“选择"未从 List<String> 填充在支柱 [英] "Select" not populated from List<String> in struts
问题描述
我有以下来源:
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.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:
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:
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>
现在我有一个问题，如果我从 Action ProductSearchForward 转到 JSP 站点 SearchProduct.jsp，我总是会收到以下错误:
Now I have the problem, that I always get the following error if I come from Action ProductSearchForward to the JSP site SearchProduct.jsp:
org.apache.jasper.JasperException:标签选择"，字段列表"，名称产品.search.category":请求的列表键类别"无法解析为集合/数组/映射/枚举/迭代器类型.示例:人或人.{name} - [未知位置]
org.apache.jasper.JasperException: tag 'select', field 'list', name 'product.search.category': The requested list key 'categories' could not be resolved as a collection/array/map/enumeration/iterator type. Example: people or people.{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就可以了.
I just want the DropDownList to be populated from the given ArrayList<String> (List<String>), but it is not working. If I set the list content directly it works fine.
推荐答案
<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.
You are listing a List<String> and trying to access, through OGNL . (dot notation), fields that do not exist.
在 OGNL 中
product.search.category
相当于Java
getProduct().getSearch().getCategory()
由于您要列出字符串，因此只需省略 key 属性，因为您的键和值都将是字符串本身.
Since you are listing Strings, just omit key attribute, because both your key and value will be the String itself.
您似乎也将 key 与 name 混淆了:key 是 的键code> 元素，而 name 是 Action 的属性，它将通过其 Setter 接收所选值.
It seems that you are confusing key with name too: key is the key of the <option> element, while name is the Action's attribute that will receive the chosen value through its Setter.
<s:select list = "categories"
name = "chosenCategory" />
<小时>
编辑:为了成功的生活，实施 Preparable Interface 并在那里加载你的静态"数据:
EDIT: for a succesful living, implement Preparable Interface and load there your "static" data:
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 */
}
而且你必须为 struts.xml 中的每个标签指定完全限定的类名...
And you must specify fully qualified class names for each tag in struts.xml...
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