Question

我需要将archetype-catalog.xml文件的内容解析为Java Object结构。为此，我想我会使用好的JAXB。所以，我查找了xml文件的xsd定义，并从中生成了jaxb类：

ArchetypeCatalog.java

import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlType;


/**
 *  0.0.0+
 * 
 * <p>Java class for ArchetypeCatalog complex type.
 * 
 * <p>The following schema fragment specifies the expected content contained within this class.
 * 
 * <pre>
 * &lt;complexType name="ArchetypeCatalog">
 *   &lt;complexContent>
 *     &lt;restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
 *       &lt;all>
 *         &lt;element name="archetypes" minOccurs="0">
 *           &lt;complexType>
 *             &lt;complexContent>
 *               &lt;restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
 *                 &lt;sequence>
 *                   &lt;element name="archetype" type="{http://maven.apache.org/plugins/maven-archetype-plugin/archetype-catalog/1.0.0}Archetype" maxOccurs="unbounded" minOccurs="0"/>
 *                 &lt;/sequence>
 *               &lt;/restriction>
 *             &lt;/complexContent>
 *           &lt;/complexType>
 *         &lt;/element>
 *       &lt;/all>
 *     &lt;/restriction>
 *   &lt;/complexContent>
 * &lt;/complexType>
 * </pre>
 * 
 * 
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "ArchetypeCatalog", propOrder = {

})
public class ArchetypeCatalog {

    protected ArchetypeCatalog.Archetypes archetypes;

    /**
     * Gets the value of the archetypes property.
     * 
     * @return
     *     possible object is
     *     {@link ArchetypeCatalog.Archetypes }
     *     
     */
    public ArchetypeCatalog.Archetypes getArchetypes() {
        return archetypes;
    }

    /**
     * Sets the value of the archetypes property.
     * 
     * @param value
     *     allowed object is
     *     {@link ArchetypeCatalog.Archetypes }
     *     
     */
    public void setArchetypes(ArchetypeCatalog.Archetypes value) {
        this.archetypes = value;
    }


    /**
     * <p>Java class for anonymous complex type.
     * 
     * <p>The following schema fragment specifies the expected content contained within this class.
     * 
     * <pre>
     * &lt;complexType>
     *   &lt;complexContent>
     *     &lt;restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
     *       &lt;sequence>
     *         &lt;element name="archetype" type="{http://maven.apache.org/plugins/maven-archetype-plugin/archetype-catalog/1.0.0}Archetype" maxOccurs="unbounded" minOccurs="0"/>
     *       &lt;/sequence>
     *     &lt;/restriction>
     *   &lt;/complexContent>
     * &lt;/complexType>
     * </pre>
     * 
     * 
     */
    @XmlAccessorType(XmlAccessType.FIELD)
    @XmlType(name = "", propOrder = {
        "archetype"
    })
    public static class Archetypes {

        protected List<Archetype> archetype;

        /**
         * Gets the value of the archetype property.
         * 
         * <p>
         * This accessor method returns a reference to the live list,
         * not a snapshot. Therefore any modification you make to the
         * returned list will be present inside the JAXB object.
         * This is why there is not a <CODE>set</CODE> method for the archetype property.
         * 
         * <p>
         * For example, to add a new item, do as follows:
         * <pre>
         *    getArchetype().add(newItem);
         * </pre>
         * 
         * 
         * <p>
         * Objects of the following type(s) are allowed in the list
         * {@link Archetype }
         * 
         * 
         */
        public List<Archetype> getArchetype() {
            if (archetype == null) {
                archetype = new ArrayList<Archetype>();
            }
            return this.archetype;
        }

    }

}

Archetype.java

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlType;


/**
 * 
 *              Informations to point to an Archetype referenced in the catalog.
 *          
 * 
 * <p>Java class for Archetype complex type.
 * 
 * <p>The following schema fragment specifies the expected content contained within this class.
 * 
 * <pre>
 * &lt;complexType name="Archetype">
 *   &lt;complexContent>
 *     &lt;restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
 *       &lt;all>
 *         &lt;element name="groupId" type="{http://www.w3.org/2001/XMLSchema}string" minOccurs="0"/>
 *         &lt;element name="artifactId" type="{http://www.w3.org/2001/XMLSchema}string" minOccurs="0"/>
 *         &lt;element name="version" type="{http://www.w3.org/2001/XMLSchema}string" minOccurs="0"/>
 *         &lt;element name="repository" type="{http://www.w3.org/2001/XMLSchema}string" minOccurs="0"/>
 *         &lt;element name="description" type="{http://www.w3.org/2001/XMLSchema}string" minOccurs="0"/>
 *       &lt;/all>
 *     &lt;/restriction>
 *   &lt;/complexContent>
 * &lt;/complexType>
 * </pre>
 * 
 * 
 */
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "Archetype", propOrder = {

})
public class Archetype {

    protected String groupId;
    protected String artifactId;
    protected String version;
    protected String repository;
    protected String description;

    /**
     * Gets the value of the groupId property.
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getGroupId() {
        return groupId;
    }

    /**
     * Sets the value of the groupId property.
     * 
     * @param value
     *     allowed object is
     *     {@link String }
     *     
     */
    public void setGroupId(String value) {
        this.groupId = value;
    }

    /**
     * Gets the value of the artifactId property.
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getArtifactId() {
        return artifactId;
    }

    /**
     * Sets the value of the artifactId property.
     * 
     * @param value
     *     allowed object is
     *     {@link String }
     *     
     */
    public void setArtifactId(String value) {
        this.artifactId = value;
    }

    /**
     * Gets the value of the version property.
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getVersion() {
        return version;
    }

    /**
     * Sets the value of the version property.
     * 
     * @param value
     *     allowed object is
     *     {@link String }
     *     
     */
    public void setVersion(String value) {
        this.version = value;
    }

    /**
     * Gets the value of the repository property.
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getRepository() {
        return repository;
    }

    /**
     * Sets the value of the repository property.
     * 
     * @param value
     *     allowed object is
     *     {@link String }
     *     
     */
    public void setRepository(String value) {
        this.repository = value;
    }

    /**
     * Gets the value of the description property.
     * 
     * @return
     *     possible object is
     *     {@link String }
     *     
     */
    public String getDescription() {
        return description;
    }

    /**
     * Sets the value of the description property.
     * 
     * @param value
     *     allowed object is
     *     {@link String }
     *     
     */
    public void setDescription(String value) {
        this.description = value;
    }

}

ObjectFactory.java

import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.XmlElementDecl;
import javax.xml.bind.annotation.XmlRegistry;
import javax.xml.namespace.QName;


@XmlRegistry
public class ObjectFactory {

    private final static QName _ArchetypeCatalog_QNAME = new QName("http://maven.apache.org/plugins/maven-archetype-plugin/archetype-catalog/1.0.0", "archetype-catalog");


    public ObjectFactory() {
    }

    /**
     * Create an instance of {@link ArchetypeCatalog }
     * 
     */
    public ArchetypeCatalog createArchetypeCatalog() {
        return new ArchetypeCatalog();
    }

    /**
     * Create an instance of {@link Archetype }
     * 
     */
    public Archetype createArchetype() {
        return new Archetype();
    }

    /**
     * Create an instance of {@link ArchetypeCatalog.Archetypes }
     * 
     */
    public ArchetypeCatalog.Archetypes createArchetypeCatalogArchetypes() {
        return new ArchetypeCatalog.Archetypes();
    }

    /**
     * Create an instance of {@link JAXBElement }{@code <}{@link ArchetypeCatalog }{@code >}}
     * 
     */
    @XmlElementDecl(namespace = "http://maven.apache.org/plugins/maven-archetype-plugin/archetype-catalog/1.0.0", name = "archetype-catalog")
    public JAXBElement<ArchetypeCatalog> createArchetypeCatalog(ArchetypeCatalog value) {
        return new JAXBElement<ArchetypeCatalog>(_ArchetypeCatalog_QNAME, ArchetypeCatalog.class, null, value);
    }

}

然而，当实际解组example文件以进行测试时，我得到以下内容：

堆栈跟踪：

Exception in thread "main" java.lang.RuntimeException: an error occurred while unmarshalling xml into com.catalogupdater.plugin.jaxb.ArchetypeCatalog object
    at com.catalogupdater.plugin.converter.JAXBConverter.stringToObject(JAXBConverter.java:48)
    at Main.main(Main.java:60)
Caused by: javax.xml.bind.UnmarshalException: unexpected element (uri:"http://maven.apache.org/plugins/maven-archetype-plugin/archetype-catalog/1.0.0", local:"archetype-catalog"). Expected elements are (none)

有什么建议这里出了什么问题？亲切的问候

修改：以下是我正在使用的完整解组逻辑：

   public static <T> T stringToObject( final String textClazz, final Class<T> clazz )
   {
      T returnedValue = null;
      try
      {
         final JAXBContext jaxbContext = JAXBContext.newInstance( clazz );
         final Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
         final StringReader reader = new StringReader( textClazz );
         returnedValue = ( T ) unmarshaller.unmarshal( reader );
      }
      catch ( final JAXBException e )
      {
         throw new RuntimeException(
               "an error occurred while unmarshalling xml into " + clazz.getCanonicalName() + " object", e );
      }
      return returnedValue;
   }

Answer 1

您应该执行以下操作：

     final JAXBContext jaxbContext = JAXBContext.newInstance( clazz.getPackage().getName() );
     final Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
     final StringReader reader = new StringReader( textClazz );
     returnedValue = ( T ) unmarshaller.unmarshal( reader ).getValue();

显然，如果您只是创建JAXBContext的{{1}}，则不会考虑clazz。 ObjectFactory是一个所谓的＆＃34; XML注册表＆＃34;其中说哪个类应该用于哪个根元素。

从解组中获得的是ObjectFactory，其中包含JAXBContext<SomeType>类型的值（在您的情况下为SomeType）以及根元素的名称。您可以通过ArchetypeCatalog获得您感兴趣的价值。

你在答案中所做的也有效，但这不是＆＃34; JAXB方式＆＃34;这样做。

您手动添加了getValue()注释，这肯定不适合生成的代码。您可以通过@XmlRootElement等插件添加它（免责声明：我是作者）。

但最终你应该更好地使用jaxb2-annotate-plugin，因为它是它的用途。长期坚持标准模式会让你感觉更好。

Answer 2

我发现生成的@RootElement类中缺少以下ArchetypeCatalog注释：

@XmlRootElement(namespace = "http://maven.apache.org/plugins/maven-archetype-plugin/archetype-catalog/1.0.0", name = "archetype-catalog")
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "ArchetypeCatalog", propOrder = {

})
public class ArchetypeCatalog
{

 ...
}

我手动添加它，现在它工作正常。不知道为什么不生成这个。尽管如此，毕竟我认为从xsd规范生成类需要谨慎对待。

亲切的问候

编辑：正如@ulab在评论中所述，缺少@RootElement的原因是here。

编辑：此外，手动放置@XMLRootElement注释不是必需的或不可取的。更多细节可以在@lexicor撰写的答案中找到。

Answer 3

另一种选择是首先检查用于生成类的 XJC 的版本和执行它的库的版本是否相同。同样的事情发生在我身上，足以保证两个版本相同。您可以在生成的类的初始注释以及用于执行这些类的库的版本中看到此信息。

使用JAXB解组xml文件

3 个答案: