java - Struts 2中使用ModelDriven接口(interface)时无法解析select标签中的list属性

Question

我在 Struts 2 应用程序中使用接口(interface) ModelDriven。我在渲染页面时遇到问题，因为我总是收到错误:

19 nov. 2013 11:23:12 org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: "Servlet.service()" pour la servlet jsp a généré une exception
tag 'select', field 'list': The requested list key 'listeItems' could not be resolved as a collection/array/map/enumeration/iterator type. Example: people or people.{name} - [unknown location]
        at org.apache.struts2.components.Component.fieldError(Component.java:240)
        at org.apache.struts2.components.Component.findValue(Component.java:333)
        at org.apache.struts2.components.ListUIBean.evaluateExtraParams(ListUIBean.java:80)

我不知道错误出在哪里，所以我向社区求助。

struts.xml:

<?xml version="1.0" encoding="UTF-8" ?>
 
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <constant name="struts.devMode" value="false" />
    <constant name="struts.action.extension" value="do" />
    <constant name="struts.custom.i18n.resources" value="com.omb.i18n.StrutsResourceBundle" />
    <constant name="struts.objectFactory" value="org.apache.struts2.spring.StrutsSpringObjectFactory" /> 
    <constant name="struts.objectFactory.spring.autoWire" value="name" />
    <constant name="struts.i18n.encoding" value="ISO-8859-1" />
    <constant name="struts.i18n.reload" value="false" />
    <constant name="struts.configuration.xml.reload" value="false" />
    <constant name="struts.locale" value="fr" />
    <constant name="struts.multipart.maxSize" value="100000000000" />
    <constant name="struts.enable.SlashesInActionNames" value="true" />
    <constant name="struts.mapper.alwaysSelectFullNamespace" value="false"/>
 
    <constant name="struts.codebehind.classSuffix" value="Controller"/>
    <constant name="struts.codebehind.action.checkImplementsAction" value="false"/>
    <constant name="struts.codebehind.action.checkAnnotation" value="false"/>
    <constant name="struts.codebehind.action.defaultMethodName" value="index"/>
    <constant name="struts.configuration.classpath.defaultParentPackage" value="rest-default" />
 
    <package name="default" extends="tiles-default" namespace="/">
 
        <interceptors>
 
            <interceptor name="params-filter"
                class="com.opensymphony.xwork2.interceptor.ParameterFilterInterceptor" />
 
            <interceptor-stack name="defaultStack">
                <interceptor-ref name="exception" />
                <interceptor-ref name="alias" />
                <interceptor-ref name="servletConfig" />
                <interceptor-ref name="i18n" />
                <interceptor-ref name="chain" />
                <interceptor-ref name="modelDriven" />
                <interceptor-ref name="fileUpload">
                    <param name="maximumSize">11204928</param>
                </interceptor-ref>
                <interceptor-ref name="staticParams" />
                <interceptor-ref name="conversionError" />
                <interceptor-ref name="params" />
                <interceptor-ref name="prepare" />
                                <interceptor-ref name="basicStack"/>
                <interceptor-ref name="validation" />
                <interceptor-ref name="workflow" />
            </interceptor-stack>
 
        </interceptors>
 
        <default-interceptor-ref name="defaultStack" />
 
        <global-results>
            <result name="technicalError" type="chain">
                errorAction
            </result>
            <result name="sessionInvalidError" type="tiles">
                sessionInvalid
            </result>
            <result name="blank" type="tiles">blank</result>
        </global-results>
 
        <global-exception-mappings>
            <exception-mapping exception="java.lang.Exception"
                result="technicalError" />
            <exception-mapping
                exception="com.omb.service.exception.UserSessionInvalidException"
                result="sessionInvalidError" />
 
        </global-exception-mappings>
 
    </package>
 
    <package name="omb" extends="default" namespace="/omb">
        <action name="*Action" class="myAction" method="{1}">
            <result name="success" type="redirectAction">
                <param name="namespace">/omb</param>
                <param name="actionName">displayResult</param>
            </result>
            <result name="error" type="redirectAction">
                <param name="namespace">/error</param>
                <param name="actionName">displayError</param>
            </result>
        </action>
    </package>
</struts>

MyAction.java:

package com.omb.actions;
 
public class MyAction extends ActionSupport implements ModelDriven<MyModel>{
 
    private MyModel myModel = new MyModel();
    
    public MyModel getModel() {
        return myModel;
    }
 
    public String execute() throws Exception {
        myModel.add(new Item("A", "Item A"));
        myModel.add(new Item("B", "Item B"));
        return SUCCESS;
    }
    
    public String doAction() {
        // do something
        return "SUCCESS";
    }
 
    public MyModel getMyModel() {
        return this.myModel;
    }
 
    public void setMyModel(MyModel myModel) {
        this.myModel = myModel;
    }
}

MyModel.java:

package com.omb.modele;

import java.util.ArrayList;
import java.util.List;

import com.omb.item.Item;

public class MyModel {

    private String idItem;

    private List<Item> listeItems = new ArrayList<Item>();

    public String getIdItem() {
        return this.idItem;
    }

    public void setIdItem(String idItem) {
        this.idItem = idItem;
    }

    public List<Item> getListeItems() {
        return this.listeItems;
    }

    public void setListeItems(List<Item> listeItems) {
        this.listeItems = listeItems;
    }
}

Item.java:

package com.omb.item;

import java.io.Serializable;

public class Item implements Serializable {

    private static final long serialVersionUID = 1L;

    private String id;

    private String label;
 
    public Item() {
        super();    
    }

    public Item(String id, String label) {
        this.id = id;
        this.label = label;
    }
    
    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getLabel() {
        return label;
    }

    public void setLabel(String label) {
        this.label = label;
    }
}

JSP 文件:

<%@ taglib prefix="s" uri="/struts-tags"%>

<table width="100%">

    <tr>
        <td><label><s:property value="%{getText('label')}" /></label></td>
    </tr>
    <tr>
        <td><s:select id="idSelectItem"
                emptyOption="true" list="listeItems" value="idItem"
                listKey="id" listValue="label" />
        </td>
    </tr>

</table>

Answer 1

删除 method="{1}" 因为您没有使用通配符映射，并且您的操作没有 execute 以外的方法，并且只有此方法进行初始化列表。如果列表未初始化，则会出现上述错误。如果您有其他方法没有显示，您应该实现 Preparable并将初始化列表的代码移至此处。

public class MyAction extends ActionSupport implements ModelDriven<MyModel>, Preparable {

  public void prepare() {
    myModel = new MyModel();
    myModel.add(new Item("A", "Item A"));
    myModel.add(new Item("B", "Item B"));
  }
  ...
}