Groovy example source code file (ClosureWriter.java)

This example Groovy source code file (ClosureWriter.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

acc_public, classnode, classnode, fieldnode, innerclassnode, innerclassnode, parameter, parameter, string, string, tupleexpression, util, variable, variableexpression, variablescope

The Groovy ClosureWriter.java source code

/*
 * Copyright 2003-2009 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.classgen.asm;

import java.util.HashMap;
import java.util.Iterator;
import java.util.List;

import org.codehaus.groovy.GroovyBugError;
import org.codehaus.groovy.ast.ASTNode;
import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.CodeVisitorSupport;
import org.codehaus.groovy.ast.ConstructorNode;
import org.codehaus.groovy.ast.FieldNode;
import org.codehaus.groovy.ast.InnerClassNode;
import org.codehaus.groovy.ast.MethodNode;
import org.codehaus.groovy.ast.Parameter;
import org.codehaus.groovy.ast.Variable;
import org.codehaus.groovy.ast.VariableScope;
import org.codehaus.groovy.ast.expr.ArgumentListExpression;
import org.codehaus.groovy.ast.expr.ClassExpression;
import org.codehaus.groovy.ast.expr.ClosureExpression;
import org.codehaus.groovy.ast.expr.ConstantExpression;
import org.codehaus.groovy.ast.expr.ConstructorCallExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.expr.FieldExpression;
import org.codehaus.groovy.ast.expr.MethodCallExpression;
import org.codehaus.groovy.ast.expr.TupleExpression;
import org.codehaus.groovy.ast.expr.VariableExpression;
import org.codehaus.groovy.ast.stmt.BlockStatement;
import org.codehaus.groovy.ast.stmt.ExpressionStatement;
import org.codehaus.groovy.ast.stmt.ReturnStatement;
import org.codehaus.groovy.classgen.AsmClassGenerator;
import org.codehaus.groovy.classgen.Verifier;
import org.objectweb.asm.MethodVisitor;

import static org.objectweb.asm.Opcodes.*;

public class ClosureWriter {
    
    protected interface UseExistingReference {}

    private HashMap<Expression,ClassNode> closureClassMap;
    private WriterController controller;
    
    public ClosureWriter(WriterController wc) {
        this.controller = wc;
        closureClassMap = new HashMap<Expression,ClassNode>();
    }

    public void writeClosure(ClosureExpression expression) {
        CompileStack compileStack = controller.getCompileStack();
        MethodVisitor mv = controller.getMethodVisitor();
        ClassNode classNode = controller.getClassNode();
        AsmClassGenerator acg = controller.getAcg();
        
        ClassNode closureClass = getOrAddClosureClass(expression, 0);
        String closureClassinternalName = BytecodeHelper.getClassInternalName(closureClass);
        List constructors = closureClass.getDeclaredConstructors();
        ConstructorNode node = (ConstructorNode) constructors.get(0);

        Parameter[] localVariableParams = node.getParameters();

        mv.visitTypeInsn(NEW, closureClassinternalName);
        mv.visitInsn(DUP);
        if (controller.isStaticMethod() || compileStack.isInSpecialConstructorCall()) {
            (new ClassExpression(classNode)).visit(acg);
            (new ClassExpression(controller.getOutermostClass())).visit(acg);
        } else {
            mv.visitVarInsn(ALOAD, 0);
            controller.getOperandStack().push(ClassHelper.OBJECT_TYPE);
            loadThis();
        }

        // now let's load the various parameters we're passing
        // we start at index 2 because the first variable we pass
        // is the owner instance and at this point it is already
        // on the stack
        for (int i = 2; i < localVariableParams.length; i++) {
            Parameter param = localVariableParams[i];
            String name = param.getName();

            // compileStack.containsVariable(name) means to ask if the variable is already declared
            // compileStack.getScope().isReferencedClassVariable(name) means to ask if the variable is a field
            // If it is no field and is not yet declared, then it is either a closure shared variable or
            // an already declared variable.
            if (!compileStack.containsVariable(name) && compileStack.getScope().isReferencedClassVariable(name)) {
                acg.visitFieldExpression(new FieldExpression(classNode.getDeclaredField(name)));
            } else {
                BytecodeVariable v = compileStack.getVariable(name, !classNodeUsesReferences());
                if (v == null) {
                    // variable is not on stack because we are
                    // inside a nested Closure and this variable
                    // was not used before
                    // then load it from the Closure field
                    FieldNode field = classNode.getDeclaredField(name);
                    mv.visitVarInsn(ALOAD, 0);
                    mv.visitFieldInsn(GETFIELD, controller.getInternalClassName(), name, BytecodeHelper.getTypeDescription(field.getType()));
                } else {
                    mv.visitVarInsn(ALOAD, v.getIndex());
                }
                if (param.getNodeMetaData(ClosureWriter.UseExistingReference.class)==null) {
                        param.setNodeMetaData(ClosureWriter.UseExistingReference.class,Boolean.TRUE);
                }
                controller.getOperandStack().push(ClassHelper.REFERENCE_TYPE);
            }
        }

        // we may need to pass in some other constructors
        //cv.visitMethodInsn(INVOKESPECIAL, innerClassinternalName, "<init>", prototype + ")V");
        mv.visitMethodInsn(
                INVOKESPECIAL,
                closureClassinternalName,
                "<init>",
                BytecodeHelper.getMethodDescriptor(ClassHelper.VOID_TYPE, localVariableParams));
        controller.getOperandStack().replace(ClassHelper.CLOSURE_TYPE, localVariableParams.length);
    }

    public ClassNode getOrAddClosureClass(ClosureExpression expression, int mods) {
        ClassNode closureClass = closureClassMap.get(expression);
        if (closureClass == null) {
            closureClass = createClosureClass(expression, mods);
            closureClassMap.put(expression, closureClass);
            controller.getAcg().addInnerClass(closureClass);
            closureClass.addInterface(ClassHelper.GENERATED_CLOSURE_Type);
        }
        return closureClass;
    }

    private boolean classNodeUsesReferences() {
        ClassNode classNode = controller.getClassNode();
        boolean ret = classNode.getSuperClass() == ClassHelper.CLOSURE_TYPE;
        if (ret) return ret;
        if (classNode instanceof InnerClassNode) {
            InnerClassNode inner = (InnerClassNode) classNode;
            return inner.isAnonymous();
        }
        return false;
    }
    
    private ClassNode createClosureClass(ClosureExpression expression, int mods) {
        ClassNode classNode = controller.getClassNode();
        ClassNode outerClass = controller.getOutermostClass();
        MethodNode methodNode = controller.getMethodNode();
        String name = outerClass.getName() + "$"
                + controller.getContext().getNextClosureInnerName(outerClass, classNode, methodNode); // add a more informative name
        boolean staticMethodOrInStaticClass = controller.isStaticMethod() || classNode.isStaticClass();

        Parameter[] parameters = expression.getParameters();
        if (parameters == null) {
            parameters = Parameter.EMPTY_ARRAY;
        } else if (parameters.length == 0) {
            // let's create a default 'it' parameter
            Parameter it = new Parameter(ClassHelper.OBJECT_TYPE, "it", ConstantExpression.NULL);
            parameters = new Parameter[]{it};
            Variable ref = expression.getVariableScope().getDeclaredVariable("it");
            if (ref!=null) it.setClosureSharedVariable(ref.isClosureSharedVariable());
        }

        Parameter[] localVariableParams = getClosureSharedVariables(expression);
        removeInitialValues(localVariableParams);

        InnerClassNode answer = new InnerClassNode(classNode, name, mods, ClassHelper.CLOSURE_TYPE); // closures are local inners and not public
        answer.setEnclosingMethod(controller.getMethodNode());
        answer.setSynthetic(true);
        answer.setUsingGenerics(outerClass.isUsingGenerics());
        answer.setSourcePosition(expression);

        if (staticMethodOrInStaticClass) {
            answer.setStaticClass(true);
        }
        if (controller.isInScriptBody()) {
            answer.setScriptBody(true);
        }
        MethodNode method =
                answer.addMethod("doCall", ACC_PUBLIC, ClassHelper.OBJECT_TYPE, parameters, ClassNode.EMPTY_ARRAY, expression.getCode());
        method.setSourcePosition(expression);

        VariableScope varScope = expression.getVariableScope();
        if (varScope == null) {
            throw new RuntimeException(
                    "Must have a VariableScope by now! for expression: " + expression + " class: " + name);
        } else {
            method.setVariableScope(varScope.copy());
        }
        if (parameters.length > 1
                || (parameters.length == 1
                && parameters[0].getType() != null
                && parameters[0].getType() != ClassHelper.OBJECT_TYPE)) {

            // let's add a typesafe call method
            MethodNode call = answer.addMethod(
                    "call",
                    ACC_PUBLIC,
                    ClassHelper.OBJECT_TYPE,
                    parameters,
                    ClassNode.EMPTY_ARRAY,
                    new ReturnStatement(
                            new MethodCallExpression(
                                    VariableExpression.THIS_EXPRESSION,
                                    "doCall",
                                    new ArgumentListExpression(parameters))));
            call.setSourcePosition(expression);
        }

        // let's make the constructor
        BlockStatement block = new BlockStatement();
        // this block does not get a source position, because we don't
        // want this synthetic constructor to show up in corbertura reports
        VariableExpression outer = new VariableExpression("_outerInstance");
        outer.setSourcePosition(expression);
        block.getVariableScope().putReferencedLocalVariable(outer);
        VariableExpression thisObject = new VariableExpression("_thisObject");
        thisObject.setSourcePosition(expression);
        block.getVariableScope().putReferencedLocalVariable(thisObject);
        TupleExpression conArgs = new TupleExpression(outer, thisObject);
        block.addStatement(
                new ExpressionStatement(
                        new ConstructorCallExpression(
                                ClassNode.SUPER,
                                conArgs)));

        // let's assign all the parameter fields from the outer context
        for (Parameter param : localVariableParams) {
            String paramName = param.getName();
            ClassNode type = param.getType();
            if (true) {
                VariableExpression initialValue = new VariableExpression(paramName);
                initialValue.setAccessedVariable(param);
                initialValue.setUseReferenceDirectly(true);
                ClassNode realType = type;
                type = ClassHelper.makeReference();
                param.setType(ClassHelper.makeReference());
                FieldNode paramField = answer.addField(paramName, ACC_PRIVATE | ACC_SYNTHETIC, type, initialValue);
                paramField.setOriginType(ClassHelper.getWrapper(param.getOriginType()));
                paramField.setHolder(true);
                String methodName = Verifier.capitalize(paramName);

                // let's add a getter & setter
                Expression fieldExp = new FieldExpression(paramField);
                answer.addMethod(
                        "get" + methodName,
                        ACC_PUBLIC,
                        realType,
                        Parameter.EMPTY_ARRAY,
                        ClassNode.EMPTY_ARRAY,
                        new ReturnStatement(fieldExp));
            }
        }

        Parameter[] params = new Parameter[2 + localVariableParams.length];
        params[0] = new Parameter(ClassHelper.OBJECT_TYPE, "_outerInstance");
        params[1] = new Parameter(ClassHelper.OBJECT_TYPE, "_thisObject");
        System.arraycopy(localVariableParams, 0, params, 2, localVariableParams.length);

        ASTNode sn = answer.addConstructor(ACC_PUBLIC, params, ClassNode.EMPTY_ARRAY, block);
        sn.setSourcePosition(expression);
        
        correctAccessedVariable(answer,expression);
        
        return answer;
    }

    private void correctAccessedVariable(final InnerClassNode closureClass, ClosureExpression ce) {
        CodeVisitorSupport visitor = new CodeVisitorSupport() {
            @Override
            public void visitVariableExpression(VariableExpression expression) {
                Variable v = expression.getAccessedVariable(); 
                if (v==null) return;
                if (!(v instanceof FieldNode)) return;
                String name = expression.getName();
                FieldNode fn = closureClass.getDeclaredField(name);
                if (fn != null) { // only overwrite if we find something more specific
                    expression.setAccessedVariable(fn);
                }
            }  
        };
        visitor.visitClosureExpression(ce);
    }

    /*
     * this method is called for local variables shared between scopes.
     * These variables must not have init values because these would
     * then in later steps be used to create multiple versions of the
     * same method, in this case the constructor. A closure should not
     * have more than one constructor!
     */
    private void removeInitialValues(Parameter[] params) {
        for (int i = 0; i < params.length; i++) {
            if (params[i].hasInitialExpression()) {
                Parameter p = new Parameter(params[i].getType(), params[i].getName());
                p.setOriginType(p.getOriginType());
                params[i] = p;
            }
        }
    }

    public boolean addGeneratedClosureConstructorCall(ConstructorCallExpression call) {
        ClassNode classNode = controller.getClassNode();
        if (!classNode.declaresInterface(ClassHelper.GENERATED_CLOSURE_Type)) return false;

        AsmClassGenerator acg = controller.getAcg();
        OperandStack operandStack = controller.getOperandStack();
        
        MethodVisitor mv = controller.getMethodVisitor();
        mv.visitVarInsn(ALOAD, 0);
        ClassNode callNode = classNode.getSuperClass();
        TupleExpression arguments = (TupleExpression) call.getArguments();
        if (arguments.getExpressions().size()!=2) throw new GroovyBugError("expected 2 arguments for closure constructor super call, but got"+arguments.getExpressions().size());
        arguments.getExpression(0).visit(acg);
        operandStack.box();
        arguments.getExpression(1).visit(acg);
        operandStack.box();
        //TODO: replace with normal String, p not needed
        Parameter p = new Parameter(ClassHelper.OBJECT_TYPE,"_p");
        String descriptor = BytecodeHelper.getMethodDescriptor(ClassHelper.VOID_TYPE, new Parameter[]{p,p});
        mv.visitMethodInsn(INVOKESPECIAL, BytecodeHelper.getClassInternalName(callNode), "<init>", descriptor);
        operandStack.remove(2);
        return true;
    }

    protected Parameter[] getClosureSharedVariables(ClosureExpression ce) {
        VariableScope scope = ce.getVariableScope();
        Parameter[] ret = new Parameter[scope.getReferencedLocalVariablesCount()];
        int index = 0;
        for (Iterator iter = scope.getReferencedLocalVariablesIterator(); iter.hasNext();) {
            Variable element = (org.codehaus.groovy.ast.Variable) iter.next();
            Parameter p = new Parameter(element.getType(), element.getName());
            p.setOriginType(element.getOriginType());
            p.setClosureSharedVariable(element.isClosureSharedVariable());
            ret[index] = p;
            index++;
        }
        return ret;
    }
    
    private void loadThis() {
        MethodVisitor mv = controller.getMethodVisitor();
        mv.visitVarInsn(ALOAD, 0);
        if (controller.isInClosure()) {
            mv.visitMethodInsn(
                    INVOKEVIRTUAL,
                    "groovy/lang/Closure",
                    "getThisObject",
                    "()Ljava/lang/Object;"
            );
            controller.getOperandStack().push(ClassHelper.OBJECT_TYPE);
        } else {
            controller.getOperandStack().push(controller.getClassNode());
        }
    }
}