Question

我正在尝试根据单选按钮组件的值验证输入文本组件，但它会抛出NullPointerException，我不明白为什么。

以下是观点：

<h:form id="formId">
    <p:inputText validator="#{searchBean.validate}" id="name"
        required="true" requiredMessage="should contain only characters">
        <f:validateRegex pattern="[a-zA-Z]*" />
        <f:validator validatorId="inputValidator" />
    </p:inputText>
    <p:selectOneRadio value="#{searchBean.searchForm.selectedRadio}" id="customRadio">
        <f:selectItem itemLabel="city" itemValue="1" />
        <f:selectItem itemLabel="zipcode" itemValue="2" />
        <f:selectItem itemLabel="state" itemValue="3" />
    </p:selectOneRadio>
    <p:commandButton value="Search" action="results.jsf" />
</h:form>

这是验证器：

public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
    UIViewRoot ui = new UIViewRoot();
    UIInput radio = (UIInput) ui.findComponent("formId:customRadio");
    boolean convertedAndValidatedValue = (Boolean) radio.getValue(); // This line is throwing the exception.
    System.out.println("Validate"+convertedAndValidatedValue);

    if (searchForm.selectedRadio.equals("city")) {
        validateForCity(convertedAndValidatedValue);
    } else if (searchForm.selectedRadio.equals("zipcode")) {
        validateForZipcode(convertedAndValidatedValue);
    } else {
        validateForState(convertedAndValidatedValue);
    }
}

以下是例外：

javax.faces.FacesException
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:80)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:97)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:114)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:308)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:679) 
Caused by: java.lang.NullPointerException
    at com.placessearch.action.SearchBean.validate(SearchBean.java:76)
    at javax.faces.component.UIInput.validateValue(UIInput.java:1142)
    at javax.faces.component.UIInput.validate(UIInput.java:960)
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1204)
    at javax.faces.component.UIInput.processValidators(UIInput.java:693)
    at javax.faces.component.UIForm.processValidators(UIForm.java:240)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1081)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1081)
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1159)
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:72) 
    ... 19 more

Answer 1

JSF组件按其在组件树中显示的顺序进行转换和验证。您的验证器附加到输入文本组件，该组件在单选按钮组件之前出现。但是，您尝试访问单选按钮组件的已转换和验证值，而尚未在该点进行转换和验证。

boolean convertedAndValidatedValue = (Boolean) radio.getValue();

它只会返回null，而您又会尝试自动装箱到boolean，这只会导致NullPointerException。

您需要获取提交的值。请注意，您指定的项目值绝对不是布尔值。这是数字。另请注意，提交的值总是 String（因为这正是request.getParameter()返回的类型，也因为此时它尚未被JSF / EL转换）

String submittedRadioValue = (String) radio.getSubmittedValue(); if (submittedRadioValue != null) { int convertedRadioValue = Integer.valueOf(submittedRadioValue); // ... }

更新：由于其出乎意料的特性，我忽略了另一个原因如下：

UIViewRoot ui = new UIViewRoot();

这绝对也不对。您应该从faces上下文中检索当前的一个，而不是手动创建一个完全空的。

UIViewRoot ui = context.getViewRoot();

否则radio仍然是null，因此是NullPointerException的另一个潜在原因。

如何根据单选按钮组件的值验证输入文本组件

1 个答案: