iReport Ultimate Guide - Nimsoft Library

Report ElementsTable 5-4TypeImage Expression Class Values, continuedInterpretationjava.net.URLjava.io.InputStreamjava.awt.ImageJRRenderableSpecifies the java.net.URL object. It is useful when you have to export the report inHTML format. A correct expression could be:new java.net.URL(“http://127.0.0.1/test.jpg”)Specifies a java.io.InputStream object which is ready for reading. In this case,we do not consider that the image exists and that it is in a file. In particular, we couldread the image from a database and return the inputStream for reading. A correctexpression could be:MyUtil.getInputStream(${MyField})Specifies a java.awt.Image object; it is probably the simplest object to return whenan image has to be created dynamically. A correct expression could be:MyUtil.createImage()Specifies an object that uses thenet.sf.jasperreports.engine.JRRenderable interface.You are free to add an image by explicitly defining the full absolute path of the image file in your expression. This is an easyway to add an image to the report, but, overall, it has a big impact on the report’s portability, since the file may not be found onanother machine (for instance, after deploying the report on a web server or running the report on a different computer).There are two best practices here:• Parametrize the image expression containing the folder where your images resides (possibly using a parameter with adefault value), then composing the expression like this:$P{MY_IMAGES_DIRECTORY} + “myImage.png”At run time in a hypothetical application, the value for the parameter MY_IMAGES_DIRECTORY can be set by theapplication itself. If a value for the parameter is not provided, we can still return a default value (we’ll see how to create aparameter and set a default value in the next chapter). The advantage of this solution is that the location of the directorywhere the images reside is not defined discretely within the report, but can be provided dynamically.• The second option is to use the classpath. The classpath defines the directories and JAR file locations where a Javaapplication like UR looks for classes and resources. If the application uses the Java Virtual Machine, it isusually easy to add directories to the classpath.In iReport, the classpath can be extended from the Options dialog (Window > Options > iReport > Classpath). When animage is in the classpath, the only required information UR needs in order to find and render the image is theresource name (that is a kind of path that is relative to the classpath). By default, when executing a report, iReport adds thedirectory in which the report resides to the classpath. Suppose you have a report in a certain directory, let’s sayc:\test\myReport.jrxml, and in the same directory you have an image named myImage.png. To use it in the report, you canset Image Expression to myImage.png. Since the report’s directory is in the classpath, the image will be foundautomatically.This process is still valid if the image resides in a subdirectory of the classpath. You will have to specify the subdirectorypath, using a Unix-style path notation. For example, if your image resides in c:\test\images rather than c:\test, the resourceis found with the expression /images/myImage.png.This method of resolving resource locations is applied in many other parts of UR, as well (for example, inlocating a subreport Jasper file, a resource bundle, a scriptlet class, and so on).77