没有bean属性的JSF组件绑定抛出转换错误

Question

在表格的一列中，我尝试将组件值绑定到局部范围的 EL 变量，然后将该变量用作参数：

        <h:column>
            <h:outputLabel value="Enter a quantity to put into the cart" for="qty"/>
            <h:inputText id="qty" binding="#{qty}" converter="javax.faces.Number"/>
        </h:column>
        <h:column>
            <h:commandButton value="Put into cart" type="submit"
                             action="#{shoppingCart.addToCart(product, qty)}"/>
        </h:column>

其中product 是数据表的当前元素（不在购物车中的已过滤或未过滤产品的列表）。

现在，当尝试将产品添加到购物车（例如数量为 12）时，它会引发以下异常：

javax.faces.el.EvaluationException: java.lang.IllegalArgumentException: Cannot convert javax.faces.component.html.HtmlInputText@377c8b02 of type class javax.faces.component.html.HtmlInputText to class java.lang.Integer
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIData.broadcast(UIData.java:1108)
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:658)
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:416)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:283)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:283)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:200)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:132)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:111)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:536)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
at java.lang.Thread.run(Thread.java:745)

我正在使用带有 JSF 2.2.12 版的 Glassfish 4.1.1。

如有任何想法，我将不胜感激

澄清

正如 BalusC 在这个问题 JSF component binding without bean property 和其他人中指出的那样，binding="#{var}" 实际上是有效的 XHTML。这样就不需要支持 bean，并且声明的变量是请求范围的。我发现这个选项更优雅，因此想坚持下去。

Answer 1

而不是binding="#{qty}"（它应该用于将您的输入组件绑定到托管bean 中组件的Java 实例），使用：value="#{shoppingCart.quantityAsInteger}"，或者如果您正在处理购物车项目列表： value="#{shoppingCartItem.quantityAsInteger}".

除了正确的值绑定之外，这还将使您受益于将数量作为模型的一部分。此外，当value 绑定到Integer 时，无需添加转换器。 JSF 会处理Integer (and some other types) conversion by default。

因此，请确保您有一个包含数量的托管 bean 或每个都有数量的购物车项目列表。如果是购物车物品列表，您最终会得到如下内容：

ShoppingCart.java

// You will probably already have something like this for your table
private List<ShoppingCartItem> shoppingCartItems;

ShoppingCartItem.java

// Quantity used for binding (add getter and setter).
private Integer quantity;

private Product product;

XHTML

<h:column>
    <h:outputLabel value="Enter a quantity to put into the cart" for="qty"/>
    <h:inputText id="qty" binding="#{shoppingCartItem.quantity}" />
</h:column>

Answer 2

尝试在h:inputText 中使用value 属性而不是binding 属性，并在表格组件上使用binding 属性。这样您就可以在操作方法中访问选定（单击）的行：如果表的binding 属性值为#{bean.dataTable}，则可以通过getDataTable.getRowData() 之类的方法获取行数据。

Answer 3

虽然声明 EL 变量是有效的 XHTML，但如果使用 binding 属性，组件本身将绑定到变量。使用带有value 属性的EL 变量时不会引发转换错误，如下所示：

        <h:inputText id="qty" value="#{qty}" converter="javax.faces.Number"/>
        ....
        <h:commandButton value="Put into cart" type="submit"
                         action="#{shoppingCart.addToCart(product, qty)}"/>