dom4j解析xml文件

一、利用dom4j创建一个内容如下的xml文件SqlMapConfig.xml

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration PUBLIC "-//ibatis.apache.org//DTD Config 3.0//EN"
 3                        "ibatis-3-config.dtd">
 4 <configuration>
 5    <environments default="development">
 6       <environment id="MySQL">
 7          <transactionManager type="JDBC">123</transactionManager>
 8          <dataSource type="POOLED">
 9              <property name="driver" value="com.mysql.jdbc.Driver"/>
10              <property name="url" value="jdbc:mysql://127.0.0.1:3306/test"/>
11              <property name="username" value="root"/>
12              <property name="password" value="admin"/>
13          </dataSource>
14       </environment>
15    </environments>
16    
17    <mappers>
18       <mapper resource="com/pojo/sql/DepMap.xml"/>
19       <mapper resource="com/pojo/sql/EmpMap.xml"/>
20    </mappers>
21 </configuration>

步骤：
1.创建一个输出流，指定创建的SqlMapConfig.xml文件的位置-------OutputStream
    OutputStream os = new FileOutputStream("d:/SqlMapConfig.xml");
2.创建一个xml编写器-------XMLWriter
    XMLWriter writer = new XMLWriter(os,OutputFormat.createPrettyPrint());
    这里os是前面新建的一个输出流，OutputFormat.createPrettyPrint()是指定输出的格式的，这里代表内容缩进。
3.创建xml文档-------Document、DocumentHelper
    Document document = DocumentHelper.createDocument();
4.创建里面的所有结点元素-------Elemenet
    Element configuration = document.addElement("configuration");
   ..............
    新建结点元素的形式是：Element 子结点 = 父节点.addElement("子结点名");
    给结点元素添加属性是：结点.addAttribute("属性名", "属性值");
5.保存xml
    writer.write(document);
代码如下：

 1 public class CreateXML {
 2 
 3     /**
 4      * @param args
 5      * @throws IOException 
 6      */
 7     public static void main(String[] args) throws IOException {
 8         //创建一个输出流，指定创建的xml文件的位置
 9         OutputStream os = new FileOutputStream("d:/SqlMapConfig.xml");
10         
11         XMLWriter writer = new XMLWriter(os,OutputFormat.createPrettyPrint());
12         
13         //创建Document
14         Document document = DocumentHelper.createDocument();
15         
16         Element configuration = document.addElement("configuration");
17         
18         Element environments = configuration.addElement("environments");
19         environments.addAttribute("default", "development");
20         
21         Element environment = environments.addElement("environment");
22         environment.addAttribute("id", "MySQL");
23         Element transactionManager = environment.addElement("transactionManager");
24         transactionManager.addAttribute("type", "JDBC");
25         transactionManager.setText("123");
26         
27         Element dataSource = environment.addElement("dataSource");
28         dataSource.addAttribute("type", "POOLED");
29         Element driver = dataSource.addElement("property");
30         driver.addAttribute("name", "driver");
31         driver.addAttribute("value", "com.mysql.jdbc.Driver");
32         Element url = dataSource.addElement("property");
33         url.addAttribute("name", "url");
34         url.addAttribute("value", "jdbc:mysql://127.0.0.1:3306/test");
35         Element username = dataSource.addElement("property");
36         username.addAttribute("name", "username");
37         username.addAttribute("value", "root");
38         Element password = dataSource.addElement("property");
39         password.addAttribute("name", "password");
40         password.addAttribute("value", "admin");
41         
42         Element mappers = configuration.addElement("mappers");
43         Element mapper1 = mappers.addElement("mapper");
44         mapper1.addAttribute("resource", "com/pojo/sql/DepMap.xml");
45         Element mapper2 = mappers.addElement("mapper");
46         mapper2.addAttribute("resource", "com/pojo/sql/EmpMap.xml");
47         //保存xml
48         writer.write(document);
49         writer.close();
50     }
51 }

二、查找xml文件的内容
查找xml文件内容有两种情况，第一种就是查找出所有同名的结点元素然后遍历、第二种就是直接找到某个结点元素
比如遍历SqlMapConfig.xml,将driver、url、username、password的值读取出来就有两种方法，代码如下
方法一：

 1 public class GetNodes {
 2 
 3     /**方法一：
 4      * 遍历新建的xml,将driver、url、username、password的值读取出来
 5      * @param args
 6      * @throws IOException 
 7      * @throws DocumentException 
 8      */
 9     public static void main(String[] args) throws IOException, DocumentException {
10         SAXReader reader = new SAXReader();
11         Document document = reader.read("d:/SqlMapConfig.xml");
12         List<Element> elements = document.selectNodes("/configuration/environments/environment/dataSource/property");
13         String driver = "";
14         String url = "";
15         String username = "";
16         String password = "";
17         for (Element e : elements) {
18             String name = e.attributeValue("name");
19             String value = e.attributeValue("value");
20             if("driver".equals(name)){
21                 driver = value;
22             }else if("url".equals(name)){
23                 url = value;
24             }else if("username".equals(name)){
25                 username = value;
26             }else if("password".equals(name)){
27                 password = value;
28             }
29         }
30         System.out.println("driver:"+driver+",url:"+url+",username:"+username+",password:"+password);
31     }
32 }

　　这里List<Element> elements = document.selectNodes("/configuration/environments/environment/dataSource/property")是指将名为property的结点元素全部找出来，用一个List接收。
方法二：

 1 public class GetNodes1 {
 2 
 3     /**方法二：
 4      * 将driver、url、username、password的值读取出来
 5      * @param args
 6      * @throws IOException 
 7      * @throws DocumentException 
 8      */
 9     public static void main(String[] args) throws IOException, DocumentException {
10         SAXReader reader = new SAXReader();
11         Document document = reader.read("d:/SqlMapConfig.xml");
12         Element driverElement = (Element)document.selectSingleNode("/configuration/environments/environment/dataSource/property[@name='driver']");
13         Element urlElement = (Element)document.selectSingleNode("/configuration/environments/environment/dataSource/property[@name='url']");
14         Element usernameElement = (Element)document.selectSingleNode("/configuration/environments/environment/dataSource/property[@name='username']");
15         Element passwordElement = (Element)document.selectSingleNode("/configuration/environments/environment/dataSource/property[@name='password']");
16         String driver = driverElement.attributeValue("value");
17         String url = urlElement.attributeValue("value");
18         String username = usernameElement.attributeValue("value");
19         String password = passwordElement.attributeValue("value");
20         
21         System.out.println("driver:"+driver+",url:"+url+",username:"+username+",password:"+password);
22     }
23 }

　　这种方法就没有遍历了，就是直接将要查找的结点找出来，用selectSingleNode()函数。这里的[@name='driver']是指名找到哪一个property结点，相当于一个键值对，表示找有name="driver"属性的property结点。
形式为[@属性名='属性值']。

三、修改XML文件
    步骤：
    1.读取要修改的xml文件
    2.查找到要修改的结点
    3.保存
代码如下：

 1 public class UpdateNode {
 2 
 3     /**
 4      * 修改密码为123456
 5      * @param args
 6      * @throws DocumentException 
 7      * @throws IOException 
 8      */
 9     public static void main(String[] args) throws DocumentException, IOException {
10         //读取并修改
11         SAXReader reader = new SAXReader();
12         Document document = reader.read("d:/SqlMapConfig.xml");
13         Element passwordElement = (Element)document.selectSingleNode("/configuration/environments/environment/dataSource/property[@name='password']");
14         passwordElement.addAttribute("value", "123456");
15         //保存
16         OutputStream os = new FileOutputStream("d:/SqlMapConfig.xml");
17         XMLWriter writer = new XMLWriter(os,OutputFormat.createPrettyPrint());
18         writer.write(document);
19         writer.close();
20         os.close();
21     }
22 
23 }

四、删除XML文件的某个结点元素
　　删除和修改一样，也是要先找到要删除的结点，然后删除之，最后保存修改过的文件。删除结点的形式为：父节点.remove(子节点);
代码如下：

 1 public class DeleteNode {
 2 
 3     /**
 4      * 删除密码结点
 5      * @param args
 6      * @throws DocumentException 
 7      * @throws IOException 
 8      */
 9     public static void main(String[] args) throws DocumentException, IOException {
10         //找到结点并删除
11         SAXReader reader = new SAXReader();
12         Document document = reader.read("d:/SqlMapConfig.xml");
13         Element passwordElement = (Element) document.selectSingleNode("/configuration/environments/environment/dataSource/property[@name='password']");
14         passwordElement.getParent().remove(passwordElement);
15         
16         //保存
17         OutputStream os = new FileOutputStream("d:/SqlMapConfig.xml");
18         XMLWriter writer = new XMLWriter(os,OutputFormat.createPrettyPrint());
19         writer.write(document);
20         writer.close();
21         os.close();
22     }
23 }