Java：Apache Commons 工具類介紹及簡單使用

本文轉載自查看原文 2020-12-01 20:46 3757 2-3-Java

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，減少重復勞動。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。

Commons簡介

組件	功能介紹
commons-beanutils	提供了對於JavaBean進行各種操作，克隆對象,屬性等等.
commons-betwixt	XML與Java對象之間相互轉換.
commons-codec	處理常用的編碼方法的工具類包例如DES、SHA1、MD5、Base64等.
commons-collections	java集合框架操作.
commons-compress	java提供文件打包壓縮類庫.
commons-configuration	一個java應用程序的配置管理類庫.
commons-dbcp	提供數據庫連接池服務.
commons-dbutils	提供對jdbc 的操作封裝來簡化數據查詢和記錄讀取操作.
commons-email	java發送郵件對javamail的封裝.
commons-fileupload	提供文件上傳功能.
commons-httpclient	提供HTTP客戶端與服務器的各種通訊操作. 現在已改成HttpComponents
commons-io	io工具的封裝.
commons-lang	Java基本對象方法的工具類包如：StringUtils,ArrayUtils,DateUtils,DateFormatUtils等等.
commons-logging	提供的是一個Java 的日志接口.
commons-validator	提供了客戶端和服務器端的數據驗證框架.

Maven依賴

<!-- https://mvnrepository.com/artifact/commons-beanutils/commons-beanutils -->
<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.3</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-betwixt/commons-betwixt -->
<dependency>
    <groupId>commons-betwixt</groupId>
    <artifactId>commons-betwixt</artifactId>
    <version>0.8</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-codec/commons-codec -->
<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.10</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-collections4</artifactId>
    <version>4.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-collections/commons-collections -->
<dependency>
    <groupId>commons-collections</groupId>
    <artifactId>commons-collections</artifactId>
    <version>3.2.1</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-compress -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-compress</artifactId>
    <version>1.18</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-configuration2 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-configuration2</artifactId>
    <version>2.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-configuration/commons-configuration -->
<dependency>
    <groupId>commons-configuration</groupId>
    <artifactId>commons-configuration</artifactId>
    <version>1.10</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-dbcp2 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-dbcp2</artifactId>
    <version>2.1.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-dbcp/commons-dbcp -->
<dependency>
    <groupId>commons-dbcp</groupId>
    <artifactId>commons-dbcp</artifactId>
    <version>1.4</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-dbutils/commons-dbutils -->
<dependency>
    <groupId>commons-dbutils</groupId>
    <artifactId>commons-dbutils</artifactId>
    <version>1.6</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-email -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-email</artifactId>
    <version>1.4</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-email/commons-email -->
<dependency>
    <groupId>commons-email</groupId>
    <artifactId>commons-email</artifactId>
    <version>1.0</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.1</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.12</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-httpclient/commons-httpclient -->
<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.6</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-io -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-io</artifactId>
    <version>1.3.2</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.9</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-lang/commons-lang -->
<dependency>
    <groupId>commons-lang</groupId>
    <artifactId>commons-lang</artifactId>
    <version>2.6</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-logging/commons-logging -->
<dependency>
    <groupId>commons-logging</groupId>
    <artifactId>commons-logging</artifactId>
    <version>1.2</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-validator/commons-validator -->
<dependency>
    <groupId>commons-validator</groupId>
    <artifactId>commons-validator</artifactId>
    <version>1.6</version>
</dependency>

1、commons-beanutils

提供了對於JavaBean進行各種操作，比如對象,屬性復制等等。

import java.util.HashMap;
import java.util.Map;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.beanutils.PropertyUtils;

public class CommonsBeanUtils {
    public static void main(String[] args) throws Exception {
        // ****************************************************************************
        Person person = new Person();
        person.setName("tom");
        person.setAge(21);
        // 克隆對象
        Person person2 = (Person) BeanUtils.cloneBean(person);
        System.out.println(person2.getName() + ">>" + person2.getAge());
        // ****************************************************************************
        Map<String, String> map = new HashMap<String, String>();
        map.put("name", "tom");
        map.put("email", "tom@");
        map.put("age", "21");
        // 將map轉化為一個Person對象
        Person person3 = new Person();
        BeanUtils.populate(person3, map);
        System.out.println(person3.getName() + ">>" + person3.getAge());
        // 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<String, String> map2 = BeanUtils.describe(person3);
        System.out.println(map2.get("name") + ">>" + map2.get("age"));
        // ****************************************************************************
        Person person4 = new Person();
        person4.setName("andy");
        // 反射調用get方法
        String name = (String) PropertyUtils.getProperty(person4, "name");
        System.out.println(name);
        // 反射調用set方法
        PropertyUtils.setProperty(person4, "age", 25);
        System.out.println(person4.getAge());
    }
}

2、commons-betwixt

XML與Java對象之間相互轉換。

import java.io.StringReader;
import java.io.StringWriter;
import org.apache.commons.betwixt.io.BeanReader;
import org.apache.commons.betwixt.io.BeanWriter;

public class CommonsBetwixt {
    public static void main(String[] args) throws Exception {
        // ****************************創建一個例子Bean，並將它轉化為XML ************************************************
        // 先創建一個StringWriter，我們將把它寫入為一個字符串
        StringWriter outputWriter = new StringWriter();
        // Betwixt在這里僅僅是將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將自己猜測是什么
        // 但是讓我們將例子Bean名作為根節點吧
        beanWriter.write("person", new Person("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，
        // 但這里僅僅是一個例子，不會做更多事情，所以可以關掉
        outputWriter.close();
        // ****************************將XML轉化為JavaBean ************************************************
        // 先創建一個XML，由於這里僅是作為例子，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);
        // 注冊beans，以便betwixt知道XML將要被轉化為一個什么Bean
        beanReader.registerBeanClass("person", Person.class);
        // 現在我們對XML進行解析
        Person person = (Person) beanReader.parse(xmlReader);
        // 輸出結果
        System.out.println(person);
    }
}

3、commons-codec

公共的編解碼實現，比如Base64, Hex, MD5,Phonetic and URLs等等。

import org.apache.commons.codec.binary.Base64;

public class CommonsCodec {
    public static void main(String[] args) throws Exception {
        Base64 base64 = new Base64();
        String encodestr = base64.encodeToString("abcd".getBytes("UTF-8"));
        System.out.println("Base64 編碼后：" + encodestr);
        
        String decodestr = new String(Base64.decodeBase64("YWJjZA=="));  
        System.out.println("Base64 解碼后："+decodestr);  
    }
}

4、commons-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

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.apache.commons.collections.BidiMap;
import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.collections.OrderedMap;
import org.apache.commons.collections.bidimap.TreeBidiMap;
import org.apache.commons.collections.map.LinkedMap;

public class CommonsCollections {
    public static void main(String[] args) {
        //得到集合里按順序存放的key之后的某一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里的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、commons-compress

commons compress中的打包、壓縮類庫。

import java.io.File;
import java.io.FileInputStream;

import org.apache.commons.compress.archivers.zip.ZipArchiveEntry;
import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream;

public class CommonsCompress {
    public static void main(String[] args) throws Exception {
        // 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、commons-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

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、commons-dbcp

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

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.sql.DataSource;
import org.apache.commons.dbcp.ConnectionFactory;
import org.apache.commons.dbcp.DriverManagerConnectionFactory;
import org.apache.commons.dbcp.PoolableConnectionFactory;
import org.apache.commons.dbcp.PoolingDataSource;
import org.apache.commons.pool.ObjectPool;
import org.apache.commons.pool.impl.GenericObjectPool;

public class CommonsDbcp {
    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, null, null, connectURI, false, false);

        // 獲取GenericObjectPool 連接的實例
        ObjectPool connectionPool = new GenericObjectPool(poolableConnectionFactory);

        // 創建 PoolingDriver
        PoolingDataSource dataSource = new PoolingDataSource(connectionPool);

        return dataSource;
    }
}

8、commons-dbutils

Apache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
Qrery Runner類：執行SQL語句的類

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;

public class CommonsDbutils {

    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);
        //****************************轉換成list  ************************************
        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("age:" + p.getAge() + ",name:" + p.getName());
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DbUtils.closeQuietly(conn);
        }
        //****************************轉換成map  ************************************
        try {
            conn = DriverManager.getConnection(url, user, password);
            QueryRunner qr = new QueryRunner();
            List results = (List) qr.query(conn, "select age,name from person",new MapListHandler());
            for (int i = 0; i < results.size(); i++) {
                Map map = (Map) results.get(i);
                System.out.println("age:" + map.get("age") + ",name:"+ map.get("name"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DbUtils.closeQuietly(conn);
        }
    }
}

9、commons-email

提供的一個開源的API，是對javamail的封裝。

import org.apache.commons.mail.DefaultAuthenticator;
import org.apache.commons.mail.Email;
import org.apache.commons.mail.EmailException;
import org.apache.commons.mail.SimpleEmail;

public class CommosEmail {
    public static void main(String[] args) throws EmailException {
        Email email = new SimpleEmail();
        email.setHostName("smtp.googlemail.com");
        email.setSmtpPort(465);
        email.setAuthenticator(new DefaultAuthenticator("username", "password"));
        email.setSSLOnConnect(true);
        email.setFrom("user@gmail.com");
        email.setSubject("TestMail");
        email.setMsg("This is a test mail ... :-)");
        email.addTo("foo@bar.com");
        email.send();
    }
}

10、commons-fileupload

java web文件上傳功能。

//檢查請求是否含有上傳文件  
    boolean isMultipart = ServletFileUpload.isMultipartContent(request);  

    //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
    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 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。
    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
    if (item.isFormField()) {  
        String name = item.getFieldName();  
        String value = item.getString();  
        //...省略步驟  
    }  
  
    //如果是提交的文件：  
    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  
    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
    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
    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、commons-httpclient

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。

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 CommonsHttpclient {
    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();
        }

        // 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對於要求接受后繼服務的請求，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、commons-io

對java.io的擴展操作文件非常方便。

import java.io.BufferedReader;
import java.io.File;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.List;

import org.apache.commons.io.FileSystemUtils;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOUtils;

public class CommonsIo {
    public static void main(String[] args) throws Exception {
        // 1．讀取Stream
        // 標准代碼：
        InputStream in = new URL("http://jakarta.apache.org").openStream();
        InputStreamReader inR = new InputStreamReader(in);
        BufferedReader buf = new BufferedReader(inR);
        String line;
        while ((line = buf.readLine()) != null) {
            System.out.println(line);
        }
        in.close();
        
        // 使用IOUtils
        InputStream in2 = new URL("http://jakarta.apache.org").openStream();
        try {
            System.out.println(IOUtils.toString(in2));
        } 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:/");
    }
}

13、commos-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。

import java.util.Calendar;
import java.util.Date;

import org.apache.commons.lang.ArrayUtils;
import org.apache.commons.lang.ClassUtils;
import org.apache.commons.lang.RandomStringUtils;
import org.apache.commons.lang.StringEscapeUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.time.DateFormatUtils;
import org.apache.commons.lang.time.DateUtils;

public class CommonsLang {
    public static void main(String[] args) throws Exception {
        //********************************ArrayUtils***************************************
        // 將兩個數組合並為一個數組
        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());
        //********************************StringUtils***************************************
        // 截取從from開始字符串
        StringUtils.substringAfter("SELECT * FROM PERSON ", "from");
        // 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
        // 取得類名
        System.out.println(ClassUtils.getShortClassName(CommonsLang.class));
        // 取得其包名
        System.out.println(ClassUtils.getPackageName(CommonsLang.class));
        // 五位的隨機字母和數字 
        System.out.println(RandomStringUtils.randomAlphanumeric(5));
        // StringEscapeUtils
        System.out.println(StringEscapeUtils.escapeHtml("<html>"));
        // 輸出結果為<html>
        System.out.println(StringEscapeUtils.escapeJava("String"));
        // 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(s1, ","));
        // 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));
        //********************************DateFormatUtils***************************************
        System.out.println(DateFormatUtils.format(new Date(), "yyyy-MM-dd HH:mm:ss"));
        //直接將日期格式化為內置的固定格式
        System.out.println(DateFormatUtils.ISO_DATE_FORMAT.format(new Date()));
        //字符型日期轉化為Date
        System.out.println(DateUtils.parseDate("2014-11-11 11:11:11", new String[] { "yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd HH:mm", "yyyy-MM-dd", "yyyy/MM/dd" }));
        //日期舍入與截整
        System.out.println(DateUtils.truncate(new Date(), Calendar.DATE));
        //判斷是否是同一天
        System.out.println(DateUtils.isSameDay(new Date(), new Date()));
        //加天數
        System.out.println(DateUtils.addDays(new Date(), 10));
    }
}

14、commos-logging

提供的是一個Java 的日志接口,同時兼顧輕量級和不依賴於具體的日志實現工具。

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class CommosLogging {
    private static Log log = LogFactory.getLog(CommosLogging.class);

    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   = "^([A-Z]*)(?:\\-)([A-Z]*)*$"  
      String regex2   = "^([A-Z]*)$";  
      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");

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