Question

我有以下资料来源：

struts.xml中

<?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.enable.DynamicMethodInvocation" value="true" />
    <constant name="struts.devMode" value="true" />
    <constant name="struts.custom.i18n.resources" value="ApplicationResources" />

    <package name="vislabWebShop" extends="struts-default">

        <action name="UserForward">
            <result>/pages/Login.jsp</result>
        </action>

        <action name="UserLogin" class="vislabWebShop.controller.LoginAction">
            <result name="success">/pages/Welcome.jsp</result>
            <result name="input">/pages/Login.jsp</result>
        </action>

        <action name="UserRegister" class="vislabWebShop.controller.RegisterAction">
            <result name="success">/pages/RegisterSuccess.jsp</result>
            <result name="input">/pages/Register.jsp</result>
        </action>

        <action name="UserRegisterNew">
            <result>/pages/Register.jsp</result>
        </action>

        <action name="UserRegisterSuccess">
            <result>/pages/Login.jsp</result>
        </action>

        <action name="ProductSearchForward">
            <result>/pages/SearchProduct.jsp</result>
        </action>

        <action name="ProductSearch" class="vislabWebShop.controller.ProductSearchAction">
            <result name="success">/pages/Login.jsp</result>
        </action>
    </package>
</struts>

ProductSearchAction.java：

package vislabWebShop.controller;

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

import com.opensymphony.xwork2.ActionSupport;

public class ProductSearchAction extends ActionSupport
{
  private List<String> categories;
  private String chosenCategory;

  public ProductSearchAction()
  {
    categories = new ArrayList<String>();
    categories.add("Eins");
    categories.add("Zwei");
    categories.add("Drei");
  }

  @Override
  public String execute() throws Exception
  {
    return SUCCESS;
  }

  public List<String> getCategories()
  {
    return categories;
  }

  public void setCategories(List<String> categories)
  {
    this.categories = categories;
  }

  public String getChosenCategory()
  {
    return chosenCategory;
  }

  public void setChosenCategory(String chosenCategory)
  {
    this.chosenCategory = chosenCategory;
  }
}

SearchProduct.jsp：

    <%@ page language="java" contentType="text/html; charset=ISO-8859-1"
        pageEncoding="ISO-8859-1"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <%@ taglib prefix="s" uri="/struts-tags"%>

    <html>
    <head>
    <title><s:text name="welcome.title" /></title>
    </head>

    <body bgcolor="white">

        <font color="red"> <s:actionmessage />
        </font>

    <p>
        <b><s:text name="product.search.title" /></b>
    </p>

    <s:form action="ProductSearch" focusElement="description">
        <s:textfield name="description" key="prompt.description" size="20" />
        <s:textfield name="minprice" key="prompt.price.min" size="20" />
        <s:textfield name="maxprice" key="prompt.price.max" size="20" />
        <s:select key="product.search.category" headerKey="-1" 
        headerValue="Bitte wählen Sie eine Kategorie"
            list="categories" />
        <s:submit value="Produkt suchen" align="right" />
    </s:form>

    <font color="red"> <s:actionerror label="label" />
    </font>


</body>
</html>

现在我遇到了问题，如果我从Action ProductSearchForward到JSP网站SearchProduct.jsp，我总是会收到以下错误：

org.apache.jasper.JasperException：标记'select'，字段'list'，名称'product.search.category'：请求的列表键'categories'无法解析为collection / array / map / enumeration / iterator类型。例如：人或人。{name} - [unknown location]

我只想从给定的ArrayList<String>（List<String>）填充DropDownList，但它不起作用。如果我直接设置列表内容，它可以正常工作。

Answer 1

<s:select list = "categories" 
           key = "product.search.category" />

您正在列出List<String>并尝试通过OGNL .（点表示法）访问不存在的字段。

在OGNL

product.search.category

相当于Java

getProduct().getSearch().getCategory()

由于您列出了字符串，只需省略键属性，因为您的键和值都将是字符串本身。

您似乎也在key与name混淆：key是<option>元素的关键，而name是Action的属性将通过其Setter收到所选的值。

<s:select list = "categories" 
          name = "chosenCategory" />

编辑：为了获得成功，请实施Preparable Interface并在那里加载“静态”数据：

public class ProductSearchAction extends ActionSupport implements Preparable {
    private List<String> categories;
    private String chosenCategory;

    @override
    public void prepare() throws Exception {      
        categories = new ArrayList<String>();
        categories.add("Eins");
        categories.add("Zwei");
        categories.add("Drei");
    }

    @Override
    public String execute() throws Exception {
        return SUCCESS;
    }

    /* GETTERS AND SETTERS */
}

您必须为struts.xml中的每个标记指定完全限定的类名...

“选择”未从struts </string>中的List <string>填充

1 个答案: