Groovy example source code file (MixinASTTransformation.java)

This example Groovy source code file (MixinASTTransformation.java) 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

annotatednode, annotatednode, annotationnode, annotationnode, blockstatement, blockstatement, classexpression, classnode, classnode, expression, listexpression, mixinasttransformation, parameter, propertyexpression, util

The Groovy MixinASTTransformation.java source code

/*
 * Copyright 2008 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
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.codehaus.groovy.ast;

import groovy.lang.Mixin;
import org.codehaus.groovy.ast.expr.*;
import org.codehaus.groovy.ast.stmt.BlockStatement;
import org.codehaus.groovy.ast.stmt.ExpressionStatement;
import org.codehaus.groovy.control.CompilePhase;
import org.codehaus.groovy.control.SourceUnit;
import org.codehaus.groovy.transform.ASTTransformation;
import org.codehaus.groovy.transform.GroovyASTTransformation;
import org.objectweb.asm.Opcodes;

import java.util.Arrays;

@GroovyASTTransformation(phase = CompilePhase.CANONICALIZATION)
public class MixinASTTransformation implements ASTTransformation {
    private static final ClassNode MY_TYPE = ClassHelper.make(Mixin.class);

    // TODO would it be better to actually statically mixin the methods?
    public void visit(ASTNode nodes[], SourceUnit source) {
        if (nodes.length != 2 || !(nodes[0] instanceof AnnotationNode) || !(nodes[1] instanceof AnnotatedNode)) {
            throw new RuntimeException("Internal error: expecting [AnnotationNode, AnnotatedNode] but got: " + Arrays.asList(nodes));
        }
        AnnotationNode node = (AnnotationNode) nodes[0];
        AnnotatedNode parent = (AnnotatedNode) nodes[1];

        if (!MY_TYPE.equals(node.getClassNode()))
            return;

        final Expression expr = node.getMember("value");
        if (expr == null) {
            return;
        }

        Expression useClasses = null;
        if (expr instanceof ClassExpression) {
            useClasses = expr;
        } else if (expr instanceof ListExpression) {
            ListExpression listExpression = (ListExpression) expr;
            for (Expression ex : listExpression.getExpressions()) {
                if (!(ex instanceof ClassExpression))
                    return;
            }
            useClasses = expr;
        }

        if (useClasses == null)
            return;

        if (parent instanceof ClassNode) {
            ClassNode annotatedClass = (ClassNode) parent;

            final Parameter[] noparams = new Parameter[0];
            MethodNode clinit = annotatedClass.getDeclaredMethod("<clinit>", noparams);
            if (clinit == null) {
                clinit = annotatedClass.addMethod("<clinit>", Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC | Opcodes.ACC_SYNTHETIC, ClassHelper.VOID_TYPE, noparams, null, new BlockStatement());
                clinit.setSynthetic(true);
            }

            final BlockStatement code = (BlockStatement) clinit.getCode();
            code.addStatement(
                    new ExpressionStatement(
                            new MethodCallExpression(
                                    new PropertyExpression(new ClassExpression(annotatedClass), "metaClass"),
                                    "mixin",
                                    useClasses
                            )
                    )
            );
        }
    }
}