org.springframework.data.util.ClassTypeInformation.java Source code

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Here is the source code for org.springframework.data.util.ClassTypeInformation.java

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/*
 * Copyright 2011-2019 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
 *
 *      https://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.springframework.data.util;

import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.springframework.core.GenericTypeResolver;
import org.springframework.util.Assert;
import org.springframework.util.ConcurrentReferenceHashMap;
import org.springframework.util.ConcurrentReferenceHashMap.ReferenceType;

/**
 * {@link TypeInformation} for a plain {@link Class}.
 *
 * @author Oliver Gierke
 * @author Christoph Strobl
 */
@SuppressWarnings({ "unchecked", "rawtypes" })
public class ClassTypeInformation<S> extends TypeDiscoverer<S> {

    public static final ClassTypeInformation<Collection> COLLECTION = new ClassTypeInformation(Collection.class);
    public static final ClassTypeInformation<List> LIST = new ClassTypeInformation(List.class);
    public static final ClassTypeInformation<Set> SET = new ClassTypeInformation(Set.class);
    public static final ClassTypeInformation<Map> MAP = new ClassTypeInformation(Map.class);
    public static final ClassTypeInformation<Object> OBJECT = new ClassTypeInformation(Object.class);

    private static final Map<Class<?>, ClassTypeInformation<?>> CACHE = new ConcurrentReferenceHashMap<>(64,
            ReferenceType.WEAK);

    static {
        Arrays.asList(COLLECTION, LIST, SET, MAP, OBJECT).forEach(it -> CACHE.put(it.getType(), it));
    }

    private final Class<S> type;

    /**
     * Simple factory method to easily create new instances of {@link ClassTypeInformation}.
     *
     * @param <S>
     * @param type must not be {@literal null}.
     * @return
     */
    public static <S> ClassTypeInformation<S> from(Class<S> type) {

        Assert.notNull(type, "Type must not be null!");

        return (ClassTypeInformation<S>) CACHE.computeIfAbsent(type, ClassTypeInformation::new);
    }

    /**
     * Creates a {@link TypeInformation} from the given method's return type.
     *
     * @param method must not be {@literal null}.
     * @return
     */
    public static <S> TypeInformation<S> fromReturnTypeOf(Method method) {

        Assert.notNull(method, "Method must not be null!");
        return (TypeInformation<S>) ClassTypeInformation.from(method.getDeclaringClass())
                .createInfo(method.getGenericReturnType());
    }

    /**
     * Creates {@link ClassTypeInformation} for the given type.
     *
     * @param type
     */
    ClassTypeInformation(Class<S> type) {
        super(ProxyUtils.getUserClass(type), getTypeVariableMap(type));
        this.type = type;
    }

    /**
     * Little helper to allow us to create a generified map, actually just to satisfy the compiler.
     *
     * @param type must not be {@literal null}.
     * @return
     */
    private static Map<TypeVariable<?>, Type> getTypeVariableMap(Class<?> type) {
        return getTypeVariableMap(type, new HashSet<>());
    }

    private static Map<TypeVariable<?>, Type> getTypeVariableMap(Class<?> type, Collection<Type> visited) {

        if (visited.contains(type)) {
            return Collections.emptyMap();
        } else {
            visited.add(type);
        }

        Map<TypeVariable, Type> source = GenericTypeResolver.getTypeVariableMap(type);
        Map<TypeVariable<?>, Type> map = new HashMap<>(source.size());

        for (Entry<TypeVariable, Type> entry : source.entrySet()) {

            Type value = entry.getValue();
            map.put(entry.getKey(), entry.getValue());

            if (value instanceof Class) {

                for (Entry<TypeVariable<?>, Type> nestedEntry : getTypeVariableMap((Class<?>) value, visited)
                        .entrySet()) {
                    if (!map.containsKey(nestedEntry.getKey())) {
                        map.put(nestedEntry.getKey(), nestedEntry.getValue());
                    }
                }
            }
        }

        return map;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.util.TypeDiscoverer#getType()
     */
    @Override
    public Class<S> getType() {
        return type;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.util.TypeDiscoverer#getRawTypeInformation()
     */
    @Override
    public ClassTypeInformation<?> getRawTypeInformation() {
        return this;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.util.TypeDiscoverer#isAssignableFrom(org.springframework.data.util.TypeInformation)
     */
    @Override
    public boolean isAssignableFrom(TypeInformation<?> target) {
        return getType().isAssignableFrom(target.getType());
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.util.TypeDiscoverer#specialize(org.springframework.data.util.ClassTypeInformation)
     */
    @Override
    public TypeInformation<? extends S> specialize(ClassTypeInformation<?> type) {
        return (TypeInformation<? extends S>) type;
    }

    /*
     * (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return type.getName();
    }
}