https://spring.io/projects/spring-boot: Spring Boot (Pivotal Software, Inc.) 
/*
 * Copyright 2012-2019 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.springframework.boot.context.properties;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.core.annotation.AliasFor;


Annotation for externalized configuration. Add this to a class definition or a @Bean method in a @Configuration class if you want to bind and validate some external Properties (e.g. from a .properties file). 
 Binding is either performed by calling setters on the annotated class or, if @ConstructorBinding is in use, by binding to the constructor parameters. 
 Note that contrary to @Value, SpEL expressions are not evaluated since property values are externalized. 
Author:Dave Syer
See Also:
Since:1.0.0
/**
 * Annotation for externalized configuration. Add this to a class definition or a
 * {@code @Bean} method in a {@code @Configuration} class if you want to bind and validate
 * some external Properties (e.g. from a .properties file).
 * <p>
 * Binding is either performed by calling setters on the annotated class or, if
 * {@link ConstructorBinding @ConstructorBinding} is in use, by binding to the constructor
 * parameters.
 * <p>
 * Note that contrary to {@code @Value}, SpEL expressions are not evaluated since property
 * values are externalized.
 *
 * @author Dave Syer
 * @since 1.0.0
 * @see ConfigurationPropertiesScan
 * @see ConstructorBinding
 * @see ConfigurationPropertiesBindingPostProcessor
 * @see EnableConfigurationProperties
 */
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ConfigurationProperties {

	
The prefix of the properties that are valid to bind to this object. Synonym for prefix(). A valid prefix is defined by one or more words separated with dots (e.g. "acme.system.feature"). 
Returns:the prefix of the properties to bind
/**
	 * The prefix of the properties that are valid to bind to this object. Synonym for
	 * {@link #prefix()}. A valid prefix is defined by one or more words separated with
	 * dots (e.g. {@code "acme.system.feature"}).
	 * @return the prefix of the properties to bind
	 */
	@AliasFor("prefix")
	String value() default "";

	
The prefix of the properties that are valid to bind to this object. Synonym for value(). A valid prefix is defined by one or more words separated with dots (e.g. "acme.system.feature"). 
Returns:the prefix of the properties to bind
/**
	 * The prefix of the properties that are valid to bind to this object. Synonym for
	 * {@link #value()}. A valid prefix is defined by one or more words separated with
	 * dots (e.g. {@code "acme.system.feature"}).
	 * @return the prefix of the properties to bind
	 */
	@AliasFor("value")
	String prefix() default "";

	
Flag to indicate that when binding to this object invalid fields should be ignored.
Invalid means invalid according to the binder that is used, and usually this means
fields of the wrong type (or that cannot be coerced into the correct type).

Returns:the flag value (default false)
/**
	 * Flag to indicate that when binding to this object invalid fields should be ignored.
	 * Invalid means invalid according to the binder that is used, and usually this means
	 * fields of the wrong type (or that cannot be coerced into the correct type).
	 * @return the flag value (default false)
	 */
	boolean ignoreInvalidFields() default false;

	
Flag to indicate that when binding to this object unknown fields should be ignored.
An unknown field could be a sign of a mistake in the Properties.

Returns:the flag value (default true)
/**
	 * Flag to indicate that when binding to this object unknown fields should be ignored.
	 * An unknown field could be a sign of a mistake in the Properties.
	 * @return the flag value (default true)
	 */
	boolean ignoreUnknownFields() default true;

}