I’m working with Google Web Toolkit and trying to understand how it manages dependencies and class loading. I know that regular Java applications use the standard classpath for both compilation and runtime, but I’m curious about GWT’s approach.
Specifically, I want to know if GWT’s compiler uses a different classpath system than what we normally see in Java development. Also, when a GWT application is running, does it use its own way of finding and loading classes that’s different from how the JRE normally handles the runtime classpath?
I’m asking because I’ve noticed some differences in how GWT behaves compared to regular Java apps, and I want to make sure I understand the underlying mechanisms properly.
gwt’s classpath is kinda strange - it actually needs the .java source files, not just the compiled stuff like normal java. also, there’s the client/server thing. client code turns into js, so the jvm classpath isn’t really involved, but server-side still sticks to normal java classpaths.
GWT handles classpath differently than standard Java, starting with the same foundations. During development, its compiler employs a modified classpath that includes your application code alongside GWT libraries. The critical distinction lies in GWT’s translation of Java source code into JavaScript, focusing solely on classes that will ultimately convert into JS. Server-side code within the same project adheres to conventional Java classpath rules. At runtime, traditional class loading does not occur in the browser since everything is transpiled to JavaScript. GWT’s runtime operates independently of the JRE’s ClassLoader, using JavaScript’s module loading alongside the compiled output from GWT. An interesting aspect is that GWT requires actual source code on the classpath, not merely compiled .class files, as the compiler must analyze and transform the original Java source during transpilation.
GWT’s classpath is confusing if you’re used to regular Java development. The tricky part is that GWT creates two separate runtime environments in the same project. The compiler needs access to source files and libraries, but it’s picky about what it processes based on your module definitions. I’ve worked on bigger GWT projects where dependency management gets messy - you have to make sure libraries actually work with GWT’s transpilation. Most standard Java libraries won’t work client-side because they use JVM features that don’t convert to JavaScript. GWT’s module system filters your classpath, deciding what gets compiled for the client versus what stays server-side only.