java generate class file at runtime

Question

I need to generate class at runtime, each class is mapped to a database table. Such class is model class used in ORM.

When client specify a database table to work with, my application check for existence of corresponding model class , if it does not exist, generate it and load it for use and save it, so next time we don't need to generate this class again

my question is:

1. Is that possible?
2. What open source library to use for generating class at runtime ?

some example code that illustrating how to generate simple POJO class is welcome!

best regards!

Answer 1

Yes, this is possible. And you don't need an external lib. The JDK provides everything you need:

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
int compilationResult = compiler.run(null, null, null, fileToCompile);
if (compilationResult == 0) {
    System.out.println("Compilation is successful");
} else {
    System.out.println("Compilation Failed");
}

Check out the JavaCompiler docs.