You establish a connection by completing two actions:

1. Load Informix JDBC Driver.

2. Create a connection to either a database server or a specific database.

try 
    {
    Class.forName("com.informix.jdbc.IfxDriver");
    } 
catch (Exception e)
    {
    System.out.println("ERROR: failed to load Informix JDBC driver.");
    e.printStackTrace();
    return;
    }

Once you have loaded Informix JDBC Driver, you are ready to connect to an Informix database or database server.

Windows

If you are writing an applet that will be viewed with Microsoft Internet Explorer, you might need to explicitly register Informix JDBC Driver to avoid platform incompatibilities.

To explicitly register the driver, use the DriverManager.registerDriver() method, as shown in the following code example:

DriverManager.registerDriver((Driver)
Class.forName("com.informix.jdbc.IfxDriver").newInstance());

This method might register Informix JDBC Driver twice, which will not cause a problem.

Creating a Connection

The DriverManager class keeps track of the available drivers and handles connection requests between appropriate drivers and databases or database servers. The url parameter of the getConnection() method is a database URL that specifies the subprotocol (the database connectivity mechanism), the database or database server identifier, and a list of properties. A second parameter to the getConnection() method, property, is the property list. See "Specifying Environment Variables with the Properties Class" for an example of how to specify a property list.

The following example shows a database URL that connects to a database called testDB:

jdbc:informix-
sqli://123.45.67.89:1533/testDB:INFORMIXSERVER=myserver;user=rdtest;password-
test

The following code example from the CreateDB.java program shows how to connect to database testDB using Informix JDBC Driver. In the full example, the url variable, described in the preceding example, is passed in as a parameter when the program is run at the command line.

try 
    {
    conn = DriverManager.getConnection(url);
    } 
catch (SQLException e) 
    {
    System.out.println("ERROR: failed to connect!");
    System.out.println("ERROR: " + e.getMessage());
    e.printStackTrace();
    return;
    }

Important: Not all methods of the Connection interface are supported by Informix JDBC Driver. For a list of unsupported methods, see "Restrictions and Limitations".

jdbc:informix-sqli://{<ip-address>|<host-name>}:<port-number>[/<dbname>]:
	INFORMIXSERVER=<server-name>;user=<username>;password=<password>
	[;<name>=<value>[;<name>=<value>]...]

• curly brackets ( {} ) together with vertical lines ( | ) denote more than one choice of variable.
• angle brackets ( <> ) denote a variable value.
• brackets ( [] ) denote an optional value.
• words or symbols not enclosed in either angle brackets or brackets are required (INFORMIXSERVER=, for example).

Important: Blank spaces are not allowed in the database URL.

Database Versus Database Server Connections

To create a connection to an Informix database, specify the name of the database in the <dbname> variable of the database URL. If you do not specify the name of a database, a connection is made to the database server specified by the INFORMIXSERVER environment variable instead.

If you connect directly to an Informix database server, you can execute an SQL statement that connects to a database later in your Java program.

All connections to both databases and database servers must include the name of an Informix database server via the INFORMIXSERVER environment variable.

Important: If you are connecting to an INFORMIX-OnLine 5.x database server, you must specify the USEV5SERVER environment variable in the database URL or property list. Its value should be 1, such as "USERV5SERVER=1".

The example given in "Creating a Connection" shows how to create a connection directly to the Informix database called testDB with the database URL.

The following example from the DBConnection.java program shows how to first create a connection to the Informix database server called myserver and then connect to the database testDB later in the Java program using the Statement.executeUpdate() method.

The database URL that is passed in as a parameter to the program when the program is run at the command line is as follows; note that the URL does not include the name of a database:

jdbc:informix-
sqli://123.45.67.89:1533:INFORMIXSERVER=myserver;user=rdtest;password-test

String cmd = null;
int rc;

Connection conn = null;

try 
    {
    Class.forName("com.informix.jdbc.IfxDriver");
    } 
catch (Exception e)
    {
    System.out.println("ERROR: failed to load Informix JDBC driver.");
    }

try 
    {
    conn = DriverManager.getConnection(url);
    } 
catch (SQLException e) 
    {
    System.out.println("ERROR: failed to connect!");
    }

try
    {
    Statement stmt = conn.createStatement();
    cmd = "database testDB;";
    rc = stmt.executeUpdate(cmd);
    stmt.close();
    }
catch (SQLException e)
    {
    System.out.println("ERROR: execution failed - statement: " + cmd);
    System.out.println("ERROR: " + e.getMessage());
    }

To specify Informix environment variables in the name-value pairs of the connection database URL, refer to "Format of Database URLs".

To specify Informix environment variables via a property list, use the java.util.Properties class to build the list of properties. The list of properties might include Informix environment variables, such as INFORMIXSERVER, as well as <user> and <password>. After you have built the property list, pass it to the DriverManager.getConnection() method as a second parameter. You still need to include a database URL as the first parameter, although in this case you do not need to include the list of properties in the URL.

The following code from the optofc.java example shows how to use the java.util.Properties class to set connection properties. It first uses the Properties.put() method to set the environment variable OPTOFC to 1; then it connects to the database.

The DriverManager.getConnection() method in this example takes two parameters: the database URL and the property list. The example creates a connection similar to the example given in "Creating a Connection".

try 
    {
    Class.forName("com.informix.jdbc.IfxDriver");
    }
catch (Exception e)
    {
    System.out.println("ERROR: failed to load Informix JDBC driver.");
    }

try
    {
    Properties pr = new Properties();
    pr.put("OPTOFC","1");
    conn = DriverManager.getConnection(newUrl, pr);
    }
catch (SQLException e)
    {
    System.out.println("ERROR: failed to connect!");
    }

Important: The variable DBDATE is not supported. To be compatible with the JDBC API specification, the DBDATE format has been hard-coded as Y4MD-, such as 1998-05-01.

Supported Informix Environment Variables	Description
DBANSIWARN	Checks for Informix extensions to ANSI standard syntax.
DBSPACETEMP	Specifies the dbspaces in which temporary tables will be built.
DBUPSPACE	Specifies the amount of system disk space that the UPDATE STATISTICS statement can use when it simultaneously constructs multiple-column distributions.
DELIMIDENT	Specifies that strings set off by double quotes are delimited identifiers.
FET_BUF_SIZE	Overrides the default setting for the size of the fetch buffer for all data except large objects.
IFX_AUTOFREE	When set to 1, specifies that the Statement.close() method does not require a network round-trip to free the server cursor resources if the cursor has already been closed in the database server. The database server automatically frees the cursor resources after the cursor is closed, either explicitly by the ResultSet.close() method or implicitly by the OPTOFC environment variable. Once the cursor resources have been freed, the cursor can no longer be referenced.
INFORMIXCONRETRY	Specifies the maximum number of additional connection attempts that should be made to each database server by the client during the time limit specified by the default value of the INFORMIXCONTIME environment variable (15 seconds).
INFORMIXOPCACHE	Specifies the size of the memory cache for the staging-area blobspace of the client application.
INFORMIXSERVER	Specifies the default database server to which an explicit or implicit connection is made by a client application.
INFORMIXSTACKSIZE	Specifies the stack size, in kilobytes, that the database server uses for a particular client session.
NODEFDAC	When set to YES, prevents default table and routine privileges from being granted to the PUBLIC user when a new table or routine is created in a database that is not ANSI compliant. Default is NO.
OPTCOMPIND	Specifies the join method that the query optimizer should use.
OPTOFC	When set to 1, the ResultSet.close() method does not require a network round-trip if all the qualifying rows have already been retrieved in the client's tuple buffer. The database server automatically closes the cursor after all the rows have been retrieved. Informix JDBC Driver might or might not have additional rows in the client's tuple buffer before the next ResultSet.next() method is called. Therefore, unless Informix JDBC Driver has received all the rows from the database server, the ResultSet.close() method might still require a network round-trip when OPTOFC is set to 1.
PATH	Specifies the directories that should be searched for executable programs.
PDQPRIORITY	Determines the degree of parallelism used by the database server.
PLCONFIG	Specifies the name of the configuration file used by the high-performance loader.
PSORT_DBTEMP	Specifies one or more directories to which the database server writes the temporary files it uses when performing a sort.
PSORT_NPROCS	Enables the database server to improve the performance of the parallel-process sorting package by allocating more threads for sorting.
USEV5SERVER	When set to YES, specifies that the Java program is connecting to an INFORMIX-OnLine 5.x database server. This environment variable is mandatory if you are connecting to an INFORMIX-OnLine 5.x database server.

For a detailed description of a particular environment variable, refer to Informix Guide to SQL: Reference. You can find the on-line version of this guide at the following Web site:

http://www.informix.com/answers