虽然Google的guava对Java的IO操作进行了一定封装，但是它更偏向于集合、并发和缓存，在实际项目中，我非常喜欢guava，同时我也非常喜欢Apache的一个工具包org.apache.commons.io，这两个工具包提供非常强大的工具能力，能够简化代码逻辑，提高开发效率和质量，是每个Java程序员都应该掌握的工具包。此文简单介绍一下org.apache.commons.io，详细的可参考其API注，此文绝大部分内容翻译自http://www.javacodegeeks.com/2014/10/apache-commons-io-tutorial.html，感兴趣的查看原文，本文源码请移步
Apache Commons IO是Apache开源的一个工具包，其封装了对IO的常见操作，使开发人员只需要少量的代码就能完成大量的IO操作，此文主要介绍如下几个工具类
1、Utils（FileUtils，FilenameUtils，FileSystemUtils）这三个类主要提供了对文件、文件名及文件系统的操作，API非常简单，通过API名称都能知道其作用，
示例如下
//文件绝对路径
private static final String EXAMPLE_TXT_PATH =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio/commonio.txt";
//文件父目录
private static final String PARENT_DIR =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio";
public static void runExample() throws IOException {
System.out.println("Utility Classes example...");
// FilenameUtils类示例
//获取完整路径
System.out.println("Full path of exampleTxt: " +
FilenameUtils.getFullPath(EXAMPLE_TXT_PATH));
//获取名称
System.out.println("Full name of exampleTxt: " +
FilenameUtils.getName(EXAMPLE_TXT_PATH));
//获取扩展名
System.out.println("Extension of exampleTxt: " +
FilenameUtils.getExtension(EXAMPLE_TXT_PATH));
System.out.println("Base name of exampleTxt: " +
FilenameUtils.getBaseName(EXAMPLE_TXT_PATH));
// FileUtils类示例
// 通过FileUtils.getFile(String)创建File对象，然后根据FileUtils.lineIterator(File)
//获取行迭代器
File exampleFile = FileUtils.getFile(EXAMPLE_TXT_PATH);
LineIterator iter = FileUtils.lineIterator(exampleFile);
System.out.println("Contents of exampleTxt...");
while (iter.hasNext()) {
System.out.println("\t" + iter.next());
}
iter.close();
// 目录是否已经包含文件
File parent = FileUtils.getFile(PARENT_DIR);
System.out.println("Parent directory contains exampleTxt file: " +
FileUtils.directoryContains(parent, exampleFile));
// IOCase类示例
String str1 = "This is a new String.";
String str2 = "This is another new String, yes!";
System.out.println("Ends with string (case sensitive): " +
IOCase.SENSITIVE.checkEndsWith(str1, "string."));
System.out.println("Ends with string (case insensitive): " +
IOCase.INSENSITIVE.checkEndsWith(str1, "string."));
System.out.println("String equality: " +
IOCase.SENSITIVE.checkEquals(str1, str2));
// FileSystemUtils类示例
System.out.println("Free disk space (in KB): " + FileSystemUtils.freeSpaceKb("/Users"));
System.out.println("Free disk space (in MB): " + FileSystemUtils.freeSpaceKb("/Users") / 1024);
}示例如下
private static final String XML_PATH =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio/test.xml";
public static void runExample() {
System.out.println("Input example...");
XmlStreamReader xmlReader = null;
try {
// XmlStreamReader:读取一个xml文件，提供了过去文件编码API
File xml = FileUtils.getFile(XML_PATH);
xmlReader = new XmlStreamReader(xml);
System.out.println("XML encoding: " + xmlReader.getEncoding());
} catch (IOException e) {
e.printStackTrace();
} finally {
try { xmlReader.close(); }
catch (IOException e) { e.printStackTrace(); }
}
}3、Output，其提供的TeeInputStream，TeeOutputStream类能将输入流快速拷贝到输出流中
private static final String INPUT = "This should go to the output.";
public static void runExample() {
System.out.println("Output example...");
TeeInputStream tee=null;
TeeInputStream teeIn = null;
TeeOutputStream teeOut = null;
try {
//TeeInputStream能将输入流快速拷贝到输出流中
ByteArrayInputStream in = new ByteArrayInputStream(INPUT.getBytes("US-ASCII"));
ByteArrayOutputStream out = new ByteArrayOutputStream();
tee = new TeeInputStream(in, out, true);
tee.read(new byte[INPUT.length()]);
System.out.println("Output stream: " + out.toString());
//能将输入流同时拷贝到两个输出流
ByteArrayOutputStream out1 = new ByteArrayOutputStream();
ByteArrayOutputStream out2 = new ByteArrayOutputStream();
teeOut = new TeeOutputStream(out1, out2);
teeIn = new TeeInputStream(in, teeOut, true);
teeIn.read(new byte[INPUT.length()]);
System.out.println("Output stream 1: " + out1.toString());
System.out.println("Output stream 2: " + out2.toString());
} catch (IOException e) {
e.printStackTrace();
} finally {
//此处不需要关闭teeOut，当关闭teeIn时，同时会关闭teeOut
try { teeIn.close();
tee.close();}
catch (IOException e) { e.printStackTrace(); }
}
}示例如下
private static final String PARENT_DIR =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio";
public static void runExample() {
System.out.println("File Filter example...");
// NameFileFilter：获取指定目录下，符合给定文件列表的文件
//例如获取此例，获取PARENT_DIR目录下commonios和commonio.txt文件
File dir = FileUtils.getFile(PARENT_DIR);
String[] acceptedNames = {"commonios", "commonio.txt"};
for (String file: dir.list(new NameFileFilter(acceptedNames, IOCase.INSENSITIVE))) {
System.out.println("File found, named: " + file);
}
//WildcardFileFilter：支持正则匹配，获取指定目录下，满足正则的文件
for (String file: dir.list(new WildcardFileFilter("*common*"))) {
System.out.println("Wildcard file found, named: " + file);
}
// PrefixFileFilter：获取以给定字符串为前缀的文件名
for (String file: dir.list(new PrefixFileFilter("common"))) {
System.out.println("Prefix file found, named: " + file);
}
// SuffixFileFilter：：获取以给定字符串为后缀的文件名
for (String file: dir.list(new SuffixFileFilter(".txt"))) {
System.out.println("Suffix file found, named: " + file);
}
// OrFileFilter：支持传入多个过滤器，过滤器之间是或的关系
for (String file: dir.list(new OrFileFilter(
new WildcardFileFilter("*ample*"), new SuffixFileFilter(".txt")))) {
System.out.println("Or file found, named: " + file);
}
//AndFileFilter：支持传入多个过滤器，过滤器之间是且的关系
for (String file: dir.list(new AndFileFilter(
new WildcardFileFilter("*ample*"),
new NotFileFilter(new SuffixFileFilter(".txt"))))) {
System.out.println("And/Not file found, named: " + file);
}
}简单示例如下
private static final String PARENT_DIR =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio";
private static final String FILE_1 =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio/commonio.txt";
private static final String FILE_2 =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio/test.xml";
public static void runExample() {
System.out.println("Comparator example...");
//NameFileComparator:根据文件名称排序，IOCase表示是否大小写敏感
File parentDir = FileUtils.getFile(PARENT_DIR);
NameFileComparator comparator = new NameFileComparator(IOCase.SENSITIVE);
File[] sortedFiles = comparator.sort(parentDir.listFiles());
System.out.println("Sorted by name files in parent directory: ");
for (File file: sortedFiles) {
System.out.println("\t"+ file.getAbsolutePath());
}
// SizeFileComparator：根据文件大小排序，小文件在前，其构造器支持传一个boolean类型的参数，
//true表示需要计算该目录下的目录大小
//flase表示不需要计算该目录下的目录大小（0）
SizeFileComparator sizeComparator = new SizeFileComparator(true);
File[] sizeFiles = sizeComparator.sort(parentDir.listFiles());
System.out.println("Sorted by size files in parent directory: ");
for (File file: sizeFiles) {
System.out.println("\t"+ file.getName() + " with size (kb): " + file.length());
}
// LastModifiedFileComparator：根据修改时间排序，最新修改排前
LastModifiedFileComparator lastModified = new LastModifiedFileComparator();
File[] lastModifiedFiles = lastModified.sort(parentDir.listFiles());
System.out.println("Sorted by last modified files in parent directory: ");
for (File file: lastModifiedFiles) {
Date modified = new Date(file.lastModified());
System.out.println("\t"+ file.getName() + " last modified on: " + modified);
}
}示例如下
private static final String EXAMPLE_PATH =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio/commonio.txt";
private static final String PARENT_DIR =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio";
private static final String NEW_DIR =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio/newDir";
private static final String NEW_FILE =
"/Users/fly/work/GitHub/algorithm/src/main/java/com/fly/practice/apachecommonsio/newFile.txt";
public static void runExample() {
System.out.println("File Monitor example...");
// FileEntry
// We can monitor changes and get information about files
// using the methods of this class.
FileEntry entry = new FileEntry(FileUtils.getFile(EXAMPLE_PATH));
System.out.println("File monitored: " + entry.getFile());
System.out.println("File name: " + entry.getName());
System.out.println("Is the file a directory?: " + entry.isDirectory());
// 文件（目录）监控
// 给指定目录创建观察者，并添加监听器，对事件作出响应
File parentDir = FileUtils.getFile(PARENT_DIR);
FileAlterationObserver observer = new FileAlterationObserver(parentDir);
observer.addListener(new FileAlterationListenerAdaptor() {
@Override
public void onFileCreate(File file) {
System.out.println("File created: " + file.getName());
}
@Override
public void onFileDelete(File file) {
System.out.println("File deleted: " + file.getName());
}
@Override
public void onDirectoryCreate(File dir) {
System.out.println("Directory created: " + dir.getName());
}
@Override
public void onDirectoryDelete(File dir) {
System.out.println("Directory deleted: " + dir.getName());
}
});
// 创建一个每隔500毫秒就做一次检查的监控
FileAlterationMonitor mOnitor= new FileAlterationMonitor(500, observer);
try {
monitor.start();
//启动监控后，对监控目录做一些文件操作，触发监听器
File newDir = new File(NEW_DIR);
File newFile = new File(NEW_FILE);
newDir.mkdirs();
newFile.createNewFile();
Thread.sleep(1000);
FileDeleteStrategy.NORMAL.delete(newDir);
FileDeleteStrategy.NORMAL.delete(newFile);
Thread.sleep(1000);
monitor.stop();
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}以上只是对commons-io的一个简单介绍，从中可以看出该工具包提供了强大的IO操作，更多功能还需实际项目中不断探索Apache Commons IO简介
京公网安备 11010802041100号 | 京ICP备19059560号-4 | PHP1.CN 第一PHP社区 版权所有 