apache commons工具集代碼詳解

Apache Commons包含了很多開源的工具，用於解決平時編程經常會遇到的問題，減少重複勞動。下面是我這幾年做開發過程中自己用過的工具類做簡單介紹。

1、BeanUtils 提供了對於JavaBean進行各種操作， 比如對象,屬性複制等等。

 //1、 克隆對象// 新創建一個普通Java Bean，用來作為被克隆的對象public class Person {private String name = "";private String email = "";private int age;//省略set,get方法}// 再創建一個Test類，其中在main方法中代碼如下： import java.lang.reflect.InvocationTargetException;import java.util.HashMap;import java.util.Map;import org.apache.commons.beanutils.BeanUtils;import org.apache.commons.beanutils.ConvertUtils;public class Test {/** * @param args */public static void main(String[] args) {Person person = new Person();person.setName("tom");person.setAge(21);try {//克隆Person person2 = (Person)BeanUtils.cloneBean(person);System.out.println(person2.getName()+">>"+person2.getAge());}catch (IllegalAccessException e) {e.printStackTrace();}catch (InstantiationException e) {e.printStackTrace();}catch (InvocationTargetException e) {e.printStackTrace();}catch (NoSuchMethodException e) {e.printStackTrace();}}}// 原理也是通過Java的反射機制來做的。 // 2、 將一個Map對象轉化為一個Bean // 這個Map對象的key必須與Bean的屬性相對應。 Map map = new HashMap();map.put("name","tom");map.put("email","tom@");map.put("age","21");//將map轉化為一個Person對象Person person = new Person();BeanUtils.populate(person,map);// 通過上面的一行代碼，此時person的屬性就已經具有了上面所賦的值了。 // 將一個Bean轉化為一個Map對象了，如下： Map map = BeanUtils.describe(person)

2、Betwixt XML與Java對象之間相互轉換。

 //1、 將JavaBean轉為XML內容// 新創建一個Person類public class Person{private String name;private int age;/** Need to allow bean to be created via reflection */public PersonBean() {}public PersonBean(String name, int age) {this.name = name;this.age = age;}//省略set, get方法public String toString() {return "PersonBean[name='" + name + "',age='" + age + "']";}}//再創建一個WriteApp類： import java.io.StringWriter;import org.apache.commons.betwixt.io.BeanWriter;public class WriteApp {/** * 創建一個例子Bean，並將它轉化為XML. */public static final void main(String [] args) throws Exception {// 先創建一個StringWriter，我們將把它寫入為一個字符串StringWriter outputWriter = new StringWriter();// Betwixt在這裡僅僅是將Bean寫入為一個片斷// 所以如果要想完整的XML內容，我們應該寫入頭格式outputWriter.write(“<?xml version='1.0′ encoding='UTF-8′ ?>/n”);// 創建一個BeanWriter，其將寫入到我們預備的stream中BeanWriter beanWriter = new BeanWriter(outputWriter);// 配置betwixt // 更多詳情請參考java docs 或最新的文檔beanWriter.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);beanWriter.getBindingConfiguration().setMapIDs(false);beanWriter.enablePrettyPrint();// 如果這個地方不傳入XML的根節點名，Betwixt將自己猜測是什麼// 但是讓我們將例子Bean名作為根節點吧beanWriter.write(“person”, new PersonBean(“John Smith”, 21));//輸出結果System.out.println(outputWriter.toString());// Betwixt寫的是片斷而不是一個文檔，所以不要自動的關閉掉writers或者streams， //但這裡僅僅是一個例子，不會做更多事情，所以可以關掉outputWriter.close();}}//2、 將XML轉化為JavaBean import java.io.StringReader;import org.apache.commons.betwixt.io.BeanReader;public class ReadApp {public static final void main(String args[]) throws Exception{// 先創建一個XML，由於這裡僅是作為例子，所以我們硬編碼了一段XML內容StringReader xmlReader = new StringReader( "<?xml version='1.0′ encoding='UTF-8′ ?> <person><age>25</age><name>James Smith</name></person>");//創建BeanReader BeanReader beanReader = new BeanReader();//配置reader beanReader.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);beanReader.getBindingConfiguration().setMapIDs(false);//註冊beans，以便betwixt知道XML將要被轉化為一個什麼Bean beanReader.registerBeanClass("person", PersonBean.class);//現在我們對XML進行解析PersonBean person = (PersonBean) beanReader.parse(xmlReader);//輸出結果System.out.println(person);}}

3、Codec 提供了一些公共的編解碼實現，比如Base64, Hex, MD5,Phonetic and URLs等等。

 //Base64編解碼private static String encodeTest(String str){Base64 base64 = new Base64();try {str = base64.encodeToString(str.getBytes("UTF-8"));}catch (UnsupportedEncodingException e) {e.printStackTrace();}System.out.println("Base64 編碼後："+str);return str;}private static void decodeTest(String str){Base64 base64 = new Base64();//str = Arrays.toString(Base64.decodeBase64(str)); str = new String(Base64.decodeBase64(str));System.out.println("Base64 解碼後："+str);}

4、Collections 對java.util的擴展封裝，處理數據還是挺靈活的。

org.apache.commons.collections Commons Collections自定義的一組公用的接口和工具類

org.apache.commons.collections.bag 實現Bag接口的一組類

org.apache.commons.collections.bidimap 實現BidiMap系列接口的一組類

org.apache.commons.collections.buffer 實現Buffer接口的一組類

org.apache.commons.collections.collection 實現java.util.Collection接口的一組類

org.apache.commons.collections.comparators 實現java.util.Comparator接口的一組類

org.apache.commons.collections.functors Commons Collections自定義的一組功能類

org.apache.commons.collections.iterators 實現java.util.Iterator接口的一組類

org.apache.commons.collections.keyvalue 實現集合和鍵/值映射相關的一組類

org.apache.commons.collections.list 實現java.util.List接口的一組類

org.apache.commons.collections.map 實現Map系列接口的一組類

org.apache.commons.collections.set 實現Set系列接口的一組類

/** * 得到集合裡按順序存放的key之後的某一Key */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" /** * 通過key得到value * 通過value得到key * 將map裡的key和value對調*/BidiMap bidi = new TreeBidiMap();bidi.put("SIX", "6");bidi.get("SIX");// returns "6" bidi.getKey("6");// returns "SIX" // bidi.removeValue("6"); // removes the mapping BidiMap inverse = bidi.inverseBidiMap();// returns a map with keys and values swapped System.out.println(inverse);/** * 得到兩個集合中相同的元素*/List<String> list1 = new ArrayList<String>();list1.add("1");list1.add("2");list1.add("3");List<String> list2 = new ArrayList<String>();list2.add("2");list2.add("3");list2.add("5");Collection c = CollectionUtils.retainAll(list1, list2);System.out.println(c);

5、Compress commons compress中的打包、壓縮類庫。

 //創建壓縮對象ZipArchiveEntry entry = new ZipArchiveEntry("CompressTest");//要壓縮的文件File f=new File("e://test.pdf");FileInputStream fis=new FileInputStream(f);//輸出的對象壓縮的文件ZipArchiveOutputStream zipOutput=new ZipArchiveOutputStream(new File("e://test.zip"));zipOutput.putArchiveEntry(entry);int i=0,j;while((j=fis.read()) != -1) {zipOutput.write(j);i++;System.out.println(i);}zipOutput.closeArchiveEntry();zipOutput.close();fis.close();

6、Configuration 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

 //舉一個Properties的簡單例子# usergui.properties 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");

7、DBCP (Database Connection Pool)是一個依賴Jakarta commons-pool對像池機制的數據庫連接池,Tomcat的數據源使用的就是DBCP。

 import javax.sql.DataSource;import java.sql.Connection;import java.sql.Statement;import java.sql.ResultSet;import java.sql.SQLException;import org.apache.commons.pool.ObjectPool;import org.apache.commons.pool.impl.GenericObjectPool;import org.apache.commons.dbcp.ConnectionFactory;import org.apache.commons.dbcp.PoolingDataSource;import org.apache.commons.dbcp.PoolableConnectionFactory;import org.apache.commons.dbcp.DriverManagerConnectionFactory;//官方示例public class PoolingDataSources {public static void main(String[] args) {System.out.println("加載jdbc驅動");try {Class.forName("oracle.jdbc.driver.OracleDriver");}catch (ClassNotFoundException e) {e.printStackTrace();}System.out.println("Done.");// System.out.println("設置數據源");DataSource dataSource = setupDataSource("jdbc:oracle:thin:@localhost:1521:test");System.out.println("Done.");// Connection conn = null;Statement stmt = null;ResultSet rset = null;try {System.out.println("Creating connection.");conn = dataSource.getConnection();System.out.println("Creating statement.");stmt = conn.createStatement();System.out.println("Executing statement.");rset = stmt.executeQuery("select * from person");System.out.println("Results:");int numcols = rset.getMetaData().getColumnCount();while(rset.next()) {for (int i=0;i<=numcols;i++) {System.out.print("/t" + rset.getString(i));}System.out.println("");}}catch(SQLException e) {e.printStackTrace();}finally {try {if (rset != null) rset.close();}catch(Exception e) {}try {if (stmt != null) stmt.close();}catch(Exception e) {}try {if (conn != null) conn.close();}catch(Exception e) {}}}public static DataSource setupDataSource(String connectURI) {//設置連接地址ConnectionFactory connectionFactory = new DriverManagerConnectionFactory( connectURI, null);// 創建連接工廠PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory( connectionFactory);//獲取GenericObjectPool 連接的實例ObjectPool connectionPool = new GenericObjectPool( poolableConnectionFactory);// 創建PoolingDriver PoolingDataSource dataSource = new PoolingDataSource(connectionPool);return dataSource;}}

8、DbUtilsApache組織提供的一個資源JDBC工具類庫，它是對JDBC的簡單封裝，對傳統操作數據庫的類進行二次封裝，可以把結果集轉化成List。 ，同時也不影響程序的性能。

DbUtils類：啟動類

ResultSetHandler接口：轉換類型接口

MapListHandler類：實現類，把記錄轉化成List

BeanListHandler類：實現類，把記錄轉化成List，使記錄為JavaBean類型的對象

QreryRunner類：執行SQL語句的類

import org.apache.commons.dbutils.DbUtils;import org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.BeanListHandler;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.List;//轉換成list public class BeanLists {public static void main(String[] args) {Connection conn = null;String url = "jdbc:mysql://localhost:3306/ptest";String jdbcDriver = "com.mysql.jdbc.Driver";String user = "root";String password = "ptest";DbUtils.loadDriver(jdbcDriver);try {conn = DriverManager.getConnection(url, user, password);QueryRunner qr = new QueryRunner();List results = (List) qr.query(conn, "select id,name from person", new BeanListHandler(Person.class));for (int i = 0; i < results.size(); i++) {Person p = (Person) results.get(i);System.out.println("id:" + p.getId() + ",name:" + p.getName());}}catch (SQLException e) {e.printStackTrace();}finally {DbUtils.closeQuietly(conn);}}}public class Person{private Integer id;private String name;//省略set, get方法}import org.apache.commons.dbutils.DbUtils;import org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.MapListHandler;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.List;import java.util.Map;//轉換成map public class MapLists {public static void main(String[] args) {Connection conn = null;String url = "jdbc:mysql://localhost:3306/ptest";String jdbcDriver = "com.mysql.jdbc.Driver";String user = "root";String password = "ptest";DbUtils.loadDriver(jdbcDriver);try {conn = DriverManager.getConnection(url, user, password);QueryRunner qr = new QueryRunner();List results = (List) qr.query(conn, "select id,name from person", new MapListHandler());for (int i = 0; i < results.size(); i++) {Map map = (Map) results.get(i);System.out.println("id:" + map.get("id") + ",name:" + map.get("name"));}}catch (SQLException e) {e.printStackTrace();}finally {DbUtils.closeQuietly(conn);}}}

9、Email 提供的一個開源的API，是對javamail的封裝。

 //用commons email發送郵件public static void main(String args[]){Email email = new SimpleEmail();email.setHostName("smtp.googlemail.com");email.setSmtpPort(465);email.setAuthenticator(new DefaultAuthenticator("username", "password"));email.setSSLOnConnect(true);email.setFrom("[email protected]");email.setSubject("TestMail");email.setMsg("This is a test mail ... :-)");email.addTo("[email protected]");email.send();}

10、FileUpload java web文件上傳功能。

 //官方示例： //* 檢查請求是否含有上傳文件// Check that we have a file upload request Boolean isMultipart = ServletFileUpload.isMultipartContent(request);//現在我們得到了items的列表//如果你的應用近於最簡單的情況，上面的處理就夠了。但我們有時候還是需要更多的控制。 //下面提供了幾種控制選擇： // Create a factory for disk-based file items DiskFileItemFactory factory = new DiskFileItemFactory();// Set factory constraints factory.setSizeThreshold(yourMaxMemorySize);factory.setRepository(yourTempDirectory);// Create a new file upload handler ServletFileUpload upload = new ServletFileUpload(factory);// 設置最大上傳大小upload.setSizeMax(yourMaxRequestSize);// 解析所有請求List /* FileItem */items = upload.parseRequest(request);// Create a factory for disk-based file items DiskFileItemFactory factory = new DiskFileItemFactory( yourMaxMemorySize, yourTempDirectory);//一旦解析完成，你需要進一步處理item的列表。 // Process the uploaded items Iterator iter = items.iterator();while (iter.hasNext()) {FileItem item = (FileItem) iter.next();if (item.isFormField()) {processFormField(item);} else {processUploadedFile(item);}}//區分數據是否為簡單的表單數據，如果是簡單的數據： // processFormField if (item.isFormField()) {String name = item.getFieldName();String value = item.getString();//...省略步驟}//如果是提交的文件： // processUploadedFile if (!item.isFormField()) {String fieldName = item.getFieldName();String fileName = item.getName();String contentType = item.getContentType();Boolean isInMemory = item.isInMemory();long sizeInBytes = item.getSize();//...省略步驟}//對於這些item，我們通常要把它們寫入文件，或轉為一個流// Process a file upload if (writeToFile) {File uploadedFile = new File(...);item.write(uploadedFile);} else {InputStream uploadedStream = item.getInputStream();//...省略步驟uploadedStream.close();}//或轉為字節數組保存在內存中： // Process a file upload in memory byte[] data = item.get();//...省略步驟//如果這個文件真的很大，你可能會希望向用戶報告到底傳了多少到服務端，讓用戶了解上傳的過程//Create a progress listener ProgressListener progressListener = new ProgressListener(){public void update(long pBytesRead, long pContentLength, int pItems) {System.out.println("We are currently reading item " + pItems);if (pContentLength == -1) {System.out.println("So far, " + pBytesRead + " bytes have been read.");} else {System.out.println("So far, " + pBytesRead + " of " + pContentLength + " bytes have been read.");}}};upload.setProgressListener(progressListener);

11、HttpClien 基於HttpCore實現的一個HTTP/1.1兼容的HTTP客戶端，它提供了一系列可重用的客戶端身份驗證、HTTP狀態保持、HTTP連接管理module。

 //GET方法import java.io.IOException;import org.apache.commons.httpclient.*;import org.apache.commons.httpclient.methods.GetMethod;import org.apache.commons.httpclient.params.HttpMethodParams;public class GetSample{public static void main(String[] args) {// 構造HttpClient的實例HttpClient httpClient = new HttpClient();// 創建GET方法的實例GetMethod getMethod = new GetMethod("http://www.ibm.com");// 使用系統提供的默認的恢復策略getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler());try {// 執行getMethod int statusCode = httpClient.executeMethod(getMethod);if (statusCode != HttpStatus.SC_OK) {System.err.println("Method failed: " + getMethod.getStatusLine());}// 讀取內容byte[] responseBody = getMethod.getResponseBody();// 處理內容System.out.println(new String(responseBody));}catch (HttpException e) {// 發生致命的異常，可能是協議不對或者返回的內容有問題System.out.println("Please check your provided http address!");e.printStackTrace();}catch (IOException e) {// 發生網絡異常e.printStackTrace();}finally {// 釋放連接getMethod.releaseConnection();}}}//POST方法import java.io.IOException;import org.apache.commons.httpclient.*;import org.apache.commons.httpclient.methods.PostMethod;import org.apache.commons.httpclient.params.HttpMethodParams;public class PostSample{public static void main(String[] args) {// 構造HttpClient的實例HttpClient httpClient = new HttpClient();// 創建POST方法的實例String url = "http://www.oracle.com/";PostMethod postMethod = new PostMethod(url);// 填入各個表單域的值NameValuePair[] data = { new NameValuePair("id", "youUserName"), new NameValuePair("passwd", "yourPwd")};// 將表單的值放入postMethod中postMethod.setRequestBody(data);// 執行postMethod int statusCode = httpClient.executeMethod(postMethod);// HttpClient對於要求接受後繼服務的請求，象POST和PUT等不能自動處理轉發// 301或者302 if (statusCode == HttpStatus.SC_MOVED_PERMANENTLY || statusCode == HttpStatus.SC_MOVED_TEMPORARILY) {// 從頭中取出轉向的地址Header locationHeader = postMethod.getResponseHeader("location");String location = null;if (locationHeader != null) {location = locationHeader.getValue();System.out.println("The page was redirected to:" + location);} else {System.err.println("Location field value is null.");}return;}}}

12、IO 對java.io的擴展操作文件非常方便。

 //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．察看剩餘空間long freeSpace = FileSystemUtils.freeSpace("C:/");

13、Lang 主要是一些公共的工具集合，比如對字符、數組的操作等等。

 // 1 合併兩個數組: org.apache.commons.lang. ArrayUtils // 有時我們需要將兩個數組合併為一個數組，用ArrayUtils就非常方便，示例如下： private static void testArr() {String[] s1 = new String[] { "1", "2", "3" };String[] s2 = new String[] { "a", "b", "c" };String[] s = (String[]) ArrayUtils.addAll(s1, s2);for (int i = 0; i < s.length; i++) {System.out.println(s[i]);}String str = ArrayUtils.toString(s);str = str.substring(1, str.length() - 1);System.out.println(str + ">>" + str.length());}//2 截取從from開始字符串StringUtils.substringAfter("SELECT * FROM PERSON ", "from");//3 判斷該字符串是不是為數字(0~9)組成，如果是，返回true 但該方法不識別有小數點和請注意StringUtils.isNumeric("454534");//返回true //4.取得類名System.out.println(ClassUtils.getShortClassName(Test.class));//取得其包名System.out.println(ClassUtils.getPackageName(Test.class));//5.NumberUtils System.out.println(NumberUtils.stringToint("6"));//6.五位的隨機字母和數字System.out.println(RandomStringUtils.randomAlphanumeric(5));//7.StringEscapeUtils System.out.println(StringEscapeUtils.escapeHtml("<html>"));//輸出結果為<html> System.out.println(StringEscapeUtils.escapeJava("String"));//8.StringUtils,判斷是否是空格字符System.out.println(StringUtils.isBlank(" "));//將數組中的內容以,分隔System.out.println(StringUtils.join(test,","));//在右邊加下字符,使之總長度為6 System.out.println(StringUtils.rightPad("abc", 6, 'T'));//首字母大寫System.out.println(StringUtils.capitalize("abc"));//Deletes all whitespaces from a String 刪除所有空格System.out.println( StringUtils.deleteWhitespace(" ab c "));//判斷是否包含這個字符System.out.println( StringUtils.contains("abc", "ba"));//表示左邊兩個字符System.out.println( StringUtils.left("abc", 2));System.out.println(NumberUtils.stringToint("33"));

14、Logging 提供的是一個Java 的日誌接口,同時兼顧輕量級和不依賴於具體的日誌實現工具。

 import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;public class CommonLogTest {private static Log log = LogFactory.getLog(CommonLogTest.class);//日誌打印public static void main(String[] args) {log.error("ERROR");log.debug("DEBUG");log.warn("WARN");log.info("INFO");log.trace("TRACE");System.out.println(log.getClass());}}

15、Validator 通用驗證系統，該組件提供了客戶端和服務器端的數據驗證框架。

驗證日期

// 獲取日期驗證DateValidator validator = DateValidator.getInstance();// 驗證/轉換日期Date fooDate = validator.validate(fooString, "dd/MM/yyyy");if (fooDate == null) {// 錯誤不是日期return;}

表達式驗證

// 設置參數Boolean caseSensitive = false;String regex1 = "^([AZ]*)(?://-)([AZ]*)*$" String regex2 = "^([AZ]*)$";String[] regexs = new String[] {regex1, regex1};// 創建驗證RegexValidator validator = new RegexValidator(regexs, caseSensitive);// 驗證返回boolean Boolean valid = validator.isValid("abc-def");// 驗證返回字符串String result = validator.validate("abc-def");// 驗證返回數組String[] groups = validator.match("abc-def");

配置文件中使用驗證

<form-validation> <global> <validator name="required" classname="org.apache.commons.validator.TestValidator" method="validateRequired" methodParams="java.lang.Object, org.apache.commons.validator.Field"/> </global> <formset> </formset> </form-validation> 添加姓名驗證. <form-validation> <global> <validator name="required" classname="org.apache.commons.validator.TestValidator" method="validateRequired" methodParams="java.lang.Object, org.apache.commons.validator.Field"/> </global> <formset> <form name="nameForm"> <field property="firstName" depends="required"> <arg0 key="nameForm.firstname.displayname"/> </field> <field property="lastName" depends="required"> <arg0 key="nameForm.lastname.displayname"/> </field> </form> </formset> </form-validation>

驗證類

Excerpts from org.apache.commons.validator.RequiredNameTest //加載驗證配置文件InputStream in = this.getClass().getResourceAsStream("validator-name-required.xml");ValidatorResources resources = new ValidatorResources(in);//這個是自己創建的bean 我這裡省略了Name name = new Name();Validator validator = new Validator(resources, "nameForm");//設置參數validator.setParameter(Validator.BEAN_PARAM, name);Map results = null;//驗證results = validator.validate();if (results.get("firstName") == null) {//驗證成功} else {//有錯誤int errors = ((Integer)results.get("firstName")).intValue();}

總結

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