Apache?Commons包含了很多開源的工具，用于解決平時編程經常會遇到的問題，減少重復勞動。我選了一些比較常用的項目做簡單介紹。文中用了很多網上現成的東西，我只是做了一個匯總整理。?

一、Commons BeanUtils?

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

說明：針對Bean的一個工具集。由于Bean往往是有一堆get和set組成，所以BeanUtils也是在此基礎上進行一些包裝。?

使用示例：功能有很多，網站上有詳細介紹。一個比較常用的功能是Bean Copy，也就是copy bean的屬性。如果做分層架構開發的話就會用到，比如從PO（Persistent Object）拷貝數據到VO（Value Object）。?

傳統方法如下：?

//得到TeacherForm?

TeacherForm teacherForm=(TeacherForm)form;?

//構造Teacher對象?

Teacher teacher=new Teacher();?

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

//持久化Teacher對象到數據庫?
HibernateDAO= ;?
HibernateDAO.save(teacher);?

使用BeanUtils后，代碼就大大改觀了，如下所示：?

//得到TeacherForm?
TeacherForm teacherForm=(TeacherForm)form;?
//構造Teacher對象?
Teacher teacher=new Teacher();?

//賦值?
BeanUtils.copyProperties(teacher,teacherForm);?

//持久化Teacher對象到數據庫?
HibernateDAO= ;?
HibernateDAO.save(teacher);?

二、Commons CLI?

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

說明：這是一個處理命令的工具。比如main方法輸入的string[]需要解析。你可以預先定義好參數的規則，然后就可以調用CLI來解析。?

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?

說明：這個工具是用來編碼和解碼的，包括Base64，URL，Soundx等等。用這個工具的人應該很清楚這些，我就不多介紹了。?

四、Commons Collections?

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

說明：你可以把這個工具看成是java.util的擴展。?

使用示例：舉一個簡單的例子?

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/?

說明：這個工具是用來幫助處理配置文件的，支持很多種存儲方式?

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：舉一個Properties的簡單例子?

# 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;?



//初始化連接池?

bds.setDriverClassName(“org.postgresql.Driver”); //數據庫驅動程序?

bds.setUrl(“jdbc:postgresql://localhost:5432/myDB”); //數據庫url?

bds.setUsername(“postgres”); //dba帳號?

bds.setPassword(“XXXXXXXX”); //密碼?

bds.setInitialSize(100); //初始化連接數量?

bds.setMaxIdle(10); //最大idle數?

bds.setMaxWait(1000*60); //超時回收時間?

fac=new DataSourceConnectionFactory(bds); //得到連接工廠?

Connection conn=fac.createConnection(); //從池中獲得連接?

conn.close(); //釋放連接，回到池中?



//銷毀連接池?

bds.close();?
bds=null;?
fac=null;?

七、Commons DbUtils?

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

說明：我以前在寫數據庫程序的時候，往往把數據庫操作單獨做一個包。DbUtils就是這樣一個工具，以后開發不用再重復這樣的工作了。值得一體的是，這個工具并不是現在流行的OR-Mapping工具（比如Hibernate），只是簡化數據庫操作，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/?

說明：jsp的上傳文件功能怎么做呢？?

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/?

說明：這個工具可以方便通過編程的方式去訪問網站。?

使用示例：最簡單的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/?

說明：可以看成是java.io的擴展，我覺得用起來非常方便。?

使用示例：?

1．讀取Stream?

標準代碼：?

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．讀取文件?

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

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

十一、Commons JXPath?

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

說明：Xpath你知道吧，那么JXpath就是基于Java對象的Xpath，也就是用Xpath對Java對象進行查詢。這個東西還是很有想像力的。?

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

上述代碼等同于?
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/?

說明：這個工具包可以看成是對java.lang的擴展。提供了諸如StringUtils, StringEscapeUtils, RandomStringUtils, Tokenizer, WordUtils等工具類。?

十三、Commons Logging?

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

說明：你知道Log4j嗎？?

十四、Commons Math?

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

說明：看名字你就應該知道這個包是用來干嘛的了吧。這個包提供的功能有些和Commons Lang重復了，但是這個包更專注于做數學工具，功能更強大。?

十五、Commons Net?

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

說明：這個包還是很實用的，封裝了很多網絡協議。?

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/?

說明：用來幫助進行驗證的工具。比如驗證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/?

說明：提供對各種資源的訪問接口。支持的資源類型包括?

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?

這個包的功能很強大，極大的簡化了程序對資源的訪問。?

使用示例：?

從jar中讀取文件?

// 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() );?
}?

從smb讀取文件?
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提供的一個開源的API，是對javamail的封裝，因此在使用時要將javamail.jar加到 class path中，主要包括SimpleEmail,MultiPartEmail,HtmlEmail,EmailAttachment四個類。?

SimpleEmail:發送簡單的email,不能添加附件?
MultiPartEmail:文本郵件，可以添加多個附件?
HtmlEmail:HTML格式郵件，同時具有MultiPartEmail類所有“功能”?
EmailAttchment:附件類，可以添加本地資源，也可以指定網絡上資源，在發送時自動將網絡上資源下載發送。?

發送基本文本格式郵件：?
==============?
SimpleEmail email = new SimpleEmail();?
//smtp host?
email.setHostName("mail.test.com");?
//登陸郵件服務器的用戶名和密碼?
email.setAuthentication("test","testpassword");?
//接收人?
email.addTo("jdoe@somewhere.org", "John Doe");?
//發送人?
email.setFrom("me@apache.org", "Me");?
//標題?
email.setSubject("Test message");?
//郵件內容?
email.setMsg("This is a simple test of commons-email");?
//發送?
email.send();?

發送文本格式，帶附件郵件：?
==================?
//附件，可以定義多個附件對象?
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");?
//登陸郵件服務器的用戶名和密碼?
email.setAuthentication("test","testpassword");?
//接收人?
email.addTo("jdoe@somewhere.org", "John Doe");?
//發送人?
email.setFrom("me@apache.org", "Me");?
//標題?
email.setSubject("Test message");?
//郵件內容?
email.setMsg("This is a simple test of commons-email");?
//添加附件?
email.attach(attachment);?
//發送?
email.send();?

發送HTML格式帶附件郵件：?
=================?
//附件，可以定義多個附件對象?
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");?
//登陸郵件服務器的用戶名和密碼?
email.setAuthentication("test","testpassword");?
//接收人?
email.addTo("jdoe@somewhere.org", "John Doe");?
//發送人?
email.setFrom("me@apache.org", "Me");?
//標題?
email.setSubject("Test message");?
//郵件內容?
email.setHtmlMsg("This is a simple test of commons-email");?
//添加附件?
email.attach(attachment);?
//發送?

十九、 Commons Pool?

使用Jakarta?Commons Pool可以根據需要快速的實現自己的對象池，只需要實現PoolableObjectFactory或者 KeyedPoolableObjectFactory接口。KeyedPoolableObjectFactory和 PoolableObjectFactory的不同之處在于KeyedPoolableObjectFactory的每個方法都比 PoolableObjectFactory多了一個Object key的參數，使用這個參數可以使得對象池中的每個對象都有所不同。?
PoolableObjectFactory定義了五個方法（摘至Jakarta?Commons Pool API文檔）：?

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?

它能方便地將XML文檔所定義的元素轉化為JAVA對象，其實它的用法有點象棧(當然內在的原理就是那個古老的東西,只是提供了更高一層的封裝)。?

//生成一個digester。主要需要引進commons-logging.jar、commons-collections.jar、commons- beanutils.jar?
Digester digester = new Digester();?

//設置對XML文檔資料是否進行DTD驗證?
digester.setValidating( false );?

//當遇見 catalog 元素的時候，產生一個Catalog對象?
digester.addObjectCreate( "catalog", Catalog.class );?

//當遇見 catalog 元素下面的book的時候，產生一個Book對象?
digester.addObjectCreate( "catalog/book", Book.class );?
// 當遇見 catalog 元素下面的book的author時候，調用author屬性的Set方法?
digester.addBeanPropertySetter( "catalog/book/author", "author" );?
digester.addBeanPropertySetter( "catalog/book/title", "title" );?
//當再一次遇見 catalog 元素下面的book的時候，調用catalog類的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（）是將對應元素的屬性賦值。?
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"為XML文檔?
File input = new File( "F:\\Digester\\catalog.xml" );?
Catalog c = (Catalog)digester.parse( input );?
System.out.println( c.toString() );

總結

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