XML SAX解析xml文件

缺乏、安全感 2022-06-08 10:08 352阅读 0赞

**SAX解析xml文件**

**一、student.xml（解析的文件）**

<?xml version="1.0" encoding="utf-8" ?>
    
    <!DOCTYPE class [
            <!ELEMENT student (name,age,sex,height)>
            <!ELEMENT name (#PCDATA)>
            <!ELEMENT age (#PCDATA)>
            <!ELEMENT sex (#PCDATA)>
            <!ELEMENT height (#PCDATA)>
            ]>
    
    
    <class>
        
        <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、解析代码（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 {
                //步骤一：创建SAX解析工厂实例
                SAXParserFactory factory = SAXParserFactory.newInstance();
                //步骤二：通过工厂创建一个SAX解析器
                SAXParser sax = factory.newSAXParser();
                MyHandler myHandler = new MyHandler();
                //步骤三：指定用相应的解析器开始解析XML文档
                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 {
            }
        }
    }
    
    //指定解析处理器，编写解析规则
    class MyHandler extends DefaultHandler {
        ArrayList<Student> list = new ArrayList<>();
    
        public ArrayList<Student> getList() {
            return list;
        }
    
        private Student student;
        private String target = "";
    
        //    解析到文档的开始
        @Override
        public void startDocument() throws SAXException {
        }
    
    //    解析到开始的元素节点（包括根节点）
    
        /**
         * @param uri        命名空间
         * @param localName  元素名称【不支持了】
         * @param qName      [前缀:]元素名称（没有命名空间就不存在前缀）
         * @param attributes 属性集
         * @throws SAXException 异常
         */
        @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;
        }
    
        /**
         * 解析到文本内容（包括回车，空格，换行）
         *
         * @param ch     SAX并不是把整个文档加载到内存中，SAX会把解析到的内容缓存起来（缓存8192字节），char[] ch就是解析到的缓存内容
         * @param start  遇到文本的开始字符位置
         * @param length 当前整个文本从一个标签到下一个标签的长度
         * @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;
            }
    
        }
    
        /**
         * 解析到结束的元素节点
         *
         * @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 = "";
        }
    
        /**
         * 解析到文档的结束
         *
         * @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、解析结果**

![Center][]

注：读边解析，应用于大型XML文档

[Center]: /images/20220608/5ec2b8c5287b4ccea5eb554b03b26f4f.png