Question

我想要的是什么：我想从List集合中检索值。

我正在练习/学习struts 2框架。但是，我对OGNL行为感到困惑。这些是我的文件：

的index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ taglib uri="/struts-tags" prefix="s"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
    <hr>
    <s:action name="one" />
    <s:property value="list_fruits[0]" />
</body>
</html>

MyAction.java

package abc;

import java.util.*;
import org.apache.struts2.dispatcher.RequestMap;
import com.opensymphony.xwork2.*;

public class MyAction extends ActionSupport {
    private List list_fruits;

    public List getList_fruits() {
        return list_fruits;
    }

    public void setList_fruits(List list_fruits) {
        this.list_fruits = list_fruits;
    }

    public String doOne() {
        list_fruits = new ArrayList();
        list_fruits.add("banana");
        list_fruits.add("apple");
        list_fruits.add("mango");

        /*RequestMap rm = (RequestMap) ActionContext.getContext().get("request");
        rm.put("req_scope", list_fruits);*/
        return "sendToOne";
    }
}

one.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ taglib uri="/struts-tags" prefix="s"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
    <h1>ONE.JSP</h1>
    <br>
    <s:property value="list_fruits[0]" />
</body>
</html>

struts.xml中

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
    <constant name="devMode" value="true" />
    <package name="vns" extends="struts-default">

        <action name="one" class="abc.MyAction" method="doOne">
            <result name="sendToOne">/one.jsp</result>
        </action>

    </package>
</struts>

我遇到以下行为：

案例1 ：当我将此（下面）代码放在index.jsp中时，我会打印否值。

<s:action name="one"/>
<s:property value="list_fruits[0]"/>

= - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - =

案例2 ：当我将此（下面）代码放在index.jsp中时，该值会从one.jsp打印出来，因为在此场景中我包含了属性executeResult=”true” < / p>

<s:action name="one" executeResult="true"/>
<s:property value="list_fruits[0]"/>    <!-- still NOT printed here, but gets printed from one.jsp -->

= - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - =

案例3 ：当我将此（下面）代码放在MyAction.java和index.jsp中时，该值将打印在屏幕上（index.jsp）。

MyAction.java

RequestMap rm=(RequestMap)ActionContext.getContext().get("request");    
rm.put("req_scope", list_fruits);

的index.jsp

<s:action name="one"/> <!-- removed executeResult="true" -->
<s:property value="#request.req_scope[0]"/>

= - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - = - =

由于one.jsp而不是index.jsp

，因此在Case2值中打印

我想知道为什么我没有在 Case1 中打印任何值，而在Case2和Case3中，没有这样的问题。为什么会这样？谁能指导我？

Answer 1

AleksandrM已经回复了你，但是你说了

仍不清楚。 :(请解释。

您可以将其用于：

调用操作并使用executeResult="true"获取结果;

调用Action并将其推送到具有var属性的主页ValueStack，然后使用#引用它：

<s:action   name="one"       var="instance" /> 
<s:property value="#instance.list_fruits[0]"/>

调用在请求/会话范围内设置内容的Action，然后使用#attr或#session;
调用执行某项操作的操作（例如，将页面打开时的时间戳保留在数据库中）。

但是你可以在服务器这一方面做任何事情，并且更好。

这就是为什么你不应该使用<s:action/>标签：它打破了大多数S2框架约定和机制，这是一个不好的做法（或者至少它不是一个好的）。

无法使用<s：action> </s：action>从struts2中的值堆栈获取值

1 个答案: