Source code: com/jcorporate/expresso/core/registry/RequestRegistry.java
1 /* The Jcorporate Apache Style Software License, Version 1.2 05-07-2002
2 *
3 * Copyright (c) 1995-2002 Jcorporate Ltd. All rights reserved.
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19 * "This product includes software developed by Jcorporate Ltd.
20 * (http://www.jcorporate.com/)."
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29 * 5. Products derived from this software may not be called "Expresso",
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60 * Portions of this software are based upon other open source
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62 */
63
64 package com.jcorporate.expresso.core.registry;
65
66 import com.jcorporate.expresso.core.security.User;
67
68 import java.util.Stack;
69
70 /**
71 * The request registry provides several useful utility functions that
72 * allow isolation of Expresso specifics away from the domain model where
73 * they don't belong. To use it, use the static methods, which in turn
74 * return threadlocal data.
75 * <p>Example Usage:</p>
76 * <p/>
77 * <code><pre>
78 * String dataContext = RequestRegistry.getDataContext();
79 * </pre></code>
80 * </p>
81 * <p>The pattern for this class is originally defined by Martin Fowler
82 * in his book <em>Patterns of Enterprise Application Architecture</em>
83 * as the registry pattern. Supplemental information for the
84 * casual reader can be found at:
85 * <a href="http://www.martinfowler.com/eaaCatalog/registry.html">
86 * http://www.martinfowler.com/eaaCatalog/registry.html</a>
87 * </p>
88 * <p/>
89 * In the concept of Interface vs Concrete Class. In this case, the
90 * static methods for this class are the interface to the class. Actual
91 * member manipulation is done in subclasses to the RequestRegistry.
92 * </p>
93 * <p>Dependencies: Note that ExpressoThreadContext depends heavily on
94 * the RequestRegistry. If you change the interface of this class by
95 * adding new members, you MUST change the ExpressoThreadContext
96 * and MutableRequestRegistry as well.</p>
97 *
98 * @author Michael Rimov
99 * @version 1.0
100 */
101 abstract public class RequestRegistry {
102
103 /**
104 * The data context for the Expresso request.
105 */
106 protected String dataContext = null;
107
108 /**
109 * The security context for the Expresso request.
110 */
111 protected User user = null;
112
113
114 /**
115 * A stack for allowing credential changes mid-request. Use superUser()
116 * and revertUser() to push and pop users off the stack, much the
117 * way that unix <code>su</code> performs.
118 */
119 private Stack superUserStack = null;
120
121 /**
122 * The threadlocal instance for this class.
123 */
124 static private ThreadLocal threadLocal = new ThreadLocal();
125
126 /**
127 * Default constructor. Adds this class to the threadlocal context.
128 */
129 protected RequestRegistry() {
130 synchronized (threadLocal) {
131 threadLocal.set(this);
132 }
133 }
134
135 /**
136 * Retrieves the current thread's data context.
137 *
138 * @return String java.lang.String
139 * @throws java.lang.IllegalStateException
140 * if this method is called
141 * before anybody constructed it.
142 */
143 static public String getDataContext() {
144 return getInstance().dataContext;
145 }
146
147 /**
148 * Method that gets the actual registry threadlocal instance and makes
149 * sure that it has been built prior to getting.
150 *
151 * @return RequestRegistry the registry instance for this thread.
152 * @throws java.lang.IllegalStateException
153 * if this method is called
154 * before anybody constructed it.
155 */
156 protected static RequestRegistry getInstance() throws IllegalStateException {
157 RequestRegistry requestRegistry = (RequestRegistry) threadLocal.get();
158 if (requestRegistry == null) {
159 throw new IllegalStateException("No request registry has been associated with this thread yet."
160 + " If you are running inside a servlet engine, please add "
161 + "RequestRegistryFilter as a servlet filter within web.xml. See the " +
162 " web.xml in the Expresso source tree as an example.");
163 }
164 return requestRegistry;
165 }
166
167 /**
168 * Retrieves the current thread's user.
169 *
170 * @return User instance
171 * @throws java.lang.IllegalStateException
172 * if this method is called
173 * before anybody constructed it.
174 */
175 static public User getUser() {
176 return getInstance().user;
177 }
178
179 /**
180 * Changes user credentials mid-thread request. It allows for
181 * <code>su</code>-like abilities. The old user context is stored
182 * in a stack that may be reverted by calling {@link #revertUser}.
183 * restrict who can su based on a java security policy.
184 *
185 * @param newUser User the user to change thread credentials to.
186 */
187 static public void superUser(User newUser) {
188 RequestRegistry requestRegistry = getInstance();
189 Stack userStack = requestRegistry.getUserStack();
190 userStack.push(requestRegistry.user);
191 requestRegistry.user = newUser;
192 }
193
194 /**
195 * Retrieves the user stack, constructing a new one if necessary.
196 *
197 * @return Stack the user stack.
198 */
199 protected Stack getUserStack() {
200 if (superUserStack == null) {
201 superUserStack = new Stack();
202 }
203
204 return superUserStack;
205 }
206
207 /**
208 * Reverts the user credentials
209 *
210 * @return the now current User.
211 * @throws java.lang.ArrayIndexOutOfBoundsException
212 * if the stack
213 * was already empty.... <em>ie</em> you did not have matching superUser()
214 * to revertUser() calls.
215 */
216 static public User revertUser() {
217 RequestRegistry requestRegistry = getInstance();
218 Stack userStack = requestRegistry.getUserStack();
219 if (userStack.isEmpty()) {
220 throw new java.lang.ArrayIndexOutOfBoundsException("Stack is empty. " +
221 "You have mismatching superUser() and revertUser() calls");
222 }
223
224 requestRegistry.user = (User) userStack.pop();
225 return requestRegistry.user;
226
227 }
228
229 /**
230 * Releases all data associated with this registry.
231 */
232 protected void releaseSettings() {
233 superUserStack = null;
234 user = null;
235 dataContext = null;
236 }
237
238
239 }