Also (c) (related to my "emeddable" note) - in an environment like
J2EE, where there are layers upon layers of explicit and implicit
containers between the VM and the application code, having a static
object storage buried in a framework is a bad practice - it prevents
the container layers from performing their functions of isolating
"contexts" for various users (whatever those contexts might be).
Andrus
On Sep 16, 2008, at 5:30 PM, Andrus Adamchik wrote:
-1. Unmanaged static caches are bad, especially in an embeddable
framework like Cayenne. This is (a) a potential memory leak and (b)
a potential synchronization nightmare (Expression is not immutable
and can be modified by the caller).
Andrus
On Sep 16, 2008, at 5:24 PM, [EMAIL PROTECTED] wrote:
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cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/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Modified: cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/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http://svn.apache.org/viewvc/cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/exp/Expression.java?rev=695898&r1=695897&r2=695898&view=diff
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=====================================================================
--- cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/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+++ cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/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);
