org.inferred.freebuilder.processor.MethodFinder.java Source code

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Here is the source code for org.inferred.freebuilder.processor.MethodFinder.java

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/*
 * Copyright 2014 Google Inc. All rights reserved.
 *
 * 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.inferred.freebuilder.processor;

import static javax.lang.model.util.ElementFilter.methodsIn;

import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;

import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.Name;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.type.TypeKind;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.Elements;

import org.inferred.freebuilder.processor.Analyser.CannotGenerateCodeException;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.LinkedHashMultimap;
import com.google.common.collect.SetMultimap;

/**
 * Static utility method for finding all methods, declared and inherited, on a type.
 */
public class MethodFinder {

    /**
     * Returns all methods, declared and inherited, on {@code type}, except those specified by
     * {@link Object}.
     *
     * <p>If method B overrides method A, only method B will be included in the return set.
     * Additionally, if methods A and B have the same signature, but are on unrelated interfaces,
     * one will be arbitrarily picked to be returned.
     */
    public static ImmutableSet<ExecutableElement> methodsOn(TypeElement type, Elements elements)
            throws CannotGenerateCodeException {
        TypeElement objectType = elements.getTypeElement(Object.class.getCanonicalName());
        SetMultimap<Signature, ExecutableElement> methods = LinkedHashMultimap.create();
        for (TypeElement supertype : getSupertypes(type)) {
            for (ExecutableElement method : methodsIn(supertype.getEnclosedElements())) {
                if (method.getEnclosingElement().equals(objectType)) {
                    continue; // Skip methods specified by Object.
                }
                Signature signature = new Signature(method);
                Iterator<ExecutableElement> iterator = methods.get(signature).iterator();
                while (iterator.hasNext()) {
                    ExecutableElement otherMethod = iterator.next();
                    if (elements.overrides(method, otherMethod, type)
                            || method.getParameters().equals(otherMethod.getParameters())) {
                        iterator.remove();
                    }
                }
                methods.put(signature, method);
            }
        }
        return ImmutableSet.copyOf(methods.values());
    }

    private static ImmutableSet<TypeElement> getSupertypes(TypeElement type) throws CannotGenerateCodeException {
        Set<TypeElement> supertypes = new LinkedHashSet<TypeElement>();
        addSupertypesToSet(type, supertypes);
        return ImmutableSet.copyOf(supertypes);
    }

    private static void addSupertypesToSet(TypeElement type, Set<TypeElement> mutableSet)
            throws CannotGenerateCodeException {
        for (TypeMirror iface : type.getInterfaces()) {
            addSupertypesToSet(asTypeElement(iface), mutableSet);
        }
        if (type.getSuperclass().getKind() != TypeKind.NONE) {
            addSupertypesToSet(asTypeElement(type.getSuperclass()), mutableSet);
        }
        mutableSet.add(type);
    }

    private static TypeElement asTypeElement(TypeMirror iface) throws CannotGenerateCodeException {
        if (iface.getKind() != TypeKind.DECLARED) {
            throw new CannotGenerateCodeException();
        }
        Element element = ((DeclaredType) iface).asElement();
        if (!(element.getKind().isClass() || element.getKind().isInterface())) {
            throw new CannotGenerateCodeException();
        }
        return (TypeElement) element;
    }

    /**
     * Key type. Two methods with different {@code Signature}s will never return true when passed to
     * {@link Elements#overrides}.
     */
    private static class Signature {
        final Name name;
        final int params;

        Signature(ExecutableElement method) {
            name = method.getSimpleName();
            params = method.getParameters().size();
        }

        @Override
        public int hashCode() {
            return name.hashCode() * 31 + params;
        }

        @Override
        public boolean equals(Object obj) {
            if (!(obj instanceof Signature)) {
                return false;
            }
            Signature other = (Signature) obj;
            return (name.equals(other.name) && params == other.params);
        }
    }

    private MethodFinder() {
    }
}