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Groovy example source code file (

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

Java - Groovy tags/keywords

annotation, argumentlistexpression, argumentlistexpression, attributeexpression, classexpression, classnode, classnode, expression, javautilloggingstrategy, loggingstrategy, methodcallexpression, methodcallexpression, string, string, target

The Groovy source code

 * Copyright 2003-2010 the original author or authors.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package groovy.util.logging;

import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.FieldNode;
import org.codehaus.groovy.ast.expr.*;
import org.codehaus.groovy.transform.GroovyASTTransformationClass;
import org.codehaus.groovy.transform.LogASTTransformation.LoggingStrategy;
import org.objectweb.asm.Opcodes;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

 * This local transform adds a logging ability to your program using
 * java.util.logging. Every method call on a unbound variable named <i>log
 * will be mapped to a call to the logger. For this a <i>log field will be
 * inserted in the class. If the field already exists the usage of this transform
 * will cause a compilation error. The method name will be used to determine
 * what to call on the logger.
 * <pre>
 * </pre>is mapped to
 * <pre>
 * if (log.isLoggable(Level.NAME) {
 * }</pre>
 * Here name is a place holder for info, fine, finer, finest, config, warning, severe.
 * NAME is name transformed to upper case. if anything else is used it will result in
 * an exception at runtime. If the expression exp is a constant or only a variable access
 * the method call will not be transformed. But this will still cause a call on the injected
 * logger.
 * @author Guillaume Laforge
 * @author Jochen Theodorou
 * @author Dinko Srkoc
 * @author Hamlet D'Arcy
 * @author Raffaele Cigni
 * @author Alberto Vilches Raton
 * @since 1.8.0
public @interface Log {
    String value() default "log";
    Class<? extends LoggingStrategy> loggingStrategy() default JavaUtilLoggingStrategy.class;

     * This class contains the logic of how to weave a Java Util Logging logger into the host class.
    public static class JavaUtilLoggingStrategy implements LoggingStrategy {
        public FieldNode addLoggerFieldToClass(ClassNode classNode, String logFieldName) {
            return classNode.addField(logFieldName,
                        Opcodes.ACC_FINAL | Opcodes.ACC_TRANSIENT | Opcodes.ACC_STATIC | Opcodes.ACC_PRIVATE,
                        new ClassNode("java.util.logging.Logger", Opcodes.ACC_PUBLIC, ClassHelper.OBJECT_TYPE),
                        new MethodCallExpression(
                                new ClassExpression(new ClassNode("java.util.logging.Logger", Opcodes.ACC_PUBLIC, ClassHelper.OBJECT_TYPE)),
                                new ConstantExpression(classNode.getName())));

        public boolean isLoggingMethod(String methodName) {
            return methodName.matches("severe|warning|info|fine|finer|finest");

        public Expression wrapLoggingMethodCall(Expression logVariable, String methodName, Expression originalExpression) {
            ClassNode levelClass = new ClassNode("java.util.logging.Level", 0, ClassHelper.OBJECT_TYPE);
            AttributeExpression logLevelExpression = new AttributeExpression(
                    new ClassExpression(levelClass),
                    new ConstantExpression(methodName.toUpperCase()));

            ArgumentListExpression args = new ArgumentListExpression();
            MethodCallExpression condition = new MethodCallExpression(logVariable, "isLoggable", args);

            return new TernaryExpression(
                    new BooleanExpression(condition),


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