xml，文件操作功能类的示例代码详解

FileUtil.xml

package com.novel.util;     import java.io.File;  import java.io.FileInputStream;  import java.io.FileOutputStream;  import java.io.IOException;  import java.io.InputStream;  import java.io.InputStreamReader;     /**   * @author cy   *   * @date 2015年7月24日 上午8:38:38   *   * @Description 关于文件的一些工具   */  public class FileUtils {      /**       * 将文件中所有内容读取到字符串中       *        * @param filePath       *            文件路径       * @return 文件内容       */      public static String getStringFromFile(String filePath) {          File file = new File(filePath) ;          if(!file.exists()){               return "" ;          }          /**           * 处理文件读取乱码问题 :           * 只要判定两种常见的编码就可以了：GBK和UTF-8。由于中文Windows默认的编码是GBK，所以一般只要判定UTF-8编码格式。              *对于UTF-8编码格式的文本文件，其前3个字节的值就是-17、-69、-65           */          try{              byte[] firstThreeByte = new byte[3] ;              InputStream in = new FileInputStream(file) ;              in.read(firstThreeByte) ;              in.close() ;              String encoding = "" ;              if(firstThreeByte[0] == -17 && firstThreeByte[1] == -16 && firstThreeByte[2] == -65){                  encoding = "utf-8" ;              }else{                  encoding = "gbk" ;              }               InputStreamReader read = new InputStreamReader(new FileInputStream(file),encoding);                    Long filelength = file.length() / 2 ; // 该方法获取的是文件字节长度，                                                    //而我要创建的是char数组，char占两个字节，                                                    //byte一个字节，所以除以2表示的是该文件的字符长度              char[] filecontent = new char[filelength.intValue()] ;               read.read(filecontent) ;              return new String(filecontent) ;          }catch(Exception e ){              e.printStackTrace();              return "" ;          }      }         /**       * 将字符串写入文件       *        * @param content       *            字符串内容       * @param filePath       *            文件路径       * @throws IOException       */      public static void writeStringToFile(String content, String filePath)              throws IOException {             File file = new File(filePath);          if (!file.exists()) {              file.createNewFile();          }          FileOutputStream out = new FileOutputStream(file);          out.write(content.getBytes());          out.close();      }      /**       * 删除指定的文件        * @param filePath文件路径        */      public static void deleteFile(String filePath ) {          File file = new File(filePath) ;          if(file.exists()){              file.delete() ;          }      }  }

XmlUtil.java

package com.novel.util;     import java.io.File;  import java.io.IOException;  import java.util.ArrayList;  import java.util.HashMap;  import java.util.List;  import java.util.Map;     import javax.xml.parsers.DocumentBuilder;  import javax.xml.parsers.DocumentBuilderFactory;  import javax.xml.parsers.ParserConfigurationException;  import javax.xml.transform.OutputKeys;  import javax.xml.transform.Transformer;  import javax.xml.transform.TransformerConfigurationException;  import javax.xml.transform.TransformerException;  import javax.xml.transform.TransformerFactory;  import javax.xml.transform.TransformerFactoryConfigurationError;  import javax.xml.transform.dom.DOMSource;  import javax.xml.transform.stream.StreamResult;     import org.w3c.dom.Document;  import org.w3c.dom.Element;  import org.w3c.dom.Node;  import org.w3c.dom.NodeList;  import org.w3c.dom.Text;  import org.xml.sax.SAXException;     import com.novel.entity.Novel;  import com.novel.entity.User;     /**   * @author cy   *   * @date 2015年7月23日 下午3:19:06   *   * @Description 关于xml的操作   */  public class XmlUtil {      /**       * 目标xml为 config/users.xml       *        * @param user       *            将要被写入xml的User对象       * @return 是否成功       */      public static boolean writeUserToXml(User user) {          try {              Document doc = getDocumentFromXml("config/users.xml");              Element newUserElement = doc.createElement("user");              Element newUsernameElement = doc.createElement("name");              Text nameTextNode = doc.createTextNode("nameValue");              nameTextNode.setNodeValue(user.getName());              newUsernameElement.appendChild(nameTextNode);              Element newUserPwdElement = doc.createElement("pwd");              Text pwdTextNode = doc.createTextNode("pwdValue");              pwdTextNode.setNodeValue(user.getName());              newUserPwdElement.appendChild(pwdTextNode);              newUserElement.appendChild(newUsernameElement);              newUserElement.appendChild(newUserPwdElement);              Element usersElement = (Element) doc.getElementsByTagName("users")                      .item(0);              usersElement.appendChild(newUserElement);                 writeDocumentToFile(doc, "config/users.xml");              return true;          } catch (Exception e) {              e.printStackTrace();              return false;          }      }         /**       *        * @param doc       *            XML中的Document对象       * @param filePath       *            输出的文件路径       * @throws TransformerFactoryConfigurationError       * @throws TransformerConfigurationException       * @throws TransformerException       */      private static void writeDocumentToFile(Document doc, String filePath)              throws TransformerFactoryConfigurationError,              TransformerConfigurationException, TransformerException {          // 写入到硬盘          TransformerFactory tFactory = TransformerFactory.newInstance();          Transformer transformer = tFactory.newTransformer();          /** 编码 */          transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8");          DOMSource source = new DOMSource(doc);          StreamResult result = new StreamResult(new File(filePath));          transformer.transform(source, result);      }         /**       * 加载config/users.xml中用户信息到对象中       *        * @return 加载后的对象       */      public static Map<String, User> initUser() {          InitUser.users = new HashMap<String, User>();          try {              Document doc = getDocumentFromXml("config/users.xml");              NodeList usersNodeList = doc.getElementsByTagName("user");              for (int i = 0; i < usersNodeList.getLength(); i++) {                  Element userElement = (Element) usersNodeList.item(i);                  String userName = ((Element) (userElement                          .getElementsByTagName("name").item(0))).getFirstChild()                          .getNodeValue();                  String passwd = ((Element) (userElement                          .getElementsByTagName("pwd").item(0))).getFirstChild()                          .getNodeValue();                  InitUser.users.put(userName, new User(userName, passwd));              }          } catch (Exception e) {              e.printStackTrace();          } finally {              return InitUser.users;          }      }         /**       * 从xml中获取服务器运行的端口       *        * @return server.xml文件中的端口号       */      public static int getServerPort() {          try {              Document doc = getDocumentFromXml("config/server.xml");              int serverPort = Integer.parseInt(doc                      .getElementsByTagName("server-port").item(0)                      .getFirstChild().getNodeValue());              return serverPort;          } catch (Exception e) {              e.printStackTrace();              return 0;          }      }         /**       *        * @param xmlPath       *            xml文件的位置       * @return 这个xml文件相应的Document对象       * @throws SAXException       * @throws IOException       * @throws ParserConfigurationException       */      public static Document getDocumentFromXml(String xmlPath)              throws SAXException, IOException, ParserConfigurationException {          DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();          DocumentBuilder builder = factory.newDocumentBuilder();          Document doc = builder.parse(xmlPath);          return doc;      }         /**       * 读取xml中小说的信息到List中       *        * @param novelId       *            小说id       * @return 小说列表       * @throws ParserConfigurationException        * @throws IOException        * @throws SAXException        */      public static List<Novel> getNovelListFromXml(String filePath) throws SAXException, IOException, ParserConfigurationException {          List<Novel> novelList = new ArrayList<Novel>();          Document doc = getDocumentFromXml(filePath);          NodeList novels = doc.getElementsByTagName("novel");          for (int i = 0; i < novels.getLength(); i++) {              Element novel = ((Element) novels.item(i));              int id = Integer.parseInt(novel.getElementsByTagName("id").item(0)                      .getFirstChild().getNodeValue());              String name = novel.getElementsByTagName("name").item(0)                      .getFirstChild().getNodeValue();              String author = novel.getElementsByTagName("author").item(0)                      .getFirstChild().getNodeValue();              String category = novel.getElementsByTagName("category").item(0)                      .getFirstChild().getNodeValue();              String description = novel.getElementsByTagName("description")                      .item(0).getFirstChild().getNodeValue();                             Novel oneNovel = new Novel(id, category, name, author, description);              novelList.add(oneNovel);          }          return novelList ;      }      /**       * 将Novel信息写入到config/novelsInfo.xml中并且将小说内容写入到novel文件夹下       * @param novel 小说对象       * @return 是否写入成功        * TODO：确定原子操作       */      public static boolean writeNovelToFile(Novel novel ) {          /**           * 先将小说内容写入到novel文件夹下，再将小说信息写入到config/novelsInfo.xml中           */          try{              FileUtils.writeStringToFile(novel.getContent(), "novel/" + novel.getName() + ".txt");              XmlUtil.writeNovelInfoToXml(novel) ;              return true ;          }catch(Exception e ){              /**               * 如果写入小说到文件中出现问题，要将已经写入的信息删除               * 这段代码应该很少执行到 ~~~~               *                */              System.out.println("小说写入文件失败，正在回滚~~");              FileUtils.deleteFile("novel/" + novel.getName() + ".txt") ;              XmlUtil.deleteNovelInfoFromXml(novel) ;              e.printStackTrace();              return false ;          }      }         /**       * 从config/novelsInfo.xml中删除与novel对象相对应的的novel标签，根据ID号判断是否相同       *        * @param novel       *            小说对象       */      public static void deleteNovelInfoFromXml(Novel novel) {          try {              Document doc = getDocumentFromXml("config/novelsInfo.xml");              Element novelsElement = (Element) doc                      .getElementsByTagName("novels").item(0);              NodeList novelElements = novelsElement                      .getElementsByTagName("novel");                 Node deleteElement = null;              for (int i = 0; i < novelElements.getLength(); i++) {                  String id = ((Element) novelElements.item(i))                          .getElementsByTagName("id").item(0).getFirstChild()                          .getNodeValue();                  if (id.equals(String.valueOf(novel.getId()))) {                      deleteElement = novelElements.item(i);                      break;                  }              }              novelsElement.removeChild(deleteElement);              writeDocumentToFile(doc, "config/novlesInfo.xml");          } catch (Exception e) {              e.printStackTrace();          }      }      /**       * 将小说信息写入到config/novelsInfo.xml文件中       * @param novel小说对象       */      public static void writeNovelInfoToXml(Novel novel){          Document doc = null ;          try {              doc = getDocumentFromXml("config/novelsInfo.xml");          } catch (Exception e) {              e.printStackTrace();              return ;          }          Element novelDocument = (Element)doc.createElement("novel") ;          // id          Element novelIdDocument = (Element)doc.createElement("id") ;          Text novelIdTextNode = doc.createTextNode("idValue") ;          novelIdTextNode.setNodeValue(String.valueOf(novel.getId()));          novelIdDocument.appendChild(novelIdTextNode);          // name          Element novelNameDocument = (Element)doc.createElement("name") ;          Text novelNameTextNode = doc.createTextNode("nameValue") ;          novelNameTextNode.setNodeValue(String.valueOf(novel.getName()));          novelNameDocument.appendChild(novelNameTextNode);          // author          Element novelAuthorDocument = (Element)doc.createElement("author") ;          Text novelAuthorTextNode = doc.createTextNode("authorValue") ;          novelAuthorTextNode.setNodeValue(String.valueOf(novel.getAuthor()));          novelAuthorDocument.appendChild(novelAuthorTextNode);          // category          Element novelCategoryDocument = (Element)doc.createElement("category") ;          Text novelCategoryTextNode = doc.createTextNode("categoryValue") ;          novelCategoryTextNode.setNodeValue(String.valueOf(novel.getCategory()));          novelCategoryDocument.appendChild(novelCategoryTextNode);          // description           Element novelDescriptionDocument = (Element)doc.createElement("description") ;          Text novelDescriptionTextNode = doc.createTextNode("descriptionValue") ;          novelDescriptionTextNode.setNodeValue(String.valueOf(novel.getDescription()));          novelDescriptionDocument.appendChild(novelDescriptionTextNode);                     novelDocument.appendChild(novelIdDocument) ;          novelDocument.appendChild(novelNameDocument) ;          novelDocument.appendChild(novelAuthorDocument) ;          novelDocument.appendChild(novelCategoryDocument) ;          novelDocument.appendChild(novelDescriptionDocument) ;          doc.getElementsByTagName("novels").item(0).appendChild(novelDocument) ;          // 写到文件中          try {              writeDocumentToFile(doc, "config/novelsInfo.xml");          } catch (Exception e) {              e.printStackTrace();          }      }  }

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