Creating a Dynamic Jasper Report (Dynamic Columns)

(still in draft state).

Are you using JasperReports?
Do you have a requirement to show columns dynamically based on the user selection?
Or at least - Do you want to know how to add columns dynamically to jasper reports?
If yes, then go ahead and read this....
In general, to generate a report using Jasper - we should have the following:

1. The report template (JRXML file) - usually created using a design tool such as iReport.
2. The report data - usually created / provided by a datasource provider (DSP). By default Jasper supports several data source providers, but in this blog - we will consider a custom data source provider.
3. A DTO (Data Transfer Object) - in effect a java bean with public getters and setters.
4. A Java class that compiles the JRXML file, creates the data using the DSP, fills the template with the data.

Basically the DSP will create a list of DTOs. Each DTO corresponds to a Row in the report output.
Generally, we would be defining a set of fields in the JRXML file (apart from variables, parameters). Each such field corresponds/is bound to an attribute / property / member variable in the DTO.
Jasper uses ognl/java reflection to fetch the actual value from the DTO - while filling the report.

Now if we plan to have dynamic columns, let us see what we need to do.

1. The number of columns has to be dynamic. The fields (each corresponds to a single column) has to be dynamic => the JRXML file has to be dynamic.
2. The fields in JRXML are dynamic => the DTO has to be dynamic.
3. The DSP has to be dynamic (basically the place where you create the DTO).

Let us go step by step with a small sample.
Assume we need to generate a report that would be the amount of .... (yet to write)

Creating a dynamic JRXML file.***

Report design tools such as iReport - provide a GUI interface to create the JRXML file.
But our requirement is to create it on the fly - based on some criteria - such as user selection.

I have used Velocity template to create a JRXML file on the fly.

I have used a JrxmlMetadata bean. The client .... (yet to write)

*** There are other ways to achieve this. You don't need to generate the JRXML. You can directly create a JasperReport Object on the fly - using Java / Jasper Reports API. (When you compile the JRXML file - what you get is a JasperReport Object only). Doing so reduces the dependency on Velocity. But has few drawbacks. Hence I have ignored it :-(

Best Regards,
Madhusudhan.

"Paropakarartham Idham Budhim"
(The very purpose of this mind/knowledge is to help others).