org.apache.derby.client.am.stmtcache
Class JDBCStatementCache

java.lang.Object
  extended by org.apache.derby.client.am.stmtcache.JDBCStatementCache

public final class JDBCStatementCache
extends java.lang.Object

A cache for JDBC statement objects.

The entries in the cache contains objects implementing the java.sql.PreparedStatement interface, and they are inserted with a key object implementing the interface StatementKey. The cached objects can be either java.sql.PreparedStatement or java.sql.CallableStatement. These two should be separated by using different types of keys.

The cache only contains free statement objects, and on a successful request for a cached statement the statement is removed from the cache. The cache is not intended to hold duplicate statements. The physical prepared statement should be (re-)inserted into the cache when close is called on the logical prepared statement using it.

There is a maximum number of cached statements associated with the cache. If this number is exceeded, the oldest entry will be thrown out. One can always throw out an entry, because the fact that it is in the cache means it is free and not in use.


Nested Class Summary
private static class JDBCStatementCache.BoundedLinkedHashMap
          A LinkedHashMap with an upper bound on the number of entries.
 
Field Summary
private  java.util.LinkedHashMap statements
          Structure holding the cached prepared statement objects.
 
Constructor Summary
JDBCStatementCache(int maxSize)
          Creates a new, empty JDBC statement cache.
 
Method Summary
 boolean cacheStatement(StatementKey statementKey, java.sql.PreparedStatement ps)
          Cache the prepared statement if it does not already exist.
 java.sql.PreparedStatement getCached(StatementKey statementKey)
          Retrieves a cached prepared statement if one exists.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

statements

private final java.util.LinkedHashMap statements
Structure holding the cached prepared statement objects.

Constructor Detail

JDBCStatementCache

public JDBCStatementCache(int maxSize)
Creates a new, empty JDBC statement cache.

Parameters:
maxSize - maximum number of statements in the cache
Throws:
java.lang.IllegalArgumentException - if maxSize is less than one
Method Detail

getCached

public java.sql.PreparedStatement getCached(StatementKey statementKey)
Retrieves a cached prepared statement if one exists.

Parameters:
statementKey - key for the prepared statement to look up
Returns:
A cached statement if one exists, null otherwise.

cacheStatement

public boolean cacheStatement(StatementKey statementKey,
                              java.sql.PreparedStatement ps)
Cache the prepared statement if it does not already exist.

Parameters:
statementKey - key to insert prepared statement with
ps - prepared statement to cache
Returns:
true if added to the cache, false if not.

Built on Thu 2010-12-23 20:49:13+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.