Parameter Description
username The connection username to be passed to our JDBC driver to establish a
connection.
password The connection password to be passed to our JDBC driver to establish a
connection.
url The connection URL to be passed to our JDBC driver to establish a
connection.
driverClassName The fully qualified Java class name of the JDBC driver to be used.
connectionProperties The connection properties that will be sent to our JDBC driver when
establishing new connections.
Format of the string must be [propertyName=property;]*
NOTE - The "user" and "password" properties will be passed explicitly, so
they do not need to be included here.
Parameter Default Description
defaultAutoCommit true The default auto-commit state of connections created by
this pool.
defaultReadOnly driver
default
The default read-only state of connections created by this
pool. If not set then the setReadOnly method will not be
called. (Some drivers don't support read only mode, ex:
Informix)
defaultTransactionIsolation driver
default
The default TransactionIsolation state of connections
created by this pool. One of the following: (see javadoc)
NONE
READ_COMMITTED
READ_UNCOMMITTED
REPEATABLE_READ
SERIALIZABLE
defaultCatalog The default catalog of connections created by this pool.
Parameter Default Description
initialSize 0 The initial number of connections that are created when the pool is
started.
Since: 1.2
maxActive 8 The maximum number of active connections that can be allocated from
this pool at the same time, or negative for no limit.
maxIdle 8 The maximum number of connections that can remain idle in the pool,
without extra ones being released, or negative for no limit.
minIdle 0 The minimum number of connections that can remain idle in the pool,
without extra ones being created, or zero to create none.
maxWait indefinitely The maximum number of milliseconds that the pool will wait (when
there are no available connections) for a connection to be returned
before throwing an exception, or -1 to wait indefinitely.
NOTE: If maxIdle is set too low on heavily loaded systems it is possible you will see connections
being closed and almost immediately new connections being opened. This is a result of the active
threads momentarily closing connections faster than they are opening them, causing the number of
idle connections to rise above maxIdle. The best value for maxIdle for heavily loaded system will
vary but the default is a good starting point.
Parameter Default Description
validationQuery The SQL query that will be used to validate
connections from this pool before returning them to
the caller. If specified, this query MUST be an SQL
SELECT statement that returns at least one row.
testOnBorrow true The indication of whether objects will be validated
before being borrowed from the pool. If the object
fails to validate, it will be dropped from the pool, and
we will attempt to borrow another.
NOTE - for a true value to have any effect,
thevalidationQuery parameter must be set to a
non-null string.
testOnReturn false The indication of whether objects will be validated
before being returned to the pool.
NOTE - for a true value to have any effect,
thevalidationQuery parameter must be set to a
non-null string.
testWhileIdle false The indication of whether objects will be validated by
the idle object evictor (if any). If an object fails to
validate, it will be dropped from the pool.
NOTE - for a true value to have any effect,
thevalidationQuery parameter must be set to a
non-null string.
timeBetweenEvictionRunsMillis -1 The number of milliseconds to sleep between runs of
the idle object evictor thread. When non-positive, no
idle object evictor thread will be run.
numTestsPerEvictionRun 3 The number of objects to examine during each run of
the idle object evictor thread (if any).
minEvictableIdleTimeMillis 1000 *
60 * 30
The minimum amount of time an object may sit idle
in the pool before it is eligable for eviction by the idle
object evictor (if any).
connectionInitSqls . null A Collection of SQL statements that will be used to
initialize physical connections when they are first
created. These statements are executed only once -
when the configured connection factory creates the
connection.
NOTE: Versions 1.3 and 1.4 of DBCP incorrectly
use "initConnectionSqls" as the name of this property
for JNDI object factory configuration. Until
1.3.1/1.4.1 are released, "initConnectionSqls" must be
used as the name for this property when using
BasicDataSoureFactory to create BasicDataSource
instances via JNDI
Parameter Default Description
poolPreparedStatements false Enable prepared statement pooling for this pool.
maxOpenPreparedStatements unlimited The maximum number of open statements that can be
allocated from the statement pool at the same time, or
zero for no limit.
This component has also the ability to pool PreparedStatements. When enabled a statement pool
will be created for each Connection and PreparedStatements created by one of the following methods
will be pooled:
public PreparedStatement prepareStatement(String sql)
public PreparedStatement prepareStatement(String sql, int resultSetType, int
resultSetConcurrency)
NOTE - Make sure your connection has some resources left for the other statements. Pooling
PreparedStatements may keep their cursors open in the database, causing a connection to run out of
cursors, especially if maxOpenPreparedStatements is left at the default (unlimited) and an application
opens a large number of different PreparedStatements per connection. To avoid this problem,
maxOpenPreparedStatements should be set to a value less than the maximum number of cursors that
can be open on a Connection.
Parameter Default Description
accessToUnderlyingConnectionAllowed false Controls if the PoolGuard allows access to the
underlying connection.
When allowed you can access the underlying connection using the following construct:
Connection conn = ds.getConnection();
Connection dconn = ((DelegatingConnection) conn).getInnermostDelegate();
...
conn.close()
Default is false, it is a potential dangerous operation and misbehaving programs can do harmfull
things. (closing the underlying or continue using it when the guarded connection is already closed) Be
carefull and only use when you need direct access to driver specific extentions.
NOTE: Do not close the underlying connection, only the original one.
Parameter Default Description
removeAbandoned false Flag to remove abandoned connections if they exceed the
removeAbandonedTimout.
If set to true a connection is considered abandoned and
eligible for removal if it has been idle longer than the
removeAbandonedTimeout. Setting this to true can recover
db connections from poorly written applications which fail
to close a connection.
removeAbandonedTimeout 300 Timeout in seconds before an abandoned connection can be
removed.
logAbandoned false Flag to log stack traces for application code which
abandoned a Statement or Connection.
Logging of abandoned Statements and Connections adds
overhead for every Connection open or new Statement
because a stack trace has to be generated.
If you have enabled "removeAbandoned" then it is possible that a connection is reclaimed by the
pool because it is considered to be abandoned. This mechanism is triggered when (getNumIdle() < 2)
and (getNumActive() > getMaxActive() - 3)
For example maxActive=20 and 18 active connections and 1 idle connection would trigger the
"removeAbandoned". But only the active connections that aren't used for more then
"removeAbandonedTimeout" seconds are removed, default (300 sec). Traversing a resultset doesn't
count as being used.
© 2001-2010 The Apache Software Foundation
摘自:http://commons.apache.org/dbcp/configuration.html
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