用java去解析一个最简单的XML文件，java解析xml

用java去解析一个最简单的XML文件，java解析xml

此处仅仅是去解析最基本的XML文件，XML文件如下：

<Books>
    <Book>
        <Name>Java入门</Name>
        <Price>30.00</Price>
    </Book>
    <Book>
        <Name>Java基础</Name>
        <Price>130.00</Price>
    </Book>
    <Book>
        <Name>Java精通</Name>
        <Price>256.00</Price>
    </Book>
    <Book>
        <Name>Java进阶</Name>
        <Price>998.00</Price>
    </Book>
    <Book>
        <Name>程序员之禅</Name>
        <Price>122.00</Price>
    </Book>
    <Book>
        <Name>颈椎指南</Name>
        <Price>50.00</Price>
    </Book>
    <Book>
        <Name>活着</Name>
        <Price>26.00</Price>
    </Book>
    <Book/>
</Books>

上图是一个书的XML文件，我们创建一个Book类用来存储上面的图书实体

package learn;

public class Book implements Comparable<Book>{
    private String name;
    private float price;

    public Book() {
    }

    public Book(String name, float price) {
        this.name = name;
        this.price = price;
    }

    public String getName() {
        return name;
    }

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

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", price=" + price +
                '}';
    }

    @Override
    public int hashCode() {
        System.out.println("Book.hashCode");
        return ((int) price);
    }

    @Override
    public boolean equals(Object obj) {
        System.out.println("Book.equals");
        if (obj instanceof Book) {
            Book book = (Book) obj;
            return price == book.price && name.equals(book.name);
        }
        return false;
    }

    @Override
    public int compareTo(Book o) {
        int result = (int) (price - o.price);
        if (result == 0) {
            result = name.compareTo(o.name);
        }
        return result;
    }
}

下面是解析XML的代码

package learn;

import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test01 {
    public static void main(String[] args) {
        String str = "<Books>\n" +
                "    <Book>\n" +
                "        <Name>Java入门</Name>\n" +
                "        <Price>30.00</Price>\n" +
                "    </Book>\n" +
                "    <Book>\n" +
                "        <Name>Java基础</Name>\n" +
                "        <Price>130.00</Price>\n" +
                "    </Book>\n" +
                "    <Book>\n" +
                "        <Name>Java精通</Name>\n" +
                "        <Price>256.00</Price>\n" +
                "    </Book>\n" +
                "    <Book>\n" +
                "        <Name>Java进阶</Name>\n" +
                "        <Price>998.00</Price>\n" +
                "    </Book>\n" +
                "    <Book>\n" +
                "        <Name>程序员之禅</Name>\n" +
                "        <Price>122.00</Price>\n" +
                "    </Book>\n" +
                "    <Book>\n" +
                "        <Name>颈椎指南</Name>\n" +
                "        <Price>50.00</Price>\n" +
                "    </Book>\n" +
                "    <Book>\n" +
                "        <Name>活着</Name>\n" +
                "        <Price>26.00</Price>\n" +
                "    </Book>\n" +
                "    <Book/>\n" +
                "</Books>";
        List<Book> list = null;
        Stack<Book> stack = new Stack<>();
        Pattern pattern = Pattern.compile("<(/?)([^<>/]+)(/?)>");//此正则可能匹配到的是<>
        Matcher matcher = pattern.matcher(str);
        Stack<Integer> last = new Stack<>();//用来存放匹配到的<>，里面没有/，记录匹配到的<>的末尾位置
        while (matcher.find()) {
            if (matcher.group(1).isEmpty()) {  //如果<...>里面的首个括号内是空
                last.push(matcher.end());      //记录匹配到的<...>的末尾位置
                switch (matcher.group(2)) {
                    case "Books":
                        list = new ArrayList<>();
                        break;
                    case "Book":
                        stack.push(new Book());
                        break;
                }
                if (!matcher.group(3).isEmpty()) {  //匹配第三个括号里有/，即<../>
                    last.pop();                     //匹配到<../>，栈顶元素出栈
                    switch (matcher.group(2)) {
                        case "Book":
                            list.add(stack.pop());
                            break;
                    }

                }
            } else {

//如果</...>里面的首个括号内不是空

Integer pop = last.pop(); //记录上一个<..>或<../>的matcher.end() switch (matcher.group(2)) { case "Book": list.add(stack.pop()); break; case "Name": stack.peek().setName(str.substring(pop, matcher.start())); break; case "Price": stack.peek().setPrice(Float.parseFloat(str.substring(pop, matcher.start()))); break; } } } for (Book book : list) { //遍历得到的list，里面存入的是Book的实体 System.out.println(book); } }}