带有转换器的 JSF selectManyListBox 不起作用
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【中文标题】带有转换器的 JSF selectManyListBox 不起作用【英文标题】：JSF selectManyListBox with converter not working 【发布时间】：2014-01-01 22:36:16 【问题描述】：直截了当，我得到 ClassCastException: java.lang.String cannot be cast com.jsf.domain.Owner 我认为转换器有问题，但我不知道它在哪里。
html：
<h:selectManyListbox value="#myBean.target" converter="#myConverter">
<f:selectItems value="#myBean.source" var="c" itemValue="#c" itemLabel="#c.name #c.surname"/>
</h:selectManyListbox>
<h:commandButton value="Ok" action="#myBean.add()"/>
Bean 只剩下最重要的部分：
@SessionScoped
@Named("myBean")
public class MyFormBean implements Serializable
//Car has manytomany relationship with the owner
private Car car = new Car();
private List<Owner> target;
@Inject
OwnerManager om;
@Inject
CarManager mm;
public String add()
mm.addOwners(car.getId(), target);
retur null;
public List<Owner> getSource()
om.getAllOwners();
public List<Owner> getTarget()
return target;
public void setTarget(List<Owner> target)
this.target = target;
这是我的转换器：
@FacesConverter("myConverter")
public class myConverter implements Converter
@Inject
CarManger mm;
@Override Object getAsObject(FacesContext context, UIComponent component, String value)
if(value == null)
return null;
return mm.getEntityManager.find(Owner.class, LongValueOf(value));
@Override String getAsString(FacesContext context, UIComponent component, Object value)
if(value == null)
return null;
if(value instanceof Car)
return String.valueOf(((Owner) value).getId());
return null;
还有一个问题，希望我不会被告知要为此单独发帖。我是否正确理解，当源是一个复杂对象时，首先在检索它时调用 getAsString 方法，然后在将它返回到源时调用 getAsObject ？感谢所有帮助。
编辑：
[2014-01-01T22:03:34.266+0100] [glassfish 4.0] [WARNING] [] [javax.enterprise.web] [tid: _ThreadID=18 _ThreadName=http-listener-1(1)] [timeMillis: 1388610214266] [levelValue: 900] [[
StandardWrapperValve[FacesServlet]: Servlet.service() for servlet FacesServlet threw exception
java.lang.ClassCastException: java.lang.String cannot be cast to com.jsf.domain.Owner
at com.jsf.domain.CarManager.addOwnerToCar(CarManager.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1081)
at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1153)
at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:4695)
at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:630)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:822)
at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:582)
at org.jboss.weld.ejb.AbstractEJBRequestScopeActivationInterceptor.aroundInvoke(AbstractEJBRequestScopeActivationInterceptor.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:883)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:822)
at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:582)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doCall(SystemInterceptorProxy.java:163)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:140)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:883)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:822)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:369)
at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:4667)
at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:4655)
at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:212)
at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:88)
at com.sun.proxy.$Proxy386.addOwnerToCar(Unknown Source)
at com.jsf.service.__EJB31_Generated__CarManager__Intf____Bean__.addOwnerToCar(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.jboss.weld.util.reflection.Reflections.invokeAndUnwrap(Reflections.java:396)
at org.jboss.weld.bean.proxy.EnterpriseBeanProxyMethodHandler.invoke(EnterpriseBeanProxyMethodHandler.java:108)
at org.jboss.weld.bean.proxy.EnterpriseTargetBeanInstance.invoke(EnterpriseTargetBeanInstance.java:56)
at org.jboss.weld.bean.proxy.InjectionPointPropagatingEnterpriseTargetBeanInstance.invoke(InjectionPointPropagatingEnterpriseTargetBeanInstance.java:63)
at org.jboss.weld.bean.proxy.ProxyMethodHandler.invoke(ProxyMethodHandler.java:101)
at com.jsf.service.CarManager$Proxy$_$$_Weld$EnterpriseProxy$.addOwnerToCar(Unknown Source)
at com.jsf.web.MyBean.addCar(MyBean.java:61)
at com.jsf.web.MyBean$Proxy$_$$_WeldClientProxy.addCar(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at javax.el.ELUtil.invokeMethod(ELUtil.java:326)
at javax.el.BeanELResolver.invoke(BeanELResolver.java:536)
at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:256)
at com.sun.el.parser.AstValue.invoke(AstValue.java:269)
at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:304)
at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
at org.glassfish.grizzly.strategies.Abstractiostrategy.fireIOEvent(AbstractIOStrategy.java:113)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
at java.lang.Thread.run(Thread.java:724)
]]
addOwners 方法
@PersistenceContext
EntityManager em;
public void addOwners(Long carId, List<Owner> owners)
Car car = em.find(Car.class, carId);
for(Owner o : owners)
car.getOwners().add(o);
【问题讨论】：
您能提供更多细节吗？异常的堆栈跟踪和上面代码中的标记相关行？ 我编辑了我的帖子。这是出现异常的相关行mm.addOwners(car.getId(), target);
stacktrace 显示CarManager 中的方法引发了异常。您确定这与转换器有关吗？看起来传递的是 String 而不是 Owner 对象，但在将值传递到后端的那一刻，使用了 getAsObject 方法，该方法确实返回了 Owner 对象......
我添加了方法，我对 JSF 很陌生，所以我可能错了，但是为什么将 List第一个问题是 Converter 不能从它的 getAsString 方法返回 null。来自the javadoc：
返回：如果值为null，则返回零长度字符串，否则为转换结果
如果您违反该合同并返回 null，预计事情会破裂。 （说真的，我已经看到它在 Mojarra 中引起了一些非常奇怪的行为。）
第二个问题是converter="#myConverter" 是一个表达式，它需要一个名为 myConverter 的作用域变量，但没有这样的变量。 @FacesConverter("myConverter") 注释不会将变量放入任何范围，因此它不会以任何方式使 #myConverter 成为有效表达式。相反，使用注释注册在 JSF 应用程序中的转换器类下 converter ID 作为注释的 value 参数给出，使用 addConverter(String, String) method of javax.faces.application.Application。
删除converter= 属性，并在
<f:converter converterId="myConverter"/>
【讨论】：
谢谢，我现在才注意到我在转换器中做了一个表达式。当我将它更改为简单的 myConverter 时，它突然起作用了，我会记住不要在 getAsString 中返回 null。再次感谢您，祝您有美好的一天！以上是关于带有转换器的 JSF selectManyListBox 不起作用的主要内容，如果未能解决你的问题，请参考以下文章
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