unable to initialize a list from custom simple tag handler

I have a class called Movie looks like

Then I have a another class called SimpleTagTest5 which is basically a tag handler looks like

The tld file and the way it is invoked in index.jsp file looks like as follows

simple.tld

index.jsp:

It is giving me NullPointerException because i have not initialized ${movieCollections}. How to make this program work. I wrote the scriplet code in index.jsp initializing ${movieCollections}, bu still it didn't work. Code is also not complete in the book (head first Servlets and JSP).

The exact error message is

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: Exception in JSP: /index.jsp:16

13: %>
14: SimpleTagTest5<br>
15: <table>
16: <myTags:simple5 movieList="${movieCollection}">
17: <tr>
18: <td>${movie.name}</td>
19: <td>${movie.genre}</td>

Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:451)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

root cause

java.lang.NullPointerException
	foo.SimpleTagTest5.doTag(SimpleTagTest5.java:20)
	org.apache.jsp.index_jsp._jspx_meth_myTags_005fsimple5_005f0(index_jsp.java:91)
	org.apache.jsp.index_jsp._jspService(index_jsp.java:63)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

Where is the problem?

regards

Anil Deshpande

Hi,

1.) I would say, you should check if field movieList is null or not.

2.) What is correct ${movieCollections} or ${movieCollection}? I ask this, because you used this to different names in code and discription.
How did you initialized movieCollection?

it is ${movieCollection} not ${movieCollections}

And I did changes in the code to check if the movieList is null. It is null as expected. If I want to initialize it what and how it can be done?

And I did changes in the code to check if the movieList is null. It is null as expected. If I want to initialize it what and how it can be done?

Preferably in servlet ,

1)create Movie bean object using setters ,
2) Add to a list say movieList.
3) repeat above steps if you want to add more than 1 movie.
4) Make the movieList (list) available as attribute in session scope as "movieCollection"
5) forward your request to JSP using RequesDispatcher

Hi,

the simplest way to do this is to write a little peace of java code inside jsp:

Note: this is not a clean way.
Normally you should init movieCollection inside a controller (e.g servlet) and put them into the current used session or the request.

the simplest way to do this is to write a little peace of java code inside jsp:

Neither preach , nor practice.

Hey,

I would just like to say your tag is pretty much exactly the same as the <c:forEach> tag from the JSTL (only it will only work with your specific type of list).

I did the changes in the index.jsp to include a scriplet code to initialize movieCollection. It is working fine now. Thanks a lot. Everybody I appreciate replies.