Groovy example source code file (ReadWriteLockASTTransformation.java)

This example Groovy source code file (ReadWriteLockASTTransformation.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, classnode, constantexpression, error, methodcallexpression, methodcallexpression, methodnode, reentrantlock, runtimeexception, runtimeexception, string, string, util

The Groovy ReadWriteLockASTTransformation.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.WithReadLock;
import groovy.transform.WithWriteLock;
import org.codehaus.groovy.ast.*;
import org.codehaus.groovy.ast.expr.*;
import org.codehaus.groovy.ast.stmt.*;
import org.codehaus.groovy.control.CompilePhase;
import org.codehaus.groovy.control.SourceUnit;
import org.codehaus.groovy.syntax.Token;
import org.objectweb.asm.Opcodes;

import java.util.Arrays;
import java.util.concurrent.locks.ReentrantReadWriteLock;


/**
 * Handles generation of code for the {@code @}WithReadLock and {@code @}WithWriteLock annotation. <br/>
 * This transformation adds an instance of ReentrantReadWriteLock to the class. <br/>
 * Any method annotated with @WithReadLock will obtain a read lock and release it in a finally block.<br/>
 * Any method annotated with @WithWriteLock will obtain a write lock and release it in a finally block.<br/>
 * For more information see {@link WithReadLock} and {@link WithWriteLock}<br/>
 * @author Hamlet D'Arcy
 */
@GroovyASTTransformation(phase = CompilePhase.CANONICALIZATION)
public class ReadWriteLockASTTransformation implements ASTTransformation, Opcodes {

    private static final ClassNode READ_LOCK_TYPE = ClassHelper.make(WithReadLock.class);
    private static final ClassNode WRITE_LOCK_TYPE = ClassHelper.make(WithWriteLock.class);
    private static final ClassNode LOCK_TYPE = ClassHelper.make(ReentrantReadWriteLock.class);
    private static final Token ASSIGN = Token.newSymbol("=", -1, -1);

    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];
        final boolean isWriteLock;
        if (READ_LOCK_TYPE.equals(node.getClassNode())) {
            isWriteLock = false;
        } else if (WRITE_LOCK_TYPE.equals(node.getClassNode())) {
            isWriteLock = true;
        } else {
            throw new RuntimeException("Internal error: expecting [" + READ_LOCK_TYPE.getName() + ", " + WRITE_LOCK_TYPE.getName() + "]" + " but got: " + node.getClassNode().getName());
        }

        String myTypeName = "@" + node.getClassNode().getNameWithoutPackage();

        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(), myTypeName);

            // get lock type
            final Expression lockType;
            if (isWriteLock) {
                lockType = new MethodCallExpression(new VariableExpression(lockExpr), "writeLock", ArgumentListExpression.EMPTY_ARGUMENTS);
            } else {
                lockType = new MethodCallExpression(new VariableExpression(lockExpr), "readLock", ArgumentListExpression.EMPTY_ARGUMENTS);
            }

            MethodCallExpression acquireLock = new MethodCallExpression(lockType, "lock", ArgumentListExpression.EMPTY_ARGUMENTS);
            MethodCallExpression releaseLock = new MethodCallExpression(lockType, "unlock", ArgumentListExpression.EMPTY_ARGUMENTS);
            Statement originalCode = mNode.getCode();

            BlockStatement body = new BlockStatement();
            body.addStatement(new ExpressionStatement(acquireLock));
            body.addStatement(new TryCatchStatement(originalCode, new ExpressionStatement(releaseLock)));
            mNode.setCode(body);
        }
    }

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

    private Expression createLockObject() {
        return new ConstructorCallExpression(LOCK_TYPE, MethodCallExpression.NO_ARGUMENTS);
    }
}