFER_SIZE = 4096;
    private IOHelper() {
    }

    public static String getDefaultDataDirectory() {
        return getDefaultDirectoryPrefix() + "activemq-data";
    }

    public static String getDefaultStoreDirectory() {
        return getDefaultDirectoryPrefix() + "amqstore";
    }

    /**
     * Allows a system property to be used to overload the default data
     * directory which can be useful for forcing the test cases to use a target/
     * prefix
     */
    public static String getDefaultDirectoryPrefix() {
        try {
            return System.getProperty("org.apache.activemq.default.directory.prefix", "");
        } catch (Exception e) {
            return "";
        }
    }
    
    public static boolean deleteFile(File fileToDelete) {
        if (fileToDelete == null || !fileToDelete.exists()) {
            return true;
        }
        boolean result = deleteChildren(fileToDelete);
        result &= fileToDelete.delete();
        return result;
    }
    
    public static boolean deleteChildren(File parent) {
        if (parent == null || !parent.exists()) {
            return false;
        }
        boolean result = true;
        if (parent.isDirectory()) {
            File[] files = parent.listFiles();
            if (files == null) {
                result = false;
            } else {
                for (int i = 0; i < files.length; i++) {
                    File file = files[i];
                    if (file.getName().equals(".")
                            || file.getName().equals("..")) {
                        continue;
                    }
                    if (file.isDirectory()) {
                        result &= deleteFile(file);
                    } else {
                        result &= file.delete();
                    }
                }
            }
        }
       
        return result;
    }
    
    
    public static void moveFile(File src, File targetDirectory) throws IOException {
        if (!src.renameTo(new File(targetDirectory, src.getName()))) {
            throw new IOException("Failed to move " + src + " to " + targetDirectory);
        }
    }
    
    public static void copyFile(File src, File dest) throws IOException {
        FileInputStream fileSrc = new FileInputStream(src);
        FileOutputStream fileDest = new FileOutputStream(dest);
        copyInputStream(fileSrc, fileDest);
    }
    
    public static void copyInputStream(InputStream in, OutputStream out) throws IOException {
        byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
        int len = in.read(buffer);
        while (len >= 0) {
            out.write(buffer, 0, len);
            len = in.read(buffer);
        }
        in.close();
        out.close();
    }
    
    static {
        MAX_DIR_NAME_LENGTH = Integer.valueOf(System.getProperty("MaximumDirNameLength","200")).intValue();  
        MAX_FILE_NAME_LENGTH = Integer.valueOf(System.getProperty("MaximumFileNameLength","64")).intValue();             
    }

    
    public static void mkdirs(File dir) throws IOException {
        if (dir.exists()) {
            if (!dir.isDirectory()) {
                throw new IOException("Failed to create directory '" + dir +"', regular file already existed with that name");
            }
            
        } else {
            if (!dir.mkdirs()) {
                throw new IOException("Failed to create directory '" + dir+"'");
            }
        }
    }
}