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Example 3.1. JDBC example
This simplified example assumes that you are using the transactional JDBC driver provided with JBossTS. For details about how to configure and use this driver see the previous Chapter.
public class JDBCTest
{
public static void main (String[] args)
{
/*
*/
Connection conn = null;
Connection conn2 = null;
Statement stmt = null; // non-tx statement
Statement stmtx = null; // will be a tx-statement
Properties dbProperties = new Properties();
try
{
System.out.println("\nCreating connection to database: "+url);
/*
* Create conn and conn2 so that they are bound to the JBossTS
* transactional JDBC driver. The details of how to do this will
* depend on your environment, the database you wish to use and
* whether or not you want to use the Direct or JNDI approach. See
* the appropriate chapter in the JTA Programmers Guide.
*/
stmt = conn.createStatement(); // non-tx statement
try
{
stmt.executeUpdate("DROP TABLE test_table");
stmt.executeUpdate("DROP TABLE test_table2");
}
catch (Exception e)
{
// assume not in database.
}
try
{
stmt.executeUpdate("CREATE TABLE test_table (a INTEGER,b INTEGER)");
stmt.executeUpdate("CREATE TABLE test_table2 (a INTEGER,b INTEGER)");
}
catch (Exception e)
{
}
try
{
System.out.println("Starting top-level transaction.");
com.arjuna.ats.jta.UserTransaction.userTransaction().begin();
stmtx = conn.createStatement(); // will be a tx-statement
System.out.println("\nAdding entries to table 1.");
stmtx.executeUpdate("INSERT INTO test_table (a, b) VALUES (1,2)");
ResultSet res1 = null;
System.out.println("\nInspecting table 1.");
res1 = stmtx.executeQuery("SELECT * FROM test_table");
while (res1.next())
{
System.out.println("Column 1: "+res1.getInt(1));
System.out.println("Column 2: "+res1.getInt(2));
}
System.out.println("\nAdding entries to table 2.");
stmtx.executeUpdate("INSERT INTO test_table2 (a, b) VALUES (3,4)");
res1 = stmtx.executeQuery("SELECT * FROM test_table2");
System.out.println("\nInspecting table 2.");
while (res1.next())
{
System.out.println("Column 1: "+res1.getInt(1));
System.out.println("Column 2: "+res1.getInt(2));
}
System.out.print("\nNow attempting to rollback changes.");
com.arjuna.ats.jta.UserTransaction.userTransaction().rollback();
com.arjuna.ats.jta.UserTransaction.userTransaction().begin();
stmtx = conn.createStatement();
ResultSet res2 = null;
System.out.println("\nNow checking state of table 1.");
res2 = stmtx.executeQuery("SELECT * FROM test_table");
while (res2.next())
{
System.out.println("Column 1: "+res2.getInt(1));
System.out.println("Column 2: "+res2.getInt(2));
}
System.out.println("\nNow checking state of table 2.");
stmtx = conn.createStatement();
res2 = stmtx.executeQuery("SELECT * FROM test_table2");
while (res2.next())
{
System.out.println("Column 1: "+res2.getInt(1));
System.out.println("Column 2: "+res2.getInt(2));
}
com.arjuna.ats.jta.UserTransaction.userTransaction().commit(true);
}
catch (Exception ex)
{
ex.printStackTrace();
System.exit(0);
}
}
catch (Exception sysEx)
{
sysEx.printStackTrace();
System.exit(0);
}
}
This class implements the XAResourceRecovery interface for XAResources. The parameter supplied in setParameters
can contain arbitrary information necessary to initialize the class once created. In this example, it contains the
name of the property file in which the database connection information is specified, as well as the number of
connections that this file contains information on. Each item is separated by a semicolon.
This is only a small example of the sorts of things an XAResourceRecovery implementer could do. This implementation uses a property file that is assumed to contain sufficient information to recreate connections used during the normal run of an application so that recovery can be performed on them. Typically, user-names and passwords should never be presented in raw text on a production system.
Example 3.2. Database parameter format for the properties file
DB_x_DatabaseURL=
DB_x_DatabaseUser=
DB_x_DatabasePassword=
DB_x_DatabaseDynamicClass=
x is the number of the connection information.
Some error-handling code is missing from this example, to make it more readable.
Example 3.3. Failure recovery example with BasicXARecovery
/*
* Some XAResourceRecovery implementations will do their startup work here,
* and then do little or nothing in setDetails. Since this one needs to know
* dynamic class name, the constructor does nothing.
*/
public BasicXARecovery () throws SQLException
{
numberOfConnections = 1;
connectionIndex = 0;
props = null;
}
/**
* The recovery module will have chopped off this class name already. The
* parameter should specify a property file from which the url, user name,
* password, etc. can be read.
*
* @message com.arjuna.ats.internal.jdbc.recovery.initexp An exception
* occurred during initialisation.
*/
public boolean initialise (String parameter) throws SQLException
{
if (parameter == null)
return true;
int breakPosition = parameter.indexOf(BREAKCHARACTER);
String fileName = parameter;
if (breakPosition != -1)
{
fileName = parameter.substring(0, breakPosition - 1);
try
{
numberOfConnections = Integer.parseInt(parameter
.substring(breakPosition + 1));
}
catch (NumberFormatException e)
{
return false;
}
}
try
{
String uri = com.arjuna.common.util.FileLocator
.locateFile(fileName);
jdbcPropertyManager.propertyManager.load(XMLFilePlugin.class
.getName(), uri);
props = jdbcPropertyManager.propertyManager.getProperties();
}
catch (Exception e)
{
return false;
}
return true;
}
/**
* @message com.arjuna.ats.internal.jdbc.recovery.xarec {0} could not find
* information for connection!
*/
public synchronized XAResource getXAResource () throws SQLException
{
JDBC2RecoveryConnection conn = null;
if (hasMoreResources())
{
connectionIndex++;
conn = getStandardConnection();
if (conn == null) conn = getJNDIConnection();
}
return conn.recoveryConnection().getConnection().getXAResource();
}
public synchronized boolean hasMoreResources ()
{
if (connectionIndex == numberOfConnections)
return false;
else
return true;
}
private final JDBC2RecoveryConnection getStandardConnection ()
throws SQLException
{
String number = new String("" + connectionIndex);
String url = new String(dbTag + number + urlTag);
String password = new String(dbTag + number + passwordTag);
String user = new String(dbTag + number + userTag);
String dynamicClass = new String(dbTag + number + dynamicClassTag);
Properties dbProperties = new Properties();
String theUser = props.getProperty(user);
String thePassword = props.getProperty(password);
if (theUser != null)
{
dbProperties.put(TransactionalDriver.userName, theUser);
dbProperties.put(TransactionalDriver.password, thePassword);
String dc = props.getProperty(dynamicClass);
if (dc != null)
dbProperties.put(TransactionalDriver.dynamicClass, dc);
return new JDBC2RecoveryConnection(url, dbProperties);
}
else
return null;
}
private final JDBC2RecoveryConnection getJNDIConnection ()
throws SQLException
{
String number = new String("" + connectionIndex);
String url = new String(dbTag + jndiTag + number + urlTag);
String password = new String(dbTag + jndiTag + number + passwordTag);
String user = new String(dbTag + jndiTag + number + userTag);
Properties dbProperties = new Properties();
String theUser = props.getProperty(user);
String thePassword = props.getProperty(password);
if (theUser != null)
{
dbProperties.put(TransactionalDriver.userName, theUser);
dbProperties.put(TransactionalDriver.password, thePassword);
return new JDBC2RecoveryConnection(url, dbProperties);
}
else
return null;
}
private int numberOfConnections;
private int connectionIndex;
private Properties props;
private static final String dbTag = "DB_";
private static final String urlTag = "_DatabaseURL";
private static final String passwordTag = "_DatabasePassword";
private static final String userTag = "_DatabaseUser";
private static final String dynamicClassTag = "_DatabaseDynamicClass";
private static final String jndiTag = "JNDI_";
/*
* Example:
*
* DB2_DatabaseURL=jdbc\:arjuna\:sequelink\://qa02\:20001
* DB2_DatabaseUser=tester2 DB2_DatabasePassword=tester
* DB2_DatabaseDynamicClass=com.arjuna.ats.internal.jdbc.drivers.sequelink_5_1
*
* DB_JNDI_DatabaseURL=jdbc\:arjuna\:jndi DB_JNDI_DatabaseUser=tester1
* DB_JNDI_DatabasePassword=tester DB_JNDI_DatabaseName=empay
* DB_JNDI_Host=qa02 DB_JNDI_Port=20000
*/
private static final char BREAKCHARACTER = ';'; // delimiter for parameters
You can use the class com.arjuna.ats.internal.jdbc.recovery.JDBC2RecoveryConnection to
create a new connection to the database using the same parameters used to create the initial connection.