用java去解析一个最简单的XML文件

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); } }}