JAXP Dom 案例对xml文件进行增加查找删除-白红宇

JAXP Dom 案例对xml文件进行增加查找删除

阅读量：5034 次

发布时间：2019-06-12

本文共 5643 字，大约阅读时间需要 18 分钟。

利用 JAXP 对 XML文件的处理，把xml当做一个数据库来对待

Student对象定义类

public class Student {    private String idcard;//身份证号    private String examid;//准考证号    private String name;//姓名    private String location;//籍贯    private float grade;//成绩       public Student(){}          public Student(String idcard, String examid, String name, String location,            float grade) {        super();        this.idcard = idcard;        this.examid = examid;        this.name = name;        this.location = location;        this.grade = 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 float getGrade() {        return grade;    }    public void setGrade(float grade) {        this.grade = grade;    }    @Override    public String toString() {        return "Student [idcard=" + idcard + ", examid=" + examid + ", name="                + name + ", location=" + location + ", grade=" + grade + "]";    }   }

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StudentDao 接口类

//原则：抽象和实现分离

//根据功能要求

//接口中的每个方法：注释要写的清清楚楚，做到没有歧义

1 public interface StudentDao { 2  3     /** 4  5      * 添加学生信息到数据库 6  7      * @param s 封装了要保存的信息的学生对象 8  9      * @return 成功了返回true，否则false10 11      */12 13     boolean addStudent(Student s);14 15     /**16 17      * 根据准考证号查询学生的信息18 19      * @param examid 准考证号20 21      * @return 没有找到返回null22 23      */24 25     Student findByExamid(String examid);26 27     /**28 29      * 根据姓名删除学生信息30 31      * @param name 学生的姓名32 33      * @return 删除成功返回true。删除失败或学生不存在都返回false34 35      */36 37     boolean delStudentByName(String name);38 39 }

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StudentDaoimpl 实现类

1 public class StudentDaoImpl implements StudentDao {  2   3    4   5      public boolean addStudent(Student s) {  6   7          boolean result = false;  8   9          try { 10  11               //得到Document对象 12  13               Document doc = JaxpUtil.getDocument();//异常怎么办？抛：调用者得有能力处理。处理 14  15               //创建
      
       ：设置属性 16  17               Element studentE = doc.createElement("student");//
        18  19               studentE.setAttribute("idcard", s.getIdcard()); 20  21               studentE.setAttribute("examid", s.getExamid());//
       
         22  23               //依次创建
        
         
          
           并设置主体内容 24  25               Element nameE = doc.createElement("name");//
            26  27               nameE.setTextContent(s.getName());// 
           
            郭美美
            28  29               30  31               Element locationE = doc.createElement("location"); 32  33               locationE.setTextContent(s.getLocation()); 34  35               36  37               Element gradeE = doc.createElement("grade"); 38  39               gradeE.setTextContent(s.getGrade()+""); 40  41               //建立与student元素的父子关系 42  43               studentE.appendChild(nameE); 44  45               studentE.appendChild(locationE); 46  47               studentE.appendChild(gradeE); 48  49               //把student挂接到根元素上 50  51               Node rootNode = doc.getElementsByTagName("exam").item(0); 52  53               rootNode.appendChild(studentE); 54  55               //写回xml文档中 56  57               JaxpUtil.write2xml(doc); 58  59               result = true; 60  61          } catch (Exception e) { 62  63               throw new RuntimeException(e);//编译时异常--》运行时异常：异常转义；异常链 64  65          } 66  67          return result; 68  69      } 70  71   72  73      public Student findByExamid(String examid) { 74  75          Student s = null; 76  77          try { 78  79               //得到Document对象 80  81               Document doc = JaxpUtil.getDocument(); 82  83               //得到所有的
           
            元素 84 85 NodeList nl = doc.getElementsByTagName("student"); 86 87 //遍历：判断属性的值和参数的值是否相等 88 89 for(int i=0;i

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JavaUtil

//工具类

//异常可以处理：不给调用者添麻烦

//可以抛：谁用谁处理

1 public class JaxpUtil { 2  3     public static Document getDocument() throws ParserConfigurationException, SAXException, IOException{ 4  5         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); 6  7         DocumentBuilder builder = dbf.newDocumentBuilder();//异常怎么办？哲学问题 8  9         Document document = builder.parse("src/exam.xml");10 11         return document;12 13     }14 15     public static void write2xml(Document document) throws TransformerException{16 17         TransformerFactory tf = TransformerFactory.newInstance();18 19         Transformer ts = tf.newTransformer();20 21         ts.transform(new DOMSource(document), new StreamResult("src/exam.xml"));22 23     }24 25 }

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StudentDaoImplTest 测试类

1 public class StudentDaoImplTest { 2  3     public static void main(String[] args) { 4  5        StudentDao dao = new StudentDaoImpl(); 6  7   8  9 //     Student s = new Student();10 11 //     s.setExamid("999");12 13 //     s.setIdcard("1101");14 15 //     s.setName("牛骞");16 17 //     s.setLocation("河南");18 19 //     s.setGrade(100);20 21 //     dao.addStudent(s);22 23       24 25        Student s = dao.findByExamid("999");26 27        System.out.println(s);28 29       30 31 //     boolean b = dao.delStudentByName("牛骞");32 33 //     System.out.println(b);34 35     }

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