懒惰地将JasperReports .jrxml编译为.jasper

Question

I use Jasper reports with the JasperReportsMultiFormatView class provided by the Spring framework. This class takes care of compiling the source .jrxml files to their compiled .jasper format when the Spring application context is created.

However, this compilation process is really slowing down the application startup time. Is it possible for the reports to be lazily compiled instead of compiled at startup time, ie a report is only compiled the first time it is requested?

If this is not possible, alternative suggestions for how I can reduce/eliminate the report compilation time would be welcome. Of course, I could mandate that the compiled reports must be checked into SVN along with the .jrxml files, but it's only a matter of time, before someone (most likely me) forgets.

Cheers, Don

Answer 1

I, like you, started out with the Spring helper classes for Jasper Reports but quickly abandoned them as being too coarse-grained and inflexible, which is unusual for Spring. Its like they were added as an afterthought.

The big problem I had with them was that once they were compiled, it required an appserver bounce to put in new versions. In my case, I was after a solution whereby I could change them on disk and they'd recompile, much like how JSPs normally work (if you don't turn this feature off, which many production sites would).

Alternatively, I wanted to be able to store the jrxml files in a database or run the reports remotely (eg through the JasperServer web services interface). The Spring classes just made it all but impossible to implement such features.

So my suggestion to you is: roll your own. There are a couple of gotchas along the way though, which I'll share with you to minimize the pain. Some of these things aren't obvious from the documentation.

The first thing you'll need is a jasper reports compiler. This is responsible for compiling a jrxml file into a JasperDesign object. There are several implemenations of this but the one you want is the JRJdtCompiler. You can instantiate and inject this in a Spring application context. Avoid others like the beanshell compiler since running the report as a large beanshell script is not particularly fast or efficient (I found this out the hard way before I knew any better).

You will need to include the jar files for the JRJdtCompiler. I think the full Jasper Reports dist includes this jar. Its an eclipse product.

You can store the JasperDesign anywhere you like (HttpSession, servlet context or whatever). The fillReport() method is the primary one you're interested in. It creates a JasperPrint object, which is an instance of a run report. Parameters are just passed in as a Map.

Now to create a versino in HTML, PDF, etc, you need to export it. You use classes like the JRHtmlExporter and JRPdfExporter to do this. They require certain parameters. The tricky one is the HTML exporter because HTML obviously doesn't include the images. Jasper includes an ImageServlet class that fetches these from the session (where the JRHtmlExporter has put them) but you have to get the config of both the HTML exporter and image servlet just right and its hard to tell where you're going wrong.

I don't remember the specifics of it but theres an example of all this in the Jasper Reports Definitive Guide , which I'd highly recommend you get if you're spending anytime at all with this product. Its fairly cheap at US$50. You could get the annual subscription too but in the 18+ months I've seen it I haven't seen a single change. Just buy the new version when it comes out if you need it (which you probably won't).

Hope this helps.

Answer 2

The report is compiled the first time its run, put a break point in AbstractJasperReportsView protected final JasperReport loadReport(Resource resource) method to confirm this.

However the above post is correct that you'll need to extend the JasperReportsMultiFormatView if you want to provide any specific compilation process.

A great example of dynamic compilation is here: http://javanetspeed.blogspot.com/2013/01/jasper-ireport-with-java-spring-and.html

import net.sf.jasperreports.engine.JasperReport;
import org.apache.log4j.Logger;
import org.springframework.web.servlet.view.jasperreports.JasperReportsMultiFormatView;

public class DynamicJasperReportsMultiFormatView extends JasperReportsMultiFormatView {

private static final Logger LOG = Logger.getLogger(DynamicJasperReportsMultiFormatView.class);

/**
 * The JasperReport that is used to render the view.
 */
private JasperReport jasperReport;

/**
 * The last modified time of the jrxml resource file, used to force compilation.
 */
private long jrxmlTimestamp;

@Override
protected void onInit() {
    jasperReport = super.getReport();

    try {
        String url = getUrl();
        if (url != null) {
            jrxmlTimestamp = getApplicationContext().getResource(url).getFile().lastModified();
        }
    } catch (Exception e) {
        e = null;
    }
}

@Override
protected JasperReport getReport() {
    if (this.isDirty()) {
        LOG.info("Forcing recompilation of jasper report as the jrxml has changed");
        this.jasperReport = this.loadReport();
    }
    return this.jasperReport;
}

/**
 * Determines if the jrxml file is dirty by checking its timestamp.
 *
 * @return true to force recompilation because the report xml has changed, false otherwise
 */
private boolean isDirty() {
    long curTimestamp = 0L;
    try {
        String url = getUrl();
        if (url != null) {
            curTimestamp = getApplicationContext().getResource(url).getFile().lastModified();
            if (curTimestamp > jrxmlTimestamp) {
                jrxmlTimestamp = curTimestamp;
                return true;
            }
        }
    } catch (Exception e) {
        e = null;
    }
    return false;
}

}