apache commons io包快速入门

原文参考
http://www.javacodegeeks.com/2014/10/apache-commons-io-tutorial.html

  Apache Commons IO 包绝对是好东西，地址在http://commons.apache.org/proper/commons-io/，下面用例子分别介绍：
  1）  工具类
  2） 输入
  3） 输出
  4） filters过滤
  5） Comparators
  6） 文件监控
 
   总的入口例子为：
  

public class ApacheCommonsExampleMain {

    public static void main(String[] args) {
        UtilityExample.runExample();
        
        FileMonitorExample.runExample();
        
        FiltersExample.runExample();
        
        InputExample.runExample();
        
        OutputExample.runExample();
        
        ComparatorExample.runExample();
    }
}

一  工具类包UtilityExample代码：

    这个工具类包分如下几个主要工具类：
     1） FilenameUtils:主要处理各种操作系统下对文件名的操作
     2) FileUtils:处理文件的打开，移动，读取和判断文件是否存在
    3） IOCASE：字符串的比较
    4） FileSystemUtils:返回磁盘的空间大小

   

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileSystemUtils;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.FilenameUtils;
import org.apache.commons.io.LineIterator;
import org.apache.commons.io.IOCase;

public final class UtilityExample {
    
    // We are using the file exampleTxt.txt in the folder ExampleFolder,
    // and we need to provide the full path to the Utility classes.
    private static final String EXAMPLE_TXT_PATH =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder\\exampleTxt.txt";
    
    private static final String PARENT_DIR =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample";

    public static void runExample() throws IOException {
        System.out.println("Utility Classes example...");
        
        
        // FilenameUtils
        
        System.out.println("Full path of exampleTxt: " +
                FilenameUtils.getFullPath(EXAMPLE_TXT_PATH));
        
        System.out.println("Full name of exampleTxt: " +
                FilenameUtils.getName(EXAMPLE_TXT_PATH));
        
        System.out.println("Extension of exampleTxt: " +
                FilenameUtils.getExtension(EXAMPLE_TXT_PATH));
        
        System.out.println("Base name of exampleTxt: " +
                FilenameUtils.getBaseName(EXAMPLE_TXT_PATH));
        
        
        // FileUtils
        
        // We can create a new File object using FileUtils.getFile(String)
        // and then use this object to get information from the file.
        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();
        
        // We can check if a file exists somewhere inside a certain directory.
        File parent = FileUtils.getFile(PARENT_DIR);
        System.out.println("Parent directory contains exampleTxt file: " +
                FileUtils.directoryContains(parent, exampleFile));
        
        
        // IOCase
        
        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
        System.out.println("Free disk space (in KB): " + FileSystemUtils.freeSpaceKb("C:"));
        System.out.println("Free disk space (in MB): " + FileSystemUtils.freeSpaceKb("C:") / 1024);
    }
}

输出：

Utility Classes example...
Full path of exampleTxt: C:\Users\Lilykos\workspace\ApacheCommonsExample\ExampleFolder\
Full name of exampleTxt: exampleTxt.txt
Extension of exampleTxt: txt
Base name of exampleTxt: exampleTxt
Contents of exampleTxt...
	This is an example text file.
	We will use it for experimenting with Apache Commons IO.
Parent directory contains exampleTxt file: true
Ends with string (case sensitive): false
Ends with string (case insensitive): true
String equality: false
Free disk space (in KB): 32149292
Free disk space (in MB): 31395

二  FileMonitor工具类包
   这个org.apache.commons.io.monitor 包中的工具类可以监视文件或者目录的变化，获得指定文件或者目录的相关信息，下面看例子：
  

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileDeleteStrategy;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
import org.apache.commons.io.monitor.FileAlterationMonitor;
import org.apache.commons.io.monitor.FileAlterationObserver;
import org.apache.commons.io.monitor.FileEntry;


public final class FileMonitorExample {
    
    private static final String EXAMPLE_PATH =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder\\exampleFileEntry.txt";
    
    private static final String PARENT_DIR =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder";
    
    private static final String NEW_DIR =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder\\newDir";
    
    private static final String NEW_FILE =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder\\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());
        
        
        // File Monitoring
        
        // Create a new observer for the folder and add a listener
        // that will handle the events in a specific directory and take action.
        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());
                }
        });
        
        // Add a monior that will check for events every x ms,
        // and attach all the different observers that we want.
        FileAlterationMonitor monitor = new FileAlterationMonitor(500, observer);
        try {
            monitor.start();
        
            // After we attached the monitor, we can create some files and directories
            // and see what happens!
            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();
        }
    }
}

输出如下：
  

File Monitor example...
File monitored: C:\Users\Lilykos\workspace\ApacheCommonsExample\ExampleFolder\exampleFileEntry.txt
File name: exampleFileEntry.txt
Is the file a directory?: false
Directory created: newDir
File created: newFile.txt
Directory deleted: newDir
File deleted: newFile.txt

    上面的特性的确很赞！分析下，这个工具类包下的工具类，可以允许我们创建跟踪文件或目录变化的监听句柄，当文件目录等发生任何变化，都可以用“观察者”的身份进行观察，
其步骤如下：
   1） 创建要监听的文件对象
   2） 创建FileAlterationObserver 监听对象，在上面的例子中，
   File parentDir = FileUtils.getFile(PARENT_DIR);
  FileAlterationObserver observer = new FileAlterationObserver(parentDir);
   创建的是监视parentDir目录的变化，
   3） 为观察器创建FileAlterationListenerAdaptor的内部匿名类，增加对文件及目录的增加删除的监听
   4） 创建FileAlterationMonitor监听类，每隔500ms监听目录下的变化，其中开启监视是用monitor的start方法即可。

三  过滤器 filters
   先看例子：
  

import java.io.File;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOCase;
import org.apache.commons.io.filefilter.AndFileFilter;
import org.apache.commons.io.filefilter.NameFileFilter;
import org.apache.commons.io.filefilter.NotFileFilter;
import org.apache.commons.io.filefilter.OrFileFilter;
import org.apache.commons.io.filefilter.PrefixFileFilter;
import org.apache.commons.io.filefilter.SuffixFileFilter;
import org.apache.commons.io.filefilter.WildcardFileFilter;

public final class FiltersExample {
    
    private static final String PARENT_DIR =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder";

    public static void runExample() {
        System.out.println("File Filter example...");
        
        
        // NameFileFilter
        // Right now, in the parent directory we have 3 files:
        //      directory example
        //      file exampleEntry.txt
        //      file exampleTxt.txt
        
        // Get all the files in the specified directory
        // that are named "example".
        File dir = FileUtils.getFile(PARENT_DIR);
        String[] acceptedNames = {"example", "exampleTxt.txt"};
        for (String file: dir.list(new NameFileFilter(acceptedNames, IOCase.INSENSITIVE))) {
            System.out.println("File found, named: " + file);
        }
        
        
        //WildcardFileFilter
        // We can use wildcards in order to get less specific results
        //      ? used for 1 missing char
        //      * used for multiple missing chars
        for (String file: dir.list(new WildcardFileFilter("*ample*"))) {
            System.out.println("Wildcard file found, named: " + file);
        }
        
        
        // PrefixFileFilter 
        // We can also use the equivalent of startsWith
        // for filtering files.
        for (String file: dir.list(new PrefixFileFilter("example"))) {
            System.out.println("Prefix file found, named: " + file);
        }
        
        
        // SuffixFileFilter
        // We can also use the equivalent of endsWith
        // for filtering files.
        for (String file: dir.list(new SuffixFileFilter(".txt"))) {
            System.out.println("Suffix file found, named: " + file);
        }
        
        
        // OrFileFilter 
        // We can use some filters of filters.
        // in this case, we use a filter to apply a logical 
        // or between our filters.
        for (String file: dir.list(new OrFileFilter(
                new WildcardFileFilter("*ample*"), new SuffixFileFilter(".txt")))) {
            System.out.println("Or file found, named: " + file);
        }
        
        // And this can become very detailed.
        // Eg, get all the files that have "ample" in their name
        // but they are not text files (so they have no ".txt" extension.
        for (String file: dir.list(new AndFileFilter( // we will match 2 filters...
                new WildcardFileFilter("*ample*"), // ...the 1st is a wildcard...
                new NotFileFilter(new SuffixFileFilter(".txt"))))) { // ...and the 2nd is NOT .txt.
            System.out.println("And/Not file found, named: " + file);
        }
    }
}

      可以看清晰看到，使用过滤器，可以分别在指定的目录下，寻找符合条件
的文件，比如以什么开头的文件名，支持通配符，甚至支持多个过滤器进行或的操作！
  输出如下：
 

File Filter example...
File found, named: example
File found, named: exampleTxt.txt
Wildcard file found, named: example
Wildcard file found, named: exampleFileEntry.txt
Wildcard file found, named: exampleTxt.txt
Prefix file found, named: example
Prefix file found, named: exampleFileEntry.txt
Prefix file found, named: exampleTxt.txt
Suffix file found, named: exampleFileEntry.txt
Suffix file found, named: exampleTxt.txt
Or file found, named: example
Or file found, named: exampleFileEntry.txt
Or file found, named: exampleTxt.txt
And/Not file found, named: example

四  Comparators比较器
   org.apache.commons.io.comparator包下的工具类，可以方便进行文件的比较：

import java.io.File;
import java.util.Date;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOCase;
import org.apache.commons.io.comparator.LastModifiedFileComparator;
import org.apache.commons.io.comparator.NameFileComparator;
import org.apache.commons.io.comparator.SizeFileComparator;

public final class ComparatorExample {
    
    private static final String PARENT_DIR =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder";
    
    private static final String FILE_1 =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder\\example";
    
    private static final String FILE_2 =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\ExampleFolder\\exampleTxt.txt";
    
    public static void runExample() {
        System.out.println("Comparator example...");
        
        //NameFileComparator
        
        // Let's get a directory as a File object
        // and sort all its files.
        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
        
        // We can compare files based on their size.
        // The boolean in the constructor is about the directories.
        //      true: directory's contents count to the size.
        //      false: directory is considered zero size.
        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
        
        // We can use this class to find which file was more recently modified.
        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);
        }
        
        // Or, we can also compare 2 specific files and find which one was last modified.
        //      returns > 0 if the first file was last modified.
        //      returns  0)
            System.out.println("File " + file1.getName() + " was modified last because...");
        else
            System.out.println("File " + file2.getName() + "was modified last because...");
        
        System.out.println("\t"+ file1.getName() + " last modified on: " +
                new Date(file1.lastModified()));
        System.out.println("\t"+ file2.getName() + " last modified on: " +
                new Date(file2.lastModified()));
    }
}

   输出如下：

Comparator example...
Sorted by name files in parent directory: 
	C:\Users\Lilykos\workspace\ApacheCommonsExample\ExampleFolder\comparator1.txt
	C:\Users\Lilykos\workspace\ApacheCommonsExample\ExampleFolder\comperator2.txt
	C:\Users\Lilykos\workspace\ApacheCommonsExample\ExampleFolder\example
	C:\Users\Lilykos\workspace\ApacheCommonsExample\ExampleFolder\exampleFileEntry.txt
	C:\Users\Lilykos\workspace\ApacheCommonsExample\ExampleFolder\exampleTxt.txt
Sorted by size files in parent directory: 
	example with size (kb): 0
	exampleTxt.txt with size (kb): 87
	exampleFileEntry.txt with size (kb): 503
	comperator2.txt with size (kb): 1458
	comparator1.txt with size (kb): 4436
Sorted by last modified files in parent directory: 
	exampleTxt.txt last modified on: Sun Oct 26 14:02:22 EET 2014
	example last modified on: Sun Oct 26 23:42:55 EET 2014
	comparator1.txt last modified on: Tue Oct 28 14:48:28 EET 2014
	comperator2.txt last modified on: Tue Oct 28 14:48:52 EET 2014
	exampleFileEntry.txt last modified on: Tue Oct 28 14:53:50 EET 2014
File example was modified last because...
	example last modified on: Sun Oct 26 23:42:55 EET 2014
	exampleTxt.txt last modified on: Sun Oct 26 14:02:22 EET 2014

    可以看到，在上面的代码中
NameFileComparator: 文件名的比较器，可以进行文件名称排序；
SizeFileComparator: 按照文件大小比较
LastModifiedFileComparator: 根据最新修改日期比较

五  input包
    在 common io的org.apache.commons.io.input 包中，有各种对InputStream的实现类：
我们看下其中的TeeInputStream, ，它接受InputStream和Outputstream参数，例子如下：
  

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.input.TeeInputStream;
import org.apache.commons.io.input.XmlStreamReader;


public final class InputExample {
    
    private static final String XML_PATH =
            "C:\\Users\\Lilykos\\workspace\\ApacheCommonsExample\\InputOutputExampleFolder\\web.xml";
    
    private static final String INPUT = "This should go to the output.";

    public static void runExample() {
        System.out.println("Input example...");
        XmlStreamReader xmlReader = null;
        TeeInputStream tee = null;
        
        try {
            
            // XmlStreamReader
            
            // We can read an xml file and get its encoding.
            File xml = FileUtils.getFile(XML_PATH);
            
            xmlReader = new XmlStreamReader(xml);
            System.out.println("XML encoding: " + xmlReader.getEncoding());
            
            
            // TeeInputStream
            
            // This very useful class copies an input stream to an output stream
            // and closes both using only one close() method (by defining the 3rd
            // constructor parameter as true).
            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());         
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try { xmlReader.close(); }
            catch (IOException e) { e.printStackTrace(); }
            
            try { tee.close(); }
            catch (IOException e) { e.printStackTrace(); }
        }
    }
}

输出：
  

Input example...
XML encoding: UTF-8
Output stream: This should go to the output.

   tee = new TeeInputStream(in, out, true);
   中，分别三个参数，将输入流的内容输出到输出流，true参数为最后关闭流
六 output工具类包
 
  其中的org.apache.commons.io.output 是实现了outputstream,其中好特别的是
TeeOutputStream能将一个输入流分别输出到两个输出流
  

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

import org.apache.commons.io.input.TeeInputStream;
import org.apache.commons.io.output.TeeOutputStream;

public final class OutputExample {
    
    private static final String INPUT = "This should go to the output.";

    public static void runExample() {
        System.out.println("Output example...");
        TeeInputStream teeIn = null;
        TeeOutputStream teeOut = null;
        
        try {
            
            // TeeOutputStream
            
            ByteArrayInputStream in = new ByteArrayInputStream(INPUT.getBytes("US-ASCII"));
            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 {
            // No need to close teeOut. When teeIn closes, it will also close its
            // Output stream (which is teeOut), which will in turn close the 2
            // branches (out1, out2).
            try { teeIn.close(); }
            catch (IOException e) { e.printStackTrace(); }
        }
    }
}

  输出：

Output example...
Output stream 1: This should go to the output.
Output stream 2: This should go to the output.

完整代码下载：http://a3ab771892fd198a96736e50.javacodegeeks.netdna-cdn.com/wp-content/uploads/2014/10/ApacheCommonsIOExample.rar