Given the following preview of my JSP file in my project :
<%# page contentType="text/html; charset=utf-8" language="java"%>
<%# page import="java.util.ArrayList"%>
<%# page import="beans.UserBean"%>
<jsp:useBean id="userBean" class="beans.UserBean" scope="session" />
<jsp:useBean id="students" type="ArrayList<beans.UserBean>" scope="session" />
<jsp:useBean id="teachers" type="ArrayList<beans.UserBean>" scope="session" />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
I get the following error in Eclipse :
Undefined type: ArrayList
What's wrong with it ? even though that I'm importing the ArrayList , Eclipse doesn't recognize it and shows the above message in the following two lines :
<jsp:useBean id="students" type="ArrayList<beans.UserBean>" scope="session" />
<jsp:useBean id="teachers" type="ArrayList<beans.UserBean>" scope="session" />
Any idea where did I go wrong ? Thanks
The type attribute should represent the fully qualified name of the class, not the generic declaration or so. Even more, JSP/EL is not aware of generic types in any way.
Use java.util.ArrayList instead:
<jsp:useBean id="students" type="java.util.ArrayList" scope="session" />
<jsp:useBean id="teachers" type="java.util.ArrayList" scope="session" />
All those #page import are unnecessary. They are only used when using scriptlets (those oldschool <% %> things which has been discouraged since JSP 2.0).
By the way, if those arraylists are been prepared and put in the scope by a servlet beforehand and all you need is to just access them in EL, then you do not need those <jsp:useBean> tags at all. Using the type attribute instead of the class attribute hints less or more that you're actually using a servlet. It'll work as good without those <jsp:useBean> tags. See also our servlets wiki page.
Related
This question already has an answer here:
How do I pass current item to Java method by clicking a hyperlink or button in JSP page?
(1 answer)
Closed 7 years ago.
I have a facultylist.jsp page which displays List<Faculty> as a request attribute parameter in forEach loop and I want every item in this loop to be a link to specified faculty facultyview.jsp. How can I achieve that ?
facultylist.jsp:
<%# page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%#taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Faculties</title>
</head>
<body>
<h1>Faculties list</h1>
<ul>
<c:forEach var="faculty" items="${faculties}">
<li>${faculty.name}</li>
</c:forEach>
</ul>
</body>
</html>
facultyview.jsp:
<%# page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%#taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Faculty</title>
</head>
<body>
<h1>${faculty.name}</h1>
<ul>
<li>Faculty name: <c:out value="${requestScope.name}"></c:out></li>
<li>Total seats: <c:out value="${requestScope.total_seats}"></c:out></li>
<li>Budget seats: <c:out value="${requestScope.budget_seats}"></c:out></li>
</ul>
apply for this faculty
</body>
</html>
I don't know if its may help, but I'm using following technologies: tomcat, jsp, servlets and log4j.In my project I have one FrontController, which is a servlet that interacts with Command pattern - each Command returns a path to resource and action type: forward or redirect.
You can solve your issue by adding a query params to the link, edit with respect to the comment. Note that you cannot access directly the JSP pages that reside under WEB-INF folder. Also, to encode properly the paramters, better construct url like
<c:url value="facultyview.jsp" var="url">
<c:param name="name" value="${faculty.name}"/>
<c:param name="total_seats" value="${faculty.total_seats}"/>
<c:param name="budget_seats" value="${faculty.budget_seats}"/>
</c:url>
<li>${faculty.name}</li>
and than than in your facultyview.jsp read from the query params
<li>Faculty name: ${param.name}</li>
<li>Total seats: ${param.total_seats}</li>
<li>Budget seats:${param.budget_seats}</li>
This direct JSP communication should solve your immediate issue, but a truly proper way would be to pass an id of a faculty to servlet, fetch the faculty instance, place in the model and pass to the view.
in other way is just take the selected value from the drop down with a name and forward it to front controller servlet ,there use if else conditions and depends on the value you could forward the request to corresponding jsp or servlet
<select name="value"> in jsp
String value=req.getParameter("value"); in servlet
if()
else if()
If you have a field in Faculty entity simply:
${faculty.name}
#Mark: faculty represents an entity from database, i'm not sure if I want to change it adding another field, or you mean some other way ?
Add a field does not means you must change database, you can have a Helper entity that inherits from Faculty and have more fields you can need,
public class FacultyFormHelper extends Faculty implements Serializable {
private String URL;
and in your view:
${facultyHelper.name}
But, If you don't want to modify your database, either create a helper class, you may add onclick event to the <a>
<a onclick="goToURL(${faculty.id})">
Then retrieve the data... i'm not sure how you get the urls... from a variable in the view, ajax call or wherever you have this URL...
I am trying to execute the following jsp code which contains the optiontransferselect tag. However I am getting the below exception:
org.apache.jasper.JasperException: /abc.jsp(10,0) No tag "optiontransferselect label" defined in tag library imported with prefix "s"
Please find the below code i have used.
<%# page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%# taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title>Optiontransferselect Tag Example!</title>
</head>
<body>
<s:form>
<s:optiontransferselect label="Employee Records" name="leftSideEmployeeRecords" leftTitle="RoseIndia" rightTitle="JavaJazzUp" list="{'Deepak Kumar', 'Sushil Kumar','Vinod Kumar','Deepak Monthy','Deepak Mihanti', 'Sushil Kumar', 'Ravi Kant Kumar'}" headerKey="headerKey" headerValue="--- Please Select ---" doubleName="rightSideEmployeeRecords" doubleList="{'Amar Deep Patel', 'Amit Kumar','Chandan Kumar', 'Noor Kumar','Tammana Kumari'}" doubleHeaderKey="doubleHeaderKey" doubleHeaderValue="--- Please Select ---" />
</s:form>
</body>
</html>
Please Guide.
You are using older version of struts-core-xxx.jar in your project. Are you using 2.3.16 or above?
To use optiontransferselect tag you need to use struts-core-2.3.16 or higher..
You need to include the <s:head> tag which drags in some javascript that is needed to get the <s:optiontransferselect> tag to work.
I've read most of the online resources for building a simple "Hello World" app using Java and Struts 2. I understand the simple stuff. My problem is that I'm trying to expand that learning and build a large scale app, and I just don't see how to connect the dots.
Scenario:
I've got three views to begin with: Home.jsp, MyAccount.jsp, Contact.jsp. Each has the following HTML:
<%#page contentType="text/html" pageEncoding="UTF-8"%>
<%#taglib prefix="s" uri="/struts-tags"%>
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript" src="js/common.js"></script>
...
</head>
<body>
<!-- If logged in, says "hello <s:property name="username">"
Else displays link to .show() #loginPane -->
<div id="accountHeader">...</div>
<!-- Displays <s:textfield> tags and <s:submit> tag to accept username and password -->
<div id="loginPane" style="display: none">...</div>
<header>...</header>
<nav>...</nav>
<!-- Displays view-specific content that includes Struts 2 tags -->
<div id="content">...</div>
<footer>...</footer>
</body>
</html>
So, obviously there is a lot of code common to each view (anything not in #content div).
How do I architect these views for code reuse?
What I've tried:
Placing common code in common.js and using jQuery .html() calls to populate <div>s. [Doesn't work because jQuery cannot generate code with <s:> tags.]
Using only one .jsp view file and placing view-specific code in common.js to be generated with jQuery .html() calls. [Doesn't work for the same reason -- jQuery cannot generate code with <s:> tags.]
Placing all view components in .jspf files and loading each with jQuery .load() calls from common.js. [Doesn't work -- I'm guessing the .jspf files need the Struts 2 <%taglib ...%> included in each, but jQuery .load() treats the <%taglib ...%> as text to be displayed in the <div>... and also fails to properly generate the <s:> tags.]
What is the proper way to do this? How do I architect my view(s) for code reuse?
My apologies if this isn't the proper forum to ask for architecture help, but I'm really struggling here... Perhaps point me to a more appropriate forum or an online tutorial that addresses this type of architecture?
Thanks in advance!
I've used several methods to accomplish this type of re-use of code including Tiles and tooling around with Sitemesh and other template frameworks. What I've found is that, much as Steven Benitez, in the end I preferred to use JSP taglibs, native Struts2 taglibs, and JSTL to essentially build out my own templating routines. The main reason I prefer this is that there tends to be less overhead and it's been a lot easier to maintain and extend in the long run.
Generally What I do is define my base template, index.jsp for example, and then in each independent Struts controller class I will define what page fragment is used. I try to split my controllers up in such a way that each page or function is handled by a single controller and I implement the Preparable interface. This way I can set a parameter for the page to reference. Sometimes I set it as a variable in the controller class, sometimes a sessions variable depending on what type of stating I need for the application.
Once I have a variable with the page to reference, I can just use a JSTL import or Struts include tag to load the page fragment.
The controller class would look something like this:
#Results({
#Result(name = "success", location = "/WEB-INF/content/index.jsp")
})
public class IndexController extends RestActionSupport implements Preparable{
private String page;
private String pageTitle;
#Override
public void prepare() throws Exception {
page = "home";
pageTitle= "My Home Page";
}
...
}
And then the JSP would look something like this:
<%# taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%# taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<%# taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title> ${pageTitle}</title>
</head>
<body>
<c:import url="${page}.jsp" />
</body>
</html>
EDIT: Fragment page example:
<%# taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%# taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<%# taglib prefix="s" uri="/struts-tags"%>
<div>
<h1>Welcome Home!</h1>
</div>
<script type='text/javascript'>
$(document).ready(function() {
// page specific scripting if needed
);
</script>
You can encapsulate common template code in JSP tag files, as explained in this answer or you can also use decorator frameworks such as Tiles or SiteMesh to do this.
Personally, I prefer JSP tag files. Do not attempt to write out HTML with jQuery or to put all of your code into a single JSP.
I am trying to figure out how to most effectively reuse JSP code.
I love the way Rails/erb works in that way ... with yield, layout, content_for
Example:
main_layout.erb.html
<html>
<head><%= yield :head %></head>
<body><%= yield %></body>
</html>
use
<% content_for :head do %>
<title>A simple page</title>
<% end %>
<p>Hello, Rails!</p>
in controller
layout "main_layout"
What is the closest I can get to this with JSP (without using extra frameworks)? I know about JSP include but that's not really the same as yield.
Any suggestions?
Thanks
I'm not familiar with what yield and content_for provide, but JSP tag files allow you a more robust way to template pages than JSP includes.
Example:
layout.tag
<%# tag body-content="scriptless" %>
<%# attribute name="pageTitle" required="true" type="java.lang.String" %>
<html>
<head>
<title>${pageTitle}</title>
</head>
<body>
<jsp:doBody/>
</body>
</html>
An individual JSP
<%# taglib prefix="z" tagdir="/WEB-INF/tags" %>
<z:layout pageTitle="A simple page">
<p>Hello, JSP!</p>
</z:layout>
Just place your layout.tag in the /WEB-INF/tags directory. You can use any available prefix you want, I just used "z" for the example.
While you mentioned wanting no frameworks on top of stock jsp, the Layout functionality of the Stripes Framework does pretty much exactly what you're asking for.
i have the following JSP:
<%# page contentType="text/html" pageEncoding="UTF-8"%>
<%# taglib uri="http://java.sun.com/jstl/core" prefix="c" %>
<%# page isELIgnored="false"%>
<!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=UTF-8">
<title><c:out value="${it.title}"/></title>
</head>
<body>
<c:forEach var="speaker" items="${it.speakers}" varStatus="stat">
<ul>
<li><c:out value="${speaker.person.firstName}" /> <c:out value="${speaker.person.lastName}" />, <c:out value="${speaker.person.address.city.zip}" /> <c:out value="${speaker.person.address.city.name}" /></li>
</ul>
</c:forEach>
</body>
</html>
Eclipse warns me about every instance of EL Expressions in my code:
Warning [line 10]: "value" does not support runtime expressions
Warning [line 13]: "items" does not support runtime expressions
...
this is however not true, EL gets evaluated correctly by the server.
Can anyone hint me in the right direction why eclipse is warning me about those EL expressions?
Your taglib directive imports a JSTL 1.0 taglib. It should be JSTL 1.1 instead (note the difference in URI):
<%# taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
Possible solution (found here):
Twin Libraries
The JSTL tag libraries come in two
versions which differ only in the way
they support the use of runtime
expressions for attribute values.
In the JSTL-RT tag library,
expressions are specified in the
page's scripting language. This is
exactly how things currently work in
current tag libraries.
In the JSTL-EL tag library,
expressions are specified in the JSTL
expression language. An expression is
a String literal in the syntax of the
EL.
When using the EL tag library you
cannot pass a scripting language
expression for the value of an
attribute. This rule makes it possible
to validate the syntax of an
expression at translation time.
So maybe your eclipse and the server use different tag libraries.
try this:
change this:
<%#taglib prefix="c" uri="http://java.sun.com/jstl/core"%>
to yes:
<%#taglib prefix="c" uri="http://java.sun.com/jstl/core_rt"%>
hope it works for you. I got this from www.csdn.net.