Skip to main content

Attribute 'for' of label component with id xxxx is not defined


I got the warning in the log file when I have used the tag <h:outputLabel> without attribute "for" in xhtml file. It was really polluting my server log files.

The logged information actually makes sense anyway! We could find an answer as the following:

"Having h:outputLabel without a "for" attribute is meaningless. If you are not attaching the label, you should be using h:outputText instead of h:outputLabel."

However, these solutions are not possible just for my situation. Instead of using h:outputText for only displaying text, my team has used h:outputLabel too many places. We were nearly in our release time (next day) so it is quite risky and takes much efforts if we try to correct it. Because the style (with CSS) is already done with h:ouputLabel. The alternative by adding attribute "for" the existing h:outputLabel is not reasonable either. I really need to find another solution.

Fortunately, I came across a way if I change to use p:outputLabel, the warning won't be logged! What?

I was just curious to know why; so then I decided to delve into the implementation of outputLabel of both Primefaces and Myfaces source code (at grepcode.com). I found the reason is:

In Myfaces (1.2.2), we can easily to find the line of code below in method "encodeBegin" in class "HtmlLabelRenderer". It is executed whether the attribute "for" is null.

log.warn("Attribute 'for' of label component with id " 
+ uiComponent.getClientId(facesContext)+" is not defined");

However, Primefaces (5.2) does not. In class "OutputLabelRenderer", it uses the default implementation of method "encodeBegin" from superclass without logging. Ahh! The method "encodeBegin" is just a hook!

Okay! The reason is clear. I saw that the only difference of HTML rendering between h:outputLabel and p:outputLabel is as below:

1. <h:ouputLabel> will be rendered  to become <label>
2. <p:outputLabel> will be rendered to become <label class="ui-outputlabel">

It should be an acceptable approach to fix the issue in my case. I just do a little bit more with style and I can achieve my goal without spending much efforts for testing whole the application again. Yeah!

Something like this:

1. XHTML

<h:panelGroup layout="block" styleClass="child-add-ons-container">

    <ul>

        <li>

            <h:panelGroup layout="block" styleClass="type-of-check">

                <p:outputLabel value="bonity"></p:outputLabel>

            </h:panelGroup>

        <li>

        ....

    <ul>

</h:panelGroup>

2. CSS: just make sure the style of p:outputLabel is the same with current style of h:outputLabel, for example:
.add-ons-compliance-check .type-of-check label.ui-outputlabel {

    font-style: normal; /*style of tag label in our app*/

    color: inherit;  /*style of tag label in our app*/

    font: inherit;  /*style of tag label in our app*/

}

References
[1]. http://stackoverflow.com/questions/12744264/attribute-for-of-label-error
[2]. http://docs.oracle.com/javaee/5/javaserverfaces/1.2/docs/tlddocs/h/outputLabel.html
[3]. http://grokbase.com/t/myfaces/users/143vdzqp11/how-to-disable-label-warnings
[4]. http://grepcode.com/file/repo1.maven.org/maven2/org.primefaces/primefaces/5.2/org/primefaces/component/outputlabel/OutputLabelRenderer.java?av=f
[5]. http://grepcode.com/file/repository.springsource.com/org.apache.myfaces/com.springsource.org.apache.myfaces/1.2.2/org/apache/myfaces/renderkit/html/HtmlLabelRenderer.java?av=f

Comments

Popular posts from this blog

My 2017 Review

Passion for System Design After finishing a one year project, my longest stable team (3 years) was separated into two smaller teams. Sadly, but that was a good chance for me to become a key member in my new team. My preferred skills is about system architectures; therefore most of the tasks of building the application structures are handled by me. In order to enhance my design system skills, I have spent much my time for reading books closely after work. These following books helps me a lot.
- Object-Oriented Thought Process | Matt Weisfeld
- Head First Design Pattern | Elisabeth Freeman and Kathy Sierra
- Java 8 in Action: Lambdas, Streams, and Functional-style Programming | Alan Mycroft and Mario Fusco
Junior Technical Architect I was requested to join a technical architect team (aka Team. Alpha) where I actually has gained experiences almost on interviewing candidates for my company (lol). Besides, I noticed myself must improve the skills of convincing people because I have had a …

AngularJS - Build a custom validation directive for using multiple emails in textarea

AngularJS already supports the built-in validation with text input with type email. Something simple likes the following:
<input name="input" ng-model="email.text" required="" type="email" /> <span class="error" ng-show="myForm.input.$error.email"> Not valid email!</span>
However, I used a text area and I wanted to enter some email addresses that's saparated by a comma (,). I had a short research and it looked like AngualarJS has not supported this functionality so far. Therefore, I needed to build a custom directive that I could add my own validation functions. My validation was done only on client side, so I used the $validators object.

Note that, there is the $asyncValidators object which handles asynchronous validation, such as making an $http request to the backend.

This is just my implementation on my project. In order to understand that, I supposed you already had experiences with Angular…

Strategy Design Pattern

For example, I have an program with an Animal abstract class and two sub-classes Dog and Bird. I want to add a new behavior for the class Animal, this is "fly".  Now, I face to two approaches to solve this issue:

1. Adding an abstract method "fly" into the class Animal. Then, I force the sub-classes should be implemented this method, something like:

public abstract class Animal{ //bla bla public abstract void fly(); } public class Bird extends Animal{ //bla bla public void fly(){ System.out.println("Fly high"); } } public class Dog extends Animal{ //bla bla public void fly(){ System.out.println("Cant fly"); } }
2. Creating an interfaces with method "fly" inside. The same issue to abstract class, I force the classes these implement this interface should have a method "fly" inside:

public interface Flyable{ public void fly(); } public class Bird implements Flyable{ //bla bla public void fly(){ System.out.println…

How did I start practising BDD?

At the beginning days I have practised TDD (Test Driven Development) with using JUnit, I approached that I should test methods belong to a class. For example:

I have a class with some methods:

public class A{ public void method1(){ } public void method2(){ } }
And then, I wrote some test methods to check the corresponding ones, for example:

public class ATest{ @Test public void testMethod1(){ .... assertTrue(...); ..... assertEquals(...); } @Test public void testMethod2(){ } }
After that, I know that a test method (ex: testMethod1) should just only tests one thing, so I decided to write more methods for each cases. It looks like the following:

@Test public void testMethod1_When_Case1(){ .... assertTrue(...); } @Test public void testMethod1_When_Case2(){ .... assertEquals(...); }
However, it was not a really good approach because it seems that I just focused on test the functionality of the method of the class. With TDD approach, I knew that I should test the…

Styling Sort Icons Using Font Awesome for Primefaces' Data Table

So far, Primefaces has used image sprites for displaying the sort icons. This leads a problem if we want to make a different style for these icons; for example, I would make the icon "arrow up" more blurry at the first time table loading because I want to highlight the icon "arrow down". I found a way that I can replace these icons to Font Awesome icons.


We will use "CSS Pseudo-classes" to archive it. The hardest thing here is that we should handle displaying icons in different cases. There is a case both "arrow up" and "arrow down" showing and other case is only one of these icons is shown.

.ui-sortable-column-icon.ui-icon.ui-icon-carat-2-n-s { background-image: none; margin-left: 5px; font-size: 1.1666em; position: relative; } .ui-sortable-column-icon.ui-icon.ui-icon-carat-2-n-s:not(.ui-icon-triangle-1-s)::before { content: "\f106"; font-family: "FontAwesome"; position: absolute; t…