Network Server sample programs for embedded and client connections

This Derby Network Server sample program demonstrates how to obtain an embedded connection and client connections to the same database using the Network Server. This program shows how to use either the DriverManager or a DataSource to obtain client connections.

For a database to be consistent, only one JVM can access it at a time. The embedded driver is loaded when the Network Server is started. The JVM that starts the Network Server can get an embedded connection to the same database that the Network Server is accessing to serve clients from other JVMs. This solution allows you to take advantage of the performance benefits of the embedded driver while also allowing client connections from other JVMs to connect to the same database.

This topic contains the following sections:

• The SimpleNetworkServerSample Program
• Running the SimpleNetworkServerSample Program
• Connecting a Client to the Network Server with the SimpleNetworkClientSample program
• Running the SimpleNetworkClientSample Program

The SimpleNetworkServerSample program starts the Derby Network Server as well as the embedded driver and waits for clients to connect. The program performs the following tasks.

• starts the Derby Network Server using a property and also loads the embedded driver
• checks if the Network Server is up and running
• creates the database NSSimpleDB if it is not already created
• obtains an embedded database connection
• tests the database connection by executing a sample query.
• allows client connections to connect to the server until you decide to stop the server and exit the program
• closes the connection
• shuts down the Network Server before exiting the program.

To run the sample program, the following files should be installed in the %DERBY_INSTALL%\demo\programs\nserverdemo\ directory:

• The source file: SimpleNetworkServerSample.java
• The compiled class file: SimpleNetworkServerSample.class

To run the Derby Network Server sample program:

1. Open a command prompt and change directories to the %DERBY_INSTALL%\demo\programs\nserverdemo directory, where %DERBY_INSTALL% is the directory where you installed Derby.
2. Set the CLASSPATH to include the following jar files in order to run this program:
   • the current directory (".")
   • derbynet.jar

     The Network Server jar file. It must be in your CLASSPATH because we start the Network Server in this program.

   • derby.jar

     The database engine jar file.

3. Test the CLASSPATH settings by running the following Java command:

   java org.apache.derby.tools.sysinfo
   

   This command will show the Derby jar files that are in the CLASSPATH.

4. Once you have set up your environment correctly, execute the application from the same directory:

   java SimpleNetworkServerSample
   

You should receive output similar to the following if the program runs successfully:

Starting Network Server
Testing if Network Server is up and running!
Derby Network Server now running
Got an embedded connection.
Testing embedded connection by executing a sample query
number of rows in sys.systables = 16
While my app is busy with embedded work, ij might connect like this:
 
        $ java -Dij.user=me -Dij.password=pw -Dij.protocol=
            jdbc:derby:net:\\localhost:1527\ org.apache.derby.tools.ij
        ij> connect 'NSSimpleDB:retrieveMessagesFromServerOnGetMessage=true;';
Watch that punctuation.  Put a ':' before the jcc
attributes and a ';' after each one (even the last).
 
 
Clients can continue to connect:
Press [Enter] to stop Server

Running the SimpleNetworkServerSample program will also create the following new directories and files:

• NSSimpleDB

  This directory makes up the NSSimpleDB database.

• derby.log

  This log file contains Derby progress and error messages.

The SimpleNetworkClientSample program is a client program that interacts with the Derby Network Server from another JVM. The program performs the following tasks.

• loads the DB2 Universal JDBC Driver
• obtains a client connection using the DriverManager
• obtains a client connection using a DataSource
• tests the database connections by executing a sample query
• closes the connections and then exits the program.

The following files should be installed in the %DERBY_INSTALL%\demo\programs\nserverdemo\ directory in order to run the sample program:

• The source file: SimpleNetworkClientSample.java
• The compiled class file: SimpleNetworkClientSample.class

To connect to the Network Server that has been started as part of the SimpleNetworkServerSample program:

1. Open a command prompt and change directories to the %DERBY_INSTALL%\demo\programs\nserverdemo directory, where %DERBY_INSTALL% is the directory where you installed Derby.
2. Network Server clients need only the following jar files in the CLASSPATH to connect to the Network Server. Set the CLASSPATH to include the following jar files:
   • the current directory (".")
   • db2jcc.jar

     This jar file must be in your CLASSPATH to use the DB2 JDBC Universal Driver.

   • db2jcc_license_c.jar

     This jar file is the license file for the Universal Driver for Derby.

3. Once you have set up your environment correctly, execute the application from the same directory:

   java SimpleNetworkClientSample
   

You should receive output similar to the following if the program runs successfully:

Starting Sample client program
Got a client connection via the DriverManager.
connection from datasource; getDriverName = 
    IBM DB2 JDBC Universal Driver Architecture
Got a client connection via a DataSource.
Testing the connection obtained via DriverManager by executing a sample query
number of rows in sys.systables = 16
Testing the connection obtained via a DataSource by executing a sample query
number of rows in sys.systables = 16
Goodbye!