JSF Mini Book – Tips, concepts and good practices

How to receive null value from the view

Good development practices say: “avoid passing null values inside your application”; following this good practice we will be reducing the possibility of the famous NullPointerException. By default the JSF will handle all requests parameters to be not null. An integer will be equals to zero, a Boolean to false and a String will be “” (empty but not null).

If the business rule is to receive null instead some default value, there is a way to notify the JSF to do not provide the default values. The first step is to add the configuration below to the web.xml file.

<context-param>
    <param-name>javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL</param-name>
    <param-value>true</param-value>
</context-param>

If the application is running in the Glassfish container just the configuration above will complete the task. If the application is running in the Tomcat/JBoss, this configuration alone will not be enough to bring the value as null. This happens because the Tomcat/JBoss will ignore the configuration. To force the container to “respect” the configuration add the following configuration to the container JVM: -Dorg.apache.el.parser.COERCE_TO_ZERO=”false”. The Tomcat/JBoss will keep the empty value as null and will not provide the default JSF values.

18 thoughts on “JSF Mini Book – Tips, concepts and good practices

  1. Really cool material! I agree with Tim. If this could be distributed in pdf format, you will become a little more famous. :) Thanks, good job!

  2. I’m not able to see this library applied in my program.
    Output is: Real Madrid, Champion!!! (No image and style)

    Please let me know what I’m missing.

  3. I was trying to learn Spring MVC for last 2 months, Every time i try to start, i get stuck somewhere. 2 Months passed, and i did not learn anything. I purchased two books for spring. Finally i quit Java web programming. One day I thought to give a try to JSF. and found some tutorials online, worked on them and I loved it. Your tutorials are going to help me a lot.
    Thank you so much.
    I would like to tell people here, don’t go near spring, It’s a piece of crap.

    • Arslan,

      Thanks for the feedback.

      My next post will be a full web application with Spring MVC.

      Maybe this application will help you understanding better the Spring, it is a good tool! =D

      See you later.

  4. With your code lines

    and

    eclipse was giving error that:

    Multiple annotations found at this line:
    – Invalid location of text (“) in tag ().
    – Invalid location of text (=”) in tag ().
    – Element type “h:outputStylesheetlibrary” must be followed by either attribute specifications, “>”
    or “/>”.

    So I’ve corrected it by changing lines to

    But I think as you mentioned in case of versions of resources, it will automatically picks up latest version. but the code I’m using will not control the version. It looks like hard-coded.

    What you say about it?

    Moreover, You wrote:
    “To use a mapped library by the ResourceHandler let us create a folder named “index.xhtml” inside the folder “/WebContent”.”

    I think you have not created a folder name “index.xhtml” but you have created a file named “index.xhtml”. If I’m right then you need to correct it. :)

    • Hello Arslan, how are you?

      Unfortunately the xml are not displayed here. =/

      Could you send me an email with the code and the texts that you wrote?

      Thanks for your support and passing by.

      My email is contato (at] uaihebert (d0T) com

      Thanks

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