意外异常在'类xxx上设置了'xxx':错误设置表达式'xxx',其值为['x',]

Question

我将一些参数传递给ModelDriven<Transporter>通过查询字符串实现的动作类.

<s:form namespace="/admin_side" action="Test" id="dataForm" name="dataForm">
    <s:url id="editURL" action="EditTest" escapeAmp="false">
        <s:param name="transporterId" value="1"/>
        <s:param name="transporterName" value="'DHL'"/>
    </s:url>
    <s:a href="%{editURL}">Click</s:a>
</s:form>

动作类如下.

@Namespace("/admin_side")
@ResultPath("/WEB-INF/content")
@ParentPackage(value = "struts-default")
public final class TestAction extends ActionSupport 
                           implements Serializable, Preparable, ModelDriven<Transporter>
{
    private static final long serialVersionUID = 1L;
    private Transporter transporter = new Transporter();

    @Action(value = "Test",
    results = {
        @Result(name = ActionSupport.SUCCESS, location = "Test.jsp"),
        @Result(name = ActionSupport.INPUT, location = "Test.jsp")},
    interceptorRefs = {
        @InterceptorRef(value = "paramsPrepareParamsStack", 
                 params = {"params.acceptParamNames", "transporterId, transporterName"})})
    public String load() throws Exception {
        return ActionSupport.SUCCESS;
    }

    @Action(value = "EditTest",
    results = {
        @Result(name = ActionSupport.SUCCESS, location = "Test.jsp"),
        @Result(name = ActionSupport.INPUT, location = "Test.jsp")},
    interceptorRefs = {
        @InterceptorRef(value = "paramsPrepareParamsStack", 
                 params = {"params.acceptParamNames", "transporterId, transporterName"})})
    public String edit() {
        System.out.println(transporter.getTransporterId() 
                         + " : " + transporter.getTransporterName());
        return ActionSupport.SUCCESS;
    }

    @Override
    public Transporter getModel() {
        return transporter;
    }

    @Override
    public void prepare() throws Exception {}
}

服务器终端显示以下消息.

Jan 09, 2014 4:06:32 PM com.opensymphony.xwork2.interceptor.ParametersInterceptor error
SEVERE: Developer Notification (set struts.devMode to false to disable this message):
Unexpected Exception caught setting 'transporterId' on 'class actions.TestAction: Error setting expression 'transporterId' with value ['1', ]
Jan 09, 2014 4:06:32 PM com.opensymphony.xwork2.interceptor.ParametersInterceptor error
SEVERE: Developer Notification (set struts.devMode to false to disable this message):
Unexpected Exception caught setting 'transporterName' on 'class actions.TestAction: Error setting expression 'transporterName' with value ['DHL', ]

即使日志级别为SEVERE,但这些参数的值在操作类中也可用

System.out.println(transporter.getTransporterId() 
                 + " : " + transporter.getTransporterName());

在edit()方法中.

如果paramsPrepareParamsStack被替换为defaultStackthen,则这些消息将消失.

表达式['DHL', ]表示数组.transporterId并且transporterName在模型中分别是类型Long和类型String.

我究竟做错了什么？

Answer 1

这里没有涉及数组问题(即使看起来像这样):这种异常意味着Struts无法为您的参数找到Setter:

来自ParametersInterceptor文档:

缺少参数的警告

如果没有给定参数名称的setter,则会在devMode中记录如下所示的警告消息:

SEVERE: Developer Notification (set struts.devMode to false to disable this 
message):
Unexpected Exception caught setting 'search' on 'class demo.ItemSearchAction: 
Error setting expression 'search' with value ['search', ]
Error setting expression 'search' with value ['search', ] - [unknown location] 
  at com.opensymphony.xwork2.ognl.OgnlValueStack.handleRuntimeException(OgnlValueStack.java:201)
  at com.opensymphony.xwork2.ognl.OgnlValueStack.setValue(OgnlValueStack.java:178)
  at com.opensymphony.xwork2.ognl.OgnlValueStack.setParameter(OgnlValueStack.java:152)

因此,预期行为允许开发人员在参数名称或setter中发现缺少的setter或拼写错误.

您可以通过在JSP中放置一个Action中不存在的元素来轻松地重现此错误.

由于您的属性存在(与他们的二传手)在模型中,并且使用的是ModelDriven和paramsPrepareParamsStack,我想是怎么回事是:

• ModelDriven Interceptor 被委派处理Model对象;
• 你第一次打电话Parameters Interceptor,ModelDriven Interceptor还没有跑;
• 然后你的Action对Model对象一无所知,并尝试在Action中找到参数的Setters,而不是在Model中.
• 第二个拦截器改为在ModelDriven之后运行,并且确切地知道在何处设置参数.这就是您在Action方法中正确设置参数的原因.

但是,如果这是真的,那么你应该不能够在检索这些参数prepare()的方法(即您使用该堆栈的原因...):
请尝试,并张贴在这里的结果.

我想到解决这个问题的第一件事就是把它放在第一个ModelDriven Interceptor之前Parameters Interceptor(通过复制它,或者通过移动它,我不确定它会产生哪种副作用,如果有的话)在这种情况下,您应该再次尝试在此报告).

然后定义以下堆栈,并使用它.

<interceptor-stack name="modelParamsPrepareParamsStack">
    <interceptor-ref name="exception"/>
    <interceptor-ref name="alias"/>
    <interceptor-ref name="i18n"/>
    <interceptor-ref name="checkbox"/>
    <interceptor-ref name="multiselect"/>

    <!-- NEW ModelDriven Position -->
    <interceptor-ref name="modelDriven"/>

    <interceptor-ref name="params">
        <param name="excludeParams">^dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,^parameters\..*,^action:.*,^method:.*</param>
    </interceptor-ref>
    <interceptor-ref name="servletConfig"/>
    <interceptor-ref name="prepare"/>
    <interceptor-ref name="chain"/>

    <!-- OLD ModelDriven Position -->
    <!--interceptor-ref name="modelDriven"/-->

    <interceptor-ref name="fileUpload"/>
    <interceptor-ref name="staticParams"/>
    <interceptor-ref name="actionMappingParams"/>
    <interceptor-ref name="params">
        <param name="excludeParams">^dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,^parameters\..*,^action:.*,^method:.*</param>
    </interceptor-ref>
    <interceptor-ref name="conversionError"/>
    <interceptor-ref name="validation">
        <param name="excludeMethods">input,back,cancel,browse</param>
    </interceptor-ref>
    <interceptor-ref name="workflow">
        <param name="excludeMethods">input,back,cancel,browse</param>
    </interceptor-ref>
</interceptor-stack>

希望有所帮助.