1 /*
2 * Copyright (c) 2001, 2003, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package com.sun.corba.se.spi.extension ;
27
28 import org.omg.CORBA.Policy ;
29 import org.omg.CORBA.LocalObject ;
30 import com.sun.corba.se.impl.orbutil.ORBConstants ;
31
32 /** Policy used to implement servant caching optimization in the POA.
33 * Creating a POA with an instance pol of this policy where
34 * pol.getType() > NO_SERVANT_CACHING will cause the servant to be
35 * looked up in the POA and cached in the LocalClientRequestDispatcher when
36 * the ClientRequestDispatcher is colocated with the implementation of the
37 * objref. This greatly speeds up invocations at the cost of violating the
38 * POA semantics. In particular, every request to a particular objref
39 * must be handled by the same servant. Note that this is typically the
40 * case for EJB implementations.
41 * <p>
42 * If servant caching is used, there are two different additional
43 * features of the POA that are expensive:
44 * <ol>
45 * <li>POA current semantics
46 * <li>Proper handling of POA destroy.
47 * </ol>
48 * POA current semantics requires maintaining a ThreadLocal stack of
49 * invocation information that is always available for POACurrent operations.
50 * Maintaining this stack is expensive on the timescale of optimized co-located
51 * calls, so the option is provided to turn it off. Similarly, causing
52 * POA.destroy() calls to wait for all active calls in the POA to complete
53 * requires careful tracking of the entry and exit of invocations in the POA.
54 * Again, tracking this is somewhat expensive.
55 */
56 public class ServantCachingPolicy extends LocalObject implements Policy
57 {
58 /** Do not cache servants in the ClientRequestDispatcher. This will
59 * always support the full POA semantics, including changing the
60 * servant that handles requests on a particular objref.
61 */
62 public static final int NO_SERVANT_CACHING = 0 ;
63
64 /** Perform servant caching, preserving POA current and POA destroy semantics.
65 * We will use this as the new default, as the app server is making heavier use
66 * now of POA facilities.
67 */
68 public static final int FULL_SEMANTICS = 1 ;
69
70 /** Perform servant caching, preservent only POA current semantics.
71 * At least this level is required in order to support selection of ObjectCopiers
72 * for co-located RMI-IIOP calls, as the current copier is stored in
73 * OAInvocationInfo, which must be present on the stack inside the call.
74 */
75 public static final int INFO_ONLY_SEMANTICS = 2 ;
76
77 /** Perform servant caching, not preserving POA current or POA destroy semantics.
78 */
79 public static final int MINIMAL_SEMANTICS = 3 ;
80
81 private static ServantCachingPolicy policy = null ;
82 private static ServantCachingPolicy infoOnlyPolicy = null ;
83 private static ServantCachingPolicy minimalPolicy = null ;
84
85 private int type ;
86
87 public String typeToName()
88 {
89 switch (type) {
90 case FULL_SEMANTICS:
91 return "FULL" ;
92 case INFO_ONLY_SEMANTICS:
93 return "INFO_ONLY" ;
94 case MINIMAL_SEMANTICS:
95 return "MINIMAL" ;
96 default:
97 return "UNKNOWN(" + type + ")" ;
98 }
99 }
100
101 public String toString()
102 {
103 return "ServantCachingPolicy[" + typeToName() + "]" ;
104 }
105
106 private ServantCachingPolicy( int type )
107 {
108 this.type = type ;
109 }
110
111 public int getType()
112 {
113 return type ;
114 }
115
116 /** Return the default servant caching policy.
117 */
118 public synchronized static ServantCachingPolicy getPolicy()
119 {
120 return getFullPolicy() ;
121 }
122
123 public synchronized static ServantCachingPolicy getFullPolicy()
124 {
125 if (policy == null)
126 policy = new ServantCachingPolicy( FULL_SEMANTICS ) ;
127
128 return policy ;
129 }
130
131 public synchronized static ServantCachingPolicy getInfoOnlyPolicy()
132 {
133 if (infoOnlyPolicy == null)
134 infoOnlyPolicy = new ServantCachingPolicy( INFO_ONLY_SEMANTICS ) ;
135
136 return infoOnlyPolicy ;
137 }
138
139 public synchronized static ServantCachingPolicy getMinimalPolicy()
140 {
141 if (minimalPolicy == null)
142 minimalPolicy = new ServantCachingPolicy( MINIMAL_SEMANTICS ) ;
143
144 return minimalPolicy ;
145 }
146
147 public int policy_type ()
148 {
149 return ORBConstants.SERVANT_CACHING_POLICY ;
150 }
151
152 public org.omg.CORBA.Policy copy ()
153 {
154 return this ;
155 }
156
157 public void destroy ()
158 {
159 // NO-OP
160 }
161 }