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From mgen...@apache.org
Subject svn commit: r695898 - /cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/exp/Expression.java
Date Tue, 16 Sep 2008 14:24:12 GMT
Author: mgentry
Date: Tue Sep 16 07:24:11 2008
New Revision: 695898

URL: http://svn.apache.org/viewvc?rev=695898&view=rev
Log:
Updated Expression.fromString to cache the parsed expressions instead of re-parsing them every
time.

Modified:
    cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/exp/Expression.java

Modified: cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/exp/Expression.java
URL: http://svn.apache.org/viewvc/cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/exp/Expression.java?rev=695898&r1=695897&r2=695898&view=diff
==============================================================================
--- cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/exp/Expression.java
(original)
+++ cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/exp/Expression.java
Tue Sep 16 07:24:11 2008
@@ -26,6 +26,7 @@
 import java.io.StringWriter;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -119,21 +120,36 @@
 
     protected int type;
 
+    private static Map<String, Expression> expressionCache =
+        Collections.synchronizedMap(new HashMap<String, Expression>(32));
+
     /**
      * Parses string, converting it to Expression. If string does not represent a
      * semantically correct expression, an ExpressionException is thrown.
      * 
      * @since 1.1
      */
-    // TODO: cache expression strings, since this operation is pretty slow
     public static Expression fromString(String expressionString) {
         if (expressionString == null) {
             throw new NullPointerException("Null expression string.");
         }
 
-        Reader reader = new StringReader(expressionString);
+        // Retrieve, if possible, the expression from the cache.
+        Expression expression = expressionCache.get(expressionString);
+
+        // If the expression was cached, return it immediately without parsing.
+        if (expression != null)
+            return expression;
+
+        // Couldn't find expression, parse, cache, and return it.
         try {
-            return new ExpressionParser(reader).expression();
+            Reader reader = new StringReader(expressionString);
+
+            expression = new ExpressionParser(reader).expression();
+
+            expressionCache.put(expressionString, expression);
+
+            return expression;
         }
         catch (ParseException ex) {
             throw new ExpressionException(ex.getMessage(), ex);



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