org.apache.juneau.rest.annotation.RestInit Maven / Gradle / Ivy

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package org.apache.juneau.rest.annotation;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;

import java.lang.annotation.*;

import jakarta.servlet.*;

import org.apache.juneau.rest.*;

/**
 * Identifies a method that gets called during servlet initialization.
 *
 * 
 * This method is called from within the {@link Servlet#init(ServletConfig)} method after the {@link org.apache.juneau.rest.RestContext.Builder}
 * object has been created and initialized with the annotations defined on the class, but before the
 * {@link RestContext} object has been created.
 *
 * 

 * The only valid parameter type for this method is {@link org.apache.juneau.rest.RestContext.Builder} which can be used to configure the servlet.
 *
 * 

 * An example of this is the PetStoreResource class that uses an init method to perform initialization
 * of an internal data structure.
 *
 * 
Example:
 * 
 * 	@Rest(...)
 * 	public class PetStoreResource extends BasicRestServlet implements BasicUniversalJenaConfig {
 *
 * 		// Our database.
 * 		private Map<Integer,Pet> petDB;
 *
 * 		@RestInit
 * 		public void onInit(RestContext.Builder builder) throws Exception {
 * 			// Load our database from a local JSON file.
 * 			petDB = JsonParser.DEFAULT.parse(getClass().getResourceAsStream("PetStore.json"), LinkedHashMap.class, Integer.class, Pet.class);
 * 		}
 * 	}
 * 
 *
 * Notes:

 * 	
 * 		The method should return void although if it does return any value, the value will be ignored.
 * 	

 * 		The method should be public although other visibilities are valid if the security manager allows it.
 * 	

 * 		Static methods can be used.
 * 	

 * 		Multiple init methods can be defined on a class.
 * 		
Init methods on parent classes are invoked before init methods on child classes.
 * 		
The order of init method invocations within a class is alphabetical, then by parameter count, then by parameter types.
 * 	

 * 		The method can throw any exception causing initialization of the servlet to fail.
 * 	

 * 		Note that if you override a parent method, you probably need to call super.parentMethod(...).
 * 		
The method is still considered part of the parent class for ordering purposes even though it's
 * 		overridden by the child class.
 * 
 *
 * See Also:

 * 	Lifecycle Hooks
 * 
 */
@Target({METHOD,TYPE})
@Retention(RUNTIME)
@Inherited
@Repeatable(RestInitAnnotation.Array.class)
public @interface RestInit {

	/**
	 * Dynamically apply this annotation to the specified methods.
	 *
	 * See Also:

	 * 	Dynamically Applied Annotations
	 * 
	 *
	 * @return The annotation value.
	 */
	String[] on() default {};
}