concepts about JSTL

Question

I want to understrand what happens when i use JSTL to access maps,in Hidden features of JSP/Servlet in @blausC's answer, he explained what happend, but when i try to use the following code

     <c:set var="resultMap" value="validationResults" scope="request"></c:set>
     <c:if test="${resultMap['userName'] != null}">
          ${resultMap['userName'].details}
    </c:if>

a confused exception happend

Caused by: javax.el.PropertyNotFoundException: Property 'userName' not found on type java.lang.String

The key of the map should be string, so whay is this exception, i tried the examples in the above question and the same exception,Can some one tell me where I have misunderstanding?

Edit: I populate the map in the servlet and send it to jsp

 Map<String, ValidationResult> result = new HashMap<String, ValidationResult>();
 aValidationResult = new ValidationResult();
 check whether the field is valid or not if not fill the map
 result.put("userName", aValidationResult);
 result.put("group", aValidationResult);

if map is not empty, return the map to jsp

request.setAttribute("validationResults", result);

the map is filled when i make server side validation ,

Thanx in advance.

gbakernet · Answer 1 · 2010-12-17T04:45:56.867

3

resultMap is a String because of this line

 <c:set var="resultMap" value="validationResults" scope="request"></c:set>

You need to use EL to assign the value

 <c:set var="resultMap" value="${validationResults}" scope="request"></c:set>

Edit: The following is working code

 <c:set var="validationResults" value="<%= new java.util.HashMap() %>" />
 <c:set target="${validationResults}" property="username" value="Hello World" />
 <c:set var="resultMap" value="${validationResults}" />
 <c:out value="${resultMap['username']}"></c:out>

edited Dec 17 '10 at 04:45

answered Dec 17 '10 at 04:28

gbakernet

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2
5

it doesn't work when i make the value like this value="${validationResults}" ,it works ad @Enriquw answered,but i didn't understand why? – palAlaa Dec 17 '10 at 04:31

score 1 · Accepted Answer · answered Dec 17 '10 at 04:02

1

This is caused because String class does not have a method called getUserName()

answered Dec 17 '10 at 04:02

Enrique

9,920
7
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I doubt that would be the reason , but what should I do with map, since it's keys are string?? – palAlaa Dec 17 '10 at 04:04
How are you populating the resultMap? – Enrique Dec 17 '10 at 04:05
Have you debugged if resultMap is a java.util.Map or java.lang.String? – gbakernet Dec 17 '10 at 04:08
@gbakernet, resultMap is java.util.Map – palAlaa Dec 17 '10 at 04:09
Can you post how are you inserting values into resultMap? – Enrique Dec 17 '10 at 04:09
@ Enrique-what do u mean with populating the map? – palAlaa Dec 17 '10 at 04:10
By populating I mean filling the map – Enrique Dec 17 '10 at 04:11
1

Try with ${validationResults['userName'] – Enrique Dec 17 '10 at 04:22
@Enrique- it works, but what is the difference ,why it doesn't work when i use the variable? Really strange!! – palAlaa Dec 17 '10 at 04:24
– gbakernet Dec 17 '10 at 04:25
Because in jsp files you reference the variables using the name you specify in the first argument of the setAttribute method. – Enrique Dec 17 '10 at 04:32
@Enrique-I totally agree, but what dose var mean in tag? – palAlaa Dec 17 '10 at 04:37
It is used to set the variable name. You can change value="validationResults" with value="${validationResults}" and then use resultMap as your variable name as gbakernet said. – Enrique Dec 17 '10 at 04:39
since i can set the variable name, why cannot i use it instead of the vairable itself?? – palAlaa Dec 17 '10 at 04:41
You can do It in both ways(validationResults,resultMap), is your choice. – Enrique Dec 17 '10 at 04:44
i want to get why when I use resultMap in my question above doesn't work, even it reference to validationResults? – palAlaa Dec 17 '10 at 04:46
1

Because as gbakernet said you missed to use ${} – Enrique Dec 17 '10 at 04:47

concepts about JSTL

2 Answers2