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 + "]"; } }
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false 10 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null 22 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false 34 35 */ 36 37 boolean delStudentByName(String name); 38 39 }
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<student>：设置属性 16 17 Element studentE = doc.createElement("student");//<student></student> 18 19 studentE.setAttribute("idcard", s.getIdcard()); 20 21 studentE.setAttribute("examid", s.getExamid());//<student idcard="370101" examid="438"> 22 23 //依次创建<name><location><grade>并设置主体内容 24 25 Element nameE = doc.createElement("name");//<name></name> 26 27 nameE.setTextContent(s.getName());// <name>郭美美</name> 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<student>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<nl.getLength();i++){ 90 91 //相等：读取属性和子元素的文本，封装到Student对象中 92 93 Node node = nl.item(i); 94 95 if(node.getNodeType()==Node.ELEMENT_NODE){ 96 97 Element e = (Element)node; 98 99 if(e.getAttribute("examid").equals(examid)){ 100 101 s = new Student(); 102 103 s.setIdcard(e.getAttribute("idcard")); 104 105 s.setExamid(examid); 106 107 s.setName(e.getElementsByTagName("name").item(0).getTextContent()); 108 109 s.setLocation(e.getElementsByTagName("location").item(0).getTextContent()); 110 111 s.setGrade(Float.parseFloat(e.getElementsByTagName("grade").item(0).getTextContent())); 112 113 break; 114 115 } 116 117 } 118 119 } 120 121 //返回数据 122 123 } catch (Exception e) { 124 125 throw new RuntimeException(e);//编译时异常--》运行时异常：异常转义；异常链 126 127 } 128 129 return s; 130 131 } 132 133 134 135 public boolean delStudentByName(String name) { 136 137 boolean result = false; 138 139 try { 140 141 //得到Document对象 142 143 Document doc = JaxpUtil.getDocument(); 144 145 //得到所有的name元素 146 147 NodeList nl = doc.getElementsByTagName("name"); 148 149 //遍历：判断元素的文本和参数是否相等 150 151 for(int i=0;i<nl.getLength();i++){ 152 153 Node node = nl.item(i); 154 155 if(node.getTextContent().equals(name)){ 156 157 //如果是：爷爷干掉爸爸 158 159 node.getParentNode().getParentNode().removeChild(node.getParentNode()); 160 161 //写回xml文档 162 163 JaxpUtil.write2xml(doc); 164 165 //设置标记为true 166 167 result = true; 168 169 } 170 171 } 172 173 } catch (Exception e) { 174 175 throw new RuntimeException(e);//编译时异常--》运行时异常：异常转义；异常链 176 177 } 178 179 return result; 180 181 } 182 183 184 185 }
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 }
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 }