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Groovy example source code file (AbstractInterruptibleASTTransformation.java)

This example Groovy source code file (AbstractInterruptibleASTTransformation.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, expecting, expecting, expression, found, found, override, sourceunit, statement, string, string, util

The Groovy AbstractInterruptibleASTTransformation.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 org.codehaus.groovy.GroovyBugError;
import org.codehaus.groovy.ast.*;
import org.codehaus.groovy.ast.expr.*;
import org.codehaus.groovy.ast.stmt.*;
import org.codehaus.groovy.control.SourceUnit;
import org.codehaus.groovy.runtime.DefaultGroovyMethods;
import org.objectweb.asm.Opcodes;

import java.util.Arrays;
import java.util.List;

/**
 * Base class for AST Transformations which will automatically throw an {@link InterruptedException} when
 * some conditions are met.
 *
 * @author Cedric Champeau
 * @author Hamlet D'Arcy
 * @since 1.8.0
 */
public abstract class AbstractInterruptibleASTTransformation extends ClassCodeVisitorSupport implements ASTTransformation, Opcodes {

    protected static final String CHECK_METHOD_START_MEMBER = "checkOnMethodStart";
    protected static final String PROPAGATE_TO_COMPILE_UNIT = "applyToAllClasses";
    protected static final String THROWN_EXCEPTION_TYPE = "thrown";
    protected SourceUnit source;
    protected boolean checkOnMethodStart;
    protected boolean applyToAllClasses;
    protected ClassNode thrownExceptionType;

    protected SourceUnit getSourceUnit() {
        return source;
    }

    protected abstract ClassNode type();

    /**
     * Subclasses should implement this method to set the condition of the interruption statement
     */
    protected abstract Expression createCondition();

    /**
     * Subclasses should implement this method to provide good error resolution. 
     */
    protected abstract String getErrorMessage();

    protected void setupTransform(AnnotationNode node) {
        checkOnMethodStart = getBooleanAnnotationParameter(node, CHECK_METHOD_START_MEMBER, true);
        applyToAllClasses = getBooleanAnnotationParameter(node, PROPAGATE_TO_COMPILE_UNIT, true);
        thrownExceptionType = getClassAnnotationParameter(node, THROWN_EXCEPTION_TYPE, ClassHelper.make(InterruptedException.class));
    }

    public void visit(ASTNode[] nodes, SourceUnit source) {
        if (nodes.length != 2 || !(nodes[0] instanceof AnnotationNode) || !(nodes[1] instanceof AnnotatedNode)) {
            internalError("Expecting [AnnotationNode, AnnotatedClass] but got: " + Arrays.asList(nodes));
        }

        this.source = source;
        AnnotationNode node = (AnnotationNode) nodes[0];
        AnnotatedNode annotatedNode = (AnnotatedNode) nodes[1];

        if (!type().equals(node.getClassNode())) {
            internalError("Transformation called from wrong annotation: " + node.getClassNode().getName());
        }

        setupTransform(node);

        // should be limited to the current SourceUnit or propagated to the whole CompilationUnit
        final ModuleNode tree = source.getAST();
        if (applyToAllClasses) {
            // guard every class and method defined in this script
            if (tree != null) {
                final List<ClassNode> classes = tree.getClasses();
                for (ClassNode classNode : classes) {
                    visitClass(classNode);
                }
            }
        } else if (annotatedNode instanceof ClassNode) {
            // only guard this particular class
            this.visitClass((ClassNode) annotatedNode);
        } else {
            // only guard the script class
            if (tree != null) {
                final List<ClassNode> classes = tree.getClasses();
                for (ClassNode classNode : classes) {
                    if (classNode.isScript()) {
                        visitClass(classNode);
                    }
                }
            }
        }
    }


    protected static boolean getBooleanAnnotationParameter(AnnotationNode node, String parameterName, boolean defaultValue) {
        Expression member = node.getMember(parameterName);
        if (member != null) {
            if (member instanceof ConstantExpression) {
                try {
                    return DefaultGroovyMethods.asType(((ConstantExpression) member).getValue(), Boolean.class);
                } catch (Exception e) {
                    internalError("Expecting boolean value for " + parameterName + " annotation parameter. Found " + member + "member");
                }
            } else {
                internalError("Expecting boolean value for " + parameterName + " annotation parameter. Found " + member + "member");
            }
        }
        return defaultValue;
    }

    protected static ClassNode getClassAnnotationParameter(AnnotationNode node, String parameterName, ClassNode defaultValue) {
        Expression member = node.getMember(parameterName);
        if (member != null) {
            if (member instanceof ClassExpression) {
                try {
                    return member.getType();
                } catch (Exception e) {
                    internalError("Expecting class value for " + parameterName + " annotation parameter. Found " + member + "member");
                }
            } else {
                internalError("Expecting class value for " + parameterName + " annotation parameter. Found " + member + "member");
            }
        }
        return defaultValue;
    }

    protected static void internalError(String message) {
        throw new GroovyBugError("Internal error: " + message);
    }

    /**
     * @return Returns the interruption check statement.
     */
    protected Statement createInterruptStatement() {
        return new IfStatement(
                new BooleanExpression(
                        createCondition()
                ),
                new ThrowStatement(
                        new ConstructorCallExpression(thrownExceptionType,
                                new ArgumentListExpression(new ConstantExpression(getErrorMessage())))
                ),
                new EmptyStatement()
        );
    }

    /**
     * Takes a statement and wraps it into a block statement which first element is the interruption check statement.
     *
     * @param statement the statement to be wrapped
     * @return a {@link BlockStatement block statement}   which first element is for checking interruption, and the
     *         second one the statement to be wrapped.
     */
    protected final Statement wrapBlock(Statement statement) {
        BlockStatement stmt = new BlockStatement();
        stmt.addStatement(createInterruptStatement());
        stmt.addStatement(statement);
        return stmt;
    }

    @Override
    public final void visitForLoop(ForStatement forStatement) {
        visitLoop(forStatement);
        super.visitForLoop(forStatement); 
    }

    /**
     * Shortcut method which avoids duplicating code for every type of loop.
     * Actually wraps the loopBlock of different types of loop statements.
     */
    private void visitLoop(LoopingStatement loopStatement) {
        Statement statement = loopStatement.getLoopBlock();
        loopStatement.setLoopBlock(wrapBlock(statement));
    }

    @Override
    public final void visitDoWhileLoop(DoWhileStatement doWhileStatement) {
        visitLoop(doWhileStatement); 
        super.visitDoWhileLoop(doWhileStatement);
    }

    @Override
    public final void visitWhileLoop(WhileStatement whileStatement) {
        visitLoop(whileStatement);
        super.visitWhileLoop(whileStatement);
    }
}

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