how driver manager works in java

java.sql
Class DriverManager

java.lang.Object
  extended by java.sql.DriverManager

public class DriverManager

extends Object

The basic service for managing a set of JDBC drivers.
NOTE: The DataSource interface, new in the JDBC 2.0 API, provides another way to connect to a data source. The use of a DataSource object is the preferred means of connecting to a data source.
As part of its initialization, the DriverManager class will attempt to load the driver classes referenced in the "jdbc.drivers" system property. This allows a user to customize the JDBC Drivers used by their applications. For example in your ~/.hotjava/properties file you might specify:
 jdbc.drivers=foo.bah.Driver:wombat.sql.Driver:bad.taste.ourDriver
The DriverManager methods getConnection and getDrivers have been enhanced to support the Java Standard Edition Service Provider mechanism. JDBC 4.0 Drivers must include the file META-INF/services/java.sql.Driver. This file contains the name of the JDBC drivers implementation of java.sql.Driver. For example, to load the my.sql.Driver class, the META-INF/services/java.sql.Driver file would contain the entry:
 my.sql.Driver
Applications no longer need to explictly load JDBC drivers using Class.forName(). Existing programs which currently load JDBC drivers using Class.forName() will continue to work without modification.
When the method getConnection is called, the DriverManager will attempt to locate a suitable driver from amongst those loaded at initialization and those loaded explicitly using the same classloader as the current applet or application.
Starting with the Java 2 SDK, Standard Edition, version 1.3, a logging stream can be set only if the proper permission has been granted. Normally this will be done with the tool PolicyTool, which can be used to grantpermission java.sql.SQLPermission "setLog".


See Also:
Driver, Connection

Method Summary
static voidderegisterDriver(Driver driver)
          Drops a driver from the DriverManager's list.
static ConnectiongetConnection(String url)
          Attempts to establish a connection to the given database URL.
static ConnectiongetConnection(String url, Properties info)
          Attempts to establish a connection to the given database URL.
static ConnectiongetConnection(String url, String user, String password)
          Attempts to establish a connection to the given database URL.
static DrivergetDriver(String url)
          Attempts to locate a driver that understands the given URL.
static Enumeration<Driver>getDrivers()
          Retrieves an Enumeration with all of the currently loaded JDBC drivers to which the current caller has access.
static intgetLoginTimeout()
          Gets the maximum time in seconds that a driver can wait when attempting to log in to a database.
static PrintStreamgetLogStream()
          Deprecated.  
static PrintWritergetLogWriter()
          Retrieves the log writer.
static voidprintln(String message)
          Prints a message to the current JDBC log stream.
static voidregisterDriver(Driver driver)
          Registers the given driver with the DriverManager.
static voidsetLoginTimeout(int seconds)
          Sets the maximum time in seconds that a driver will wait while attempting to connect to a database.
static voidsetLogStream(PrintStream out)
          Deprecated.  
static voidsetLogWriter(PrintWriter out)
          Sets the logging/tracing PrintWriter object that is used by the DriverManager and all drivers.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait


Method Detail

getLogWriter

public static PrintWriter getLogWriter()
Retrieves the log writer. The getLogWriter and setLogWriter methods should be used instead of the get/setlogStream methods, which are deprecated.
Returns:
a java.io.PrintWriter object
Since:
1.2
See Also:
setLogWriter(java.io.PrintWriter)

setLogWriter

public static void setLogWriter(PrintWriter out)
Sets the logging/tracing PrintWriter object that is used by the DriverManager and all drivers.There is a minor versioning problem created by the introduction of the method setLogWriter. The method setLogWriter cannot create a PrintStream object that will be returned by getLogStream---the Java platform does not provide a backward conversion. As a result, a new application that uses setLogWriter and also uses a JDBC 1.0 driver that uses getLogStream will likely not see debugging information written by that driver.
Starting with the Java 2 SDK, Standard Edition, version 1.3 release, this method checks to see that there is an SQLPermission object before setting the logging stream. If a SecurityManager exists and itscheckPermission method denies setting the log writer, this method throws a java.lang.SecurityException.
Parameters:
out - the new logging/tracing PrintStream object; null to disable logging and tracing
Throws:
SecurityException - if a security manager exists and its checkPermission method denies setting the log writer
Since:
1.2
See Also:
SecurityManager.checkPermission(java.security.Permission), getLogWriter()

getConnection

public static Connection getConnection(String url,
                                       Properties info)
                                throws SQLException
Attempts to establish a connection to the given database URL. The DriverManager attempts to select an appropriate driver from the set of registered JDBC drivers.
Parameters:
url - a database url of the form jdbc:subprotocol:subname
info - a list of arbitrary string tag/value pairs as connection arguments; normally at least a "user" and "password" property should be included
Returns:
a Connection to the URL
Throws:
SQLException - if a database access error occurs

getConnection

public static Connection getConnection(String url,
                                       String user,
                                       String password)
                                throws SQLException
Attempts to establish a connection to the given database URL. The DriverManager attempts to select an appropriate driver from the set of registered JDBC drivers.
Parameters:
url - a database url of the form jdbc:subprotocol:subname
user - the database user on whose behalf the connection is being made
password - the user's password
Returns:
a connection to the URL
Throws:
SQLException - if a database access error occurs

getConnection

public static Connection getConnection(String url)
                                throws SQLException
Attempts to establish a connection to the given database URL. The DriverManager attempts to select an appropriate driver from the set of registered JDBC drivers.
Parameters:
url - a database url of the form jdbc:subprotocol:subname
Returns:
a connection to the URL
Throws:
SQLException - if a database access error occurs

getDriver

public static Driver getDriver(String url)
                        throws SQLException
Attempts to locate a driver that understands the given URL. The DriverManager attempts to select an appropriate driver from the set of registered JDBC drivers.
Parameters:
url - a database URL of the form jdbc:subprotocol:subname
Returns:
a Driver object representing a driver that can connect to the given URL
Throws:
SQLException - if a database access error occurs

registerDriver

public static void registerDriver(Driver driver)
                           throws SQLException
Registers the given driver with the DriverManager. A newly-loaded driver class should call the method registerDriver to make itself known to the DriverManager.
Parameters:
driver - the new JDBC Driver that is to be registered with the DriverManager
Throws:
SQLException - if a database access error occurs

deregisterDriver

public static void deregisterDriver(Driver driver)
                             throws SQLException
Drops a driver from the DriverManager's list. Applets can only deregister drivers from their own classloaders.
Parameters:
driver - the JDBC Driver to drop
Throws:
SQLException - if a database access error occurs

getDrivers

public static Enumeration<Driver> getDrivers()
Retrieves an Enumeration with all of the currently loaded JDBC drivers to which the current caller has access.Note: The classname of a driver can be found using d.getClass().getName()
Returns:
the list of JDBC Drivers loaded by the caller's class loader

setLoginTimeout

public static void setLoginTimeout(int seconds)
Sets the maximum time in seconds that a driver will wait while attempting to connect to a database.
Parameters:
seconds - the login time limit in seconds; zero means there is no limit
See Also:
getLoginTimeout()

getLoginTimeout

public static int getLoginTimeout()
Gets the maximum time in seconds that a driver can wait when attempting to log in to a database.
Returns:
the driver login time limit in seconds
See Also:
setLoginTimeout(int)

setLogStream

public static void setLogStream(PrintStream out)
Deprecated. 
Sets the logging/tracing PrintStream that is used by the DriverManager and all drivers.In the Java 2 SDK, Standard Edition, version 1.3 release, this method checks to see that there is an SQLPermission object before setting the logging stream. If a SecurityManager exists and itscheckPermission method denies setting the log writer, this method throws a java.lang.SecurityException.
Parameters:
out - the new logging/tracing PrintStream; to disable, set to null
Throws:
SecurityException - if a security manager exists and its checkPermission method denies setting the log stream
See Also:
SecurityManager.checkPermission(java.security.Permission), getLogStream()

getLogStream

public static PrintStream getLogStream()
Deprecated. 
Retrieves the logging/tracing PrintStream that is used by the DriverManager and all drivers.
Returns:
the logging/tracing PrintStream; if disabled, is null
See Also:
setLogStream(java.io.PrintStream)

println

public static void println(String message)

Prints a message to the current JDBC log stream.
Parameters:
message - a log or tracing message

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