Looking for ideas

Hi Everyone,

I have BIRT running wonderfully with my Flex application, but I have already hit my URL limitation of 2048 characters. Looks like my original idea of passing parameters through the URL is just not going to cut it as reports grow and objects that can be included as parameters get longer and longer.

Some background, my application is a flex front-end with a coldfusion backend and mysql database. Right now coldfusion handles all the authentication type stuff, as well as populating objects that can be reported on in Flex, but once the user figures out what report they are going to run and selects their parameters, it's all just passed along to the application server hosting birt as a URL string. This works great. I have a SEcurity filter written in java to make sure only authenticated users are able to see a report. This was bliss until the URL limitation hit.

So now on to some new ideas

One idea I thought of was to have coldfusion actually write the query and store it in a database table with a report_key. The user would select their report and params, coldfusion would process it and store the query_string in the database, returning a report_key, this in turn would be passed into the URL for the report request. This way the user runs the report, and then only passes the report_key in URL. Somehow, BIRT would then go to the database and find the query associated with that report_key. But how would I do that? Basically I would have a table that looked like this:

tbl_report_keys
report_key | query_string
15d5221 | SELECT * FROM tbl_calls where call_id IN (24,59,64)

So BIRT would need to first go out to that table and grab that query_string, then store it in a variable and run it. Any ideas on how I could get this to work?

Also, any other ideas would totally be welcomed. What are other people doing to alleviate URL limitations?

Thanks in advance!
Amanda

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Comments

bhanley

Your idea sounds quite clever. I think it adds complexity to your process, but it brings with it a ton of flexibility so it is worth looking into.

To do the query look-up, I would use a Java Event Handler. This can be a simple POJO that the report invokes during the initialization process. The Object can handle all the heavy lifting in terms of database interaction. Once you have grabbed the query, set the text on a Global Persistent Variable. This will make it available throughout the report. Most importantly, it will be available to your Data Set's onCreate event. There you can set the Query text to your query form the data store.

One thing to bear in mind is that your query will have to adhere to a standardized scheme both in the number of columns retrieved and the data type on each column. The report's structure and data bindings rely on knowing this schema information at design time. Where you populate this schema from can vary, but the structure cannot be altered.

Good Luck!

DreamCoder

Thanks Brian. I am working on doing that now. I am running into an issue tho. I have a little testing scenario going to get the hang of how BIRT deals with java event handlers. All it has is a label, and through an event handler on that label, I am changing the background to yellow and the text to something. Well this works great. I have it all written using eclipse so I can change my java class and then run again and see changes. Very sweet.

The issue I seem to be having is when I try to add some additional code to grab a database connection. This apparently fails because if I try to change the label anywhere after this line:

conn = DriverManager.getConnection(connectionString,"username","password");

the label doesn't change. It doesn't error out either...not really. Just any code after that line doesn't seem to do anything.

When I run the debug on the java class using the Report debug (which I just figured out yesterday), it will end in this error:

java.lang.NoClassDefFoundError: org/eclipse/birt/core/exception/BirtException
Caused by: java.lang.ClassNotFoundException: org.eclipse.birt.core.exception.BirtException
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Exception in thread "main"

But I'm not sure thats really relevent either since it ends in that regardless of what code I have in the class.

Any ideas?

Thanks,
Amanda

bhanley

Looks like you need to add a JAR to your classpath (or build path inside Eclipse). The Jar containing this Exception class is org.eclipse.birt.core_version.jar ("version" will be specific to your install). This file is stored in the plugins folder under your BIRT install. Add it to your project's build path. Then wrap the offending line of code in a try block and catch the BirtException: 
 
<pre class='_prettyXprint _lang-auto _linenums:0'>
import org.eclipse.birt.core.exception.BirtException;
...
try{
conn = DriverManager.getConnection(connectionString,"username","password");
}catch(BirtException be){
// Do something like log the messsage or end processing
}
</pre>

DreamCoder

Thanks Brian

I actually have it working quite nicely now. Love it. I have it set up so that you could send in several report keys (because different parts of the report may be set up to use a different dataset), and then my java handler loops through those report keys, grabs the associated query and a query_name and saves it to a global persistent variable in birt, giving the global variable the name of the query_name, this way I control what dataset uses what variable, and it's all dynamic on the java side.

Works wonderful.

So quick question, I think I read somewhere that if you have a javascript handler written for an object event, and then also specify a java event handler, that the javascript one will be the only one to execute. What about for different events on the same object. For example, what if i have a java event handler for the initialize() event, but then want to write a javascript handler for the beforeFactory() event. Can I do that? Or do I have to write it all in java...

Thanks,
Amanda

bhanley

You should be fine mixing the two event handling methods. Just make sure you do not handle the same even in both spots, or the JavaScript (as you note) will win out and you may not see the results you expect.

Glad everything is working so well!

DreamCoder

Awesome! Thanks!