Passing in content when generating JasperServer report using the REST API

After several hours spent on research, I think I'm ready to answer my own question.

JasperReports Server ("JRS" below) is fundamentally designed to fetch data by itself. Although it would be possible to force feed JRS with data, I've decided not to.

One of the most obvious drawback of not letting JRS fetch the data itself is that it would no longer be possible to generate reports from the JRS web interface. Integration from other systems also becomes impossible or difficult if the client application is responsible for supplying the data in a predefined format.

In the project I'm working on, we've decided to build a custom JRS DataSource based on the Remote XML DataSource, that invokes the client application's XML API. In other words, the client application requests a report from JRS, and JRS then requests it's data from the client application. The XML API will have to be expanded to cover all of our reporting needs, but that's a good thing in my opinion. Good API coverage will come in handy in the future.

I hope these thoughts helps someone having similar questions.

As you wrote, fetching data is more natural way for JRS. However, I needed to go the opposite way - I POST data to report sitting in JRS repo via a REST call.

I pass XML data in my parameter "xmlDocument" and, by means of a "trick", an executed report can use this XML for further X-path queries.

xmlDocument is just a simple String:

<parameter name="xmlDocument" class="java.lang.String">
    <defaultValueExpression><![CDATA["<?xml version=\"1.0\" encoding=\"UTF-8\"?><documentData></documentData>"]]></defaultValueExpression>
</parameter>

At designing phase I create XML data adapter with XML file that I use for previewing. Note that a new parameter XML_INPUT_STREAM appeared after choosing XML adapter.

Then I publish the report to JRS. During report execution, when the report is not linked to any data source, it reads XML_INPUT_STREAM parameter instead (as fallback data source), that looks as follows:

<parameter name="XML_INPUT_STREAM" class="java.io.InputStream" isForPrompting="false">
    <defaultValueExpression><![CDATA[new java.io.ByteArrayInputStream($P{xmlDocument}.getBytes("UTF-8"))]]></defaultValueExpression>
</parameter>

I wrap "xmlDocument" string to InputStream.