使用 XML 工具： jaxb

Steven大约 1 分钟

介绍 Java 原生 oxm 工具 jaxb 的使用。

JAXB 教程

https://github.com/LawssssCat/blog/tree/master/code/demo-java-xml/n11-digester-usage/test/java/org/example/

读

XML 文件

<?xml version="1.0" encoding="utf-8" ?>
<my-content>
    <web-site>http://www.example.org</web-site>
    <owner>steven</owner>
    <description>原生 java xml 操作测试消息</description>
    <posts>
        <!-- 我是注释 -->
        <post id="P001">
            <title>文章标题01</title>
            <content>hello world 01！</content>
        </post>
        <post id="P002">
            <title>文章标题02</title>
            <content>hello world 02！</content>
        </post>
    </posts>
</my-content>

测试用例

package org.example;

import org.example.entity.JAXBMyContent;
import org.example.entity.JAXBPost;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;

public class XmlJaxbReadTest {
    @Test
    void test() {
        JAXBMyContent myContent;
        try {
            JAXBContext jaxbContext = JAXBContext.newInstance(JAXBMyContent.class);
            Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
            myContent = (JAXBMyContent) unmarshaller.unmarshal(XmlJaxbWriteTest.FILE);
        } catch (JAXBException e) {
            throw new RuntimeException(e);
        }
        System.out.println("myContent = " + myContent);
        Assertions.assertNotNull(myContent.getOwner());
        Assertions.assertNotNull(myContent.getWebSite());
        Assertions.assertNotNull(myContent.getDescription());
        Assertions.assertEquals(2, myContent.getPosts().size());
        Assertions.assertArrayEquals(new String[] {"P000", "P001"},
                myContent.getPosts().stream().map(JAXBPost::getId).toArray());
        Assertions.assertArrayEquals(new String[] {"JAXP-TITLE-0", "JAXP-TITLE-1"},
                myContent.getPosts().stream().map(JAXBPost::getTitle).toArray());
    }
}

写

package org.example;

import org.example.entity.JAXBMyContent;
import org.example.entity.JAXBPost;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import utils.IOUtils;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

public class XmlJaxbWriteTest {
    public static File FILE = new File(
            Objects.requireNonNull(XmlJaxbWriteTest.class.getResource("/")).getFile(),
            XmlJaxbWriteTest.class.getName() + ".xml"
    );
    @Test
    void test() throws IOException {
        try {
            JAXBContext jaxbContext = JAXBContext.newInstance(JAXBMyContent.class);
            Marshaller marshaller = jaxbContext.createMarshaller();
            // marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE); // 格式化输出
            marshaller.setProperty(Marshaller.JAXB_ENCODING, StandardCharsets.UTF_8.name());
            marshaller.marshal(buildMyContent(), FILE);
        } catch (JAXBException e) {
            throw new RuntimeException(e);
        }
        Assertions.assertTrue(FILE.exists());
        String xmlContent = IOUtils.readFile(FILE);
        Assertions.assertEquals("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>" +
                        "<my-content>" +
                        "<description>build by jaxp</description><owner>steven</owner>" +
                        "<posts>" +
                            "<post id=\"P000\">" +
                                "<content>JAXP-POST-CONTENT</content>" +
                                "<title>JAXP-TITLE-0</title>" +
                            "</post>" +
                            "<post id=\"P001\">" +
                                "<content>JAXP-POST-CONTENT</content>" +
                                "<title>JAXP-TITLE-1</title>" +
                            "</post>" +
                        "</posts>" +
                        "<web-site>https://org.example</web-site>" +
                        "</my-content>",
                xmlContent);
        Assertions.assertTrue(xmlContent.contains("my-content"));
        Assertions.assertTrue(xmlContent.contains("web-site"));
        Assertions.assertTrue(xmlContent.contains("<post id=\"P000\">"));
    }

    private JAXBMyContent buildMyContent() {
        // 报错1： [com.sun.istack.internal.SAXException2: 由于类型 "org.example.entity.MyContent" 缺少 @XmlRootElement 注释, 无法将该类型编集为元素]
        // 解决1： 需要 JAXPMyContent 类上添加 @XmlRootElement 注解
        // 报错2： [com.sun.istack.internal.SAXException2: 由于类型 "org.example.entity.JAXPMyContent" 对此上下文是未知的, 无法将该类型编集为元素。]
        // 解决2： 需要 MyContent 类上加 @XmlSeeAlso({JAXPMyContent.class}) 注解
        // MyContent myContent = new MyContent();
        JAXBMyContent myContent = new JAXBMyContent();
        myContent.setWebSite("https://org.example");
        myContent.setOwner("steven");
        myContent.setDescription("build by jaxp");
        List<JAXBPost> posts = new ArrayList<>();
        for (int i = 0; i < 2; i++) {
            JAXBPost post = new JAXBPost();
            post.setId("P00" + i);
            post.setTitle("JAXP-TITLE-"+i);
            post.setContent("JAXP-POST-CONTENT");
            posts.add(post);
        }
        myContent.setPosts(posts);
        return myContent;
    }
}

maven 插件 jaxb2-maven-plugin

jaxb2-maven-plugin 是一个用来代替 xjc 和 schemagen 用来完成 java 类和 schema 文件之间互相转换的 maven 插件。

官方地址：https://www.mojohaus.org/jaxb2-maven-plugin/Documentation/v2.2/open in new window （⭐⭐⭐）
github：https://github.com/mojohaus/jaxb2-maven-pluginopen in new window \

mvn jaxb2:schemagen  —— 从 Java 类生成 schema
mvn jaxb2:xjc        —— 从 schema 文件生成 Java 类

例子： https://github.com/LawssssCat/blog/tree/master/code/demo-java-maven/plugin-usage-jaxb2-maven-plugin/

依赖和插件配置

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.example</groupId>
        <artifactId>demo-java-maven</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <artifactId>plugin-usage-jaxb2-maven-plugin</artifactId>

    <dependencies>
        <dependency>
            <groupId>jakarta.xml.bind</groupId>
            <artifactId>jakarta.xml.bind-api</artifactId>
        </dependency>
    </dependencies>

    <build>
        <resources>
            <resource>
                <directory>${project.basedir}/src/main/resources/</directory>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>jaxb2-maven-plugin</artifactId>
                <version>3.2.0</version>
                <executions>
                    <!-- Java to Schema -->
                    <execution>
                        <id>schemagen</id>
                        <goals>
                            <goal>schemagen</goal>
                        </goals>
                        <configuration>
                            <encoding>UTF-8</encoding>
                            <sources>
                                <source>${project.build.sourceDirectory}/org/example/entity/Person.java</source>
                            </sources>
                            <outputDirectory>${project.basedir}/src/main/jaxb2/schemagen/</outputDirectory>
                        </configuration>
                    </execution>
                    <!-- Schema to Java -->
                    <execution>
                        <id>xjc</id>
                        <goals>
                            <goal>xjc</goal>
                        </goals>
                        <configuration>
                            <clearOutputDir>false</clearOutputDir>
                            <packageName>org.example.gen.entity</packageName>
                            <sources>
                                <source>${project.basedir}/src/main/jaxb2/schemagen/schema1.xsd</source>
                            </sources>
                            <outputDirectory>${project.build.sourceDirectory}</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

Java 类（源）

package org.example.entity;

import jakarta.xml.bind.annotation.XmlAccessType;
import jakarta.xml.bind.annotation.XmlAccessorType;
import jakarta.xml.bind.annotation.XmlElement;
import jakarta.xml.bind.annotation.XmlRootElement;

/**
 * 人员信息
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
public class Person {
    /**
     * 人员名称
     */
    @XmlElement(name = "username", required = true)
    private String name;
    /**
     * 人员住址
     */
    private String address;
    /**
     * 人员年龄
     */
    private int age;

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", address='" + address + '\'' +
                ", age=" + age +
                '}';
    }

    public String getName() {
        return name;
    }

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

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public int getAge() {
        return age;
    }

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

}

Schema 文件（生成）

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" version="1.0">
    
  <xs:element name="person" type="person"/>
    
  <xs:complexType name="person">
    <xs:annotation>
      <xs:documentation>
        <![CDATA[人员信息]]>
      </xs:documentation>
    </xs:annotation>
        
    <xs:sequence>
            
      <xs:element name="username" type="xs:string">
        <xs:annotation>
          <xs:documentation>
            <![CDATA[人员名称]]>
          </xs:documentation>
        </xs:annotation>
      </xs:element>
            
      <xs:element minOccurs="0" name="address" type="xs:string">
        <xs:annotation>
          <xs:documentation>
            <![CDATA[人员住址]]>
          </xs:documentation>
        </xs:annotation>
      </xs:element>
            
      <xs:element name="age" type="xs:int">
        <xs:annotation>
          <xs:documentation>
            <![CDATA[人员年龄]]>
          </xs:documentation>
        </xs:annotation>
      </xs:element>
          
    </xs:sequence>
      
  </xs:complexType>
  
</xs:schema>

Java 类（生成）

//
// 此文件是由 Eclipse Implementation of JAXB v3.0.2 生成的
// 请访问 https://eclipse-ee4j.github.io/jaxb-ri 
// 在重新编译源模式时, 对此文件的所有修改都将丢失。
// 生成时间: 2024.04.29 时间 08:08:06 AM CST 
//


package org.example.gen.entity;

import jakarta.xml.bind.annotation.XmlAccessType;
import jakarta.xml.bind.annotation.XmlAccessorType;
import jakarta.xml.bind.annotation.XmlElement;
import jakarta.xml.bind.annotation.XmlType;


/**
 * 
 *         人员信息
 *       
 * 
 * <p>person complex type的 Java 类。
 * 
 * <p>以下模式片段指定包含在此类中的预期内容。
 * 
 * <pre>
 * &lt;complexType name="person"&gt;
 *   &lt;complexContent&gt;
 *     &lt;restriction base="{http://www.w3.org/2001/XMLSchema}anyType"&gt;
 *       &lt;sequence&gt;
 *         &lt;element name="username" type="{http://www.w3.org/2001/XMLSchema}string"/&gt;
 *         &lt;element name="address" type="{http://www.w3.org/2001/XMLSchema}string" minOccurs="0"/&gt;
 *         &lt;element name="age" type="{http://www.w3.org/2001/XMLSchema}int"/&gt;
 *       &lt;/sequence&gt;
 *     &lt;/restriction&gt;
 *   &lt;/complexContent&gt;
 * &lt;/complexType&gt;
 * </pre>
 * 
 * 
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "person", propOrder = {
    "username",
    "address",
    "age"
})
public class Person {

    @XmlElement(required = true)
    protected String username;
    protected String address;
    protected int age;

    /**
     * 获取username属性的值。
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getUsername() {
        return username;
    }

    /**
     * 设置username属性的值。
     * 
     * @param value
     *     allowed object is
     *     {@link String }
     *     
     */
    public void setUsername(String value) {
        this.username = value;
    }

    /**
     * 获取address属性的值。
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getAddress() {
        return address;
    }

    /**
     * 设置address属性的值。
     * 
     * @param value
     *     allowed object is
     *     {@link String }
     *     
     */
    public void setAddress(String value) {
        this.address = value;
    }

    /**
     * 获取age属性的值。
     * 
     */
    public int getAge() {
        return age;
    }

    /**
     * 设置age属性的值。
     * 
     */
    public void setAge(int value) {
        this.age = value;
    }

}

maven 插件 maven-jaxb2-plugin

maven 插件 maven-jaxb2-plugin 实现了基于 xsd 配置文件生成对应的 Java 类的功能。在配置各种模型，属性很多的时候，生成相关文件非常方便。

Github： https://github.com/highsource/jaxb-tools?tab=readme-ov-file#jaxb-maven-pluginopen in new window

<plugin>
  <groupId>org.jvnet.jaxb2.maven2</groupId>
  <artifactId>maven-jaxb2-plugin</artifactId>
  <version>0.14.0</version>
  <executions>
    <execution>
      <id>generate</id>
      <goals>
        <goal>generate</goal>
      </goals>
      <configuration>
        <schemaDirectory>src/main/resources/tmsad</schemaDirectory>
        <schemaIncludes>
          <include>*.xsd</include>
        </schemaIncludes>
      </configuration>
    </execution>
  </executions>
</plugin>