Groovy example source code file (SynchronizedASTTransformation.java)

This example Groovy source code file (SynchronizedASTTransformation.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, annotationnode, classnode, constantexpression, constantexpression, error, lock, lock, methodnode, my_type_name, my_type_name, runtimeexception, runtimeexception, string, util

The Groovy SynchronizedASTTransformation.java source code

/*
 * Copyright 2008-2010 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
 *
 *     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.transform;

import groovy.transform.Synchronized;
import org.codehaus.groovy.ast.*;
import org.codehaus.groovy.ast.expr.ArrayExpression;
import org.codehaus.groovy.ast.expr.ConstantExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.expr.VariableExpression;
import org.codehaus.groovy.ast.stmt.Statement;
import org.codehaus.groovy.ast.stmt.SynchronizedStatement;
import org.codehaus.groovy.control.CompilePhase;
import org.codehaus.groovy.control.SourceUnit;
import org.objectweb.asm.Opcodes;

import java.util.Arrays;


/**
 * Handles generation of code for the {@code @}Synchronized annotation.
 *
 * @author Paul King
 */
@GroovyASTTransformation(phase = CompilePhase.CANONICALIZATION)
public class SynchronizedASTTransformation implements ASTTransformation, Opcodes {

    private static final Class MY_CLASS = Synchronized.class;
    private static final ClassNode MY_TYPE = ClassHelper.make(MY_CLASS);
    private static final String MY_TYPE_NAME = "@" + MY_TYPE.getNameWithoutPackage();

    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));
        }

        AnnotatedNode parent = (AnnotatedNode) nodes[1];
        AnnotationNode node = (AnnotationNode) nodes[0];
        if (!MY_TYPE.equals(node.getClassNode())) return;
        Expression valueExpr = node.getMember("value");
        String value = null;
        if (valueExpr instanceof ConstantExpression) {
            ConstantExpression ce = (ConstantExpression) valueExpr;
            Object valueObject = ce.getValue();
            if (valueObject != null) value = valueObject.toString();
        }

        if (parent instanceof MethodNode) {
            MethodNode mNode = (MethodNode) parent;
            ClassNode cNode = mNode.getDeclaringClass();
            String lockExpr = determineLock(value, cNode, mNode.isStatic());
            Statement origCode = mNode.getCode();
            Statement newCode = new SynchronizedStatement(new VariableExpression(lockExpr), origCode);
            mNode.setCode(newCode);
        }
    }

    private String determineLock(String value, ClassNode cNode, boolean isStatic) {
        if (value != null && value.length() > 0 && !value.equalsIgnoreCase("$lock")) {
            if (cNode.getDeclaredField(value) == null) {
                throw new RuntimeException("Error during " + MY_TYPE_NAME + " processing: lock field with name '" + value + "' not found in class " + cNode.getName());
            }
            if (cNode.getDeclaredField(value).isStatic() != isStatic) {
                throw new RuntimeException("Error during " + MY_TYPE_NAME + " processing: lock field with name '" + value + "' should " + (isStatic ? "" : "not ") + "be static");
            }
            return value;
        }
        if (isStatic) {
            FieldNode field = cNode.getDeclaredField("$LOCK");
            if (field == null) {
                int visibility = ACC_PRIVATE | ACC_STATIC | ACC_FINAL;
                cNode.addField("$LOCK", visibility, ClassHelper.OBJECT_TYPE, zeroLengthObjectArray());
            } else if (!field.isStatic()) {
                throw new RuntimeException("Error during " + MY_TYPE_NAME + " processing: $LOCK field must be static");
            }
            return "$LOCK";
        }
        FieldNode field = cNode.getDeclaredField("$lock");
        if (field == null) {
            int visibility = ACC_PRIVATE | ACC_FINAL;
            cNode.addField("$lock", visibility, ClassHelper.OBJECT_TYPE, zeroLengthObjectArray());
        } else if (field.isStatic()) {
            throw new RuntimeException("Error during " + MY_TYPE_NAME + " processing: $lock field must not be static");
        }
        return "$lock";
    }

    private Expression zeroLengthObjectArray() {
        return new ArrayExpression(ClassHelper.OBJECT_TYPE, null, Arrays.asList((Expression)new ConstantExpression(0)));
    }

}