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/*
* Copyright 2000-2016 Vaadin Ltd.
*
* 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.vaadin.data;
import java.io.Serializable;
import java.util.function.Function;
import com.vaadin.data.Binder.BindingBuilder;
import com.vaadin.server.SerializableFunction;
/**
* Interface that implements conversion between a model and a presentation type.
* <p>
* Converters must not have any side effects (never update UI from inside a
* converter).
*
* @param <PRESENTATION>
* The presentation type.
* @param <MODEL>
* The model type.
* @author Vaadin Ltd.
* @since 8.0
*/
public interface Converter<PRESENTATION, MODEL> extends Serializable {
/**
* Converts the given value from model type to presentation type.
* <p>
* A converter can optionally use locale to do the conversion.
*
* @param value
* The value to convert. Can be null
* @param context
* The value context for the conversion.
* @return The converted value compatible with the source type
*/
public Result<MODEL> convertToModel(PRESENTATION value,
ValueContext context);
/**
* Converts the given value from presentation type to model type.
* <p>
* A converter can optionally use locale to do the conversion.
*
* @param value
* The value to convert. Can be null
* @param context
* The value context for the conversion.
* @return The converted value compatible with the source type
*/
public PRESENTATION convertToPresentation(MODEL value,
ValueContext context);
/**
* Returns a converter that returns its input as-is in both directions.
*
* @param <T>
* the input and output type
* @return an identity converter
*/
public static <T> Converter<T, T> identity() {
return from(t -> Result.ok(t), t -> t);
}
/**
* Constructs a converter from two functions. Any {@code Exception}
* instances thrown from the {@code toModel} function are converted into
* error-bearing {@code Result} objects using the given {@code onError}
* function.
*
* @param <P>
* the presentation type
* @param <M>
* the model type
* @param toModel
* the function to convert to model
* @param toPresentation
* the function to convert to presentation
* @param onError
* the function to provide error messages
* @return the new converter
*
* @see Result
* @see Function
*/
public static <P, M> Converter<P, M> from(
SerializableFunction<P, M> toModel,
SerializableFunction<M, P> toPresentation,
SerializableFunction<Exception, String> onError) {
return from(val -> Result.of(() -> toModel.apply(val), onError),
toPresentation);
}
/**
* Constructs a converter from a filter and a function.
*
* @param <P>
* the presentation type
* @param <M>
* the model type
* @param toModel
* the function to convert to model
* @param toPresentation
* the function to convert to presentation
* @return the new converter
*
* @see Function
*/
public static <P, M> Converter<P, M> from(
SerializableFunction<P, Result<M>> toModel,
SerializableFunction<M, P> toPresentation) {
return new Converter<P, M>() {
@Override
public Result<M> convertToModel(P value, ValueContext context) {
return toModel.apply(value);
}
@Override
public P convertToPresentation(M value, ValueContext context) {
return toPresentation.apply(value);
}
};
}
/**
* Returns a converter that chains together this converter with the given
* type-compatible converter.
* <p>
* The chained converters will form a new converter capable of converting
* from the presentation type of this converter to the model type of the
* other converter.
* <p>
* In most typical cases you should not need this method but instead only
* need to define one converter for a binding using
* {@link BindingBuilder#withConverter(Converter)}.
*
* @param <T>
* the model type of the resulting converter
* @param other
* the converter to chain, not null
* @return a chained converter
*/
public default <T> Converter<PRESENTATION, T> chain(
Converter<MODEL, T> other) {
return new Converter<PRESENTATION, T>() {
@Override
public Result<T> convertToModel(PRESENTATION value,
ValueContext context) {
Result<MODEL> model = Converter.this.convertToModel(value,
context);
return model.flatMap(v -> other.convertToModel(v, context));
}
@Override
public PRESENTATION convertToPresentation(T value,
ValueContext context) {
MODEL model = other.convertToPresentation(value, context);
return Converter.this.convertToPresentation(model, context);
}
};
}
}
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