/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* 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.datastax.driver.extras.codecs.guava;
import com.datastax.driver.core.TypeCodec;
import com.datastax.driver.extras.codecs.MappingCodec;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
import com.google.common.reflect.TypeParameter;
import com.google.common.reflect.TypeToken;
import java.util.Collection;
import java.util.Map;
/**
* A codec that wraps other codecs around Guava's {@link Optional} API.
*
* @param <T> The wrapped Java type
*/
public class OptionalCodec<T> extends MappingCodec<Optional<T>, T> {
private final Predicate<T> isAbsent;
public OptionalCodec(TypeCodec<T> codec) {
this(codec, new Predicate<T>() {
@Override
public boolean apply(T input) {
return input == null
|| input instanceof Collection && ((Collection) input).isEmpty()
|| input instanceof Map && ((Map) input).isEmpty();
}
});
}
public OptionalCodec(TypeCodec<T> codec, Predicate<T> isAbsent) {
// @formatter:off
super(codec, new TypeToken<Optional<T>>() {}.where(new TypeParameter<T>() {}, codec.getJavaType()));
// @formatter:on
this.isAbsent = isAbsent;
}
@Override
protected Optional<T> deserialize(T value) {
return isAbsent(value) ? Optional.<T>absent() : Optional.fromNullable(value);
}
@Override
protected T serialize(Optional<T> value) {
return value.isPresent() ? value.get() : absentValue();
}
protected T absentValue() {
return null;
}
protected boolean isAbsent(T value) {
return isAbsent.apply(value);
}
}