SQLJ: Rowid Sample Application

Table Of Contents 

• Overview of the Sample Application
• Required Software
• Notations Used
• Application Set-up and Configuration
• Running the Application 
• From Oracle9i JDeveloper 
• From JDK for Windows
• From JDK for Linux
• Description of Sample Files

This sample application illustrates accessing the ROWID of a database row using SQLJ.

SQLJ enables applications programmers to embed SQL operations in Java code. A SQLJ program is a Java program containing embedded SQL statements that comply with the ISO standard SQLJ Language Reference syntax.

SQLJ consists of a translator and a runtime component (translator.jar/zip and runtime12ee.jar/zip) and is smoothly integrated into the development environment. The translation, compilation, and customization take place in a single step when the front-end utility sqlj is run. The translation process replaces embedded SQL with calls to the SQLJ runtime, which implements the SQL operations. When the end user runs the SQLJ application, the runtime is invoked to handle the SQL operations.

SQLJ runs on top of JDBC. To access an Oracle database, you would typically use an Oracle JDBC driver. In order to run SQLJ programs, apart from SQLJ classes, JDBC classes should be present in the system CLASSPATH. SQLJ code is written and saved in *.sqlj files and should be translated to *.java files before compiling using the front-end utility sqlj.

ROWIDs map directly to data blocks, and hence are unique for each row in a table; they are also the fastest way to access database rows.
Each row in the database has an address. A row's address can be examined by querying the pseudocolumn: ROWID. Values of this
pseudocolumn are strings representing the address of each row which have the datatype ROWID.

This sample application tries to demonstrate the database performance to retrieve records by using rowid and without using rowid. With a large number of records in a table, using rowid for retrieving records could better the performance.

Working of the Sample

The sample application uses a database table OTN_AIRLINES. When the application is invoked, the table is created if it does not exist. The status of the connection is shown in the status bar. Errors if any, are shown in the status bar.

The user may choose or may not choose to use rowid to retrieve records. The time taken to retrieve records is displayed at the end of the retrieval.

Here is the SQLJ code usage for using ROWID in a SQL statement. You can find more details of the code in SqljRowidSample.sqlj file under src/oracle/otnsamples/sqlj/rowid folder. Look into Description of Sample Files section for folder and file details.

   .........
   .........				
  /** Database Connection Object */
  private Connection connection = null;
     
  /** Database Connection Context object. **/
  private DefaultContext connContext = null;

  private Connection dbConnection() {
    try {

      // Load the properties file to get the connection information.
      Properties prop = loadParams("Connection");


      // Create a OracleDataSource instance.
      OracleDataSource ods = new OracleDataSource();
      .........
      .........

      // Create a connection  object.
      connection = ods.getConnection();
      
      // get a default context using above connection to execute SQLJ statement.
      connContext = new DefaultContext(connection);         

      //Set the above connection context as the default context for this
      //application.
      DefaultContext.setDefaultContext(connContext);
  } catch(Exception ex){ //Catch exceptions.

      .........
  }
  return connection;
 }			  
			  

  /**
  * Retrieve the NAME and PARTNER values for the selected row using its ROWID.
  **/
  private void selectWithRowid(ROWID rowid) {

    String name = null, partner = null;


    // Note time before start of retrieval.
    long before = System.currentTimeMillis();

    try {
      // Embedded SQL: This call fetches the name and partner values
      // from the specified row. The row to be retrieved is identified
      // by its ROWID.
      // The result of the query is bound into the class variables name
      // and partner, while the rowid for selection is bound from the class
      // variable rowid.
      #sql {SELECT name, partner INTO :name, :partner FROM OTN_AIRLINES
            WHERE rowid = :rowid };
    } catch (SQLException ex) {  // Trap SQL errors.
        ............
    }

    //Get time at completion.

    long after=System.currentTimeMillis();

    // Compute Time taken and copy to textfield.
    Integer time = new Integer((int)(after - before));

    ....................
  }

  /**
  * Retrieve the NAME and PARTNER values for the selected row using the Airline
  * CODE.
  **/
  private void selectWithoutRowid(String code) {

    String name = null, partner = null;

    // Note time before start of retrieval.
    long before = System.currentTimeMillis();


    try {
      // Embedded SQL: This call fetches the name and partner values
      // from the specified row. The row to be retrieved is identified
      // by its airline CODE.
      // The result of the query is bound into the class variables name
      // and partner, while the code for selection is bound from the class
      // variable code.
      #sql {SELECT name, partner INTO :name, :partner FROM OTN_AIRLINES
            WHERE code = :code  };
    } catch (SQLException ex) {  // Trap SQL errors.
        ...................
    }

    //Get time at completion.
    long after=System.currentTimeMillis();
	
    // Compute Time taken and copy to textfield.
    Integer time = new Integer((int)(after - before));

    ................

  }
	
 			

Note The time taken for retrieving OTN_AIRLINES records using CODE and ROWID may not be consistent; the reason being small number of rows in OTN_AIRLINES table. If a table has a large number of rows, then ROWID retrieval will take lesser time consistently.

• Oracle9i JDeveloper ( Note: Oracle9i JDeveloper is Oracle's Visual Java Development Tool and can be downloaded from here)
  or JDK1.2.x or above This can be downloaded from here.
• Oracle9i Database or higher running SQL*Net TCP/IP listener. This can be downloaded from here.
• Oracle9i SQLJ Translators, Release 9.2.0.1.0. This can be downloaded from here.
• Oracle JDBC Driver, Release 2 (9.2.0.1). This can be downloaded from here.

Note: Both JDBC and SQLJ libraries are available with Oracle Database or client installation and need not be downloaded separately.

• Unjar the provided SqljRowidSample.jar using the following command 

> jar xvf SqljRowidSample.jar

Note: You will find jar.exe in JDK_HOME\bin. Ensure JDK_HOME\bin is present in your system path. (JDK_HOME is the root directory of the JDKx.x installation). This creates a folder SqljRowidSample with all the source files.

• Edit SqljRowidSample/Connection.properties file in your favourite editor. Change the HostName, Port, SID, UserName and Password to connect to your own database.

This sample application can be run in 3 different ways listed below.

• From Oracle9i JDeveloper
• From JDK for Windows
• From JDK for Linux

From Oracle9i JDeveloper

• Open Oracle9i JDeveloper and use File/Open menu option to select the SqljRowidSample.jws from the SqljRowidSample directory.
• Next, select Project/Make SqljRowidSample.jpr from main menu.
• Now, select Run/Run SqljRowidSample.jpr from main menu to run the application.

From JDK for Windows

This section will describe steps to run the application from console using JDK on Windows. The sample can be run either manually or using a Batch file .

Run application using batch file: run.bat provided:

By setting few environment variables, the sample application could be directly run by just executing the batch file: run.bat from the command prompt, from SqljRowidSample directory. Environmental variables JAVA_HOME, SQLJ_EXE_HOME, SQLJ_LIB and JDBC_LIB have to be set before running run.bat file. Please look into Notations sections for more details on these environmental variables.

Note: If you have already run the sample application using JDeveloper, you will need to delete *.generated.java files that would have been created by JDeveloper.
Example:

D:\SqljRowidSample> set SQLJ_EXE_HOME=d:\sqlj\bin
D:\SqljRowidSample> set SQLJ_LIB=d:\sqlj\lib
D:\SqljRowidSample> set JDBC_LIB=d:\oracle9i\jdbc\lib
D:\SqljRowidSample> set JAVA_HOME=d:\jdk1.3.1
D:\SqljRowidSample> run

Running the application manually:

• Set CLASSPATH to include:
  • Oracle9i JDBC Driver file: classes12.jar/zip
  • Oracle9i SQLJ files: translator.jar/zip and runtime12ee.jar/zip
  • SqljRowidSample directory where Connection.properties exists(the current directory).
    Example: 
    D:\SqljRowidSample>set CLASSPATH=d:\sqlj\lib\translator.jar;d:\sqlj\lib\runtime12ee.jar;
    D:\oracle9i\jdbc\lib\classes12.zip;.
    
• Make sure that Java and SQLJ(where sqlj is found) are in the PATH.
  Example: D:\SqljRowidSample>set PATH=.;d:\jdk1.3.1\bin;d:\sqlj\bin;%PATH%
  
• From the directory SqljRowidSample, translate all *.sqlj files to *.java files using sqlj:
  Example: 
  D:\SqljRowidSample>sqlj -compile=false src\oracle\otnsamples\sqlj\rowid\*.sqlj
• From the same SqljRowidSample directory, now compile all *.java files using javac:
  Example: 
  D:\SqljRowidSample>javac -d . src\oracle\otnsamples\sqlj\rowid\*.java
  
• Run the class file using java from the same SqljRowidSample directory.
  Example:
  D:\SqljRowidSample>java oracle.otnsamples.sqlj.rowid.SqljRowidSample
  

From JDK for Linux

This section will describe steps to run the application from console using JDK on Red Hat Linux Advanced Server Release 2.1. The sample can be run either manually or using a script file .

Run application using script file: run.sh provided. (For Bourne Shell):

By setting few environment variables, the sample application could be directly run by just executing the script file: run.sh from the command prompt, from SqljRowidSample directory. The user will be prompted to enter the environmental variables JAVA_HOME, SQL_EXE, SQLJ_LIB and JDBC_LIB when the script is run. Please look into Notations sections for more details on these environmental variables.

• Go to SqljRowidSample directory and from the $ prompt, use the command below to run the script file:
  $sh run.sh
  

Running the application manually:

• Set CLASSPATH to include:
  • Oracle9i JDBC Driver file: classes12.jar/zip
  • Oracle9i SQLJ classes: translator.jar/zip and runtime12ee.jar/zip
  • SqljRowidSample directory where Connection.properties exists(the current directory).
    Example:
    $export CLASSPATH=/home1/idcotn/download/jdbc/lib/classes12.zip:
    /home1/idcotn/download/sqlj/lib/translator.jar:
    /home1/idcotn/download/sqlj/lib/runtime12ee.jar:.
• Make sure that Java and SQLJ (where sqlj is found) are in the PATH.
  Example: $export PATH=/usr/java/jdk1.3.1_02/bin:/home1/idcotn/download/sqlj/bin:$PATH
  
• From the directory SqljRowidSample, translate all *.sqlj files to *.java files using sqlj:
  Example: 
  $sqlj -compile=false /src/oracle/otnsamples/sqlj/rowid/*.sqlj
• From the directory SqljRowidSample, now compile all the java files using javac:
  Example:
  $javac -d . /src/oracle/otnsamples/sqlj/rowid/SqljRowidSample/*.java
• Run the class file using java from the same SqljRowidSample directory.
  Example:
  $java oracle.otnsamples.sqlj.rowid.SqljRowidSample