With JDBC, a database is represented by a URL (Uniform Resource Locator). With PostgreSQL™, this takes one of the following forms:
jdbc:postgresql:database
jdbc:postgresql://host/database
jdbc:postgresql://host:port/database
The parameters have the following meanings:
host
The host name of the server. Defaults to localhost.
To specify an IPv6 address your must enclose the
host parameter
with square brackets, for example:
jdbc:postgresql://[::1]:5740/accounting
port
The port number the server is listening on. Defaults to the PostgreSQL™ standard port number (5432).
database
The database name.
To connect, you need to get a Connection instance from
JDBC. To do this,
you use the DriverManager.getConnection() method:
Connection db = DriverManager.getConnection(url, username, password);
In addition to the standard connection parameters the driver supports a
number of additional properties which can be used to specify additional
driver behavior specific to PostgreSQL™. These
properties may be specified in either the connection
URL or an additional
Properties object parameter to
DriverManager.getConnection. The following
examples illustrate the use of both methods to establish a SSL
connection.
String url = "jdbc:postgresql://localhost/test";
Properties props = new Properties();
props.setProperty("user","fred");
props.setProperty("password","secret");
props.setProperty("ssl","true");
Connection conn = DriverManager.getConnection(url, props);
String url = "jdbc:postgresql://localhost/test?user=fred&password=secret&ssl=true"; Connection conn = DriverManager.getConnection(url);
user = StringThe database user on whose behalf the connection is being made.
password = StringThe database user's password.
sslConnect using SSL. The driver must have been compiled with SSL support. This property does not need a value associated with it. The mere presence of it specifies a SSL connection. However, for compatibility with future versions, the value "true" is preferred. For more information see Chapter 4, Using SSL.
sslfactory = String
The provided value is a class name to use as the
SSLSocketFactory when establishing a
SSL connection.
For more information see the section called “Custom SSLSocketFactory”.
sslfactoryarg = String
This value is an optional argument to the constructor of the
sslfactory class provided above.
For more information see the section called “Custom SSLSocketFactory”.
compatible = String
Act like an older version of the driver to retain compatibility with
older applications. At the moment this controls two driver behaviors:
the handling of binary data fields, and the handling of parameters set
via setString()
Older versions of the driver used this property to also control the
protocol used to connect to the backend. This is now controlled by the
protocolVersion property.
Information on binary data handling is detailed in Chapter 7, Storing Binary Data. To force the use of Large Objects set the compatible property to 7.1.
When compatible is set to 7.4 or
below, the default for the stringtype parameter is
changed to unspecified.
protocolVersion = StringThe driver supports both the V2 and V3 frontend/backend protocols. The V3 protocol was introduced in 7.4 and the driver will by default try to connect using the V3 protocol, if that fails it will fall back to the V2 protocol. If the protocolVersion property is specified, the driver will try only the specified protocol (which should be either "2" or "3"). Setting protocolVersion to "2" may be used to avoid the failed attempt to use the V3 protocol when connecting to a version 7.3 or earlier server, or to force the driver to use the V2 protocol despite connecting to a 7.4 or greater server.
loglevel = int
Set the amount of logging information printed to the DriverManager's
current value for LogStream or LogWriter. It currently supports
values of org.postgresql.Driver.DEBUG (2) and
org.postgresql.Driver.INFO (1).
INFO will log very little information while
DEBUG will produce significant detail. This
property is only really useful if you are a developer or are
having problems with the driver.
charSet = StringThe character set to use for data sent to the database or recieved from the database. This property is only relevent for server versions less than or equal to 7.2. The 7.3 release was the first with multibyte support compiled by default and the driver uses its character set translation facilities instead of trying to do it itself.
allowEncodingChanges = boolean
When using the V3 protocol the driver monitors changes in certain
server configuration parameters that should not be touched by
end users. The client_encoding setting is set
by the driver and should not be altered. If the driver detects
a change it will abort the connection. There is one legitimate
exception to this behavior though, using the COPY
command on a file residing on the server's filesystem. The only
means of specifying the encoding of this file is by altering the
client_encoding setting. The
JDBC team considers this a failing of the
COPY command and hopes to provide an alternate
means of specifying the encoding in the future, but for now there
is this URL parameter. Enable this only if
you need to override the client encoding when doing a copy.
logUnclosedConnections = boolean
Clients may leak Connection objects by
failing to call its close() method.
Eventually these objects will be garbage collected and the
finalize() method will be called which will
close the Connection if caller has
neglected to do this himself. The usage of a finalizer is just
a stopgap solution. To help developers detect and correct the
source of these leaks the logUnclosedConnections
URL parameter has been added. It captures
a stacktrace at each Connection opening
and if the finalize() method is reached without
having been closed the stacktrace is printed to the log.
prepareThreshold = int
Determine the number of PreparedStatement
executions required before switching over to use server side prepared
statements. The default is five, meaning start using server side
prepared statements on the fifth execution of the same
PreparedStatement object. More
information on server side prepared
statements is available in the section called “Server Prepared Statements”.
loginTimeout = intSpecify how long to wait for establishment of a database connection. The timeout is specified in seconds.
socketTimeout = intThe timeout value used for socket read operations. If reading from the server takes longer than this value, the connection is closed. This can be used as both a brute force global query timeout and a method of detecting network problems. The timeout is specified in seconds and a value of zero means that it is disabled.
tcpKeepAlive = boolean
Enable or disable TCP keep-alive probe. The default is
false.
unknownLength = int
Certain postgresql types such as text do not
have a well defined length. When returning meta-data about
these types through functions like
ResultSetMetaData.getColumnDisplaySize
and ResultSetMetaData.getPrecision
we must provide a value and various client tools have
different ideas about what they would like to see. This
parameter specifies the length to return for types of
unknown length.
stringtype = String
Specify the type to use when binding PreparedStatement parameters
set via setString(). If stringtype is set to
varchar (the default), such parameters will be sent to the server as
varchar parameters. If stringtype is set to
unspecified, parameters will be sent to the server as untyped values,
and the server will attempt to infer an appropriate type. This is useful if you have an
existing application that uses setString() to set parameters that
are actually some other type, such as integers, and you are unable to change the
application to use an appropriate method such as setInt().
kerberosServerName = StringThe Kerberos service name to use when authenticating with GSSAPI. This is equivalent to libpq's PGKRBSRVNAME environment variable and defaults to "postgres".
jaasApplicationName = StringSpecifies the name of the JAAS system or application login configuration.
ApplicationName = StringSpecifies the name of the application that is using the connection. This allows a database administrator to see what applications are connected to the server and what resources they are using through views like pg_stat_activity.