Groovychart Bar chart with fixed colour
In this article I show an example of creating a bar chart with a fixed colour. This was missing from the groovychart example set, and will get included into the next build. If you are unfamiliar with groovy chart then here is an introduction to Groovychart We simply tell the plot’s renderer to use the StandardBarPainter. This turns off the gradient paint that is used by default. Also this example shows one way of using multiple colours in the bars, its probably not the only way and as recommended elsewhere, I suggest the JFreeChart book for anyone intending serious usage of the library.
Generate an ATOM feed with GroovyBuilder
Lastly, we look at building an ATOM document using the same principles. ATOM provides a means for site owners to provide updates to site users. It works by providing an XML document showing recent changes to the site. Browsers that support RSS and RSS readers can then highlight these changes to users. An atom formatted document contains two main sections, the header which describes the feed, and then a list of elements, that describe the content.
Introduction to GSQL (Groovy SQL)
In this article I cover working with SQL from Groovy using the GSQL support built into the language. This is not a complete guide, rather a getting started guide, that shows you a few of the concepts. Firstly, GSQL is built on top of JDBC; which you are probably already familiar with. If not there are many good web guides and books on the subject. Lets get started looking a how to configure up GSQL and execute some statements.
Reading XML in groovy using XmlParser
Groovy has great inbuilt xml support, and allows you to treat xml paths like objects. Reading elements and attributes is so straightforward that it was one of the factors that got me started with Groovy. So to build an object tree from xml, we just use the XmlParser class. To dereference an element we use normal dot syntax, for an attribute, simply add the at symbol (@) before the name, see the example below.
Write XML with GroovyBuilder
Groovy supports the concept of builders, which provide an abstraction between the required output content and the representation of it. Groovy supports this by providing a tree like structure in groovy code that represents the required HTML or XML: import groovy.xml.MarkupBuilder // create a builder to generate xml like content from a // builder structure, in this case we choose // StringWriter as the output, but it could be any writer.
Wrapping JFreeChart as a Groovy builder
Groovychart is a library hosted on Java.net that wraps the functionality available in JFreeChart for use as a groovy builder. Currently it is available in snapshot form but hopefully time permitting, a full build will follow soon. I really like groovy as a scripting language, it's great for writing simple UI's for displaying graphical data from many sources including XML and the database. This article helps you set up and get started with groovychart.