121 lines
4.1 KiB
Java
121 lines
4.1 KiB
Java
/*
|
|
* The MIT License
|
|
* Copyright © 2014-2019 Ilkka Seppälä
|
|
*
|
|
* Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
* of this software and associated documentation files (the "Software"), to deal
|
|
* in the Software without restriction, including without limitation the rights
|
|
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
* copies of the Software, and to permit persons to whom the Software is
|
|
* furnished to do so, subject to the following conditions:
|
|
*
|
|
* The above copyright notice and this permission notice shall be included in
|
|
* all copies or substantial portions of the Software.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
|
* THE SOFTWARE.
|
|
*/
|
|
|
|
package com.iluwatar.monad;
|
|
|
|
import java.util.ArrayList;
|
|
import java.util.List;
|
|
import java.util.Objects;
|
|
import java.util.function.Function;
|
|
import java.util.function.Predicate;
|
|
|
|
/**
|
|
* Class representing Monad design pattern. Monad is a way of chaining operations on the given
|
|
* object together step by step. In Validator each step results in either success or failure
|
|
* indicator, giving a way of receiving each of them easily and finally getting validated object or
|
|
* list of exceptions.
|
|
*
|
|
* @param <T> Placeholder for an object.
|
|
*/
|
|
public class Validator<T> {
|
|
/**
|
|
* Object that is validated.
|
|
*/
|
|
private final T obj;
|
|
|
|
/**
|
|
* List of exception thrown during validation.
|
|
*/
|
|
private final List<Throwable> exceptions = new ArrayList<>();
|
|
|
|
/**
|
|
* Creates a monadic value of given object.
|
|
*
|
|
* @param obj object to be validated
|
|
*/
|
|
private Validator(T obj) {
|
|
this.obj = obj;
|
|
}
|
|
|
|
/**
|
|
* Creates validator against given object.
|
|
*
|
|
* @param t object to be validated
|
|
* @param <T> object's type
|
|
* @return new instance of a validator
|
|
*/
|
|
public static <T> Validator<T> of(T t) {
|
|
return new Validator<>(Objects.requireNonNull(t));
|
|
}
|
|
|
|
/**
|
|
* Checks if the validation is successful.
|
|
*
|
|
* @param validation one argument boolean-valued function that represents one step of validation.
|
|
* Adds exception to main validation exception list when single step validation
|
|
* ends with failure.
|
|
* @param message error message when object is invalid
|
|
* @return this
|
|
*/
|
|
public Validator<T> validate(Predicate<T> validation, String message) {
|
|
if (!validation.test(obj)) {
|
|
exceptions.add(new IllegalStateException(message));
|
|
}
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* Extension for the {@link Validator#validate(Predicate, String)} method, dedicated for objects,
|
|
* that need to be projected before requested validation.
|
|
*
|
|
* @param projection function that gets an objects, and returns projection representing element to
|
|
* be validated.
|
|
* @param validation see {@link Validator#validate(Predicate, String)}
|
|
* @param message see {@link Validator#validate(Predicate, String)}
|
|
* @param <U> see {@link Validator#validate(Predicate, String)}
|
|
* @return this
|
|
*/
|
|
public <U> Validator<T> validate(
|
|
Function<T, U> projection,
|
|
Predicate<U> validation,
|
|
String message
|
|
) {
|
|
return validate(projection.andThen(validation::test)::apply, message);
|
|
}
|
|
|
|
/**
|
|
* Receives validated object or throws exception when invalid.
|
|
*
|
|
* @return object that was validated
|
|
* @throws IllegalStateException when any validation step results with failure
|
|
*/
|
|
public T get() throws IllegalStateException {
|
|
if (exceptions.isEmpty()) {
|
|
return obj;
|
|
}
|
|
var e = new IllegalStateException();
|
|
exceptions.forEach(e::addSuppressed);
|
|
throw e;
|
|
}
|
|
}
|