SnmpUserDataFactory


1   /*
2    * @(#)file      SnmpUserDataFactory.java
3    * @(#)author    Sun Microsystems, Inc.
4    * @(#)version   1.16
5    * @(#)date      08/02/09
6    *
7    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
8    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
9    */
10  
11  package com.sun.jmx.snmp.agent;
12  
13  import com.sun.jmx.snmp.SnmpPduPacket;
14  import com.sun.jmx.snmp.SnmpPdu;
15  import com.sun.jmx.snmp.SnmpStatusException;
16  
17  /**
18   * This interface is provided to enable fine customization of the SNMP
19   * agent behaviour. 
20   * 
21   * <p>You will not need to implement this interface except if your agent
22   * needs extra customization requiring some contextual information.</p>
23   *
24   * <p>If an SnmpUserDataFactory is set on the SnmpAdaptorServer, then a new
25   * object containing user-data will be allocated through this factory
26   * for each incoming request. This object will be passed along to 
27   * the SnmpMibAgent within SnmpMibRequest objects. By default, no 
28   * SnmpUserDataFactory is set on the SnmpAdaptorServer, and the contextual
29   * object passed to SnmpMibAgent is null.</p>
30   * 
31   * <p>You can use this feature to obtain on contextual information
32   * (such as community string etc...) or to implement a caching
33   * mechanism, or for whatever purpose might be required by your specific
34   * agent implementation.</p>
35   *
36   * <p>The sequence <code>allocateUserData() / releaseUserData()</code> can 
37   * also be used to implement a caching mechanism: 
38   * <ul>
39   * <li><code>allocateUserData()</code> could be used to allocate 
40   *         some cache space,</li>
41   * <li>and <code>releaseUserData()</code> could be used to flush it.</li>
42   * </ul></p>
43   *
44   * <p><b>This API is a Sun Microsystems internal API  and is subject 
45   * to change without notice.</b></p>
46   * @see com.sun.jmx.snmp.agent.SnmpMibRequest
47   * @see com.sun.jmx.snmp.agent.SnmpMibAgent
48   * @see com.sun.jmx.snmp.daemon.SnmpAdaptorServer
49   *
50   **/
51  public interface SnmpUserDataFactory {    
52      /** 
53       * Called by the <CODE>SnmpAdaptorServer</CODE> adaptor.
54       * Allocate a contextual object containing some user data. This method
55       * is called once for each incoming SNMP request. The scope
56       * of this object will be the whole request. Since the request can be 
57       * handled in several threads, the user should make sure that this
58       * object can be accessed in a thread-safe manner. The SNMP framework
59       * will never access this object directly - it will simply pass
60       * it to the <code>SnmpMibAgent</code> within 
61       * <code>SnmpMibRequest</code> objects - from where it can be retrieved
62       * through the {@link com.sun.jmx.snmp.agent.SnmpMibRequest#getUserData() getUserData()} accessor.
63       * <code>null</code> is considered to be a valid return value.
64       *
65       * This method is called just after the SnmpPduPacket has been
66       * decoded.
67       *
68       * @param requestPdu The SnmpPduPacket received from the SNMP manager.
69       *        <b>This parameter is owned by the SNMP framework and must be 
70       *        considered as transient.</b> If you wish to keep some of its 
71       *        content after this method returns (by storing it in the 
72       *        returned object for instance) you should clone that 
73       *        information. 
74       *
75       * @return A newly allocated user-data contextual object, or 
76       *         <code>null</code>
77       * @exception SnmpStatusException If an SnmpStatusException is thrown,
78       *            the request will be aborted.
79       *
80       * @since 1.5
81       **/
82      public Object   allocateUserData(SnmpPdu requestPdu)
83      throws SnmpStatusException;
84      
85      /**
86       * Called by the <CODE>SnmpAdaptorServer</CODE> adaptor.
87       * Release a previously allocated contextual object containing user-data.
88       * This method is called just before the responsePdu is sent back to the
89       * manager. It gives the user a chance to alter the responsePdu packet
90       * before it is encoded, and to free any resources that might have
91       * been allocated when creating the contextual object.
92       *
93       * @param userData The contextual object being released. 
94       * @param responsePdu The SnmpPduPacket that will be sent back to the 
95       *        SNMP manager.
96       *        <b>This parameter is owned by the SNMP framework and must be 
97       *        considered as transient.</b> If you wish to keep some of its 
98       *        content after this method returns you should clone that
99       *        information. 
100      *
101      * @exception SnmpStatusException If an SnmpStatusException is thrown,
102      *            the responsePdu is dropped and nothing is returned to
103      *            to the manager.
104      *
105      * @since 1.5
106      **/
107     public void releaseUserData(Object   userData, SnmpPdu responsePdu)
108     throws SnmpStatusException;
109 }
110
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