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A Spring Boot starter which provides a few primitives to handle exceptions more elegantly.

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package me.alidg.errors.annotation;

import java.lang.annotation.*;

/**
 * Annotate fields/methods inside an exception with this annotation to expose its
 * value or return value for message interpolation. This way we can convey some information
 * from the exception to the translated message. For example, suppose we defined an
 * exception like the following:
 *  *
 *     @ExceptionMapping(statusCode=BAD_REQUEST, errorCode="user.exists")
 *     public class UserExistsException extends RuntimeException {
 *         @ExposeAsArg(0) private final String username;
 *
 *         // constructor and etc.
 *     }
 * 
 * With this setting, when the exception happens, the {@link me.alidg.errors.handlers.AnnotatedWebErrorHandler}
 * would pick the error code from the annotation and find an appropriate message for the error code.
 * By annotating the {@code username} property with the {@link ExposeAsArg} annotation, we can use the username
 * value to report it in the translated error message:
 *  *
 *     user.exists=Another user with {0} username is already exists.
 * 
 * When interpolating the error message from the error code, the {@code {0}} would be replaced
 * with the username value exposed with:
 *  *
 *     @ExposeAsArg(0) private final String username;
 * 
 *
 * @author Ali Dehghani
 * @see ExceptionMapping
 * @see me.alidg.errors.handlers.AnnotatedWebErrorHandler
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD})
public @interface ExposeAsArg {

    /**
     * Determines the index of the to-be-exposed argument.
     *
     * @return The argument index.
     */
    int value();

    /**
     * If the arguments are meant to be exposed, then overrides the to-be-exposed name.
     *
     * @return The to-be-exposed name.
     */
    String name() default "";
}