Java——使用DOM4j解析XML文档

阳光穿透心脏的1/2处 2022-06-06 14:37 207阅读 0赞

DOM4J是一个第三方的XML解析开发包，可以很方便的对XML文件进行增删改查等操作，可以在其开发文档中快速掌握使用方法。

1.  简单使用

package com.keixn.day3;
    
    import java.io.File;
    import java.io.FileWriter;
    import java.io.IOException;
    import java.util.Iterator;
    import java.util.Scanner;
    
    import org.dom4j.Document;
    import org.dom4j.DocumentException;
    import org.dom4j.DocumentHelper;
    import org.dom4j.Element;
    import org.dom4j.io.SAXReader;
    import org.dom4j.io.XMLWriter;
    
    /**
     * 使用DOM4j解析XML文件 需要用时查阅DOM4j使用文档/docs/index.html
     * 
     * @author KeXin
     *
     */
    public class Demo1 {
        
        // 创建解析器返回DOCUMENT对象
        public Document parse(File url) throws DocumentException {
            SAXReader reader = new SAXReader();
            Document document = reader.read(url);
            return document;
        }
    
        // Writing a document to a file
        public void write(Document document) throws IOException {
            // lets write to a file
            XMLWriter writer = new XMLWriter(new FileWriter("src/com/keixn/day3/stu_info.xml"));
            writer.write(document);
            writer.close();
        }
        // Creating a new XML node
            public Element createElement(String examid,String idcard,String name,String location,String grade) {
                Element stu = DocumentHelper.createElement("stu").addAttribute("examid", examid).addAttribute("idcard", idcard);
                Element name_node = stu.addElement("name").addText(name);
                Element location_node = stu.addElement("location").addText(location);
                Element grade_node = stu.addElement("grade").addText(grade);
                return stu;
            }
        //Update a XML node
            public void UpdateElement(Document document) throws IOException{
                Element root = document.getRootElement();
                System.out.println("请输入学生身份证号：");
                Scanner scan = new Scanner(System.in);
                String idcard = scan.nextLine();
                for ( Iterator i = root.elementIterator( "stu" ); i.hasNext(); ) {
                    Element stu = (Element) i.next();
                    if(stu.attributeValue("idcard").equals(idcard)){
                        System.out.println("已经查到该学生，请输入他的成绩：");
                        String grade = scan.nextLine();  
                        stu.element("grade").setText(grade);
                        this.write(document);
                        System.out.println("更新成功");
                        return;
                    }
                }
                System.out.println("查无此人");
            }
        public static void main(String[] args) throws DocumentException, IOException {
            Demo1 demo = new Demo1();
            Document document = demo.parse(new File("src/com/keixn/day3/stu_info.xml"));
            Element root = document.getRootElement();
            Element stu = demo.createElement("000", "122", "lisa", "北京", "86");
            root.add(stu);
            demo.write(document);
            System.out.println();
            demo.UpdateElement(document);
    
        }
    
    }

2.**作业**：用XML文件模拟数据库，使用DOM4j对学生数据进行增删改查。

package com.keixn.day3;
    
    import java.io.File;
    import java.io.FileWriter;
    import java.io.IOException;
    import java.net.URL;
    import java.util.Iterator;
    import java.util.Scanner;
    
    import org.dom4j.Document;
    import org.dom4j.DocumentException;
    import org.dom4j.Element;
    import org.dom4j.io.SAXReader;
    import org.dom4j.io.XMLWriter;
    
    public class StuTask {
        private final String xml_path = "src/com/keixn/day3/stu_info.xml";
        private final String STU = "stu", EXAM = "exam", EXAMID = "examid", IDCARD = "idcard", NAME = "name",
                LOCATION = "location", GRADE = "grade";
    
        /*
         * 添加新用户
         */
        public void AddStu() throws IOException, DocumentException {
            Student stu = new Student();
            Scanner s1 = new Scanner(System.in);
            System.out.println("请输入学生姓名");
            stu.setName(s1.nextLine());
            System.out.println("请输入准考证号");
            stu.setExamid(s1.nextLine());
            System.out.println("请输入身份证号");
            stu.setIdcard(s1.nextLine());
            System.out.println("请输入学生地址");
            stu.setLocation(s1.nextLine());
            System.out.println("请输入学生成绩");
            stu.setGrade(s1.nextLine());
            Document document = this.GetDocument(new File(xml_path));
            Element root = document.getRootElement();
            // 创建stu标签
            Element stu_node = root.addElement(STU).addAttribute(IDCARD, stu.getIdcard()).addAttribute(EXAMID,
                    stu.getExamid());
            // 创建stu标签内的name location grade标签
            Element stu_name_node = stu_node.addElement(NAME);
            stu_name_node.setText(stu.getName());
            Element stu_location_node = stu_node.addElement(LOCATION);
            stu_location_node.setText(stu.getLocation());
            Element stu_grade_node = stu_node.addElement(GRADE);
            stu_grade_node.setText(stu.getGrade());
            this.SvaeToXML(document);
            System.out.println("添加成功");
        }
    
        /*
         * 删除用户
         */
        public void DeleteStu() throws IOException, DocumentException {
            System.out.println("请输入准考证号");
            Scanner s1 = new Scanner(System.in);
            String examid = s1.nextLine();
            Document document = this.GetDocument(new File(xml_path));
            Element root = document.getRootElement();
            Iterator iterator = root.elementIterator(STU);
            Element e;
            while(iterator.hasNext()){
                e = (Element) iterator.next();
                if(e.attributeValue(EXAMID).equals(examid)){
                    root.remove(e);
                    this.SvaeToXML(document);
                    System.out.println("删除成功");
                    return;
                }
            }
            System.out.println("查无此人");
        }
    
        /*
         * 查询成绩
         */
        public void QuestStu() throws IOException, DocumentException {
            System.out.println("请输入准考证号");
            Scanner s1 = new Scanner(System.in);
            String examid = s1.nextLine();
            Document document = this.GetDocument(new File(xml_path));
            Element root = document.getRootElement();
            Iterator iterator = root.elementIterator(STU);
            Element e;
            while(iterator.hasNext()){
                e = (Element) iterator.next();
                if(e.attributeValue(EXAMID).equals(examid)){
                    System.out.println(e.elementText(GRADE));
                    return;
                }
            }
            System.out.println("查无此人");
        }
    
        public Document GetDocument(File url) throws DocumentException {
            SAXReader reader = new SAXReader();
            Document document = reader.read(url);
            return document;
        }
    
        public static void main(String[] args) throws IOException, DocumentException {
            int key = 0;
            StuTask st = new StuTask();
            Scanner scan = new Scanner(System.in);
            System.out.println("请选择操作：");
            while (key != 4) {
                System.out.println("1、添加新用户；2、删除用户；3、查询成绩；4、退出系统");
                key = scan.nextInt();
                switch (key) {
                case 1:
                    st.AddStu();
                    break;
                case 2:
                    st.DeleteStu();
                    break;
                case 3:
                    st.QuestStu();
                    break;
                default:
                    key = 4;
                }
            }
        }
    
        /*
         * 将document输出至xml文件
         */
        public void SvaeToXML(Document document) throws IOException {
            XMLWriter writer = new XMLWriter(new FileWriter("src/com/keixn/day3/stu_info.xml"));
            writer.write(document);
            writer.close();
        }
    }

Student.java:

package com.keixn.day3;
    
    public class Student {
        private String idcard;
        private String examid;
        private String name;
        private String location;
        private String grade;
    
        public String getIdcard() {
            return idcard;
        }
    
        public void setIdcard(String idcard) {
            this.idcard = idcard;
        }
    
        public String getExamid() {
            return examid;
        }
    
        public void setExamid(String examid) {
            this.examid = examid;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getLocation() {
            return location;
        }
    
        public void setLocation(String location) {
            this.location = location;
        }
    
        public String getGrade() {
            return grade;
        }
    
        public void setGrade(String grade) {
            this.grade = grade;
        }
    
        public String GetStu(Student stu) {
            String result = "";
            if (stu != null) {
                result+=stu.getName()+"\t"+stu.getExamid()+"\t"+stu.getIdcard()+"\t"+stu.getLocation()+"\t"+stu.getGrade();
            }
    
            return result;
    
        }
    
    }

stu\_info.xml:

<?xml version="1.0" encoding="UTF-8"?>
    <exam>
        <stu examid="000" idcard="122">
            <name>lisa</name>
            <location>北京</location>
            <grade>78</grade>
        </stu>
    </exam>