I have more or less been able to get it working by using GroovyClassLoader and SimpleTemplateEngine. here is the code:
class ClassBuilder {
GroovyClassLoader loader
String name
Class cls
def imports
def fields
def methods
def ClassBuilder(GroovyClassLoader loader) {
this.loader = loader
imports = []
fields = [:]
methods = [:]
}
def setName(String name) {
this.name = name
}
def addImport(Class importClass) {
imports << "${importClass.getPackage().getName()}" +
".${importClass.getSimpleName()}"
}
def addField(String name, Class type) {
fields[name] = type.simpleName
}
def addMethod(String name, Closure closure) {
methods[name] = closure
}
def getCreatedClass() {
def templateText = '''
<%imports.each {%>import $it\n <% } %>
class $name
{
<%fields.each {%> $it.value $it.key \n<% } %>
}
'''
def data = [name: name, imports: imports, fields: fields]
def engine = new groovy.text.SimpleTemplateEngine()
def template = engine.createTemplate(templateText)
def result = template.make(data)
cls = loader.parseClass(result.toString())
methods.each {
cls.metaClass."$it.key" = it.value
}
return cls
}
}
and here is an example of how I use it to create a class dynamically:
import java.util.Calendar
def builder = new ClassBuilder(this.class.classLoader)
builder.setName("MyClass");
builder.addImport(Calendar)
builder.addField('field1', Integer)
builder.addField('field2', Integer)
builder.addMethod('sum') { field1 + field2 }
builder.addMethod('product') { field1 * field2 }
builder.addMethod('testCalendar') {
println Calendar.getInstance().getTime()
}
Class myClass = builder.getCreatedClass()
def myInstance = myClass.newInstance()
myInstance.field1 = 1
myInstance.field2 = 2
println myInstance.sum()
println myInstance.product()
myInstance.setField2(1500)
println myInstance.getField2()
myInstance.testCalendar()