Question

我有一个扩展Thread的类，我希望能够将配置信息存储为xml。由于所有其他属性以及Thread类中没有的属性，这显然不起作用。在编组期间，我得到了一个很好的堆栈跟踪：

Exception in thread "main" com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 2 counts of IllegalAnnotationExceptions
java.lang.Thread$UncaughtExceptionHandler is an interface, and JAXB can't handle interfaces.
    this problem is related to the following location:
        at java.lang.Thread$UncaughtExceptionHandler
        at public java.lang.Thread$UncaughtExceptionHandler java.lang.Thread.getUncaughtExceptionHandler()
        at java.lang.Thread
        at Test
java.lang.Thread$UncaughtExceptionHandler does not have a no-arg default constructor.
    this problem is related to the following location:
        at java.lang.Thread$UncaughtExceptionHandler
        at public java.lang.Thread$UncaughtExceptionHandler java.lang.Thread.getUncaughtExceptionHandler()
        at java.lang.Thread
        at Test

    at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:451)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:283)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:126)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1142)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:130)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:248)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:235)
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:445)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:637)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
    at Test.main(Test.java:22)

这是一个简单的类来演示这个问题：

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;



@XmlRootElement
public class Test extends Thread{

    @XmlAttribute
    public String something;

    public Test(){
    }

    public static void main(String[] args) throws JAXBException {
        Test test = new Test();
        test.something = "My Value";

        JAXBContext jaxbContext = JAXBContext.newInstance(Test.class);

        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
        // output pretty printed
        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        jaxbMarshaller.marshal(test, System.out);

    }

}

基本上我只关心Test类中的内容而不是已继承的内容。如下所示：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<test something="My Value"/>

那么如何在编组/解组时忽略基类？

Answer 1

为什么要扩展Thread而不是实现Runnable？

无论如何，我认为你的解决方案不是编组和解组Thread或任何扩展它的类，而是创建一个单独的Configuration类来保存你将要编组和解组的重要状态数据。

如，

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

public class Test implements Runnable {

   private TestConfig config = new TestConfig();

   public Test() {
   }

   public void setConfigSomething(String something) {
      config.setSomething(something);
   }

   public TestConfig getConfig() {
      return config;
   }

   public void setConfig(TestConfig config) {
      this.config = config;
   }

   @Override
   public void run() {
      // foo
   }

   public static void main(String[] args) throws JAXBException {
      Test test = new Test();
      test.setConfigSomething("My Value");

      JAXBContext jaxbContext = JAXBContext.newInstance(TestConfig.class);

      Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
      jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
      jaxbMarshaller.marshal(test.getConfig(), System.out);    
   }
}

@XmlRootElement
class TestConfig {
   private String something;

   @XmlAttribute
   public String getSomething() {
      return something;
   }

   public void setSomething(String something) {
      this.something = something;
   }
}

这将产生预期的输出：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<testConfig something="My Value"/>

我认为另一种可能的解决方案是尝试使用适配器类型，例如XmlAdapter，也许最好的解决方案是使用MOXy as per Blaise Doughan's suggestion。

如何在编组/解组时忽略基类？

1 个答案: