/
Result.java
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/
Result.java
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/**
* This file is part of alf.io.
*
* alf.io is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* alf.io is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with alf.io. If not, see <http://www.gnu.org/licenses/>.
*/
package alfio.model.result;
import alfio.model.result.ValidationResult.ErrorDescriptor;
import lombok.AllArgsConstructor;
import lombok.Getter;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.lang3.tuple.Pair;
import org.springframework.validation.ObjectError;
import java.util.*;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collectors;
@AllArgsConstructor
@Getter
public class Result<T> {
private final ResultStatus status;
private final T data;
private final List<ErrorCode> errors;
public static <T> Result<T> success(T data) {
return new Result<>(ResultStatus.OK, data, Collections.emptyList());
}
public static <T> Result<T> validationError(List<ObjectError> errors) {
return new Result<>(ResultStatus.VALIDATION_ERROR, null, errors.stream().map(ErrorDescriptor::fromObjectError).collect(Collectors.toList()));
}
public static <T> Result<T> error(List<ErrorCode> errorDescriptors) {
return new Result<>(ResultStatus.ERROR, null, errorDescriptors);
}
public static <T> Result<T> error(ErrorCode errorDescriptor) {
return error(Collections.singletonList(errorDescriptor));
}
public boolean isSuccess() {
return status == ResultStatus.OK;
}
public void ifSuccess(Consumer<T> consumer) {
if(isSuccess()) {
consumer.accept(data);
}
}
public <K> Result<K> map(Function<T, K> mapper) {
if(isSuccess()) {
return Result.success(mapper.apply(data));
}
return Result.error(this.errors);
}
public <K> Result<K> flatMap(Function<T, Result<K>> mapper) {
if(isSuccess()) {
return Objects.requireNonNull(mapper.apply(data), "this method does not allow null values");
}
return Result.error(this.errors);
}
public ErrorCode getFirstErrorOrNull() {
if(isSuccess() || CollectionUtils.size(errors) == 0) {
return null;
}
return errors.get(0);
}
public String getFormattedErrors() {
if(isSuccess()) {
return null;
}
return getErrors().stream().map(ErrorCode::getDescription)
.collect(Collectors.joining("\n"));
}
public enum ResultStatus {
OK, VALIDATION_ERROR, ERROR
}
public static final class Builder<T> {
private final List<Pair<ConditionValidator, ErrorCode>> validators = new ArrayList<>();
public Builder<T> checkPrecondition(ConditionValidator validator, ErrorCode error) {
this.validators.add(Pair.of(validator, error));
return this;
}
public Result<T> build(Supplier<T> valueSupplier) {
Optional<Pair<ConditionValidator, ErrorCode>> validationError = performValidation();
return validationError.map(p -> Result.<T>error(Collections.singletonList(p.getRight())))
.orElseGet(() -> Result.success(valueSupplier.get()));
}
public Result<T> buildAndEvaluate(Supplier<Result<T>> resultSupplier) {
return performValidation().map(p -> Result.<T>error(Collections.singletonList(p.getRight())))
.orElseGet(resultSupplier);
}
private Optional<Pair<ConditionValidator, ErrorCode>> performValidation() {
return this.validators.stream()
.filter(p -> !p.getLeft().isValid())
.findFirst();
}
}
public static <T> Result<T> fromNullable(T nullable, ErrorCode justInCase) {
if(nullable == null) {
return Result.error(justInCase);
}
return Result.success(nullable);
}
@FunctionalInterface
public interface ConditionValidator {
boolean isValid();
}
}