在已实现的方法上获取java.lang.AbstractMethodError

Question

正如标题所述，我得到了java.lang.AbstractMethodError一个方法，该方法由我的班级明确实施。完整的错误消息是：

java.lang.AbstractMethodError: htmlexport.HTMLExport.getParameterFormDescriptor()Ljava/util/List;

我有一个定义方法的接口如下：

List<ParamFormElement> getParameterFormDescriptor();

正如我所说，这个方法是由实现类实现的。

该接口包含在我本地Maven存储库中的jar中。我已经尝试了mvn clean和mvn install并且碰到了版本号，但这并没有解决问题。

实现类位于另一个使用ANT脚本创建的jar文件中。然后通过主应用程序中的ClassLoader加载该文件。

为什么我收到此错误的任何线索？界面定义的所有其他方法都有效。

以下是代码

我有一个Wicket WebPage，我在这里调用了这个方法：

public class AddJobPage extends BasePage {

    public AddJobPage(final PageParameters params) {
        super(params);

        final Workable w =
                WorkableManager.getInstance().findWorkableByName(params.get("workableName").toString());
        w.getParameterFormDescriptor();
    }

}

WorkableManager在内部使用URLClassLoader加载包含实现类的jar文件。这工作正常，我得到一个实例 所需的课程。

定义方法的接口是：

public interface Workable {

    List<ParamFormElement> getParameterFormDescriptor();

}

实现类看起来像这样（Module扩展Workable）：

public class HTMLExport implements Module {

    @Override
    public final List<ParamFormElement> getParameterFormDescriptor() {
        final List<ParamFormElement> form = new ArrayList<>();
        form.add(new ParamFormElement(ParamFormElement.Type.TEXT, "Bitte eingeben:", "test"));
        return form;
    }

}

接口位于一个单独的项目中，并在我的本地Maven存储库中组装为一个jar文件。 HTMLExport类也在不同的项目中 使用Ant编译和汇编。生成的jar文件位于我的主应用程序旁边的文件夹中，正如我所说的加载类工作。主要应用 是一个Maven项目，并将接口添加为依赖项。在Eclipse中，我没有任何错误或警告。

堆栈跟踪如下：

Root cause:

java.lang.AbstractMethodError: htmlexport.HTMLExport.getParameterFormDescriptor()Ljava/util/List;
    at web.pages.AddJobPage.<init>(AddJobPage.java:30)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:171)
    at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:99)
    at org.apache.wicket.DefaultMapperContext.newPageInstance(DefaultMapperContext.java:137)
    at org.apache.wicket.core.request.handler.PageProvider.resolvePageInstance(PageProvider.java:268)
    at org.apache.wicket.core.request.handler.PageProvider.getPageInstance(PageProvider.java:166)
    at org.apache.wicket.request.handler.render.PageRenderer.getPage(PageRenderer.java:78)
    at org.apache.wicket.request.handler.render.WebPageRenderer.isPageStateless(WebPageRenderer.java:300)
    at org.apache.wicket.request.handler.render.WebPageRenderer.shouldRenderPageAndWriteResponse(WebPageRenderer.java:342)
    at org.apache.wicket.request.handler.render.WebPageRenderer.respond(WebPageRenderer.java:203)
    at org.apache.wicket.core.request.handler.RenderPageRequestHandler.respond(RenderPageRequestHandler.java:175)
    at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:837)
    at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
    at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:265)
    at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:222)
    at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:293)
    at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:261)
    at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:203)
    at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:284)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1631)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:549)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:568)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:221)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1111)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:478)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:183)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1045)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:199)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:109)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:462)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:279)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:232)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:534)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
    at java.lang.Thread.run(Thread.java:722)

Complete stack:

org.apache.wicket.WicketRuntimeException: Can't instantiate page using constructor 'public web.pages.AddJobPage(org.apache.wicket.request.mapper.parameter.PageParameters)' and argument 'workableName=[HTML Export]'. An exception has been thrown during construction!
    at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:194)
    at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:99)
    at org.apache.wicket.DefaultMapperContext.newPageInstance(DefaultMapperContext.java:137)
    at org.apache.wicket.core.request.handler.PageProvider.resolvePageInstance(PageProvider.java:268)
    at org.apache.wicket.core.request.handler.PageProvider.getPageInstance(PageProvider.java:166)
    at org.apache.wicket.request.handler.render.PageRenderer.getPage(PageRenderer.java:78)
    at org.apache.wicket.request.handler.render.WebPageRenderer.isPageStateless(WebPageRenderer.java:300)
    at org.apache.wicket.request.handler.render.WebPageRenderer.shouldRenderPageAndWriteResponse(WebPageRenderer.java:342)
    at org.apache.wicket.request.handler.render.WebPageRenderer.respond(WebPageRenderer.java:203)
    at org.apache.wicket.core.request.handler.RenderPageRequestHandler.respond(RenderPageRequestHandler.java:175)
    at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:837)
    at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
    at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:265)
    at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:222)
    at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:293)
    at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:261)

java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:171)
    at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:99)
    at org.apache.wicket.DefaultMapperContext.newPageInstance(DefaultMapperContext.java:137)
    at org.apache.wicket.core.request.handler.PageProvider.resolvePageInstance(PageProvider.java:268)
    at org.apache.wicket.core.request.handler.PageProvider.getPageInstance(PageProvider.java:166)
    at org.apache.wicket.request.handler.render.PageRenderer.getPage(PageRenderer.java:78)
    at org.apache.wicket.request.handler.render.WebPageRenderer.isPageStateless(WebPageRenderer.java:300)
    at org.apache.wicket.request.handler.render.WebPageRenderer.shouldRenderPageAndWriteResponse(WebPageRenderer.java:342)
    at org.apache.wicket.request.handler.render.WebPageRenderer.respond(WebPageRenderer.java:203)
    at org.apache.wicket.core.request.handler.RenderPageRequestHandler.respond(RenderPageRequestHandler.java:175)
    at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:837)
    at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
    at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:265)
    at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:222)
    at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:293)
    at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:261)

Answer 1

确保您的类路径中有最新的jar文件而不是旧版本。如果您在运行时看到这种情况，则由于不兼容的二进制文件而发生这种情况

来自Oracle java site

  

当应用程序尝试调用抽象方法时抛出。通常，编译器会捕获此错误; 此错误只能在运行时发生，如果自上次编译当前正在执行的方法后某些类的定义发生了不兼容的更改。

Link to Class AbstractMethodError

还要尝试-U标志强制更新依赖项。

mvn clean install -U

Answer 2

如果您的实现类jar不在类路径中或不确定

尝试下面的代码

    YourInterfaceName obj = (YourInterfaceName)Class.forName
("yourPackageName.YourInterfaceImplClassName").newInstance();

Answer 3

问题是实现类没有正确编译，Ant脚本没有将正确的类复制到jar文件中。我将它转换为maven项目，现在可以找到该方法。