SAX解析xml檔案

一、student.xml（解析的檔案）

<?xml version="1.0" encoding="utf-8" ?><!--xml文件宣告-->
<!--DTD約束-->
<!DOCTYPE class [
        <!ELEMENT student (name,age,sex,height)>
        <!ELEMENT name (#PCDATA)>
        <!ELEMENT age (#PCDATA)>
        <!ELEMENT sex (#PCDATA)>
        <!ELEMENT height (#PCDATA)>
        ]>

<!--只能有一個根標籤-->
<class>
    <!--設定屬性-->
    <student id="1" user="lisi">
        <name>李四</name>
        <age>18</age>
        <sex>男</sex>
        <height>182</height>
    </student>
    <student id="2" user="wangwu">
        <name>王五</name>
        <age>19</age>
        <sex>男</sex>
        <height>172</height>
    </student>
</class>
 

二、解析程式碼（SAXParseMain.java）

package com.xml.main;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import java.io.IOException;
import java.util.ArrayList;

public class SAXParseMain {
    public static void main(String[] args) {
        try {
            //步驟一：建立SAX解析工廠例項
            SAXParserFactory factory = SAXParserFactory.newInstance();
            //步驟二：通過工廠建立一個SAX解析器
            SAXParser sax = factory.newSAXParser();
            MyHandler myHandler = new MyHandler();
            //步驟三：指定用相應的解析器開始解析XML文件
            sax.parse("student.xml", myHandler);
            ArrayList<Student> list = myHandler.getList();
            for (int i = 0; i < list.size(); i++) {
                Student student = list.get(i);
                System.out.println(student.toString());
            }
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
        }
    }
}

//指定解析處理器，編寫解析規則
class MyHandler extends DefaultHandler {
    ArrayList<Student> list = new ArrayList<>();

    public ArrayList<Student> getList() {
        return list;
    }

    private Student student;
    private String target = "";

    //    解析到文件的開始
    @Override
    public void startDocument() throws SAXException {
    }

//    解析到開始的元素節點（包括根節點）

    /**
     * @param uri        名稱空間
     * @param localName  元素名稱【不支援了】
     * @param qName      [字首:]元素名稱（沒有名稱空間就不存在字首）
     * @param attributes 屬性集
     * @throws SAXException 異常
     */
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if ("student".equals(qName)) {
            student = new Student();
            String id = attributes.getValue("id");
            String user = attributes.getValue("user");
            student.setId(Integer.parseInt(id));
            student.setUser(user);
        }
        target = qName;
    }

    /**
     * 解析到文字內容（包括回車，空格，換行）
     *
     * @param ch     SAX並不是把整個文件載入到記憶體中，SAX會把解析到的內容快取起來（快取8192位元組），char[] ch就是解析到的快取內容
     * @param start  遇到文字的開始字元位置
     * @param length 當前整個文字從一個標籤到下一個標籤的長度
     * @throws SAXException
     */
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        String content = new String(ch, start, length);
        switch (target) {
            case "name":
                student.setName(content);
                break;
            case "age":
                student.setAge(Integer.parseInt(content));
                break;
            case "sex":
                student.setSex(content);
                break;
            case "height":
                student.setHeight(Double.parseDouble(content));
                break;
        }

    }

    /**
     * 解析到結束的元素節點
     *
     * @param uri
     * @param localName
     * @param qName
     * @throws SAXException
     */
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if ("student".equals(qName)) {
            list.add(student);
        }
        target = "";
    }

    /**
     * 解析到文件的結束
     *
     * @throws SAXException
     */
    @Override
    public void endDocument() throws SAXException {
    }

}
 

三、Student.java

package com.xml.main;

public class Student {
    private int id;
    private String user;
    private String name;
    private String sex;
    private int age;
    private double height;

    public Student() {
    }

    public Student(int id, String user, String name, String sex, int age, double height) {
        this.id = id;
        this.user = user;
        this.name = name;
        this.sex = sex;
        this.age = age;
        this.height = height;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public double getHeight() {
        return height;
    }

    public void setHeight(double height) {
        this.height = height;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", user='" + user + '\'' +
                ", name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", age=" + age +
                ", height=" + height +
                '}';
    }
}
 

四、解析結果

注：讀邊解析，應用於大型XML文件