在实现的方法上获取 java.lang.AbstractMethodError

Question

正如标题所述，我在我的班级明确实现的方法上获得了java.lang.AbstractMethodError。完整的错误信息是：

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

我有一个接口，定义方法如下：

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 存储库中的一个 jar 中。我已经尝试过mvn clean 和mvn install 并修改版本号，但这并不能解决问题。

实现类位于我使用 ANT 脚本创建的另一个 jar 文件中。然后通过主应用程序中的 ClassLoader 加载文件。

任何线索为什么我得到这个错误？接口定义的所有其他方法都在工作。

代码来了

我有一个 Wicket WebPage，我在其中调用此方法：

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

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;
    }

}

该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，并且 使用 Ant 编译和组装。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，而不是旧的副本。如果您在运行时看到这种情况，这是由于不兼容的二进制文件造成的

来自 Oracle java 网站

当应用程序尝试调用抽象方法时抛出。通常，这个错误会被编译器捕获； 只有在当前执行的方法上次编译后某些类的定义发生了不兼容的更改时，才会在运行时发生此错误。

Link to Class AbstractMethodError

还可以尝试使用 -U 标志强制更新依赖项。

mvn clean install -U

Answer 2

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。我把它转换成一个maven项目，现在可以找到方法了。

Answer 3

如果您的实现类的 jar 不在类路径中或不确定

试试下面的代码

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