java - EclipseLink MOXy OSGi 包的问题

Question

我正在开发一个非常简单的 Eclipse 插件，它使用 EclipseLink 的 MOXy 进行 XML 绑定(bind)(编码/解码)。当我在插件 (Activator.java) 的启动过程中尝试编码一个简单的类 (Person.java) 时，我遇到了一些错误。这是代码:

代码:

Person.java

package test_rcp;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Person {

    private String name;
    private int age;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

}

Activator.java

package test_rcp;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;

import org.eclipse.ui.plugin.AbstractUIPlugin;
import org.osgi.framework.BundleContext;

public class Activator extends AbstractUIPlugin {

    public void start(BundleContext context) throws Exception {
        super.start(context);
        plugin = this;

        // Just to make sure EclipseLink is already loaded
        System.out.println(org.eclipse.persistence.Version.getVersion());

        Person p1 = new Person();
        p1.setName("John Dewey");
        p1.setAge(54);
        JAXBContext jc = JAXBContext.newInstance("test_rcp",Person.class.getClassLoader());

         Marshaller marshaller = jc.createMarshaller();
         marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
         marshaller.marshal(p1, System.out);
    }
}

MANIFEST.MF

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Test-RCP
Bundle-SymbolicName: Test-RCP; singleton:=true
Bundle-Version: 1.0.0.qualifier
Bundle-Activator: test_rcp.Activator
Require-Bundle: org.eclipse.ui,
 org.eclipse.core.runtime,
 org.eclipse.persistence.core,
 org.eclipse.persistence.moxy;bundle-version="2.4.1"
Bundle-ActivationPolicy: lazy
Bundle-RequiredExecutionEnvironment: JavaSE-1.7

包 test_rcp 还包含 jaxb.in​​dex 和 jaxb.properties:

jaxb.in​​dex

Person

jaxb.properties

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

问题:

但是运行插件会抛出以下异常:

javax.xml.bind.JAXBException: Provider org.eclipse.persistence.jaxb.JAXBContextFactory could not be instantiated: 
javax.xml.bind.JAXBException: Provider class org.eclipse.persistence.jaxb.JAXBContextFactory could not be instantiated:
 javax.xml.bind.JAXBException:
 ClassCastException: attempting to cast bundleresource://43.fwk583158213/javax/xml/bind/JAXBContext.class to jar:file:/usr/lib/jvm/java-7-oracle/jre/lib/rt.jar!/javax/xml/bind/JAXBContext.class.  Please make sure that you are specifying the proper ClassLoader.

我知道问题是因为两个类加载器加载了 javax.xml.bind 包，但我不知道为什么以及如何避免这种情况。

此外，通过使用 JAXBContextFactory 而不是 JAXBContext.newInstance(建议 here )，即:

JAXBContext jc = org.eclipse.persistence.jaxb.JAXBContextFactory.createContext(new Class[] {Person.class}, null);

我会得到以下异常:

java.lang.LinkageError: loader constraint violation:
loader (instance of org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader) previously
initiated loading for a different type with name "javax/xml/bind/JAXBContext"

我已经尝试过以下解决方案但没有成功:

https://stackoverflow.com/a/12943115/2295964

https://stackoverflow.com/a/11797373/2295964

如果有人能帮助我摆脱这种痛苦，我将不胜感激!

Answer 1

您发布的 list 仅包含Require-Bundle:

Require-Bundle: org.eclipse.ui,
 org.eclipse.core.runtime,
 org.eclipse.persistence.core,
 org.eclipse.persistence.moxy;bundle-version="2.4.1"

我建议将 Import-Package: javax.xml.bind 添加到 bundle list 中。这应该允许框架将包解析为 org.eclipse.persistence.moxy 使用的包。