Question

尝试将eventbus注入组件但我得到了 “没有默认（零args）构造函数。”错误。我有什么线索做错了？对GIN来说很新，所以它可能是微不足道的。

这是我的代码：

模块：

public class MyWidgetClientModule extends AbstractGinModule { 
    protected void configure() { 
        bind(EventBus.class).to(SimpleEventBus.class).in(Singleton.class); 
    } 
}

注射器：

@GinModules(MyWidgetClientModule.class) 
public interface MyWidgetGinjector extends Ginjector { 

}

和我试图注入的组件：

public class I18NLabel extends Label implements ChangeLanguageEventHandler{ 

  private final SimpleEventBus eventBus; 
    private String key; 

    @Inject 
    public I18NLabel(SimpleEventBus eventBus) { 
        this.eventBus = eventBus; 
    } 
...

它给了我这个错误日志：

00:00:45.767  [DEBUG] Rebinding com.test.fdc.gui.gwt.client.customer.CustomerDetailView.Binder
00:00:45.767  [DEBUG] Invoking generator com.google.gwt.uibinder.rebind.UiBinderGenerator
00:00:45.767  [ERROR] com.test.fdc.gui.gwt.client.content.i18n.I18NLabel has no default (zero args) constructor. To fix this, you can define a @UiFactory method on the UiBinder's owner, or annotate a constructor of I18NLabel with @UiConstructor.
00:00:45.767  [ERROR] Deferred binding failed for 'com.test.fdc.gui.gwt.client.customer.CustomerDetailView.Binder'; expect subsequent failures

00:00:45.767  [ERROR] Uncaught exception escaped

java.lang.ExceptionInInitializerError: null
    at com.test.fdc.gui.gwt.client.FDC$4.onSuccess(FDC.java:394)
    at com.test.fdc.gui.gwt.client.FDC$4.onSuccess(FDC.java:1)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:215)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:326)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:207)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:126)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:562)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:214)
    at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:281)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:531)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:352)
    at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.RuntimeException: Deferred binding failed for 'com.test.fdc.gui.gwt.client.customer.CustomerDetailView$Binder' (did you forget to inherit a required module?)
    at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:53)
    at com.google.gwt.core.client.GWT.create(GWT.java:97)
    at com.test.fdc.gui.gwt.client.customer.CustomerDetailView.(CustomerDetailView.java:34)
    at com.test.fdc.gui.gwt.client.FDC$4.onSuccess(FDC.java:394)
    at com.test.fdc.gui.gwt.client.FDC$4.onSuccess(FDC.java:1)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:215)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:326)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:207)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:126)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:562)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:214)
    at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:281)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:531)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:352)
    at java.lang.Thread.run(Thread.java:619)
Caused by: com.google.gwt.core.ext.UnableToCompleteException: (see previous log entries)
    at com.google.gwt.dev.shell.ModuleSpace.rebind(ModuleSpace.java:596)
    at com.google.gwt.dev.shell.ModuleSpace.rebindAndCreate(ModuleSpace.java:456)
    at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:49)
    at com.google.gwt.core.client.GWT.create(GWT.java:97)
    at com.test.fdc.gui.gwt.client.customer.CustomerDetailView.(CustomerDetailView.java:34)
    at com.test.fdc.gui.gwt.client.FDC$4.onSuccess(FDC.java:394)
    at com.test.fdc.gui.gwt.client.FDC$4.onSuccess(FDC.java:1)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:215)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:326)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:207)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:126)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:562)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:214)
    at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:281)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:531)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:352)
    at java.lang.Thread.run(Thread.java:619)

Answer 1

当您在UiBinder中声明一个小部件时，GWT会尝试使用默认的零参数构造函数对其进行实例化。由于您的新Widget没有拥有无参数构造函数，因此UiBinder方法失败。

您可以查看@UiConstructor和@UiField（provided = true）注释，但两者都不会为您提供非常优雅的解决方案。最好以编程方式声明窗口小部件并将其插入到Java布局中。如果您确实想继续使用UiBinder，可以执行类似

的操作

@UiField(provided=true)
protected I18NLabel theLabel;

public MyCompositeWidgetDefinedByUiBinder()
{
   theLabel = new I18NLabel(eventBusToInject);
   initWidget(uiBinder.createAndBindUI(this));
}

但是没有优雅的方法可以通过除此之外的UiBinder注入对象。

Answer 2

这个可能有点迟了但是你注入了实现而不是接口。尝试注入EventBus而不是SimpleEventBus。 GIN会知道使用正确的，因为你将它绑定在你的模块中。

Answer 3

我假设您的SimpleEventBus没有零参数构造函数？所以Gin无法实现它，因为它不知道如何（使用哪个args）。

在这种情况下，请将其添加到MyWidgetClientModule：

// assuming you only need one event bus in whole app
// use appropriate "args.." 
private static final SimpleEventBus eventBus = new SimpleEventBus(args..);

@Provides
SimpleEventBus provideEventBus() {
    return eventBus;
}

注入EventBus GWT

3 个答案: