io.rxmicro.config.DefaultConfigValue Maven / Gradle / Ivy
/*
* Copyright (c) 2020. https://rxmicro.io
*
* 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 io.rxmicro.config;
import java.lang.annotation.Documented;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.MODULE;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.CLASS;
/**
* Allows overriding a default value for config property.
*
*
* Configuration using java classes similar to configuration using java annotations.
* The main difference between configuring with annotations and configuring with Java classes is support of the settings inheritance and
* overriding. In other words, when using configuration via annotations, the RxMicro can also read other configuration sources.
* When using configuration via Java classes, other configuration sources are always ignored.
*
*
* Please, pay attention when overriding the default value with the annotations!
* If You make a mistake when specifying a setting name (this refers to the namespace and field name),
* no error will occur upon starting! The overridden value will be simply ignored!
*
*
* This annotation can be applied to override primitive values only:
*
* - strings
* - boolean
* - numbers
* - dates
* - times
* - enums
*
*
*
* If it is necessary to override a complex value, {@link DefaultConfigValueSupplier} annotation must be used instead.
*
* @author nedis
* @see DefaultConfigValueSupplier
* @see Config
* @see Configs#getConfig(String, Class)
* @see Configs#getConfig(Class)
* @since 0.1
*/
@Documented
@Retention(CLASS)
@Target({TYPE, MODULE, ANNOTATION_TYPE})
@Repeatable(DefaultConfigValue.List.class)
public @interface DefaultConfigValue {
/**
* When overriding the configuration value, it is necessary to specify the configuration class.
*
*
* If the configuration class is specified, the namespace may not be specified.
*
*
* See {@link DefaultConfigValue#name()}.
*
*
* (It means the field of the specified configuration class.)
*
* @return config class
*/
Class configClass() default Config.class;
/**
* If no configuration class is specified, the name must contain a namespace.
*
*
* (The namespace allows You to clearly define to which configuration class the specified setting belongs.)
*
* @return property name without namespace if {@link DefaultConfigValue#configClass()} is specified
* or property name with required namespace if {@link DefaultConfigValue#configClass()} is not set
*/
String name();
/**
* Returns the overridden property value.
*
* @return the overridden property value
*/
String value();
/**
* Defines several {@link DefaultConfigValue} annotations on the same element.
*
* @author nedis
* @since 0.1
*/
@Documented
@Retention(CLASS)
@Target({TYPE, MODULE, ANNOTATION_TYPE})
@interface List {
/**
* Returns the several {@link DefaultConfigValue} annotations on the same element.
*
* @return the several {@link DefaultConfigValue} annotations on the same element.
*/
DefaultConfigValue[] value();
}
}