Apache Jakarta Commons 工具集简介

Apache Commons包含了很多开源的工具，用于解决平时编程经常会遇到的问题，减少重复劳动。我选了一些比较常用的项目做简单介绍。文中用了很多网上现成的东西，我只是做了一个汇总整理。 

一、Commons BeanUtils 

http://jakarta.apache.org/commons/beanutils/index.html 

说明：针对Bean的一个工具集。由于Bean往往是有一堆get和set组成，所以BeanUtils也是在此基础上进行一些包装。 

使用示例：功能有很多，网站上有详细介绍。一个比较常用的功能是Bean Copy，也就是copy bean的属性。如果做分层架构开发的话就会用到，比如从PO（Persistent Object）拷贝数据到VO（Value Object）。 

传统方法如下： 

//得到TeacherForm 

TeacherForm teacherForm=(TeacherForm)form; 

//构造Teacher对象 

Teacher teacher=new Teacher(); 

//赋值 
teacher.setName(teacherForm.getName()); 
teacher.setAge(teacherForm.getAge()); 
teacher.setGender(teacherForm.getGender()); 
teacher.setMajor(teacherForm.getMajor()); 
teacher.setDepartment(teacherForm.getDepartment()); 

//持久化Teacher对象到数据库 
HibernateDAO= ; 
HibernateDAO.save(teacher); 

使用BeanUtils后，代码就大大改观了，如下所示： 

//得到TeacherForm 
TeacherForm teacherForm=(TeacherForm)form; 
//构造Teacher对象 
Teacher teacher=new Teacher(); 

//赋值 
BeanUtils.copyProperties(teacher,teacherForm); 

//持久化Teacher对象到数据库 
HibernateDAO= ; 
HibernateDAO.save(teacher); 

二、Commons CLI 

http://jakarta.apache.org/commons/cli/index.html 

说明：这是一个处理命令的工具。比如main方法输入的string[]需要解析。你可以预先定义好参数的规则，然后就可以调用CLI来解析。 

使用示例： 

// create Options object 
Options options = new Options(); 
// add t option, option is the command parameter, false indicates that 
// this parameter is not required. 

options.addOption(“t”, false, “display current time”); 
options.addOption("c", true, "country code"); 

CommandLineParser parser = new PosixParser(); 
CommandLine cmd = parser.parse( options, args); 

if(cmd.hasOption("t")) { 
// print the date and time 
}else { 
// print the date 
} 

// get c option value 
String countryCode = cmd.getOptionValue("c"); 

if(countryCode == null) { 
// print default date 
}else { 
// print date for country specified by countryCode 
} 

三、Commons Codec 

http://jakarta.apache.org/commons/codec/index.html 

说明：这个工具是用来编码和解码的，包括Base64，URL，Soundx等等。用这个工具的人应该很清楚这些，我就不多介绍了。 

四、Commons Collections 

http://jakarta.apache.org/commons/collections/ 

说明：你可以把这个工具看成是java.util的扩展。 

使用示例：举一个简单的例子 

OrderedMap map = new LinkedMap(); 
map.put("FIVE", "5"); 
map.put("SIX", "6"); 
map.put("SEVEN", "7"); 
map.firstKey(); // returns "FIVE" 
map.nextKey("FIVE"); // returns "SIX" 
map.nextKey("SIX"); // returns "SEVEN" 

五、Commons Configuration 

http://jakarta.apache.org/commons/configuration/ 

说明：这个工具是用来帮助处理配置文件的，支持很多种存储方式 

1. Properties files 
2. XML documents 
3. Property list files (.plist) 
4. JNDI 
5. JDBC Datasource 
6. System properties 
7. Applet parameters 
8. Servlet parameters 

使用示例：举一个Properties的简单例子 

# usergui.properties, definining the GUI, 
colors.background = #FFFFFF 
colors.foreground = #000080 
window.width = 500 
window.height = 300 

PropertiesConfiguration config = new PropertiesConfiguration("usergui.properties"); 
config.setProperty("colors.background", "#000000); 
config.save(); 

config.save("usergui.backup.properties);//save a copy 
Integer integer = config.getInteger("window.width"); 

六、Commons DBCP 

http://jakarta.apache.org/commons/dbcp/ 

例子： 

import java.sql.*; 

import com.gwnet.games.antiLord.util.*; 

import org.apache.commons.dbcp.ConnectionFactory; 

import org.apache.commons.dbcp.BasicDataSource; 

import org.apache.commons.dbcp.DataSourceConnectionFactory; 



private static BasicDataSource bds=new BasicDataSource(); 

private static ConnectionFactory fac=null; 



//初始化连接池 

bds.setDriverClassName(“org.postgresql.Driver”); //数据库驱动程序 

bds.setUrl(“jdbc:postgresql://localhost:5432/myDB”); //数据库url 

bds.setUsername(“postgres”); //dba帐号 

bds.setPassword(“XXXXXXXX”); //密码 

bds.setInitialSize(100); //初始化连接数量 

bds.setMaxIdle(10); //最大idle数 

bds.setMaxWait(1000*60); //超时回收时间 

fac=new DataSourceConnectionFactory(bds); //得到连接工厂 

Connection conn=fac.createConnection(); //从池中获得连接 

conn.close(); //释放连接，回到池中 



//销毁连接池 

bds.close(); 
bds=null; 
fac=null; 

七、Commons DbUtils 

http://jakarta.apache.org/commons/dbutils/ 

说明：我以前在写数据库程序的时候，往往把数据库操作单独做一个包。DbUtils就是这样一个工具，以后开发不用再重复这样的工作了。值得一体的是，这个工具并不是现在流行的OR-Mapping工具（比如Hibernate），只是简化数据库操作，比如 

QueryRunner run = new QueryRunner(dataSource); 

// Execute the query and get the results back from the handler 
Object[] result = (Object[]) run.query("SELECT * FROM Person WHERE name=?", "John Doe"); 

八、Commons FileUpload 

http://jakarta.apache.org/commons/fileupload/ 

说明：jsp的上传文件功能怎么做呢？ 

使用示例： 

// Create a factory for disk-based file items 
FileItemFactory factory = new DiskFileItemFactory(); 
// Create a new file upload handler 
ServletFileUpload upload = new ServletFileUpload(factory); 

// Parse the request 
List /* FileItem */ items = upload.parseRequest(request); 
// Process the uploaded items 
Iterator iter = items.iterator(); 
while (iter.hasNext()) { 
FileItem item = (FileItem) iter.next(); 
if (item.isFormField()) { 
processFormField(item); 
} else { 
processUploadedFile(item); 
} 
} 

九、Commons HttpClient 

http://jakarta.apache.org/commons/httpclient/ 

说明：这个工具可以方便通过编程的方式去访问网站。 

使用示例：最简单的Get操作 

GetMethod get = new GetMethod("http://jakarta.apache.org"); 

// execute method and handle any error responses. 

... 

InputStream in = get.getResponseBodyAsStream(); 
// Process the data from the input stream. 
get.releaseConnection(); 

十、Commons IO 

http://jakarta.apache.org/commons/io/ 

说明：可以看成是java.io的扩展，我觉得用起来非常方便。 

使用示例： 

1．读取Stream 

标准代码： 

InputStream in = new URL( "http://jakarta.apache.org" ).openStream(); 
try { 
InputStreamReader inR = new InputStreamReader( in ); 
BufferedReader buf = new BufferedReader( inR ); 
String line; 
while ( ( line = buf.readLine() ) != null ) { 
System.out.println( line ); 
} 
} finally { 
in.close(); 
} 

使用IOUtils 

InputStream in = new URL( "http://jakarta.apache.org" ).openStream(); 
try { 
System.out.println( IOUtils.toString( in ) ); 
} finally { 
IOUtils.closeQuietly(in); 
} 

2．读取文件 

File file = new File("/commons/io/project.properties"); 
List lines = FileUtils.readLines(file, "UTF-8"); 

3．察看剩余空间 
long freeSpace = FileSystemUtils.freeSpace("C:/"); 

十一、Commons JXPath 

http://jakarta.apache.org/commons/jxpath/ 

说明：Xpath你知道吧，那么JXpath就是基于Java对象的Xpath，也就是用Xpath对Java对象进行查询。这个东西还是很有想像力的。 

使用示例： 
Address address = (Address)JXPathContext.newContext(vendor). 
getValue("locations[address/zipCode='90210']/address"); 

上述代码等同于 
Address address = null; 
Collection locations = vendor.getLocations(); 
Iterator it = locations.iterator(); 
while (it.hasNext()){ 
Location location = (Location)it.next(); 
String zipCode = location.getAddress().getZipCode(); 
if (zipCode.equals("90210")){ 
address = location.getAddress(); 
break; 
} 
} 

十二、Commons Lang 

http://jakarta.apache.org/commons/lang/ 

说明：这个工具包可以看成是对java.lang的扩展。提供了诸如StringUtils, StringEscapeUtils, RandomStringUtils, Tokenizer, WordUtils等工具类。 

十三、Commons Logging 

http://jakarta.apache.org/commons/logging/ 

说明：你知道Log4j吗？ 

十四、Commons Math 

http://jakarta.apache.org/commons/math/ 

说明：看名字你就应该知道这个包是用来干嘛的了吧。这个包提供的功能有些和Commons Lang重复了，但是这个包更专注于做数学工具，功能更强大。 

十五、Commons Net 

http://jakarta.apache.org/commons/net/ 

说明：这个包还是很实用的，封装了很多网络协议。 

1. FTP 
2. NNTP 
3. SMTP 
4. POP3 
5. Telnet 
6. TFTP 
7. Finger 
8. Whois 
9. rexec/rcmd/rlogin 
10. Time (rdate) and Daytime 
11. Echo 
12. Discard 
13. NTP/SNTP 

使用示例： 
TelnetClient telnet = new TelnetClient(); 
telnet.connect( "192.168.1.99", 23 ); 
InputStream in = telnet.getInputStream(); 
PrintStream out = new PrintStream( telnet.getOutputStream() ); 
... 
telnet.close(); 

十六、Commons Validator 

http://jakarta.apache.org/commons/validator/ 

说明：用来帮助进行验证的工具。比如验证Email字符串，日期字符串等是否合法。 

使用示例： 

// Get the Date validator 
DateValidator validator = DateValidator.getInstance(); 
// Validate/Convert the date 
Date fooDate = validator.validate(fooString, "dd/MM/yyyy"); 
if (fooDate == null) { 
// error...not a valid date 
return; 
} 

十七、Commons Virtual File System 

http://jakarta.apache.org/commons/vfs/ 

说明：提供对各种资源的访问接口。支持的资源类型包括 

1. CIFS 
2. FTP 
3. Local Files 
4. HTTP and HTTPS 
5. SFTP 
6. Temporary Files 
7. WebDAV 
8. Zip, Jar and Tar (uncompressed, tgz or tbz2) 
9. gzip and bzip2 
10. res 
11. ram 

这个包的功能很强大，极大的简化了程序对资源的访问。 

使用示例： 

从jar中读取文件 

// Locate the Jar file 
FileSystemManager fsManager = VFS.getManager(); 
FileObject jarFile = fsManager.resolveFile( "jar:lib/aJarFile.jar" ); 

// List the children of the Jar file 
FileObject[] children = jarFile.getChildren(); 
System.out.println( "Children of " + jarFile.getName().getURI() ); 
for ( int i = 0; i < children.length; i++ ){ 
System.out.println( children[ i ].getName().getBaseName() ); 
} 

从smb读取文件 
StaticUserAuthenticator auth = new StaticUserAuthenticator("username", "password", null); 
FileSystemOptions opts = new FileSystemOptions(); 
DefaultFileSystemConfigBuilder.getInstance().setUserAuthenticator(opts, auth); 
FileObject fo = VFS.getManager().resolveFile("smb://host/anyshare/dir", opts); 

十八、Commons-Email 

commons-email是apache提供的一个开源的API，是对javamail的封装，因此在使用时要将javamail.jar加到 class path中，主要包括SimpleEmail,MultiPartEmail,HtmlEmail,EmailAttachment四个类。 

SimpleEmail:发送简单的email,不能添加附件 
MultiPartEmail:文本邮件，可以添加多个附件 
HtmlEmail:HTML格式邮件，同时具有MultiPartEmail类所有“功能” 
EmailAttchment:附件类，可以添加本地资源，也可以指定网络上资源，在发送时自动将网络上资源下载发送。 

发送基本文本格式邮件： 
============== 
SimpleEmail email = new SimpleEmail(); 
//smtp host 
email.setHostName("mail.test.com"); 
//登陆邮件服务器的用户名和密码 
email.setAuthentication("test","testpassword"); 
//接收人 
email.addTo("jdoe@somewhere.org", "John Doe"); 
//发送人 
email.setFrom("me@apache.org", "Me"); 
//标题 
email.setSubject("Test message"); 
//邮件内容 
email.setMsg("This is a simple test of commons-email"); 
//发送 
email.send(); 

发送文本格式，带附件邮件： 
================== 
//附件，可以定义多个附件对象 
EmailAttachment attachment = new EmailAttachment(); 
attachment.setPath("e:\\1.pdf"); 
attachment.setDisposition(EmailAttachment.ATTACHMENT); 
attachment.setDescription("Picture of John"); 
// 
MultiPartEmail email = new MultiPartEmail(); 
//smtp host 
email.setHostName("mail.test.com"); 
//登陆邮件服务器的用户名和密码 
email.setAuthentication("test","testpassword"); 
//接收人 
email.addTo("jdoe@somewhere.org", "John Doe"); 
//发送人 
email.setFrom("me@apache.org", "Me"); 
//标题 
email.setSubject("Test message"); 
//邮件内容 
email.setMsg("This is a simple test of commons-email"); 
//添加附件 
email.attach(attachment); 
//发送 
email.send(); 

发送HTML格式带附件邮件： 
================= 
//附件，可以定义多个附件对象 
EmailAttachment attachment = new EmailAttachment(); 
attachment.setPath("e:\\1.pdf"); 
attachment.setDisposition(EmailAttachment.ATTACHMENT); 
attachment.setDescription("Picture of John"); 
// 
HtmlEmail email = new HtmlEmail (); 
//smtp host 
email.setHostName("mail.test.com"); 
//登陆邮件服务器的用户名和密码 
email.setAuthentication("test","testpassword"); 
//接收人 
email.addTo("jdoe@somewhere.org", "John Doe"); 
//发送人 
email.setFrom("me@apache.org", "Me"); 
//标题 
email.setSubject("Test message"); 
//邮件内容 
email.setHtmlMsg("This is a simple test of commons-email"); 
//添加附件 
email.attach(attachment); 
//发送 

十九、 Commons Pool 

使用Jakarta Commons Pool可以根据需要快速的实现自己的对象池，只需要实现PoolableObjectFactory或者 KeyedPoolableObjectFactory接口。KeyedPoolableObjectFactory和 PoolableObjectFactory的不同之处在于KeyedPoolableObjectFactory的每个方法都比 PoolableObjectFactory多了一个Object key的参数，使用这个参数可以使得对象池中的每个对象都有所不同。 
PoolableObjectFactory定义了五个方法（摘至Jakarta Commons Pool API文档）： 

1. makeObject is called whenever a new instance is needed. 
2. activateObject is invoked on every instance before it is returned from the pool. 
3. passivateObject is invoked on every instance when it is returned to the pool. 
4. destroyObject is invoked on every instance when it is being "dropped" from the pool (whether due to the response from validateObject, or for reasons specific to the pool implementation.) 
5. validateObject is invoked in an implementation-specific fashion to determine if an instance is still valid to be returned by the pool. It will only be invoked on an "activated" instance. 


二十、Commons Digester 

它能方便地将XML文档所定义的元素转化为JAVA对象，其实它的用法有点象栈(当然内在的原理就是那个古老的东西,只是提供了更高一层的封装)。 

//生成一个digester。主要需要引进commons-logging.jar、commons-collections.jar、commons- beanutils.jar 
Digester digester = new Digester(); 

//设置对XML文档资料是否进行DTD验证 
digester.setValidating( false ); 

//当遇见 catalog 元素的时候，产生一个Catalog对象 
digester.addObjectCreate( "catalog", Catalog.class ); 

//当遇见 catalog 元素下面的book的时候，产生一个Book对象 
digester.addObjectCreate( "catalog/book", Book.class ); 
// 当遇见 catalog 元素下面的book的author时候，调用author属性的Set方法 
digester.addBeanPropertySetter( "catalog/book/author", "author" ); 
digester.addBeanPropertySetter( "catalog/book/title", "title" ); 
//当再一次遇见 catalog 元素下面的book的时候，调用catalog类的addBook（）方法 
digester.addSetNext( "catalog/book", "addBook" ); 

digester.addObjectCreate( "catalog/magazine", Magazine.class ); 
digester.addBeanPropertySetter( "catalog/magazine/name", "name" ); 

digester.addObjectCreate( "catalog/magazine/article", Article.class ); 
//addSetProperties（）是将对应元素的属性赋值。 
digester.addSetProperties( "catalog/magazine/article", "page", "page" ); 
digester.addBeanPropertySetter( "catalog/magazine/article/headline" ); 
digester.addSetNext( "catalog/magazine/article", "addArticle" ); 

digester.addSetNext( "catalog/magazine", "addMagazine" ); 
//"F:\\Digester\\catalog.xml"为XML文档 
File input = new File( "F:\\Digester\\catalog.xml" ); 
Catalog c = (Catalog)digester.parse( input ); 
System.out.println( c.toString() );