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
Labels:

Comments

Post a Comment

Popular posts from this blog

MS SQL Server Views

"Creates a virtual table whose contents (columns and rows) are defined by a query. Use this statement to create a view of the data in one or more tables in the database. For example, a view can be used for the following purposes: - To focus, simplify, and customize the perception each user has of the database. - As a security mechanism by allowing users to access data through the view, without granting the users permissions to directly access the underlying base tables. - To provide a backward compatible interface to emulate a table whose schema has changed." [1] Beside that, our team used view in order to improve the performance of our web apps when a database has a very complicated relationship between its tables by using ORM Frameworks such as Hibernate. Example code: --create CREATE VIEW placeholders AS SELECT EMPKEY AS empkey, CONNUMB AS connumb, EMPNBR AS empNbr, ACEEMPN AS empFirstName, ACEEMPFN AS empLastName, EMPNAM AS empFullName, ...
Post a Comment
Read more

Why Functional Programming Matter

What issues do we concern when implementing and maintaining systems? One of the most concern is debugging during maintenance: "this code crashed because it observed some unexpected value." Then, it turns out that the ideas of  no side effects  and  immutability , which functional programming promotes, can help. Shared mutable data is the root cause Shared mutable data are read and updated by more than one of the methods. Share mutable data structures make it harder to track changes in different parts of your program. An immutable object is an object that can't change its state after it's instantiated so it can't be affected by the actions of a function. It would be a dream to maintain because we wouldn't have any bad surprises about some object somewhere that unexpectedly modifies a data structure. A new thinking: Declarative programming There are two ways thinking about implementing a system by writing a program. - Imperative programming: has...
Post a Comment
Read more

Coding Exercise, Episode 1

I have received the following exercise from an interviewer, he didn't give the name of the problem. Honestly, I have no idea how to solve this problem even I have tried to read it three times before. Since I used to be a person who always tells myself "I am not the one good at algorithms", but giving up something too soon which I feel that I didn't spend enough effort to overcome is not my way. Then, I have sticked on it for 24 hours. According to the given image on the problem, I tried to get more clues by searching. Thanks to Google, I found a similar problem on Hackerrank (attached link below). My target here was trying my best to just understand the problem and was trying to solve it accordingly by the Editorial on Hackerrank. Due to this circumstance, it turns me to love solving algorithms from now on (laugh). Check it out! Problem You are given a very organized square of size N (1-based index) and a list of S commands The i th command will follow t...
2 comments
Read more

Strategy Design Pattern

For example, I have a program with an Animal abstract class and two sub-classes Dog and Bird. I want to add new behavior for the class Animal, this is "fly".  Now, I face 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 interface with method "fly" inside. The same issue to an 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.pr...
Post a Comment
Read more

Java Core - Top 10 Questions Every Developer Should Know

#RandomlyPickedByMe What is the difference between Javascript and Java? Difference between StringBuilder and StringBuffer? Why do I get "SomeType@a3fde" when I print my code? Why is String immutable? Why "equals" method when we have "==" operator? Is List<Dog> a subclass of List<Animal>? Why shouldn't we use raw type? Is Java “pass-by-reference” or “pass-by-value”? What's the advantage of a Java enum versus a class with public static final fields? Why "double x = 0.1 + 0.2" and result of print(x) is 0.30000000000000004? 1. What is the difference between Javascript and Java? Holy crap! (Vietnamese: Thế quái nào lại có câu hỏi ngớ ngẩn vậy chứ?) "Java and Javascript are similar like Car and Carpet are similar." - Greg Hewgill (on StackOverflow) 2. Difference between StringBuilder and StringBuffer String is immutable. StringBuilder and StringBuffer are mutable. StringBuffer is thread-safe. String...
Post a Comment
Read more