org.instancio.settings.SettingKey Maven / Gradle / Ivy
/*
* Copyright 2022-2024 the original author or authors.
*
* 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
*
* https://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 org.instancio.settings;
import org.instancio.documentation.ExperimentalApi;
/**
* A setting key represents a configuration item that can be
* stored in a {@link Settings} instance.
*
* @param type of the value
* @see Keys
* @see Settings
* @since 1.0.1
*/
public interface SettingKey {
/**
* The type of value associated with this key.
*
* This method is used for converting a value from a string
* to the specified {@code type()} when retrieving the value
* from {@link Settings}.
*
* @return the type of value associated with this key
* @since 1.0.1
*/
Class type();
/**
* A unique property key identifying this setting.
* The property key is used to identify the setting in a properties file.
*
* @return a unique property key identifying this setting
* @since 1.2.0
*/
String propertyKey();
/**
* Default value for this key.
*
* @return default value, or {@code null} if not defined
* @since 1.0.1
*/
default T defaultValue() {
return null;
}
/**
* Indicates whether the value for this key can be set to {@code null}.
* Setting a {@code null} for a key that does not accept {@code null}
* will produce an exception.
*
* @return {@code true} if {@code null} is allowed, {@code false} otherwise
* @since 1.5.1
*/
default boolean allowsNullValue() {
return true;
}
/**
* A builder for creating custom keys.
*
* @param the type of value associated with this key
* @since 2.12.0
*/
@ExperimentalApi
interface SettingKeyBuilder {
/**
* Specifies the value's type.
*
* @param type of value
* @return key builder
* @since 2.12.0
*/
SettingKeyBuilder ofType(Class type);
/**
* Specifies the property key.
*
* When defining custom keys, it is advisable to use
* a custom prefix to distinguish from and to avoid potential clashes
* with built-in keys, for example:
*
*
{@code
* com.acme.string.length=10
* }
*
* If {@code withPropertyKey()} is not specified,
* then an auto-generated property key will be assigned.
*
* @param propertyKey a unique property key
* @return key builder
* @since 2.12.0
*/
SettingKeyBuilder withPropertyKey(String propertyKey);
/**
* Returns the created setting key.
*
* @return the setting key
* @since 2.12.0
*/
SettingKey create();
}
}