Apache Commons 工具类介绍及简单使用

薄荷味的团子 05-29 672

前言：

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1、BeanUtils

提供了对于JavaBean进行各种操作，比如对象,属性复制等等。

//1、 克隆对象 // 新创建一个普通Java Bean，用来作为被克隆的对象  public class Person {  private String name = "";  private String email = "";  private int age;  //省略 set,get方法  } // 再创建一个Test类，其中在main方法中代码如下： 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();  }  }  } // 原理也是通过Java的反射机制来做的。// 2、 将一个Map对象转化为一个Bean // 这个Map对象的key必须与Bean的属性相对应。 Map map = new HashMap();  map.put("name","tom");  map.put("email","tom@");  map.put("age","21");  //将map转化为一个Person对象  Person person = new Person();  BeanUtils.populate(person,map); // 通过上面的一行代码，此时person的属性就已经具有了上面所赋的值了。// 将一个Bean转化为一个Map对象了，如下： Map map = BeanUtils.describe(person)

2.Betwixt

XML与Java对象之间相互转换。

//1、 将JavaBean转为XML内容 // 新创建一个Person类 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 + "']";  } } //再创建一个WriteApp类：import java.io.StringWriter; import org.apache.commons.betwixt.io.BeanWriter; public class WriteApp { /** * 创建一个例子Bean，并将它转化为XML. */ public static final void main(String [] args) throws Exception {  // 先创建一个StringWriter，我们将把它写入为一个字符串  StringWriter outputWriter = new StringWriter();  // Betwixt在这里仅仅是将Bean写入为一个片断  // 所以如果要想完整的XML内容，我们应该写入头格式  outputWriter.write(“<?xml version=’1.0′ encoding=’UTF-8′ ?>\n”);  // 创建一个BeanWriter，其将写入到我们预备的stream中  BeanWriter beanWriter = new BeanWriter(outputWriter);  // 配置betwixt  // 更多详情请参考java docs 或最新的文档  beanWriter.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);  beanWriter.getBindingConfiguration().setMapIDs(false);  beanWriter.enablePrettyPrint();  // 如果这个地方不传入XML的根节点名，Betwixt将自己猜测是什么  // 但是让我们将例子Bean名作为根节点吧  beanWriter.write(“person”, new PersonBean(“John Smith”, 21));  //输出结果  System.out.println(outputWriter.toString());  // Betwixt写的是片断而不是一个文档，所以不要自动的关闭掉writers或者streams，  //但这里仅仅是一个例子，不会做更多事情，所以可以关掉  outputWriter.close();  } } //2、 将XML转化为JavaBean import java.io.StringReader; import org.apache.commons.betwixt.io.BeanReader; public class ReadApp { public static final void main(String args[]) throws Exception{  // 先创建一个XML，由于这里仅是作为例子，所以我们硬编码了一段XML内容  StringReader xmlReader = new StringReader(  "<?xml version=’1.0′ encoding=’UTF-8′ ?> <person><age>25</age><name>James Smith</name></person>");  //创建BeanReader  BeanReader beanReader = new BeanReader();  //配置reader  beanReader.getXMLIntrospector().getConfiguration().setAttributesForPrimitives(false);  beanReader.getBindingConfiguration().setMapIDs(false);  //注册beans，以便betwixt知道XML将要被转化为一个什么Bean  beanReader.registerBeanClass("person", PersonBean.class);  //现在我们对XML进行解析  PersonBean person = (PersonBean) beanReader.parse(xmlReader);  //输出结果  System.out.println(person);  } }

3.Codec

提供了一些公共的编解码实现，比如Base64, Hex, MD5,Phonetic and URLs等等。

//Base64编解码 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 编码后："+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 解码后："+str); }

4.Collections

对java.util的扩展封装，处理数据还是挺灵活的。

org.apache.commons.collections – Commons Collections自定义的一组公用的接口和工具类

org.apache.commons.collections.bag – 实现Bag接口的一组类

org.apache.commons.collections.bidimap – 实现BidiMap系列接口的一组类

org.apache.commons.collections.buffer – 实现Buffer接口的一组类

org.apache.commons.collections.collection – 实现java.util.Collection接口的一组类

org.apache.commons.collections.comparators – 实现java.util.Comparator接口的一组类

org.apache.commons.collections.functors – Commons Collections自定义的一组功能类

org.apache.commons.collections.iterators – 实现java.util.Iterator接口的一组类

org.apache.commons.collections.keyvalue – 实现集合和键/值映射相关的一组类

org.apache.commons.collections.list – 实现java.util.List接口的一组类

org.apache.commons.collections.map – 实现Map系列接口的一组类

org.apache.commons.collections.set – 实现Set系列接口的一组类

/** * 得到集合里按顺序存放的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" /** * 通过key得到value * 通过value得到key * 将map里的key和value对调 */ 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); /**  * 得到两个集合中相同的元素  */ 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、压缩类库。

//创建压缩对象 ZipArchiveEntry entry = new ZipArchiveEntry("CompressTest"); //要压缩的文件 File f=new File("e:\\test.pdf"); FileInputStream fis=new FileInputStream(f); //输出的对象 压缩的文件 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

用来帮助处理配置文件的，支持很多种存储方式。

Properties filesXML documentsProperty list files (.plist)JNDIJDBC DatasourceSystem propertiesApplet parametersServlet parameters

//举一个Properties的简单例子 # 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)是一个依赖Jakarta commons-pool对象池机制的数据库连接池,Tomcat的数据源使用的就是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("加载jdbc驱动");  try {  Class.forName("oracle.jdbc.driver.OracleDriver");  } catch (ClassNotFoundException e) {  e.printStackTrace();  }  System.out.println("Done.");  //  System.out.println("设置数据源");  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) {  //设置连接地址  ConnectionFactory connectionFactory = new DriverManagerConnectionFactory(  connectURI, null);  // 创建连接工厂  PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(  connectionFactory);  //获取GenericObjectPool 连接的实例  ObjectPool connectionPool = new GenericObjectPool(  poolableConnectionFactory);  // 创建 PoolingDriver  PoolingDataSource dataSource = new PoolingDataSource(connectionPool);  return dataSource;  } }

8.DbUtils

Apache组织提供的一个资源JDBC工具类库，它是对JDBC的简单封装，对传统操作数据库的类进行二次封装，可以把结果集转化成List。，同时也不影响程序的性能。

DbUtils类：启动类

ResultSetHandler接口：转换类型接口

MapListHandler类：实现类，把记录转化成List

BeanListHandler类：实现类，把记录转化成List，使记录为JavaBean类型的对象

Qrery Runner类：执行SQL语句的类

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; //转换成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; //转换成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

提供的一个开源的API，是对javamail的封装。

//用commons email发送邮件 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("user@gmail.com");  email.setSubject("TestMail");  email.setMsg("This is a test mail ... :-)");  email.addTo("foo@bar.com");  email.send(); }

10.FileUpload

java web文件上传功能。

//官方示例：//* 检查请求是否含有上传文件 // Check that we have a file upload request boolean isMultipart = ServletFileUpload.isMultipartContent(request); //现在我们得到了items的列表 //如果你的应用近于最简单的情况，上面的处理就够了。但我们有时候还是需要更多的控制。//下面提供了几种控制选择：// 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); // 设置最大上传大小 upload.setSizeMax(yourMaxRequestSize); // 解析所有请求 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，你需要进一步处理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);  } } //区分数据是否为简单的表单数据，如果是简单的数据：// processFormField if (item.isFormField()) {  String name = item.getFieldName();  String value = item.getString();  //...省略步骤 } //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();  //...省略步骤 } //对于这些item，我们通常要把它们写入文件，或转为一个流 // Process a file upload if (writeToFile) {  File uploadedFile = new File(...);  item.write(uploadedFile); } else {  InputStream uploadedStream = item.getInputStream();  //...省略步骤  uploadedStream.close(); } //或转为字节数组保存在内存中：// Process a file upload in memory byte[] data = item.get(); //...省略步骤 //如果这个文件真的很大，你可能会希望向用户报告到底传了多少到服务端，让用户了解上传的过程 //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.HttpClient

基于HttpCore实现的一个HTTP/1.1兼容的HTTP客户端，它提供了一系列可重用的客户端身份验证、HTTP状态保持、HTTP连接管理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) {  // 构造HttpClient的实例  HttpClient httpClient = new HttpClient();  // 创建GET方法的实例  GetMethod getMethod = new GetMethod("");  // 使用系统提供的默认的恢复策略  getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,  new DefaultHttpMethodRetryHandler());  try {  // 执行getMethod  int statusCode = httpClient.executeMethod(getMethod);  if (statusCode != HttpStatus.SC_OK) {  System.err.println("Method failed: "  + getMethod.getStatusLine());  }  // 读取内容  byte[] responseBody = getMethod.getResponseBody();  // 处理内容  System.out.println(new String(responseBody));  } catch (HttpException e) {  // 发生致命的异常，可能是协议不对或者返回的内容有问题  System.out.println("Please check your provided http address!");  e.printStackTrace();  } catch (IOException e) {  // 发生网络异常  e.printStackTrace();  } finally {  // 释放连接  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) {  // 构造HttpClient的实例  HttpClient httpClient = new HttpClient();  // 创建POST方法的实例  String url = "";  PostMethod postMethod = new PostMethod(url);  // 填入各个表单域的值  NameValuePair[] data = { new NameValuePair("id", "youUserName"),  new NameValuePair("passwd", "yourPwd") };  // 将表单的值放入postMethod中  postMethod.setRequestBody(data);  // 执行postMethod  int statusCode = httpClient.executeMethod(postMethod);  // HttpClient对于要求接受后继服务的请求，象POST和PUT等不能自动处理转发  // 301或者302  if (statusCode == HttpStatus.SC_MOVED_PERMANENTLY ||  statusCode == HttpStatus.SC_MOVED_TEMPORARILY) {  // 从头中取出转向的地址  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

对java.io的扩展操作文件非常方便。

//1．读取Stream //标准代码：InputStream in = new URL( "" ).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( "" ).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:/");

13.Lang

主要是一些公共的工具集合，比如对字符、数组的操作等等。

// 1 合并两个数组: org.apache.commons.lang. ArrayUtils // 有时我们需要将两个数组合并为一个数组，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 截取从from开始字符串 StringUtils.substringAfter("SELECT * FROM PERSON ", "from"); //3 判断该字符串是不是为数字(0~9)组成，如果是，返回true 但该方法不识别有小数点和 请注意。StringUtils.isNumeric("454534"); //返回true //4.取得类名 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")); //6.五位的随机字母和数字 System.out.println(RandomStringUtils.randomAlphanumeric(5)); //7.StringEscapeUtils System.out.println(StringEscapeUtils.escapeHtml("<html>")); //输出结果为<html> System.out.println(StringEscapeUtils.escapeJava("String")); //8.StringUtils,判断是否是空格字符 System.out.println(StringUtils.isBlank(" ")); //将数组中的内容以,分隔 System.out.println(StringUtils.join(test,",")); //在右边加下字符,使之总长度为6 System.out.println(StringUtils.rightPad("abc", 6, 'T')); //首字母大写 System.out.println(StringUtils.capitalize("abc")); //Deletes all whitespaces from a String 删除所有空格 System.out.println( StringUtils.deleteWhitespace(" ab c ")); //判断是否包含这个字符 System.out.println( StringUtils.contains("abc", "ba")); //表示左边两个字符 System.out.println( StringUtils.left("abc", 2)); System.out.println(NumberUtils.stringToInt("33"));

14.Logging

提供的是一个Java 的日志接口,同时兼顾轻量级和不依赖于具体的日志实现工具。

import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class CommonLogTest {  private static Log log = LogFactory.getLog(CommonLogTest.class);  //日志打印  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

通用验证系统，该组件提供了客户端和服务器端的数据验证框架。

1.验证日期

// 获取日期验证 DateValidator validator = DateValidator.getInstance(); // 验证/转换日期 Date fooDate = validator.validate(fooString, "dd/MM/yyyy"); if (fooDate == null) {  // 错误 不是日期  return; }

2.表达式验证

// 设置参数 boolean caseSensitive = false; String regex1 = "^([A-Z]*)(?:\\-)([A-Z]*)*$" String regex2 = "^([A-Z]*)$"; String[] regexs = new String[] {regex1, regex1}; // 创建验证 RegexValidator validator = new RegexValidator(regexs, caseSensitive); // 验证返回boolean boolean valid = validator.isValid("abc-def"); // 验证返回字符串 String result = validator.validate("abc-def"); // 验证返回数组 String[] groups = validator.match("abc-def");

3.配置文件中使用验证

<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> 添加姓名验证. <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>

4.验证类

Excerpts from org.apache.commons.validator.RequiredNameTest //加载验证配置文件 InputStream in = this.getClass().getResourceAsStream("validator-name-required.xml"); ValidatorResources resources = new ValidatorResources(in); //这个是自己创建的bean 我这里省略了 Name name = new Name(); Validator validator = new Validator(resources, "nameForm"); //设置参数 validator.setParameter(Validator.BEAN_PARAM, name); Map results = null; //验证 results = validator.validate(); if (results.get("firstName") == null) {  //验证成功 } else {  //有错误 int errors = ((Integer)results.get("firstName")).intValue(); }

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