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 }