怎样使用XPath提取xml文档数据

import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.Test;
/*
 * 使用XPath查找xml文档数据
 * 
 */
public class DemoXPath {
  @Test
  //输出book.xml中所有price元素节点的文本值
  public void test1() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    List<? extends Node> selectNodes = document.selectNodes("//price");
    for(Node node : selectNodes) {
      String text = node.getText();
      System.out.println(text);
    }
  }
   
  @Test
  //输出book.xml中第二本书的price元素节点的文本值
  public void test2() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    Node selectSingleNode = document.selectSingleNode("/bookshelf/book[2]/price");
    String text = selectSingleNode.getText();
    System.out.println(text);
  }
   
  @Test
  //输出book.xml中第二本书和第三本书的author元素节点的文本值
  public void test3() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    List<? extends Node> selectSingleNode = document.selectNodes("/bookshelf/book[position()>1]/author");
    for (Node node : selectSingleNode) {
      String text = node.getText();
      System.out.println(text);
    }
  }
   
  @Test
  //输出book.xml中含有属性id的所有name的文本值
  public void test4() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    List<? extends Node> selectSingleNode = document.selectNodes("//name[@id]");
    for (Node node : selectSingleNode) {
      String text = node.getText();
      System.out.println(text);
    }
  }
   
  @Test
  //输出book.xml中含有属性id="1111"的name的文本值
  public void test5() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    Node selectSingleNode = document.selectSingleNode("//name[@id=\"1111\"]");
    String text = selectSingleNode.getText();
    System.out.println(text);
  }
   
  @Test
  //输出book.xml中含有属性id="1112"的book的author的文本值
  public void test6() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    Node selectSingleNode = document.selectSingleNode("//book[name[@id=\"1112\"]]/author");
    String text = selectSingleNode.getText();
    System.out.println(text);
  }
   
  @Test
  //输出book.xml中第一本book的id的属性值
  public void test7() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    Node selectSingleNode = document.selectSingleNode("//book[1]/name");
    String text = selectSingleNode.valueOf("attribute::id");//获取id属性
    System.out.println(text);
  }
   
  @Test
  //输出book.xml中book的name的id的属性值为1112的对应的sn的属性值
  public void test8() throws Exception {
    SAXReader reader = new SAXReader();
    Document document = reader.read("src/main/java/book.xml");
    List<? extends Node> selectNodes = document.selectNodes("//book/name");
    for (Node node : selectNodes) {
      if(node.valueOf("attribute::id").equals("1112")) {
        System.out.println(node.valueOf("attribute::sn"));
      }
    }
  }
}

 <dependency>  
   <groupId>junit</groupId>  
   <artifactId>junit</artifactId>  
   <version>4.11</version>  
  </dependency>  
  <dependency>  
   <groupId>log4j</groupId>  
   <artifactId>log4j</artifactId>  
   <version>1.2.17</version>  
  </dependency>  
  <dependency>  
   <groupId>dom4j</groupId>  
   <artifactId>dom4j</artifactId>  
  </dependency>
<dependency>
 <groupId>jaxen</groupId>
 <artifactId>jaxen</artifactId>
 <version>1.1.6</version>
</dependency>

 <?xml version="1.0" encoding="utf-8"?>
 
<bookshelf>
 <book>
  <name id="1111" sn="sdd8">Tomorrow</name> 
  <author>Hiskell</author> 
  <price>$40</price>
 </book> 
 <book>
  <name id="1112" sn="sdd9">Goodbye to You</name> 
  <author>Giddle</author> 
  <price>$25</price>
 </book> 
 <book>
  <name id="1113" sn="sdd0">Sea and Old</name> 
  <author>Heminw</author> 
  <price>$28</price>
 </book>
</bookshelf>