Dom4j使用

Dom4j相关操作
只要不是最末端标签，都可以做

1）Element element(String Qname)获取某一层标签下的名为 Qname的标签

这获得是就是一层标签，不是一个标签范围；通过这一层标签可以获得下一层标签

2）List elements() 获取某一层标签下的所有标签的列表

一．不使用XPath表达式

///////////////////////////添加标签/////////////////////////////

/**
* 在固定的位置上添加一个新的标签
* 主要是运用list添加元素的的操作
*/
public static void addByLocation() throws Exception {
//首先的三步
SAXReader saxReader = new SAXReader();
Document document = saxReader.read("src/xml/xml1.xml");
Element root = document.getRootElement();
//获取所有一级目录的列表
List<Element> allList = root.elements("student");
//获取一级目录的第一组
Element firstE  = allList.get(0);
//获取第一组的所有标签
List<Element> list1 = firstE.elements();
//创建要插入的标签和属性
Element school = DocumentHelper.createElement("school");
school.setText("红星");
//在list1 中插入
list1.add(1,school);
//回写
XMLWriter xmlWriter = new XMLWriter(new FileOutputStream("src/xml/xml1.xml"),
OutputFormat.createPrettyPrint());
xmlWriter.write(document);//把document中的内容写到输出流中
xmlWriter.close();
}

//////////////////////////////////////////////////////////////

/**
* 在末尾添加一个新标签
*/
public static void addOne() throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read("src/xml/xml1.xml");
Element root = document.getRootElement();
List<Element> list = root.elements("student");
Element fe = list.get(0);
Elementsex1 = fe.addElement("sex");
sex1.setText("女");//注意这里是在sex1上添加，不是fe
XMLWriter xmlWriter = new XMLWriter(new FileOutputStream("src/xml/xml1.xml"),
OutputFormat.createPrettyPrint());
xmlWriter.write(document);
xmlWriter.close();
}

///////////////////////////查询标签/////////////////////////////

/**
*显示所有的人的名字
*/
public static void showAll() throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read("src/xml/xml1.xml");
Element root = document.getRootElement();
List<Element> list = root.elements("student");
for (Element element : list) {
Element e = element.element("name");
System.out.println(e.getText());
}
}
}

/////////////////////////修改标签属性///////////////////////////

/**
*修改一个标签的值
*/
public static void modifyBy() throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read("src/xml/xml1.xml");
Element root = document.getRootElement();

List<Element> allList = root.elements("student");
Element firstE = allList.get(0);
Element id = firstE.element("id");
id.setText("10");
XMLWriter xmlWriter = new XMLWriter(new FileOutputStream("src/xml/xml1.xml"),
OutputFormat.createPrettyPrint());
xmlWriter.write(document);
xmlWriter.close();
}

/////////////////////////删除标签/////////////////////////////

/**
*删除某个属性标签
*和在末尾添加一样，找到父节点，在父节点上remove一个要删除的标签
*/
public static void deleteBy() throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read("src/xml/xml1.xml");
Element root = document.getRootElement();
List<Element> allList = root.elements("student");
Element firstE = allList.get(0);//父节点
Elementsex = firstE.element("sex");//要删除的标签
firstE.remove(sex);
XMLWriter xmlWriter = new XMLWriter(
new FileOutputStream(PATH),
OutputFormat.createPrettyPrint());
xmlWriter.write(document);
xmlWriter.close();
}

/////////////////////////获取标签属性///////////////////////////

比如：
<student ID="0">
<name>张三</name>
<id>10</id> 女
</student>

要得到ID的值

/**
* 获取给定标签的属性值
*/
public  static void getAttribute() throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(PATH);
Element root = document.getRootElement();
List<Element> allList = root.elements("student");
Element firstE = allList.get(0);
String id = firstE.attributeValue("ID");
System.out.println(id);
}

一．使用XPath表达式

常用的六种表达式：

/////////////////////////查询标签///////////////////////////

/**
*
使用XPath表达式简化xml操作
*
查询
*/
public
static void test1()
throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(PATH);
List<Node> list =
document.selectNodes("//name");
for (Node node : list) {
String name = node.getText();
System.out.println(name);

}
}
public
static void test2()
throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(PATH);
Node node1 =document.selectSingleNode("//student[@ID='0']/name");
String name = node1.getText();
System.out.println(name);
}

小项目：

////////////////////////学生信息增删查///////////////////////////

方法类

public class StudentService {
private static final String PATH = "src/xml/data.xml";

/*
* 添加
*/
public void addStu(StudentInfo stu) throws Exception {
String name = stu.getName();
String age = stu.getAge();
String id = stu.getId();
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(PATH);
Element root = document.getRootElement();
Element e = root.addElement("info");
Element e1 = e.addElement("id");
Element e2 = e.addElement("name");
Element e3 = e.addElement("age");
e1.setText(id);
e2.setText(name);
e3.setText(age);
XMLWriter xmlWriter = new XMLWriter(new FileOutputStream(PATH),
OutputFormat.createPrettyPrint());
xmlWriter.write(document);
xmlWriter.close();
}

/*
* 删除
*/
public void deleteStu(String id) throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(PATH);
List<Node> list = document.selectNodes("//id");
for (Node node : list) {
String idc = node.getText();
if (idc.equals(id)) {
Element fa = node.getParent();
Element fafa = fa.getParent();
fafa.remove(fa);
}
}
XMLWriter xmlWriter = new XMLWriter(new FileOutputStream(PATH),
OutputFormat.createPrettyPrint());
xmlWriter.write(document);
xmlWriter.close();
}
/*
* 查询
*/
public StudentInfo selectStu(String id ) throws Exception{
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(PATH);
List<Node> list = document.selectNodes("//id");
StudentInfo stu = new StudentInfo();
for (Node node : list) {
String idc = node.getText();
if(idc.equals(id)){
Element fa = node.getParent();
Element name = fa.element("name");
Element age = fa.element("age");
String namec = name.getText();
String agc = age.getText();
stu.setName(namec);
stu.setAge(agc);
stu.setId(idc);
}
}
return stu;
}
/*
* 修改姓名为name的学生的学号为ID
*/
public void changeStu(String name,String id) throws Exception{
SAXReader saxReader = new SAXReader();
Document document = saxReader.read(PATH);
List<Node> list = document.selectNodes("//name");
for (Node node : list) {
String namec = node.getText();
if (namec.equals(name)) {
Element fa = node.getParent();
Element idE = fa.element("id");
idE.setText(id);
}
}
XMLWriter xmlWriter = new XMLWriter(new FileOutputStream(PATH),
OutputFormat.createPrettyPrint());
xmlWriter.write(document);
xmlWriter.close();
}
}<span style="font-family:宋体;color:#ff0000;"><span style="font-size: 11pt;"><strong>

</strong></span></span>

学生信息类：

public class StudentInfo {
private String name;
private String id;
private String age ;
public StudentInfo() {
super();
}
public String getName() {
return name;
}
public StudentInfo(String name, String id, String age) {
this.name = name;
this.id = id;
this.age = age;
}

public void setName(String name) {
this.name = name;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
@Override
public String toString() {
return "Information [name=" + name + ", id=" + id + ", age=" + age
+ "]";
}

}

主函数：

public class Test {

/**
*/
public static void main(String[] args) throws Exception {
StudentService service = new StudentService();
/*
* 添加操作
*/
//		StudentInfo stu1 = new StudentInfo("张三","0","20");
//		StudentInfo stu2 = new StudentInfo("李四","1","21");
//		StudentInfo stu3 = new StudentInfo("王五","2","22");
//		service.addStu(stu1);
//		service.addStu(stu2);
//		service.addStu(stu3);
/*
* 删除操作
*/
//		service.deleteStu("0");
/*
* 查询操作
//		 */
//		StudentInfo stu = service.selectStu("2");
//		System.out.println(stu.toString());
/*
* 修改操作
*/
service.changeStu("王五", "20");
}

}

xml文件：

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

<student>
<info>
<id>1</id>
<name>李四</name>
<age>21</age>
</info>
<info>
<id>20</id>
<name>王五</name>
<age>22</age>
</info>
</student>