/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at
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* trunk/opends/resource/legal-notices/OpenDS.LICENSE
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* or https://OpenDS.dev.java.net/OpenDS.LICENSE.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at
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* trunk/opends/resource/legal-notices/OpenDS.LICENSE. If applicable,
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* add the following below this CDDL HEADER, with the fields enclosed
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* by brackets "[]" replaced with your own identifying information:
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* Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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*
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* Portions Copyright 2006-2007 Sun Microsystems, Inc.
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*/
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package org.opends.server.util;
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import static org.opends.server.loggers.debug.DebugLogger.debugEnabled;
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import static org.opends.server.loggers.debug.DebugLogger.debugError;
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import org.opends.server.types.ErrorLogCategory;
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import org.opends.server.types.ErrorLogSeverity;
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import org.opends.server.messages.UtilityMessages;
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/**
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* This utility class provides static methods that make parameter checking
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* easier (e.g. in constructors and setters).
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* In particular the ensureNotNull methods provide an easy way to validate that
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* certain parameters are not null, and the ensureTrue methods provide the
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* ability to check arbitrary boolean conditions.
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* <p>
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* Invocation of these methods should be limited to situations where the only
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* way that they should fail is if there is a defect somewhere in the
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* system (including 3rd-party plugins).
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* <p>
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* You can think of these methods as being similar to <code>assert</code>,
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* but there are some additional advantages:
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* <ul>
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* <li>All failures are logged to the debug and error logs</li>
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* <li>Checks are always enabled (even if asserts are off)</li>
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* <li>This class tracks the number of failures, allowing it to
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* be exposed via monitoring, etc.<li>
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* <li>The unit tests can track unnoticed internal failures and
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* report on them.</li>
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* <li>Developers can catch all Validator failures with a single
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* break point.</li>
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* </ul>
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*
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* In general, you should not worry about the performance impact of calling
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* these methods. Some micro-benchmarking has shown that ensureNotNull can be
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* called 200M times per second on a single CPU laptop. The value of catching
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* defects early will almost always out-weigh any overhead that is introduced.
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* There are a couple of exceptions to this. Any execution overhead that
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* happens before the method is invoked cannot be eliminated, e.g.
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* <code>Validator.ensureTrue(someExpensiveCheck())</code> will always invoke
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* <code>someExpensiveCheck()</code>. When this code is on the critical path,
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* and we do not expect the validation to fail, you can guard the call with
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* an <code>assert</code> because each method returns true, and this code will
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* only be executed when asserts are enabled.
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* <p>
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* These methods are provided primarily to check parameter values for
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* constructors, setters, etc, and when they are used in this way, the javadoc
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* for the method must be updated to reflect what constraints are placed on the
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* parameters (e.g. attributeType cannot be null).
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* <p>
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* Feel free to add any method to this class that makes sense. Be sure to
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* ensure that they don't violate the spirit of this class in that performance
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* is second only to correctness.
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* <p>
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* There are a few issues open for remaining tasks:
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* <ul>
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* <li>757 Validator should expose a way to turn it off</li>
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* <li>758 Validator should provide a way to throttle it's error messages</li>
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* <li>759 Unit tests should always check that no unexpected Validator checks
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* failed</li>
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* </ul>
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*/
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public class Validator {
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/** This static final variable theoretically allows us to compile out all of
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* these checks. Since all of the code below is guarded with this check,
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* the compiler should eliminate it if ENABLE_CHECKS is false.
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* From doing a little bit of micro-benchmarking, it appears that setting
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* ENABLE_CHECKS=false speeds the code up by about a factor of four, but
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* it's still not the same as not having the invocation in the first place.
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* On a single CPU laptop, I was able to get 200M
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* invocations per second with ENABLE_CHECKS=true, and 350M with
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* ENABLE_CHECKS=false.
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* <p>
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* Setting this to false, will not eliminate any expensive computation
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* done in a parameter list (e.g. some self-check that returns true).*/
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public static final boolean ENABLE_CHECKS = true;
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/** A one-based array for parameter descriptions. */
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private static final String[] PARAM_DESCRIPTIONS =
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{"** A ZERO-BASED INDEX IS INVALID **",
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"(1st parameter)",
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"(2nd parameter)",
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"(3rd parameter)",
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"(4th parameter)",
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"(5th parameter)",
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"(6th parameter)",
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"(7th parameter)",
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"(8th parameter)",
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"(9th parameter)",
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"(10th parameter)"};
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/** A count of the errors detected by the methods in this class since the
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* last time that resetErrorCount was called. */
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private static long _errorCount = 0;
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/**
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* This method validates that the specified parameter is not null. It
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* throws an AssertionError if it is null after logging this error.
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* <p>
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* This should be used like an assert, except it is not turned
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* off at runtime. That is, it should only be used in situations where
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* there is a bug in someone's code if param is null.
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*
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* @param param the parameter to validate as non-null.
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* @return true always. This allows this call to be used in an assert
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* statement, which can skip this check and remove all
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* overhead from the calling code. This idiom should only be used when
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* performance testing proves that it is necessary.
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*
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* @throws AssertionError if and only if param is null
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* if assertions are enabled
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*/
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public static boolean ensureNotNull(Object param)
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throws AssertionError {
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if (ENABLE_CHECKS) {
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if (param == null) throwNull("");
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}
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return true;
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}
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/**
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* This method validates that the specified parameters are not null. It
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* throws an AssertionError if one of them are null after logging this error.
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* It's similar to the ensureNotNull(Object) call except it provides the
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* convenience of checking two parameters at once.
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* <p>
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* This should be used like an assert, except it is not turned
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* off at runtime. That is, it should only be used in situations where
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* there is a bug in someone's code if param is null.
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* <p>
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* See the class level javadoc for why we did not use varargs to
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* implement this method.
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*
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* @param param1 the first parameter to validate as non-null.
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* @param param2 the second parameter to validate as non-null.
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* @return true always. This allows this call to be used in an assert
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* statement, which can skip this check and remove all
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* overhead from the calling code. This idiom should only be used when
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* performance testing proves that it is necessary.
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*
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* @throws AssertionError if and only if any of the parameters is null
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*/
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public static boolean ensureNotNull(Object param1, Object param2)
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throws AssertionError {
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if (ENABLE_CHECKS) {
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if (param1 == null) throwNull(PARAM_DESCRIPTIONS[1]);
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if (param2 == null) throwNull(PARAM_DESCRIPTIONS[2]);
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}
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return true;
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}
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/**
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* This method validates that the specified parameters are not null. It
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* throws an AssertionError if one of them are null after logging this error.
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* It's similar to the ensureNotNull(Object) call except it provides the
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* convenience of checking three parameters at once.
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* <p>
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* This should be used like an assert, except it is not turned
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* off at runtime. That is, it should only be used in situations where
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* there is a bug in someone's code if param is null.
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* <p>
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* See the class level javadoc for why we did not use varargs to
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* implement this method.
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*
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* @param param1 the first parameter to validate as non-null.
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* @param param2 the second parameter to validate as non-null.
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* @param param3 the third parameter to validate as non-null.
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* @return true always. This allows this call to be used in an assert
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* statement, which can skip this check and remove all
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* overhead from the calling code. This idiom should only be used when
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* performance testing proves that it is necessary.
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*
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* @throws AssertionError if and only if one of the parameters is null
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*/
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public static boolean ensureNotNull(Object param1, Object param2,
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Object param3)
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throws AssertionError {
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if (ENABLE_CHECKS) {
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if (param1 == null) throwNull(PARAM_DESCRIPTIONS[1]);
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if (param2 == null) throwNull(PARAM_DESCRIPTIONS[2]);
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if (param3 == null) throwNull(PARAM_DESCRIPTIONS[3]);
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}
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return true;
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}
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/**
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* This method validates that the specified parameters are not null. It
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* throws an AssertionError if one of them are null after logging this error.
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* It's similar to the ensureNotNull(Object) call except it provides the
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* convenience of checking four parameters at once.
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* <p>
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* This should be used like an assert, except it is not turned
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* off at runtime. That is, it should only be used in situations where
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* there is a bug in someone's code if param is null.
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* <p>
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* See the class level javadoc for why we did not use varargs to
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* implement this method.
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*
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* @param param1 the first parameter to validate as non-null.
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* @param param2 the second parameter to validate as non-null.
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* @param param3 the third parameter to validate as non-null.
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* @param param4 the fourth parameter to validate as non-null.
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* @return true always. This allows this call to be used in an assert
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* statement, which can skip this check and remove all
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* overhead from the calling code. This idiom should only be used when
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* performance testing proves that it is necessary.
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*
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* @throws AssertionError if and only if one of the parameters is null
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*/
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public static boolean ensureNotNull(Object param1, Object param2,
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Object param3, Object param4)
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throws AssertionError {
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if (ENABLE_CHECKS) {
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if (param1 == null) throwNull(PARAM_DESCRIPTIONS[1]);
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if (param2 == null) throwNull(PARAM_DESCRIPTIONS[2]);
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if (param3 == null) throwNull(PARAM_DESCRIPTIONS[3]);
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if (param4 == null) throwNull(PARAM_DESCRIPTIONS[4]);
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}
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return true;
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}
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/**
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* This method validates that the specified parameter is true. It
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* throws an AssertionError if it is not true.
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* <p>
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* This should be used like an assert, except it is not turned
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* off at runtime. That is, it should only be used in situations where
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* there is a bug in someone's code if param is null. The other advantage of
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* using this method instead of an assert is that it logs the error to the
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* debug and error logs.
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*
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* @param condition the condition that must be true.
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* @return true always. This allows this call to be used in an assert
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* statement, which can skip this check and remove all
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* overhead from the calling code. This idiom should only be used when
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* performance testing proves that it is necessary.
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*
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* @throws AssertionError if condition is false
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*/
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public static boolean ensureTrue(boolean condition)
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throws AssertionError {
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if (ENABLE_CHECKS) {
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if (!condition) {
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ensureTrue(condition, "");
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}
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}
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return true;
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}
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/**
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* This method validates that the specified parameter is true. It
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* throws an AssertionError if it is not true. The supplied message is
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* included in the error message.
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* <p>
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* This should be used like an assert, except it is not turned
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* off at runtime. That is, it should only be used in situations where
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* there is a bug in someone's code if param is null. The other advantage of
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* using this method instead of an assert is that it logs the error to the
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* debug and error logs.
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*
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* @param condition the condition that must be true.
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* @param message the textual message to include in the error message.
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* @return true always. This allows this call to be used in an assert
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* statement, which can skip this check and remove all
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* overhead from the calling code. This idiom should only be used when
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* performance testing proves that it is necessary.
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*
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* @throws AssertionError if condition is false
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*/
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public static boolean ensureTrue(boolean condition, String message)
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throws AssertionError {
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if (ENABLE_CHECKS) {
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if (!condition) {
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String fullMessage = generateLineSpecificErrorMessage(
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"The specified condition must be true. " + message);
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logError(fullMessage);
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throw new AssertionError(fullMessage);
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}
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}
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return true;
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}
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////////////////////////////////////////////////////////////////////////////
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//
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// ERROR COUNT
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//
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////////////////////////////////////////////////////////////////////////////
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/**
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* Returns the number of errors that this class has detected since the
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* system started or the last time that resetErrorCount() was called.
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* <p>
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* This could be useful in the unit tests to validate that no background
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* errors occurred during a test. It could also be exposed by the monitoring
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* framekwork.
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*
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* @return the number of errors detected by this class since the error count
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* was last reset.
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*/
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public static synchronized long getErrorCount() {
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return _errorCount;
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}
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/**
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* Resets the error count to zero.
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*/
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public static synchronized void resetErrorCount() {
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_errorCount = 0;
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}
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private static synchronized void incrementErrorCount() {
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_errorCount++;
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}
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////////////////////////////////////////////////////////////////////////////
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//
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// PRIVATE
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//
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////////////////////////////////////////////////////////////////////////////
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private static String generateLineSpecificErrorMessage(String message) {
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return message + " The error occurred at " + getOriginalCallerLineInfo();
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}
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private static void throwNull(String message)
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throws AssertionError {
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String fullMessage = generateLineSpecificErrorMessage(
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"The specified parameter must not be null. " + message);
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logError(fullMessage);
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throw new AssertionError(fullMessage);
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}
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private static void logError(String message) {
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incrementErrorCount();
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String messageWithStack = message + ServerConstants.EOL + getCallingStack();
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// Log to the debug log.
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if (debugEnabled())
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{
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debugError(messageWithStack);
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}
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// Log to the error log.
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org.opends.server.loggers.Error.logError(ErrorLogCategory.CORE_SERVER,
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ErrorLogSeverity.SEVERE_ERROR,
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UtilityMessages.MSGID_VALIDATOR_PRECONDITION_NOT_MET,
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messageWithStack);
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}
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/*
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* @return a String representation of the line that called the
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* Validator method.
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*/
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private static String getOriginalCallerLineInfo() {
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StackTraceElement stackElements[] = Thread.currentThread().getStackTrace();
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int callerIndex = getOriginalCallerStackIndex(stackElements);
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return stackElements[callerIndex].toString();
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}
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/*
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* @return a stack trace rooted at the line that called the first
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* Validator method.
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*/
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private static String getCallingStack() {
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StackTraceElement stackElements[] = Thread.currentThread().getStackTrace();
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int callerIndex = getOriginalCallerStackIndex(stackElements);
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StringBuilder buffer = new StringBuilder();
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for (int i = callerIndex; i < stackElements.length; i++) {
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StackTraceElement stackElement = stackElements[i];
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buffer.append(stackElement).append(ServerConstants.EOL);
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}
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return buffer.toString();
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}
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/*
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* @return the index in the supplied stack trace of the first non-Validator
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* method.
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*/
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private static int getOriginalCallerStackIndex(StackTraceElement stack[]) {
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// Go up the stack until we find who called the first Validator method.
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StackTraceElement element = null;
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int i;
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for (i = 0; i < stack.length; i++) {
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element = stack[i];
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// The stack trace of this thread looks like
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// java.lang.Thread.dumpThreads(Native Method)
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// java.lang.Thread.getStackTrace(Thread.java:1383)
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// org.opends.server.util.Validator.getOriginalCallerLineInfo...
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// ...
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// original caller <---- this is what we want to return
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// more stack
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if (!element.getClassName().equals(Validator.class.getName()) &&
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!element.getClassName().equals(Thread.class.getName())) {
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break;
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}
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}
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return i;
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}
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}
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