java解析xml

java解析xml

xml是java工程里常用的配置文件格式，具有很强的表达力。dom4j是经典的xml解析器，本文以此为例，记录java解析xml的过程。

一、创建

$ mvn archetype:generate

# mu模板就用最常用的maven-archetype-quickstart
Confirm properties configuration:
groupId: cn.edu.zju
artifactId: dom4jdemo
version: 1.0-SNAPSHOT
package: cn.edu.zju
Y: : y

二、pom依赖项

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>dom4j</groupId>
      <artifactId>dom4j</artifactId>
      <version>1.6.1</version>
    </dependency>

    <!-- 在xPath解析式要依赖这个包 -->
    <dependency>
      <groupId>jaxen</groupId>
      <artifactId>jaxen</artifactId>
      <version>1.2.0</version>
    </dependency>

  </dependencies>

三、工程结构

➜  dom4jdemo tree
.
├── pom.xml
├── resources
│   └── test.xml # 待解析的xml文件
└── src
    ├── main
    │   └── java
    │       └── cn
    │           └── edu
    │               └── zju
    │                   └── App.java
    └── test
        └── java
            └── cn
                └── edu
                    └── zju
                        └── AppTest.java

四、待解析的xml文件

test.xml

<?xml version="1.0" encoding="UTF-8" ?>
<resources>
    <product name="QQ">
        <account id="123456789">
            <nickname>qq1</nickname>
            <password>123</password>
            <level>56</level>
        </account>
        <account id="987654321">
            <nickname>qq2</nickname>
            <password>456</password>
            <level>12</level>
        </account>
    </product>
    <product name="Netease">
        <account id="Tom">
            <password>pwdOfTom</password>
            <capacity>1024</capacity>
        </account>
        <account id="Jim">
            <password>pwdOfJim</password>
            <capacity>2560</capacity>
        </account>
    </product>
</resources>

五、代码

App.java

package cn.edu.zju;

import org.dom4j.*;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import org.dom4j.xpath.DefaultXPath;

import java.io.FileWriter;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;

/**
 * Hello world!
 */
public class App {
    private Document document;

    App() {
        SAXReader reader = new SAXReader();
        try {
            document = reader.read("resources/test.xml");
        } catch (DocumentException e) {
            e.printStackTrace();
        }
    }

    void xPathParse() {
        // 用xpath解析
        XPath xPath = new DefaultXPath("/resources/product[@name='QQ']/account[@id='987654321']/password");
        List<Element> list = xPath.selectNodes(document.getRootElement());
        for (Element element : list) {
            System.out.println(element.getTextTrim());
        }
    }

    void normalParse() {
        // 解析每个节点
        List<Element> products = document.getRootElement().selectNodes("/resources/product");
        Iterator<Element> iterator = products.iterator();
        while (iterator.hasNext()) {
            Element product = iterator.next();
            // 获得属性
            System.out.println(product.attributeValue("name"));
            List<Element> accounts = product.selectNodes("account");
            for (Element account : accounts) {
                System.out.println("--" + account.attributeValue("id"));
                // 获得值
                System.out.println("-----" + account.elementTextTrim("password"));
            }
        }
    }

    void generate() {
        Document doc = DocumentHelper.createDocument();
        Element root = doc.addElement("people");

        Element p1 = root.addElement("p1");
        p1.addAttribute("id", "12345");
        p1.addElement("sex").setText("male");
        p1.addElement("age").setText("18");

        Element p2 = root.addElement("p2");
        p2.addAttribute("id", "67890");
        p2.addElement("sex").setText("female");
        p2.addElement("age").setText("26");

        XMLWriter xmlWriter = new XMLWriter();
        try {
            xmlWriter.setWriter(new FileWriter("resources/out.xml"));
            xmlWriter.write(doc);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                xmlWriter.flush();
                xmlWriter.close();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
    }

    public static void main(String[] args) {
        App app = new App();
        app.xPathParse();
        app.normalParse();
        app.generate();
    }
}

六、运行输出

456
QQ
--123456789
-----123
--987654321
-----456
Netease
--Tom
-----pwdOfTom
--Jim
-----pwdOfJim

七、生成文件

resources/out.xml

<?xml version="1.0" encoding="UTF-8"?>
<people>
    <p1 id="12345">
        <sex>male</sex>
        <age>18</age>
    </p1>
    <p2 id="67890">
        <sex>female</sex>
        <age>26</age>
    </p2>
</people>

八、小结

感觉java的代码都可以望文成义，看着代码和注释就能明白在干什么。打通xml之后，对各种框架里面用到的xml配置解析也更加熟悉一些，甚至可以自己写。