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package javax.ws.rs.ext;
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 javax.ws.rs.DefaultValue;
/**
* Defines a contract for a delegate responsible for converting between a
* {@code String} form of a message parameter value and the corresponding custom
* Java type {@code T}. Conversion of message parameter values injected via
* {@link javax.ws.rs.PathParam @PathParam}, {@link javax.ws.rs.QueryParam @QueryParam},
* {@link javax.ws.rs.MatrixParam @MatrixParam}, {@link javax.ws.rs.FormParam @FormParam},
* {@link javax.ws.rs.CookieParam @CookieParam} and {@link javax.ws.rs.HeaderParam @HeaderParam}
* is supported.
*
* By default, when used for injection of parameter values, a selected {@code ParamConverter}
* instance MUST be used eagerly by a JAX-RS runtime to convert any {@link DefaultValue
* default value} in the resource or provider model, that is during the application deployment,
* before any value – default or otherwise – is actually required.
* This conversion strategy ensures that any errors in the default values are reported
* as early as possible.
* This default behavior may be overridden by annotating the {@code ParamConverter}
* implementation class with a {@link Lazy @Lazy} annotation. In such case any default
* value conversion delegated to the {@code @Lazy}-annotated converter will be deferred
* to a latest possible moment (i.e. until the injection of such default value is required).
*
*
* NOTE: A service implementing this contract is not recognized as a registrable
* JAX-RS extension provider. Instead, a {@link ParamConverterProvider} instance
* responsible for providing {@code ParamConverter} instances has to be registered
* as one of the JAX-RS extension providers.
*
*
* @param the supported Java type convertible to/from a {@code String} format.
* @author Marek Potociar
*/
public interface ParamConverter {
/**
* Mandates that a conversion of any {@link DefaultValue default value} delegated
* to a {@link ParamConverter parameter converter} annotated with {@code @Lazy}
* annotation SHOULD occur only once the value is actually required (e.g. to be
* injected for the first time).
*/
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public static @interface Lazy {}
/**
* Parse the supplied value and create an instance of {@code T}.
*
* @param value the string value.
* @return the newly created instance of {@code T}.
* @throws IllegalArgumentException if the supplied string cannot be
* parsed or is {@code null}.
*/
public T fromString(String value);
/**
* Convert the supplied value to a String.
*
* This method is reserved for future use. Proprietary JAX-RS extensions may leverage the method.
* Users should be aware that any such support for the method comes at the expense of producing
* non-portable code.
*
*
* @param value the value of type {@code T}.
* @return a String representation of the value.
* @throws IllegalArgumentException if the supplied object cannot be
* serialized or is {@code null}.
*/
public String toString(T value);
}