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How to raise a custom SQLWarning?

Created May 4, 2012

Lennart Jorelid

 

 

The SQLWarning class extends SQLException. You may therefore treat it as any normal Exception type with respect to throwing and catching. However, the SQLException class mimics a forward traversable, linked list of Exception objects. The reason for this behavior is that a database generated SQLException rarely occurs alone - one syntactic programming error leads to a suite of SQLException objects being generated. Use the getNextException() method of the SQLException class, as seen in the class structure below:

 

Class structure of SQLException and SQLWarning  

 

Thus, to create and traverse a custom SQLWarning structure, use code similar to the one below:

 

Creating SQLWarning   
package se.jguru.dbTests;

// Import the SQL classes
import java.sql.*;

public abstract class RasingACustomSQLWarning
{
   public static void main(String[] args)
   {
      try
      {
          // Simulate getting the DB data
          getDataFromDB();

          // All OK.
          System.out.println("Got all data.");
      }
      catch(SQLException ex)
      {
          // Printout root SQLException
          System.err.println("An SQL exception occurred: " + ex);

          // Get all chained SQLExceptions
          while((ex = ex.getNextException()) != null)
          {
             System.err.println("Contained reason: " + ex);
          }
      }
   }

   private static void getDataFromDB()
   throws SQLException
   {
       // Status flag resulting from database data
       // should be created from normal business rules in
       // a live situation. 
       boolean somethingStrangeHappened = true;

       if(somethingStrangeHappened)
       {
           // Create two custom SQL Warnings
           SQLWarning rootWarning = 
             new SQLWarning("Business rules not properly regarded");
           SQLWarning containedWarning = 
             new SQLWarning("Product too cheap!");

           // Chain the warnings
           rootWarning.setNextWarning(containedWarning);

           // Notify the caller of the warnings
           throw rootWarning;
       }
   }
}