Java 在 JSP 中遍历列表对象
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Iterating through a List Object in JSP
提问by jjcode
I am working on a project to try and teach myself spring and struts. I am currently stuck on a JSP page. I have a pojo class with variables eid and ename with getters/setters, I also have a table in sql with the same values with six populated rows.
I am accessing my database through a JdbcTemplateand have stored the result in a list, I then passed this list to my action page in which I set it as a request.setAttribute("empList",eList). In my jsp page I call that attribute and then try to iterate through it using JSTL.
However nothing shows up, I know that my list variable has data in it since i checked it using the expression tag <%=eList%>and objects show up like this:
我正在做一个项目来尝试自学 spring 和 struts。我目前被困在 JSP 页面上。我有一个带有变量 eid 和 ename 的 pojo 类，带有 getter/setter，我在 sql 中还有一个表，它的值与六个填充行相同。
我正在通过 a 访问我的数据库JdbcTemplate并将结果存储在一个列表中，然后我将此列表传递给我的操作页面，在其中将其设置为request.setAttribute("empList",eList). 在我的 jsp 页面中，我调用该属性，然后尝试使用JSTL.
但是什么也没显示，我知道我的列表变量中有数据，因为我使用表达式标签检查了它<%=eList%>，对象显示如下：
[org.classes.database.Employee@d9b02,
org.classes.database.Employee@13bce7e,
org.classes.database.Employee@171cc79,
org.classes.database.Employee@272a02,
org.classes.database.Employee@137105d,
org.classes.database.Employee@1359ad]
I thought that maybe I was missing something on jstl but I have jstl-1.2 in my META-INF/libfolder. I have also tried to add it in the configure path file and still nothing. I also have the correct tag url.
Also when I do a simple <c:out value="Hello"/>. Hello does print out. So this leads me to believe that my jstlis working properly, but when I try iterating through my list using jstlnothing shows up at all.
Anyways here is my JSP page:
我想也许我在 jstl 上遗漏了一些东西，但我的META-INF/lib文件夹中有 jstl-1.2 。我也尝试将它添加到配置路径文件中，但仍然没有。我也有正确的标签网址。
当我做一个简单的<c:out value="Hello"/>. 你好确实打印出来了。所以这让我相信我jstl的工作正常，但是当我尝试遍历我的列表时，jstl根本没有显示任何内容。
无论如何，这是我的 JSP 页面：
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO- 8859-1"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page import="java.util.List"%>
<!DOCTYPE html>
<% List eList = (List)session.getAttribute("empList");%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Employee Details</title>
</head>
<body>
<c:out value="Hello"></c:out>
<h3>Employee Details</h3>
<hr size="4" color="gray"/>
<table>
<%=eList%>
<c:forEach items="${eList}" var="employee">
<tr>
<td>Employee ID: <c:out value="${employee.eid}"/></td>
<td>Employee Pass: <c:out value="${employee.ename}"/></td>
</tr>
</c:forEach>
</table>
</body>
</html>
Any help would be highly appreciated!
任何帮助将不胜感激！
采纳答案by Sotirios Delimanolis
Before teaching yourself Spring and Struts, you should probably learn Java. Output like this
在自学 Spring 和 Struts 之前，您可能应该学习 Java。像这样输出
org.classes.database.Employee@d9b02
is the result of the Object#toString()method which all objects inherit from the Objectclass, the superclass of all classes in Java.
是Object#toString()所有对象从Object类继承的方法的结果，类是Java中所有类的超类。
The Listsub classes implement this by iterating over all the elements and calling toString()on those. It seems, however, that you haven't implemented (overriden) the method in your Employeeclass.
该List子类通过在所有迭代的元素，并呼吁实现这一toString()那些。但是，您似乎还没有在Employee类中实现（覆盖）该方法。
Your JSTL here
您的 JSTL 在这里
<c:forEach items="${eList}" var="employee">
<tr>
<td>Employee ID: <c:out value="${employee.eid}"/></td>
<td>Employee Pass: <c:out value="${employee.ename}"/></td>
</tr>
</c:forEach>
is fine except for the fact that you don't have a page, request, session, or application scoped attribute named eList.
很好，除了您没有名为 的页面、请求、会话或应用程序范围属性eList。
You need to add it
你需要添加它
<% List eList = (List)session.getAttribute("empList");
request.setAttribute("eList", eList);
%>
Or use the attribute empListin the forEach.
或使用属性empList的forEach。
<c:forEach items="${empList}" var="employee">
<tr>
<td>Employee ID: <c:out value="${employee.eid}"/></td>
<td>Employee Pass: <c:out value="${employee.ename}"/></td>
</tr>
</c:forEach>
回答by Prabhaker A
you can read empListdirectly in forEachtag.Try this
你可以empList直接在forEach标签中阅读。试试这个
<table>
<c:forEach items="${sessionScope.empList}" var="employee">
<tr>
<td>Employee ID: <c:out value="${employee.eid}"/></td>
<td>Employee Pass: <c:out value="${employee.ename}"/></td>
</tr>
</c:forEach>
</table>
回答by Alaa Abuzaghleh
change the code to the following
将代码更改为以下内容
<%! List eList = (ArrayList)session.getAttribute("empList");%>
....
<table>
<%
for(int i=0; i<eList.length;i++){%>
<tr>
<td><%= ((Employee)eList[i]).getEid() %></td>
<td><%= ((Employee)eList[i]).getEname() %></td>
</tr>
<%}%>
</table>
回答by Striker
another example with just scriplets, when iterating through an ArrayList that contains Maps.
另一个只有脚本的示例，当迭代包含 Maps 的 ArrayList 时。
<%
java.util.List<java.util.Map<String,String>> employees=(java.util.List<java.util.Map<String, String>>)request.getAttribute("employees");
for (java.util.Map employee: employees) {
%>
<tr>
<td><input value="<%=employee.get("fullName") %>"/></td>
</tr>
...
<%}%>
回答by Savan Makone
<c:forEach items="${sessionScope.empL}" var="emp">
<tr>
<td>Employee ID: <c:out value="${emp.eid}"/></td>
<td>Employee Pass: <c:out value="${emp.ename}"/></td>
</tr>
</c:forEach>
