Digester-优快云博客

本文链接：https://blog.youkuaiyun.com/iteye_16094/article/details/81935394

本文介绍了一种使用Apache Commons Digester解析XML文件的方法。通过三种不同的配置方式，演示了如何将XML数据映射到Java对象中，包括属性方式、子标签方式及callMethod-callParam方式。

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看AjaxChat的时候看到Digester。自己也写了个程序测试一下。
student.xml:

<?xml version="1.0" encoding="UTF-8"?>
<teacher name="张三丰" course="java">
	<student name="王八" age="20" id="1" />
	<student name="张飞" age="22" id="2" />
	<student name="李世民" age="21" id="3" />
	<student name="李陵" age="22" id="4" />
	<student name="高工" age="23" id="5" />
	<student name="黄夺" age="24" id="6" />
	<student name="马球" age="25" id="7" />
	<student name="琚要" age="26" id="8" />
</teacher>

teacher.xml:

<?xml version="1.0" encoding="UTF-8"?>
<teachers>
<teacher name="张三丰" course="java">
	<student>
		<name>王八</name>
		<age>20</age>
		<id>1</id>
	</student>
	<student>
		<name>张飞</name>
		<age>22</age>
		<id>1</id>
	</student>
	<student>
		<name>李世民</name>
		<age>21</age>
		<id>3</id>
	</student>
	<student>
		<name>李陵</name>
		<age>22</age>
		<id>4</id>
	</student>
	<student>
		<name>高工</name>
		<age>23</age>
		<id>5</id>
	</student>
	<student>
		<name>黄夺</name>
		<age>24</age>
		<id>6</id>
	</student>
	<student>
		<name>马球</name>
		<age>25</age>
		<id>7</id>
	</student>
	<student>
		<name>琚要</name>
		<age>26</age>
		<id>8</id>
	</student>
</teacher>
<teacher name="李小龙" course="net">
	<student>
		<name>王八2</name>
		<age>20</age>
		<id>1</id>
	</student>
	<student>
		<name>张飞2</name>
		<age>22</age>
		<id>1</id>
	</student>
	<student>
		<name>李世民2</name>
		<age>21</age>
		<id>3</id>
	</student>
	<student>
		<name>李陵2</name>
		<age>22</age>
		<id>4</id>
	</student>
	<student>
		<name>高工2</name>
		<age>23</age>
		<id>5</id>
	</student>
	<student>
		<name>黄夺2</name>
		<age>24</age>
		<id>6</id>
	</student>
	<student>
		<name>马球2</name>
		<age>25</age>
		<id>7</id>
	</student>
	<student>
		<name>琚要2</name>
		<age>26</age>
		<id>8</id>
	</student>
</teacher>
</teachers>

package gjs.domain;

public class Student {
	private int id;
	private String name;
	private int age;
        //......
}

package gjs.domain;

import java.util.ArrayList;
import java.util.List;

public class Teacher {
	private String name;
	private String course;
	private List<Student> students=new ArrayList<Student>();

	public void addStudent(String name,String age, String id){
		Student s=new Student();
		s.setAge(Integer.valueOf(age));		
		s.setId(Integer.valueOf(id));
		s.setName(name);
		this.students.add(s);
	}

	public void addStudent(Student student){
		this.students.add(student);
	}	
        //......
}

package gjs.domain;

import java.util.ArrayList;
import java.util.List;

public class TeacherList {
	private List<Teacher> teachers=new ArrayList<Teacher>();
	public void addTeachers(Teacher teacher){
		this.teachers.add(teacher);
	}
	public List<Teacher> getTeachers() {
		return teachers;
	}

	public void setTeachers(List<Teacher> teachers) {
		this.teachers = teachers;
	}
}

package gjs.test;

import java.io.File;
import java.io.IOException;
import gjs.domain.Student;
import gjs.domain.Teacher;
import gjs.domain.TeacherList;
import org.apache.commons.digester.Digester;
import org.junit.Test;
import org.xml.sax.SAXException;
import static org.junit.Assert.*;
public class DigesterTest {
	
	/**
	 * 属性方式
	 */
	@Test public void testOne(){
		Digester digester=new Digester();
		//设置不进行合法性验证
		digester.setValidating(false);
		//当遇到<teacher>时创建一个Teacher对象，放入栈顶
		digester.addObjectCreate("teacher", Teacher.class);
		digester.addSetProperties("teacher");
		//当遇到<teacher>的子元素<student>时创建一个Student对象，放入栈顶
		digester.addObjectCreate("teacher/student", Student.class);
		//设置<student>的属性值，根据属性值调用相应的set方法
		digester.addSetProperties("teacher/student");
		//当再次遇到<student>时创建一个Student对象，放入栈顶，同时调用栈次顶的addStudent方法
		digester.addSetNext("teacher/student", "addStudent", "gjs.domain.Student");
		try {
			Teacher teacher = (Teacher)digester.parse(new File("src/student.xml"));
			assertEquals(8, teacher.getStudents().size());
		} catch (IOException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		}		
	}

	/**
	 * 子标签方式(设置Property方式一)
	 */
	@Test public void testTwo(){
		Digester digester=new Digester();
		digester.setValidating(false);
		//设置栈顶
		digester.push(new TeacherList());
		digester.addObjectCreate("teachers/teacher", Teacher.class);
		digester.addSetProperties("teachers/teacher");
		digester.addObjectCreate("teachers/teacher/student", Student.class);
		//子标签方式设置属性方法之一，第三个参数是第二个参数所指方法的参数个数
		digester.addCallMethod("teachers/teacher/student/name", "setName",1);
		digester.addCallMethod("teachers/teacher/student/age", "setAge",1);
		digester.addCallMethod("teachers/teacher/student/id", "setId",1);
		digester.addSetNext("teachers/teacher/student", "addStudent", "gjs.domain.Student");
		digester.addSetNext("teachers/teacher", "addTeachers", "gjs.domain.Teacher");
		try {
			TeacherList teacher = (TeacherList)digester.parse(new File("src/teacher.xml"));
			assertEquals(2, teacher.getTeachers().size());
			assertEquals("java", teacher.getTeachers().get(0).getCourse());
			assertEquals(8, teacher.getTeachers().get(0).getStudents().size());
		} catch (IOException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 子标签方式(设置Property方式二)
	 */
	@Test public void testThree(){
		Digester digester=new Digester();
		digester.setValidating(false);
		//设置栈顶
		digester.push(new TeacherList());
		digester.addObjectCreate("teachers/teacher", Teacher.class);
		digester.addSetProperties("teachers/teacher");
		digester.addObjectCreate("teachers/teacher/student", Student.class);
		//子标签方式设置属性方法之二
		digester.addBeanPropertySetter("teachers/teacher/student/name");
		digester.addBeanPropertySetter("teachers/teacher/student/age");
		digester.addBeanPropertySetter("teachers/teacher/student/id");
		digester.addSetNext("teachers/teacher/student", "addStudent", "gjs.domain.Student");
		digester.addSetNext("teachers/teacher", "addTeachers", "gjs.domain.Teacher");
		try {
			
			TeacherList teacher = (TeacherList)digester.parse(new File("src/teacher.xml"));
			assertEquals(2, teacher.getTeachers().size());
			assertEquals("java", teacher.getTeachers().get(0).getCourse());
			assertEquals(8, teacher.getTeachers().get(0).getStudents().size());
		} catch (IOException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		}
	}
	/**
	 * 子标签方式 (callMethod callParam方式)
	 */
	@Test public void testFour(){
		Digester digester=new Digester();
		digester.setValidating(false);
		digester.push(new TeacherList());
		digester.addObjectCreate("teachers/teacher", "gjs.domain.Teacher");
		digester.addSetProperties("teachers/teacher");
		//当<student>时调用栈顶元素(Teacher)的addStudents却并不执行，等待addCallParam设置参数，3为参数个数，这里传入的参数是字符串。
		digester.addCallMethod("teachers/teacher/student", "addStudent" ,3);
		digester.addCallParam("teachers/teacher/student/name", 0);
		digester.addCallParam("teachers/teacher/student/age", 1);
		//这句之后即</student>才调用addStudents方法，并且如果再次遇到<student>重复。
		digester.addCallParam("teachers/teacher/student/id", 2);		
		digester.addSetNext("teachers/teacher", "addTeachers", "gjs.domain.Teacher");
		try {
			TeacherList teacher=(TeacherList)digester.parse(new File("src/teacher.xml"));
			assertEquals(2, teacher.getTeachers().size());
			assertEquals("java", teacher.getTeachers().get(0).getCourse());
			assertEquals(8, teacher.getTeachers().get(0).getStudents().size());
			assertEquals("李世民2", teacher.getTeachers().get(1).getStudents().get(2).getName());
		} catch (IOException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		}
	}
}