xml，文件操作功能类的示例代码详解

我一个项目中用到的，里面的方法不是太通用，但是可以从里面找到一些有用的代码，以后慢慢添补更新：

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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