With JDBC, a database is represented by a URL (Uniform Resource Locator). With PostgreSQL™, this takes one of the following forms:
databasehost/databasehost/host:port/databasehost:port/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. The default is to connect to a database with the same name as the user 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 behaviour
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 = String
The database user on whose behalf the connection is being made.
password = String
The database user's password.
ssl
Connect 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 behaviours: 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.
sendBufferSize = int
Sets SO_SNDBUF on the connection stream
recvBufferSize = int
Sets SO_RCVBUF on the connection stream
protocolVersion = String
The 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 = String
The character set to use for data sent to the database or received from the database. This property is only relevant 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 behaviour 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.
binaryTransferEnable = String
A comma separated list of types to enable binary transfer. Either OID numbers or names.
binaryTransferDisable = String
A comma separated list of types to disable binary transfer. Either OID numbers or names. Overrides values in the driver default set and values set with binaryTransferEnable.
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”.
preparedStatementCacheQueries = int
Determine the number of queries that are cached in each connection. The default is 256, meaning if you use more than 256 different queries in prepareStatement() calls, the least recently used ones will be discarded. The cache allows application to benefit from “Server Prepared Statements” prepareThreshold even if the prepared statement is closed after each execution. The value of 0 disables the cache.
Each connection has its own statement cache.
preparedStatementCacheSizeMiB = int
Determine the maximum size (in mebibytes) of the prepared queries cache
(see preparedStatementCacheQueries).
The default is 5, meaning if you happen to cache more than 5 MiB of queries
the least recently used ones will be discarded.
The main aim of this setting is to prevent OutOfMemoryError.
The value of 0 disables the cache.
If a query would consume more than a half of preparedStatementCacheSizeMiB,
then it is discarded immediately.
defaultRowFetchSize = int
Determine the number of rows fetched in ResultSet
by one fetch with trip to the database. Limiting the number of rows are fetch with
each trip to the database allow avoids unnecessary memory consumption
and as a consequence OutOfMemoryException
The default is zero, meaning that in ResultSet
will be fetch all rows at once. Negative number is not available.
loginTimeout = int
Specify how long to wait for establishment of a database connection. The timeout is specified in seconds.
connectTimeout = int
The timeout value used for socket connect operations. If connecting to the server takes longer than this value, the connection is broken. The timeout is specified in seconds and a value of zero means that it is disabled.
socketTimeout = int
The 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 = String
The Kerberos service name to use when authenticating with GSSAPI. This is equivalent to libpq's PGKRBSRVNAME environment variable and defaults to "postgres".
jaasApplicationName = String
Specifies the name of the JAAS system or application login configuration.
ApplicationName = String
Specifies 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 pgstatactivity.
gsslib = String
Force either SSPI (Windows transparent single-sign-on) or GSSAPI (Kerberos, via JSSE) to be used when the server requests Kerberos or SSPI authentication. Permissible values are auto (default, see below), sspi (force SSPI) or gssapi (force GSSAPI-JSSE).
If this parameter is auto, SSPI is attempted if the server requests SSPI authentication, the JDBC client is running on Windows, and the Waffle libraries required for SSPI are on the CLASSPATH. Otherwise Kerberos/GSSAPI via JSSE is used. Note that this behaviour does not exactly match that of libpq, which uses Windows' SSPI libraries for Kerberos (GSSAPI) requests by default when on Windows.
gssapi mode forces JSSE's GSSAPI to be used even if SSPI is available, matching the pre-9.4 behaviour.
On non-Windows platforms or where SSPI is unavailable, forcing sspi mode will fail with a PSQLException.
Since: 9.4
sspiServiceClass = String
Specifies the name of the Windows SSPI service class that forms the service class part of the SPN. The default, POSTGRES, is almost always correct.
See: SSPI authentication (Pg docs) Service Principal Names (MSDN), DsMakeSpn (MSDN) Configuring SSPI (Pg wiki).
This parameter is ignored on non-Windows platforms.
useSpnego = boolean
Use SPNEGO in SSPI authentication requests
sendBufferSize = int
Sets SO_SNDBUF on the connection stream
receiveBufferSize = int
Sets SO_RCVBUF on the connection stream
readOnly = boolean
Put the connection in read-only mode
disableColumnSanitiser = boolean
Enable optimization that disables column name sanitiser.
assumeMinServerVersion = String
Assume that the server is at least the given version, thus enabling to some optimization at connection time instead of trying to be version blind.
currentSchema = String
Specify the schema to be set in the search-path. This schema will be used to resolve unqualified object names used in statements over this connection.
targetServerType
Allows opening connections to only servers with required state, the allowed values are any, master, slave and preferSlave. The master/slave distinction is currently done by observing if the server allows writes. The value preferSlave tries to connect to slaves if any are available, otherwise allows falls back to connecting also to master.
hostRecheckSeconds = int
Controls how long in seconds the knowledge about a host state is cached in JVM wide global cache. The default value is 10 seconds.
loadBalanceHosts = boolean
In default mode (disabled) hosts are connected in the given order. If enabled hosts are chosen randomly from the set of suitable candidates.
To support simple connection fail-over it is possible to define multiple endpoints (host and port pairs) in the connection url separated by commas. The driver will try to once connect to each of them in order until the connection succeeds. If none succeed, a normal connection exception is thrown.
The syntax for the connection url is:
jdbc:postgresql://host1:port1,host2:port2/database
The simple connection fail-over is useful when running against a high availability postgres installation that has identical data on each node. For example streaming replication postgres or postgres-xc cluster.
For example an application can create two connection pools. One data source is for writes, another for reads. The write pool limits connections only to master node:
jdbc:postgresql://node1,node2,node3/accounting?targetServerType=master . And read pool balances connections between slaves nodes, but allows connections also to master if no slaves are available:
jdbc:postgresql://node1,node2,node3/accounting?targetServerType=preferSlave&loadBalanceHosts=true