StringTemplate Part 4:Generating a Builder Class using StringTemplate

Parts 1, 2 and 3 introduced StringTemplate through the use of simple SQL, HTML and plain text examples. This article switches gears and attempts to use StringTemplate to generate a more complicated text output: Java source code. In “Effective Java: Second Edition” (go read it, no really go read it) Mr. Block puts forth the idea of using a “Builder” class to help construct complicated objects. His builder uses a “fluid interface” that also has the extra side effect of looking like named parameters. Here is how you might use a builder class to create Planet objects. Planet mercury = new PlanetBuilder().name("Mercury").mass(0.06f).build(); System.out.println(mercury); Planet mars = new PlanetBuilder().name("mars").diameter(0.532f) .mass(0.11f).orbitalRadius(1.52f).orbitalPeriod(1.88f) .inclinationToSunsEquator(5.65f).orbitalEccentricity(0.093f) .rotationPeriod(1.03f).moons("Phobos","Deimos") .rings(false).atmosphere("CO2,N2").build(); System.out.println(mars); The only issue I have with this type of API is that it requires a lot of maintenance. Every time a property is added to the target class another method must be added to the builder and that data needs to be factored into the build method. I believe that with StringTemplate and a dash of reflection we can generate a builder for any (Bean) class. Lets take a look at the Planet class to see what we are up against. ...

Date: June, 13 2010
Url: http://www.java.net/blog/aberrant/archive/2010/06/13/stringtemplate-part-4generating-builder-class-using-stringtemplate

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