DOM解析xml

DOM的全称是Document Object Model，即文档对象模型。在应用程序中，基于DOM的XML解析器将一个XML文档转换成一个对象模型的集合（通常称DOM树），应用程序正是通过对这个对象模型的操作，来实现对XML文档数据的操作。通过DOM接口，应用程序可以在任何时候访问XML文档中的任何一部分数据，因此，这种利用DOM接口的机制也被称作随机访问机制。

DOM树所提供的随机访问方式给应用程序的开发带来了很大的灵活性，它可以任意地控制整个XML文档中的内容。然而，由于DOM分析器把整个XML文档转化成DOM树放在了内存中，因此，当文档比较大或者结构比较复杂时，对内存的需求就比较高。而且，对于结构复杂的树的遍历也是一项耗时的操作。所以，DOM分析器对机器性能的要求比较高，实现效率不十分理想。不过，由于DOM分析器所采用的树结构的思想与XML文档的结构相吻合，同时鉴于随机访问所带来的方便，因此，DOM分析器还是有很广泛的使用价值的。

xml

<?xml version="1.0" encoding="UTF-8"?>

<exam>

	<student examid="222">

		<name>张三</name>

		<location>沈阳</location>

		<grade>89</grade>

	</student>



	<student idcard="333">

		<name>李四</name>



		<location>大连</location>

		<grade>110</grade>

	</student>



</exam>

　　

 

实例：

  1 package com.bcrj.dom;

  2 

  3 import javax.xml.parsers.DocumentBuilder;

  4 import javax.xml.parsers.DocumentBuilderFactory;

  5 import javax.xml.parsers.ParserConfigurationException;

  6 import javax.xml.transform.Transformer;

  7 import javax.xml.transform.TransformerConfigurationException;

  8 import javax.xml.transform.TransformerException;

  9 import javax.xml.transform.TransformerFactory;

 10 import javax.xml.transform.dom.DOMSource;

 11 import javax.xml.transform.stream.StreamResult;

 12 

 13 import org.w3c.dom.Document;

 14 import org.w3c.dom.Element;

 15 import org.w3c.dom.Node;

 16 import org.w3c.dom.NodeList;

 17 

 18 public class Test1 {

 19     DocumentBuilderFactory dbf = null;

 20     DocumentBuilder db = null;

 21     private Document document = null;

 22 

 23     public Document getDocument() {

 24         return document;

 25     }

 26 

 27     public void setDocument(Document document) {

 28         this.document = document;

 29     }

 30 

 31     // 1、得到某个具体的节点内容,第一个student的location

 32     public String test1() {

 33         NodeList nl = document.getElementsByTagName("location");

 34         int index = 0;

 35         for (int i = 0; i < nl.getLength(); i++) {

 36             Node node = nl.item(i);

 37             String nodeName = node.getNodeName();

 38             if ("location".equals(nodeName)) {

 39                 index++;

 40             }

 41             if (index == 1) {

 42                 return node.getTextContent();

 43             }

 44         }

 45         return null;

 46     }

 47 

 48     // 2、遍历所有元素节点

 49     public void test2(Node node) {

 50         if (node instanceof Element) {

 51             System.out.println(node.getNodeName());

 52         }

 53         NodeList nl = node.getChildNodes();

 54         int len = nl.getLength();

 55         for (int i = 0; i < len; i++) {

 56             Node n = nl.item(i);

 57             test2(n);

 58         }

 59     }

 60 

 61     // 3、修改某个元素节点的主体内容,把第二个studnent的grade改为100

 62     public void test3() throws TransformerException {

 63         // 根元素

 64         int index = 0;

 65         Node n = document.getFirstChild();

 66         NodeList nl = n.getChildNodes();

 67         int len = nl.getLength();

 68 

 69         for (int i = 0; i < nl.getLength(); i++) {

 70             if (nl.item(i) instanceof Element) {

 71                 index++;

 72                 if (index == 2) {

 73                     NodeList nodelist = nl.item(i).getChildNodes();

 74                     for (int j = 0; j < nodelist.getLength(); j++) {

 75                         Node node = nodelist.item(j);

 76                         if (node instanceof Element) {

 77                             if (node.getNodeName().equals("grade")) {

 78                                 node.setTextContent("110");

 79                             }

 80                         }

 81                     }

 82                 }

 83             }

 84         }

 85         TransformerFactory facotry = TransformerFactory.newInstance();

 86         Transformer ts = facotry.newTransformer();

 87         ts.transform(new DOMSource(document), new StreamResult(

 88                 "src/students.xml"));

 89     }

 90 

 91     // 4、向指定元素节点中增加子元素节点,第一student中增加子元素<age>23</age>

 92     public void test4() throws TransformerException {

 93         NodeList nl = document.getElementsByTagName("student");

 94         Element element = document.createElement("age");

 95         element.setTextContent("23");

 96         nl.item(0).appendChild(element);

 97         // 写入xml

 98         TransformerFactory facotry = TransformerFactory.newInstance();

 99         Transformer ts = facotry.newTransformer();

100         ts.transform(new DOMSource(document), new StreamResult(

101                 "src/students.xml"));

102     }

103 

104     // 5、向指定元素节点上增加同级元素节点,在第二个student的location后添加<age>23</age>

105     public void test5() throws Exception {

106         NodeList nl = document.getElementsByTagName("student");

107         Element element = document.createElement("age");

108         element.setTextContent("23");

109 

110         NodeList nll = nl.item(1).getChildNodes();

111         for (int i = 0; i < nll.getLength(); i++) {

112 

113             if ((nll.item(i) instanceof Element)

114                     && "location".equals(nll.item(i).getNodeName())) {

115                 nll.item(i).getParentNode().insertBefore(element, nll.item(i));

116             }

117         }

118         TransformerFactory facotry = TransformerFactory.newInstance();

119         Transformer ts = facotry.newTransformer();

120         ts.transform(new DOMSource(document), new StreamResult(

121                 "src/students.xml"));

122     }

123 

124     // 6、删除指定元素节点，删除第二个student元素的age子元素

125     public void test6() throws Exception {

126         NodeList nl = document.getElementsByTagName("student");

127         NodeList nll = nl.item(1).getChildNodes();

128         for (int i = 0; i < nll.getLength(); i++) {

129             if ((nll.item(i) instanceof Element)

130                     && "age".equals(nll.item(i).getNodeName())) {

131                 //由父元素调用删除

132                 nll.item(i).getParentNode().removeChild(nll.item(i));

133             }

134         }

135 

136         TransformerFactory facotry = TransformerFactory.newInstance();

137         Transformer ts = facotry.newTransformer();

138         ts.transform(new DOMSource(document), new StreamResult(

139                 "src/students.xml"));

140     }

141 

142     // 7、操作XML文件属性,打印第一学生的examid

143     public void test7(){

144         NodeList nl = document.getElementsByTagName("student");

145         Element nll = (Element)nl.item(0);

146         String examid = nll.getAttribute("examid");

147         System.out.println(examid);

148         

149     }

150     

151     // 8、添加一个idcard属性给第二student

152     public void test8() throws Exception{

153         NodeList nl = document.getElementsByTagName("student");

154         Element nll = (Element)nl.item(1);

155         nll.setAttribute("idcard", "333");

156 

157         TransformerFactory facotry = TransformerFactory.newInstance();

158         Transformer ts = facotry.newTransformer();

159         ts.transform(new DOMSource(document), new StreamResult(

160                 "src/students.xml"));

161     }

162     

163     //9.删除第一个student的idcard

164     public void test9() throws Exception{

165         NodeList nl = document.getElementsByTagName("student");

166         Element nll = (Element)nl.item(0);

167         nll.removeAttribute("idcard");

168         

169         TransformerFactory facotry = TransformerFactory.newInstance();

170         Transformer ts = facotry.newTransformer();

171         ts.transform(new DOMSource(document), new StreamResult(

172                 "src/students.xml"));

173     }

174     

175     // Document 对象的一个新实例来生成一个 DOM 树

176     public Document getDomParser() throws Exception {

177         // DOM解析工厂

178         dbf = DocumentBuilderFactory.newInstance();

179         // DOM对象数解析器

180         db = dbf.newDocumentBuilder();

181         // 获取 DOM Document 对象的一个新实例来生成一个 DOM 树

182         document = db.parse("src/students.xml");

183         return document;

184     }

185 

186 }

单元测试

 1 package com.bcrj.test;

 2 

 3 import static org.junit.Assert.*;

 4 

 5 import javax.xml.transform.TransformerException;

 6 

 7 import org.junit.Assert;

 8 import org.junit.Before;

 9 import org.junit.BeforeClass;

10 import org.junit.Test;

11 import org.w3c.dom.Document;

12 

13 import com.bcrj.dom.Test1;

14 

15 public class Domtest {

16     

17     static Test1 test = null;

18     

19     @BeforeClass

20     public static  void a(){

21         test= new Test1();

22     }

23     

24     @Before

25     public void  setUp() throws Exception {

26         test.getDomParser();

27         

28     }

29 

30 //    @Test

31 //    public void testTest1() {

32 //        String str = test.test1();

33 //        Assert.assertEquals("沈阳", str);

34 //    }

35     

36 //    @Test

37 //    public void testTest2(){

38 //        Document document = test.getDocument();

39 //        test.test2(document);

40 //    }

41 //    

42 //    @Test

43 //    public void testTest3() throws TransformerException {

44 //         test.test3();

45 //        //Assert.assertEquals("沈阳", str);

46 //    }

47 //    

48 //    @Test

49 //    public void testTest4() throws TransformerException {

50 //         test.test4();

51 //        //Assert.assertEquals("沈阳", str);

52 //    }

53     

54 //    @Test

55 //    public void testTest4() throws Exception {

56 //         test.test5();

57 //        //Assert.assertEquals("沈阳", str);

58 //    }

59     

60     @Test

61     public void testTest4() throws Exception {

62          test.test9();

63         //Assert.assertEquals("沈阳", str);

64     }

65 

66 }