Make compileAutomaton synchronized, as it can break for queries that are shared constants (like a drop down list in a web interface that provides predefined query constraints. These types of queries are in most places somewhere predefined in your code and then used by different threads/servlets/whatever). As the three transient vars cannot be set atomically, a parallel running thread may see half of the fields assigned and will get NPE).

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@987118 13f79535-47bb-0310-9956-ffa450edef68

lucene/src/java/org/apache/lucene/search/AutomatonQuery.java

@@ -75,7 +75,8 @@ public class AutomatonQuery extends MultiTermQuery {
     MinimizationOperations.minimize(automaton);
   }
 
-  private void compileAutomaton() {
+  private synchronized void compileAutomaton() {
+    // this method must be synchronized, as setting the three transient fields is not atomic:
     if (runAutomaton == null) {
       runAutomaton = new ByteRunAutomaton(automaton);
       isFinite = SpecialOperations.isFinite(automaton);