http://www.jboss.org/undertow-parent/undertow-core: Undertow (JBoss by Red Hat) 
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package io.undertow.predicate;

import java.util.Map;

import io.undertow.server.HttpServerExchange;
import io.undertow.util.AttachmentKey;


A predicate.
This is mainly uses by handlers as a way to decide if a request should have certain
processing applied, based on the given conditions.

Author:Stuart Douglas
/**
 * A predicate.
 *
 * This is mainly uses by handlers as a way to decide if a request should have certain
 * processing applied, based on the given conditions.
 *
 * @author Stuart Douglas
 */
public interface Predicate {

    
Attachment key that can be used to store additional predicate context that allows the predicates to store
additional information. For example a predicate that matches on a regular expression can place additional
information about match groups into the predicate context.
Predicates must not rely on this attachment being present, it will only be present if the predicate is being
used in a situation where this information may be required by later handlers.

/**
     * Attachment key that can be used to store additional predicate context that allows the predicates to store
     * additional information. For example a predicate that matches on a regular expression can place additional
     * information about match groups into the predicate context.
     *
     * Predicates must not rely on this attachment being present, it will only be present if the predicate is being
     * used in a situation where this information may be required by later handlers.
     *
     */
    AttachmentKey<Map<String, Object>> PREDICATE_CONTEXT = AttachmentKey.create(Map.class);

    boolean resolve(final HttpServerExchange value);

}