Groovy example source code file (LoggingASTTransformation.groovy)

This example Groovy source code file (LoggingASTTransformation.groovy) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Groovy tags/keywords

argumentlistexpression, constantexpression, constantexpression, ending, list, list, methodcallexpression, methodnode, methodnode, sourceunit, starting, statement, statement, variableexpression

The Groovy LoggingASTTransformation.groovy source code

package transforms.local

import org.codehaus.groovy.transform.ASTTransformation
import org.codehaus.groovy.ast.ASTNode
import org.codehaus.groovy.control.SourceUnit
import org.codehaus.groovy.transform.GroovyASTTransformation
import org.codehaus.groovy.control.CompilePhase
import org.codehaus.groovy.ast.MethodNode
import org.codehaus.groovy.ast.ClassNode
import org.codehaus.groovy.ast.stmt.ExpressionStatement
import org.codehaus.groovy.ast.expr.MethodCallExpression
import org.codehaus.groovy.ast.expr.VariableExpression
import org.codehaus.groovy.ast.expr.ConstantExpression
import org.codehaus.groovy.ast.expr.ArgumentListExpression
import org.codehaus.groovy.ast.stmt.Statement

/**
* This transformation finds all the methods defined in a script that have
* the @WithLogging annotation on them, and then weaves in a start and stop 
* message that is logged using println. 
*
* @author Hamlet D'Arcy
*/ 
@GroovyASTTransformation(phase=CompilePhase.SEMANTIC_ANALYSIS)
public class LoggingASTTransformation implements ASTTransformation {

    public void visit(ASTNode[] nodes, SourceUnit sourceUnit) {
        List methods = sourceUnit.getAST()?.getMethods()
        // find all methods annotated with @WithLogging
        methods.findAll { MethodNode method ->
            method.getAnnotations(new ClassNode(WithLogging))
        }.each { MethodNode method ->
            Statement startMessage = createPrintlnAst("Starting $method.name")
            Statement endMessage = createPrintlnAst("Ending $method.name")

            List existingStatements = method.getCode().getStatements()
            existingStatements.add(0, startMessage)
            existingStatements.add(endMessage)
        }
    }

    /**
    * This creates the ASTNode for a println statement. 
    */ 
    private Statement createPrintlnAst(String message) {
        return new ExpressionStatement(
            new MethodCallExpression(
                new VariableExpression("this"),
                new ConstantExpression("println"),
                new ArgumentListExpression(
                    new ConstantExpression(message)
                )
            )
        )
    }
}