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（编组/解组）。当我在插件的启动过程（Activator.java）中尝试编写一个简单的类（Person.java）时，我遇到了一些错误。这是代码：

CODE：

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.index和jaxb.properties：

jaxb.index

Person

的 jaxb.properties

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

问题：

但是，运行插件会引发以下异常：

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.

据我所知，问题产生于两个类加载器已加载javax.xml.bind包，但我无法弄清楚为什么以及如何避免这种情况。

Morover，使用JAXBContextFactory代替JAXBContext.newInstance（如建议的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，我真的很感激！

Answer 1

您发布的清单仅包含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添加到捆绑包清单中。这应该允许框架将包解析为org.eclipse.persistence.moxy使用的包。

Answer 2

您需要确保导入javax.xml.bind捆绑包，而不是从JRE获取JAXB API。

EclipseLink MOXy OSGi包的问题

CODE：

问题：

2 个答案: