MOXy XPath解组的元素为空。

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英文:

MOXy XPath unmarshalling Element is null

问题

我正在尝试使用XPath将camunda:property元素解组为List，以跳过不必要的包装元素。不幸的是，我的propertyList始终为null。这位于Task类中。非常感谢任何帮助。

编辑＃1：
我按照以下链接进行了操作，这些链接应该有助于解决我的问题，但不幸的是没有成功。
http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html，这是官方指南。显然，在maven pom.xml文件中存在一些挑战。我怀疑问题出在pom文件中。
我遵循了这个指南https://www.javacodegeeks.com/2012/07/eclipselink-moxy-as-jaxb-provider.html，但仍然无法使其工作。

pom.xml文件

  1. <!-- 在这里是您的 pom.xml 内容 -->

jaxb.properties文件与我的java类位于相同的包和文件夹中（请参见附带的名称为“Project Structure”的图像）。

  1. javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

package-info.java文件

  1. /* 在这里是您的 package-info.java 内容 */

xml文件片段

  1. <!-- 在这里是您的 xml 文件片段 -->

Definitions类

  1. /* 在这里是您的 Definitions 类内容 */

Process类

  1. /* 在这里是您的 Process 类内容 */

Task类

  1. /* 在这里是您的 Task 类内容 */

Property类

  1. /* 在这里是您的 Property 类内容 */

Main类

  1. /* 在这里是您的 Main 类内容 */

项目结构

英文:

Im trying to unmarshall the camunda:property elements into a List using XPath to skip the unnecessary wrapper elements. Unfortunately my propertyList is always null. This is located in the Task Class. Any help would be greatly appreciated.

Edit#1:
I followed the following links who were supposed to help with my problem unfortunately without success. http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html which is the official guide. Apparently there are some challenges with the maven pom.xml file. I suspect that the problem lies inside the pom file.
I followed this guide https://www.javacodegeeks.com/2012/07/eclipselink-moxy-as-jaxb-provider.html but still did not get it to work.

pom.xml file

  1. &lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  2. &lt;project xmlns=&quot;http://maven.apache.org/POM/4.0.0&quot;
  3.          xmlns:xsi=&quot;http://www.w3.org/2001/XMLSchema-instance&quot;
  4.          xsi:schemaLocation=&quot;http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd&quot;&gt;
  5.     &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
  6.     &lt;groupId&gt;org.example&lt;/groupId&gt;
  7.     &lt;artifactId&gt;BPMN-Marshaller&lt;/artifactId&gt;
  8.     &lt;version&gt;1.0-SNAPSHOT&lt;/version&gt;
  9.     &lt;properties&gt;
  10.         &lt;maven.compiler.source&gt;1.8&lt;/maven.compiler.source&gt;
  11.         &lt;maven.compiler.target&gt;1.8&lt;/maven.compiler.target&gt;
  12.     &lt;/properties&gt;
  13.     &lt;repositories&gt;&lt;repository&gt;
  14.         &lt;id&gt;EclipseLink Repo&lt;/id&gt;
  15.         &lt;url&gt;http://download.eclipse.org/rt/eclipselink/maven.repo&lt;/url&gt;
  16.         &lt;name&gt;EclipseLink Repo&lt;/name&gt;
  17.     &lt;/repository&gt;&lt;/repositories&gt;
  18.     &lt;dependencies&gt;
  19.         &lt;dependency&gt;
  20.             &lt;groupId&gt;org.eclipse.persistence&lt;/groupId&gt;
  21.             &lt;artifactId&gt;org.eclipse.persistence.moxy&lt;/artifactId&gt;
  22.             &lt;version&gt;3.0.0-M1&lt;/version&gt;
  23.         &lt;/dependency&gt;
  24.         &lt;dependency&gt;
  25.             &lt;groupId&gt;com.fasterxml.jackson.core&lt;/groupId&gt;
  26.             &lt;artifactId&gt;jackson-databind&lt;/artifactId&gt;
  27.             &lt;version&gt;2.5.3&lt;/version&gt;
  28.         &lt;/dependency&gt;
  29.         &lt;!-- Runtime, com.sun.xml.bind module --&gt;
  30.         &lt;dependency&gt;
  31.             &lt;groupId&gt;org.glassfish.jaxb&lt;/groupId&gt;
  32.             &lt;artifactId&gt;jaxb-runtime&lt;/artifactId&gt;
  33.             &lt;version&gt;2.3.2&lt;/version&gt;
  34.         &lt;/dependency&gt;
  35.         &lt;dependency&gt;
  36.             &lt;groupId&gt;jakarta.xml.bind&lt;/groupId&gt;
  37.             &lt;artifactId&gt;jakarta.xml.bind-api&lt;/artifactId&gt;
  38.             &lt;version&gt;2.3.2&lt;/version&gt;
  39.         &lt;/dependency&gt;
  40.     &lt;/dependencies&gt;
  42. &lt;/project&gt;

jaxb.properties file in the same package and folder as my java classes(see attached image with name "Project Structure")

  1. javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

package-info.java file

  1. @XmlSchema(namespace=&quot;http://www.omg.org/spec/BPMN/20100524/MODEL&quot;, elementFormDefault=XmlNsForm.QUALIFIED, xmlns = {@XmlNs(prefix=&quot;bpmn&quot;, namespaceURI=&quot;http://www.omg.org/spec/BPMN/20100524/MODEL&quot;)
  2.         ,@XmlNs(prefix = &quot;camunda&quot;, namespaceURI = &quot;http://camunda.org/schema/1.0/bpmn&quot;)})
  4. package bpmn;
  6. import javax.xml.bind.annotation.*;

xml file snippet

  1. &lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  2. &lt;bpmn:definitions xmlns:bpmn=&quot;http://www.omg.org/spec/BPMN/20100524/MODEL&quot; xmlns:bpmndi=&quot;http://www.omg.org/spec/BPMN/20100524/DI&quot; xmlns:dc=&quot;http://www.omg.org/spec/DD/20100524/DC&quot; xmlns:camunda=&quot;http://camunda.org/schema/1.0/bpmn&quot; xmlns:di=&quot;http://www.omg.org/spec/DD/20100524/DI&quot; id=&quot;Definitions_13d3a6z&quot; targetNamespace=&quot;http://bpmn.io/schema/bpmn&quot; exporter=&quot;Camunda Modeler&quot; exporterVersion=&quot;4.1.1&quot;&gt;
  3.   &lt;bpmn:process id=&quot;Process_1tovjba&quot; isExecutable=&quot;true&quot;&gt;
  4.     &lt;bpmn:startEvent id=&quot;StartEvent_1&quot;&gt;
  5.       &lt;bpmn:outgoing&gt;Flow_06i118e&lt;/bpmn:outgoing&gt;
  6.     &lt;/bpmn:startEvent&gt;
  7.     &lt;bpmn:task id=&quot;Activity_1d3friu&quot; name=&quot;Task 1&quot;&gt;
  8.       &lt;bpmn:extensionElements&gt;
  9.         &lt;camunda:properties&gt;
  10.           &lt;camunda:property name=&quot;start_date&quot; value=&quot;01-04-2018&quot; /&gt;
  11.           &lt;camunda:property name=&quot;duration&quot; value=&quot;5&quot; /&gt;
  12.         &lt;/camunda:properties&gt;
  13.       &lt;/bpmn:extensionElements&gt;
  14.       &lt;bpmn:incoming&gt;Flow_06i118e&lt;/bpmn:incoming&gt;
  15.       &lt;bpmn:outgoing&gt;Flow_0linmbs&lt;/bpmn:outgoing&gt;
  16.     &lt;/bpmn:task&gt;

Definitions Class

  1. @XmlRootElement
  2. public class Definitions {
  4.  private String id;
  5.  private Process process;
  9.     public Definitions(){};
  10.     public Definitions(String id, Process process){
  11.         super();
  12.         this.id = id;
  13.         this.process = process;
  14.     }
  16.     @XmlAttribute
  17.     public String getId() {
  18.         return id;
  19.     }
  21.     public void setId(String id) {
  22.         this.id = id;
  23.     }
  25.     @XmlElement
  26.     public Process getProcess() {
  27.         return process;
  28.     }
  30.     public void setProcess(Process process) {
  31.         this.process = process;
  32.     }
  34.     @Override
  35.     public String toString(){
  36.         return &quot;Definitions [id23=&quot; + id + &quot;, process=23499999999999999&quot; + process + &quot;]&quot;;
  37.     }
  39. }

Process Class

  1. public class Process {
  3.     private String id;
  4.     private List&lt;Task&gt; taskList;
  5.     private List&lt;SequenceFlow&gt; sequenceFlowList;
  7.     public Process(){};
  8.     public Process(String id, List&lt;Task&gt; taskList, List&lt;SequenceFlow&gt; sequenceFlowList){
  9.         super();
  10.         this.id = id;
  11.         this.taskList = taskList;
  12.         this.sequenceFlowList = sequenceFlowList;
  13.     }
  15.     @XmlAttribute
  16.     public String getId() {
  17.         return id;
  18.     }
  20.     public void setId(String id) {
  21.         this.id = id;
  22.     }
  24.     @XmlElement(name = &quot;task&quot;)
  25.     public List&lt;Task&gt; getTaskList() {
  26.         return taskList;
  27.     }
  29.     public void setTaskList(List&lt;Task&gt; taskList) {
  30.         this.taskList = taskList;
  31.     }
  33.     @XmlElement(name = &quot;sequenceFlow&quot;)
  34.     public List&lt;SequenceFlow&gt; getSequenceFlowList() {
  35.         return sequenceFlowList;
  36.     }
  38.     public void setSequenceFlowList(List&lt;SequenceFlow&gt; sequenceFlowList) {
  39.         this.sequenceFlowList = sequenceFlowList;
  40.     }
  41. }

Task Class

  1. public class Task {
  3.     private String id;
  4.     private String name;
  5.     private List&lt;Property&gt; propertyList;
  7.     public Task(){}
  8.     public Task(String id, String name, List&lt;Property&gt; propertyList){
  9.         super();
  10.         this.id = id;
  11.         this.name = name;
  12.         this.propertyList = propertyList;
  13.     }
  15.     @XmlAttribute
  16.     @JsonProperty(&quot;text&quot;)
  17.     public String getName() {
  18.         return name;
  19.     }
  21.     public void setName(String name) {
  22.         this.name = name;
  23.     }
  25.     @XmlAttribute
  26.     public String getId() {
  27.         return id;
  28.     }
  30.     public void setId(String id) {
  31.         this.id = id;
  32.     }
  34.     @XmlElement(name = &quot;property&quot;)
  35.     @XmlPath(&quot;bpmn:extensionElements/camunda:properties/camunda:property&quot;)
  36.     public List&lt;Property&gt; getPropertyList() {
  37.         return propertyList;
  38.     }
  40.     public void setPropertyList(List&lt;Property&gt; propertyList) {
  41.         this.propertyList = propertyList;
  42.     }
  43. }

Property Class

  1. public class Property {
  3.     private String name;
  4.     private String value;
  6.     public Property(){}
  7.     public Property(String name, String value) {
  8.         super();
  9.         this.name = name;
  10.         this.value = value;
  11.     }
  13.     @XmlAttribute
  14.     public String getName() {
  15.         return name;
  16.     }
  18.     public void setName(String name) {
  19.         this.name = name;
  20.     }
  22.     @XmlAttribute
  23.     public String getValue() {
  24.         return value;
  25.     }
  27.     public void setValue(String value) {
  28.         this.value = value;
  29.     }
  30. }

Main Class

  1. public class XMLToObject {
  2.     public static void main(String[] args) {
  4.         try {
  6.             File file = new File(&quot;process.bpmn&quot;);
  7.             JAXBContext jaxbContext = JAXBContext.newInstance(Definitions.class);
  8.             Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
  9.             Definitions definitions = (Definitions) jaxbUnmarshaller.unmarshal(file);
  10.             System.out.println(definitions.getProcess().getTaskList().get(0).getPropertyList());
  12.         } catch (JAXBException e) {
  13.             e.printStackTrace();
  14.         }
  17.     }
  18. }

Project Structure

答案1

得分: 1

我对你的方法做了以下更改，我能够从你的XML文件中访问duration和start_date属性的数据。

顺便说一下，我正在使用OpenJDK 14。但这种方法也可以在版本8上运行正常。

我正在使用的POM具有以下依赖关系：

  1. <dependency>
  2.     <groupId>com.sun.activation</groupId>
  3.     <artifactId>javax.activation</artifactId>
  4.     <version>1.2.0</version>
  5. </dependency>
  7. <!-- 
  8.      请使用2.3.1以避免“非法反射访问操作”警告。
  9. -->
  10. <dependency>
  11.     <groupId>javax.xml.bind</groupId>
  12.     <artifactId>jaxb-api</artifactId>
  13.     <version>2.3.1</version>
  14. </dependency>
  16. <dependency>
  17.     <groupId>com.sun.xml.bind</groupId>
  18.     <artifactId>jaxb-core</artifactId>
  19.     <version>2.3.0.1</version>
  20. </dependency>
  22. <dependency>
  23.     <groupId>com.sun.xml.bind</groupId>
  24.     <artifactId>jaxb-impl</artifactId>
  25.     <version>2.3.1</version>
  26. </dependency>
  28. <dependency>
  29.     <groupId>org.eclipse.persistence</groupId>
  30.     <artifactId>eclipselink</artifactId>
  31.     <version>2.7.6</version>
  32. </dependency>

（为了这个测试，我跳过了Jackson依赖项。）

我还在我的POM末尾添加了以下部分，以处理属性文件：

  1. <!-- 复制jaxb.properties文件到其类包中的位置： -->
  2. <build>
  3.     <resources>
  4.         <resource>
  5.             <directory>src/main/java</directory>
  6.             <excludes>
  7.                 <exclude>**/*.java</exclude>
  8.             </excludes>
  9.         </resource>
  10.     </resources>
  11. </build>

这确保属性文件与其相关的类文件一起部署到正确的位置。

我添加了用于检查正在使用的JAXB提供程序的代码 - 只是作为积极的确认：

  1. private void checkProvider() throws JAXBException {
  2.     JAXBContext jc = JAXBContext.newInstance(Definitions.class);
  4.     String jaxbContextImpl = jc.getClass().getName();
  5.     if(MOXY_JAXB_CONTEXT.equals(jaxbContextImpl)) {
  6.         System.out.println("EclipseLink MOXy");
  7.     } else if(METRO_JAXB_CONTEXT.equals(jaxbContextImpl)) {
  8.         System.out.println("Metro");
  9.     } else {
  10.         System.out.println("Other");
  11.     }
  12. }

我修改了代码以循环遍历属性数据，以显式打印最终的属性值：

  1. List<Property> props = definitions.getProcess().getTaskList().get(0).getPropertyList();
  2. props.forEach(prop -> {
  3.     System.out.println(prop.getName() + " - " + prop.getValue());
  4. });

结果输出为：

  1. EclipseLink MOXy
  2. start_date - 01-04-2018
  3. duration - 5
英文:

I made the following changes to your approach, and I am able to access the duration and start_date properties data from your XML file.

I am using OpenJDK 14, by the way. But this approach runs OK using version 8 also.

The POM I am using has the following dependencies:

  1.         &lt;dependency&gt;
  2.             &lt;groupId&gt;com.sun.activation&lt;/groupId&gt;
  3.             &lt;artifactId&gt;javax.activation&lt;/artifactId&gt;
  4.             &lt;version&gt;1.2.0&lt;/version&gt;
  5.         &lt;/dependency&gt;
  7.         &lt;!-- 
  8.              Use 2.3.1 below to prevent &quot;illegal 
  9.              reflective access operation&quot; warnings.
  10.         --&gt;
  11.         &lt;dependency&gt;
  12.             &lt;groupId&gt;javax.xml.bind&lt;/groupId&gt;
  13.             &lt;artifactId&gt;jaxb-api&lt;/artifactId&gt;
  14.             &lt;version&gt;2.3.1&lt;/version&gt;
  15.         &lt;/dependency&gt;
  17.         &lt;dependency&gt;
  18.             &lt;groupId&gt;com.sun.xml.bind&lt;/groupId&gt;
  19.             &lt;artifactId&gt;jaxb-core&lt;/artifactId&gt;
  20.             &lt;version&gt;2.3.0.1&lt;/version&gt;
  21.         &lt;/dependency&gt;
  23.         &lt;dependency&gt;
  24.             &lt;groupId&gt;com.sun.xml.bind&lt;/groupId&gt;
  25.             &lt;artifactId&gt;jaxb-impl&lt;/artifactId&gt;
  26.             &lt;version&gt;2.3.1&lt;/version&gt;
  27.         &lt;/dependency&gt;
  29.         &lt;dependency&gt;
  30.             &lt;groupId&gt;org.eclipse.persistence&lt;/groupId&gt;
  31.             &lt;artifactId&gt;eclipselink&lt;/artifactId&gt;
  32.             &lt;version&gt;2.7.6&lt;/version&gt;
  33.         &lt;/dependency&gt;

(I skipped the Jackson dependency just for this test.)

I also added the following section at the end of my POM, to handle the properties file:

  1.     &lt;!-- to copy the jaxb.properties file to its class package: --&gt;
  2.     &lt;build&gt;
  3.         &lt;resources&gt;
  4.             &lt;resource&gt;
  5.                 &lt;directory&gt;src/main/java&lt;/directory&gt;
  6.                 &lt;excludes&gt;
  7.                     &lt;exclude&gt;**/*.java&lt;/exclude&gt;
  8.                 &lt;/excludes&gt;
  9.             &lt;/resource&gt;
  10.         &lt;/resources&gt;
  11.     &lt;/build&gt;

This ensures the properties file is deployed to the correct location with its related class files.

I added the code to check for which JAXB provider is being used - just as a positive confirmation:

  1.     private void checkProvider() throws JAXBException {
  2.         JAXBContext jc = JAXBContext.newInstance(Definitions.class);
  4.         String jaxbContextImpl = jc.getClass().getName();
  5.         if(MOXY_JAXB_CONTEXT.equals(jaxbContextImpl)) {
  6.             System.out.println(&quot;EclipseLink MOXy&quot;);
  7.         } else if(METRO_JAXB_CONTEXT.equals(jaxbContextImpl)) {
  8.             System.out.println(&quot;Metro&quot;);
  9.         } else {
  10.             System.out.println(&quot;Other&quot;);
  11.         }
  12.     }

I modified the code to loop through the properties data, to explicitly print the final properties values:

  1. List&lt;Property&gt; props = definitions.getProcess().getTaskList().get(0).getPropertyList();
  2. props.forEach(prop -&gt; {
  3.     System.out.println(prop.getName() + &quot; - &quot; + prop.getValue());
  4. });
  5. //System.out.println(definitions.getProcess().getTaskList().get(0).getPropertyList());

The resulting output is:

  1. EclipseLink MOXy
  2. start_date - 01-04-2018
  3. duration - 5

huangapple
  • 本文由 发表于 2020年8月18日 20:41:52
  • 转载请务必保留本文链接：https://go.coder-hub.com/63468873.html
  • java
  • jaxb
  • moxy
  • unmarshalling
  • xml
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