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Groovy example source code file (GenericsVisitor.java)

This example Groovy source code file (GenericsVisitor.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

a, classcodevisitorsupport, classnode, classnode, genericstype, genericstype, genericsvisitor, parameter, sourceunit, string, string, the, the

The Groovy GenericsVisitor.java source code

/*
 * Copyright 2003-2007 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.control;

import org.codehaus.groovy.ast.ClassCodeVisitorSupport;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.FieldNode;
import org.codehaus.groovy.ast.GenericsType;
import org.codehaus.groovy.ast.MethodNode;
import org.codehaus.groovy.ast.Parameter;

/**
 * class used to verify correct usage of generics in 
 * class header (class and superclass declaration) 
 * @author Jochen Theodorou
 */
public class GenericsVisitor extends ClassCodeVisitorSupport {
    private SourceUnit source;
    
    public GenericsVisitor(SourceUnit source) {
        this.source = source;
    }
    
    protected SourceUnit getSourceUnit() {
        return source;
    }
    
    public void visitClass(ClassNode node) {
        boolean error=checkWildcard(node);
        if (error) return;
        checkGenericsUsage(node.getUnresolvedSuperClass(false), node.getSuperClass());
        ClassNode[] interfaces = node.getInterfaces();
        for (int i = 0; i < interfaces.length; i++) {
            checkGenericsUsage(interfaces[i], interfaces[i].redirect());
        }
        node.visitContents(this);
    }
    
    public void visitField(FieldNode node) {
        ClassNode type = node.getType();
        checkGenericsUsage(type, type.redirect());
    }
    
    public void visitMethod(MethodNode node) {
        Parameter[] parameters = node.getParameters();
        for (Parameter param : parameters) {
            ClassNode paramType = param.getType();
            checkGenericsUsage(paramType, paramType.redirect());
        }
        ClassNode returnType = node.getReturnType();
        checkGenericsUsage(returnType, returnType.redirect());
    }
    
    private boolean checkWildcard(ClassNode cn) {
        ClassNode sn = cn.getUnresolvedSuperClass(false);
        if (sn==null) return false;
        GenericsType[] generics = sn.getGenericsTypes();
        if (generics==null) return false;
        boolean error=false;
        for (int i = 0; i < generics.length; i++) {
            if(generics[i].isWildcard()) {
                addError("A supertype may not specify a wildcard type",sn);
                error = true;
            }
        }
        return error;
    }

    private void checkGenericsUsage(ClassNode n, ClassNode cn) {
        if(n.isGenericsPlaceHolder()) return;
        GenericsType[] nTypes = n.getGenericsTypes();
        GenericsType[] cnTypes = cn.getGenericsTypes();
        // raw type usage is always allowed
        if (nTypes==null) return;
        // parameterize a type by using all of the parameters only
        if (cnTypes==null) {
            addError( "The class "+n.getName()+" refers to the class "+
                      cn.getName()+" and uses "+nTypes.length+
                      " parameters, but the referred class takes no parameters", n);
            return;
        }
        if (nTypes.length!=cnTypes.length) {
            addError( "The class "+n.getName()+" refers to the class "+
                      cn.getName()+" and uses "+nTypes.length+
                      " parameters, but the referred class needs "+
                      cnTypes.length, n);
            return;
        }
        // check bounds
        for (int i=0; i<nTypes.length; i++) {
            ClassNode nType = nTypes[i].getType();
            ClassNode cnType = cnTypes[i].getType();
            if (!nType.isDerivedFrom(cnType)) {
                if (cnType.isInterface() && nType.declaresInterface(cnType)) continue;
                addError("The type "+nTypes[i].getName()+
                         " is not a valid substitute for the bounded parameter <"+
                         getPrintName(cnTypes[i])+">",n);
            }
        }
    }
    
    private String getPrintName(GenericsType gt) {
        String ret = gt.getName();
        ClassNode[] upperBounds = gt.getUpperBounds();
        ClassNode lowerBound = gt.getLowerBound();
        if (upperBounds!=null) {
            ret += " extends ";
            for (int i = 0; i < upperBounds.length; i++) {
                ret += getPrintName(upperBounds[i]);
                if (i+1<upperBounds.length) ret += " & ";
            }
        } else if (lowerBound!=null) {
            ret += " super "+getPrintName(lowerBound);
        }
        return ret;

    }
    
    private String getPrintName(ClassNode cn) {
        String ret = cn.getName();
        GenericsType[] gts = cn.getGenericsTypes();
        if (gts!=null) {
            ret += "<";
            for (int i = 0; i < gts.length; i++) {
                if (i!=0) ret+=",";
                ret+=getPrintName(gts[i]);
            } 
            ret+=">";
        }
        return ret;
    }
    
    private void checkBounds(ClassNode[] given, ClassNode[] restrictions) {
        if (restrictions==null) return;
        for (int i=0; i<given.length; i++) {
            for (int j=0; j<restrictions.length; j++) {
                if (! given[i].isDerivedFrom(restrictions[j])){}
            }
        }
    }
}

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