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Functional style programming with plain JDBC
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/*
* Copyright 2024- Anatoly Kutyakov
*
* 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 buckelieg.jdbc.fn;
import static java.util.Objects.requireNonNull;
/**
* One-argument function which returns a result that might throw an exception
*
There is no requirement that a new or distinct result be returned each time the function is invoked.
*
This is a functional interface whose functional method is {@link #apply(Object)}}.
*
* @param argument type
* @param result type
* @param an exception type thrown
*/
@FunctionalInterface
public interface TryFunction {
/**
* Represents a one-argument function that might throw an Exception
*
* @param input function input.
* @return mapped value
* @throws E in case of something went wrong
*/
O apply(I input) throws E;
/**
* Returns a function that always returns its input argument
*
* @param the type of the input and output objects to the function
* @return a function that always returns its input argument
*/
static TryFunction identity() {
return t -> t;
}
/**
* Returns reference of lambda expression
*
Typical usage is:
*
{@code TryFunction.of(x -> null).andThen(nil -> null);}
*
* @param tryFunction a function
* @param argument type
* @param result type
* @param exception type
* @return lambda as {@link TryFunction} reference
* @throws NullPointerException if tryFunction is null
*/
static TryFunction of(TryFunction tryFunction) {
return requireNonNull(tryFunction);
}
/**
* Returns a composed function that first applies the {@code before} function to its input, and then applies this function to the result
*
* @param the type of input to the {@code before} function, and to the
* composed function
* @param before the function to apply before this function is applied
* @return a composed function that first applies the {@code before}
* function and then applies this function
* @throws E an exception
* @throws NullPointerException if before is null
* @see #andThen(TryFunction)
*/
default TryFunction compose(TryFunction before) throws E {
if (null == before) throw new NullPointerException("before Function must be provided");
return (V v) -> apply(before.apply(v));
}
/**
* Returns a composed function that first applies this function to its input, and then applies the {@code after} function to the result
*
* @param the type of output of the {@code after} function, and of the
* composed function
* @param after the function to apply after this function is applied
* @return a composed function that first applies this function and then
* applies the {@code after} function
* @throws E an exception
* @throws NullPointerException if after is null
* @see #compose(TryFunction)
*/
default TryFunction andThen(TryFunction after) throws E {
if (null == after) throw new NullPointerException("after Function must be provided");
return (I t) -> after.apply(apply(t));
}
}