com.palantir.conjure.java.server.jersey.Java8OptionalParamConverterProvider Maven / Gradle / Ivy

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/*
 * (c) Copyright 2017 Palantir Technologies 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 com.palantir.conjure.java.server.jersey;

import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.List;
import java.util.Optional;
import javax.inject.Inject;
import javax.ws.rs.ext.ParamConverter;
import javax.ws.rs.ext.ParamConverterProvider;
import javax.ws.rs.ext.Provider;
import org.glassfish.jersey.internal.inject.Custom;
import org.glassfish.jersey.internal.inject.InjectionManager;
import org.glassfish.jersey.internal.inject.Providers;
import org.glassfish.jersey.internal.util.ReflectionHelper;
import org.glassfish.jersey.internal.util.collection.ClassTypePair;

// The Custom annotation ensures that our custom param converters are considered first. See ParamConverterFactory.
@Custom
@Provider
public final class Java8OptionalParamConverterProvider implements ParamConverterProvider {
    private final InjectionManager injectionManager;

    @Inject
    public Java8OptionalParamConverterProvider(final InjectionManager injectionManager) {
        this.injectionManager = injectionManager;
    }

    @Override
    public  ParamConverter getConverter(
            final Class rawType, final Type genericType, final Annotation[] annotations) {
        if (Optional.class.equals(rawType)) {
            final List ctps = ReflectionHelper.getTypeArgumentAndClass(genericType);
            final ClassTypePair ctp = (ctps.size() == 1) ? ctps.get(0) : null;

            if (ctp == null || ctp.rawClass() == String.class) {
                return new ParamConverter() {
                    @Override
                    public T fromString(final String value) {
                        return rawType.cast(Optional.ofNullable(value));
                    }

                    @Override
                    public String toString(final T value) {
                        return value.toString();
                    }
                };
            }

            for (ParamConverterProvider provider :
                    Providers.getProviders(injectionManager, ParamConverterProvider.class)) {
                final ParamConverter converter = provider.getConverter(ctp.rawClass(), ctp.type(), annotations);
                if (converter != null) {
                    return new ParamConverter() {
                        @Override
                        public T fromString(final String value) {
                            return rawType.cast(Optional.ofNullable(value).map(converter::fromString));
                        }

                        @Override
                        public String toString(final T value) {
                            return value.toString();
                        }
                    };
                }
            }
        }

        return null;
    }
}