CHAPTER 5: Example Program (Category 2)

Example presented in this chapter shows an application that creates a table myTable, inserts 3 records and retrieves these records.

In order to have an example myDemo.java running, user has to do the following steps:

1. Since myDemo.java is a client application which accesses an Empress database on the machine where Empress Connectivity (or ODBC) server is running, user has to modify the getConnection parameters in the myDemo.java accordingly. For example:

      "jdbc:empress://SERVER=workstn1;PORT=6322;DATABASE=testdb",
         "joe", "code123"
   
   

   The getConnection parameters that show workstn1 as a machine where Empress ODBC server is running, 6322 is a port code of the server, testdb is an Empress database located on the server machine and accessible by the server, joe and code123 are client login name and the password account present in the Empress server password file.

2. To compile the sample code , user has to invoke java compiler.

      javac myDemo.java
   
   

   This command will generate myDemo.class.

3. To execute the generated myDemo.class, user has to invoke the java interpreter, for example:

      java myDemo
   
   

Here is the code of myDemo.java:

   import java.sql.*;
   
   public class myDemo
   {
      private static Connection      TheConnection;
      private static Statement       SqlHandle;
      private static ResultSet       Results;
      private static ResultSetMetaData MResults;
    
      public static void main (String args[])
      {
         int count;
         int num_attrs;
         String name;
         String type_name;
         int type;
    
         try
         {
            Class.forName ("empress.jdbc.empressDriver");
    
            TheConnection = DriverManager.getConnection (
               "jdbc:empress://SERVER=emery;PORT=6322;DATABASE=testdb",
               "joe", "code123");
   
            SqlHandle = TheConnection.createStatement ();
   
            SqlHandle.executeUpdate("CREATE myTable (a char,
               b double precision, c date)");
   
            SqlHandle.executeUpdate("INSERT INTO myTable VALUES 
               ('blue', 2.34, 19980213)");

            SqlHandle.executeUpdate("INSERT INTO myTable VALUES 
               ('red', 3.45, 19980214)");

            SqlHandle.executeUpdate("INSERT INTO myTable VALUES 
               ('green', 4.56, 19980215)");
   
            Results = SqlHandle.executeQuery ("SELECT * FROM myTable");
            MResults = Results.getMetaData ();
   
            num_attrs = MResults.getColumnCount ();
    
            while (Results.next () == true)
            {
               for (count=1; count<=num_attrs; count++)
               {
                  name = MResults.getColumnName (count);
                  type = MResults.getColumnType (count);
                  type_name = MResults.getColumnTypeName (count);
                  System.out.print (name+"["+type_name+"]["+
                                    MResults.getPrecision (count)+"]["+
                                    MResults.getScale(count)+"]["+
                                    MResults.isNullable (count)+"]: ");
    
                  switch (type)
                  {
                     case Types.DOUBLE:
                        System.out.println ("(double)" +
                           Results.getDouble (count));
                        break;
                     case Types.DATE:
                        System.out.println ("(date)" +
                           Results.getDate (count));
                        break;
                     default:
                        System.out.println ("(string)" +
                           Results.getString (count));
                        break;
                   }
               }
            }
         } 
         catch (SQLException ex)
         {
            SQLException eptr;
            for (eptr = ex; eptr != null; eptr = eptr.getNextException())
            {
               System.out.println ("Message: "+eptr.getMessage());
            }
            ex.printStackTrace ();
         }
         catch (Exception other)
         {
            other.printStackTrace ();
         }
      }
   }