http://www.jboss.org/undertow-parent/undertow-core: Undertow (JBoss by Red Hat) 
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 *     http://www.apache.org/licenses/LICENSE-2.0
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package io.undertow.util;

import java.util.List;


A thing which can have named attachments.

Author:David M. Lloyd
/**
 * A thing which can have named attachments.
 *
 * @author <a href="mailto:david.lloyd@redhat.com">David M. Lloyd</a>
 */
public interface Attachable {

    
Get an attachment value. If no attachment exists for this key, null is returned. 
Params:
  • key – the attachment key
Type parameters:
  • <T> – the value type
Returns:the value, or null if there is none
/**
     * Get an attachment value.  If no attachment exists for this key, {@code null} is returned.
     *
     * @param key the attachment key
     * @param <T> the value type
     * @return the value, or {@code null} if there is none
     */
    <T> T getAttachment(AttachmentKey<T> key);

    
Gets a list attachment value. If not attachment exists for this key an empty list is returned

Params:
  • key – the attachment key
Type parameters:
  • <T> – the value type
Returns:the value, or an empty list if there is none
/**
     * Gets a list attachment value. If not attachment exists for this key an empty list is returned
     *
     * @param <T> the value type
     * @param key the attachment key
     * @return the value, or an empty list if there is none
     */
    <T> List<T> getAttachmentList(AttachmentKey<? extends List<T>> key);

    
Set an attachment value. If an attachment for this key was already set, return the original value. If the value being set is null, the attachment key is removed. 
Params:
  • key – the attachment key
  • value – the new value
Type parameters:
  • <T> – the value type
Returns:the old value, or null if there was none
/**
     * Set an attachment value. If an attachment for this key was already set, return the original value. If the value being set
     * is {@code null}, the attachment key is removed.
     *
     * @param key the attachment key
     * @param value the new value
     * @param <T> the value type
     * @return the old value, or {@code null} if there was none
     */
    <T> T putAttachment(AttachmentKey<T> key, T value);

    
Remove an attachment, returning its previous value.

Params:
  • key – the attachment key
Type parameters:
  • <T> – the value type
Returns:the old value, or null if there was none
/**
     * Remove an attachment, returning its previous value.
     *
     * @param key the attachment key
     * @param <T> the value type
     * @return the old value, or {@code null} if there was none
     */
    <T> T removeAttachment(AttachmentKey<T> key);
    
Add a value to a list-typed attachment key.  If the key is not mapped, add such a mapping.

Params:
  • key – the attachment key
  • value – the value to add
Type parameters:
  • <T> – the list value type
/**
     * Add a value to a list-typed attachment key.  If the key is not mapped, add such a mapping.
     *
     * @param key the attachment key
     * @param value the value to add
     * @param <T> the list value type
     */
    <T> void addToAttachmentList(AttachmentKey<AttachmentList<T>> key, T value);
}