Query.java

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import java.sql.Connection;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.io.PrintWriter;

// combines Statement and Resultset construction and destruction
// to prevent so many nested try ... finally ... statements
//
// also catches and displays exceptions

public class Query
{
  public Statement s;
  public ResultSet r;
  public PrintWriter pw;
  
  public static final boolean DEBUG = false;
  
  public Query(Connection conn, PrintWriter pw)
  {
    this(conn, pw, null);
  }
  
  public Query(Connection conn, PrintWriter pw, String sql)
  {
    this.pw = pw;
    try
    {
      s = conn.createStatement();
      if (sql != null) query(sql);
    }
    catch(SQLException e)
    {
      Widget.ShowException(e, pw);
    }
  }
  
  public void execute(String sql)
  {
    if (DEBUG) printSql(sql);
    try
    {
      s.executeUpdate(sql);
    }
    catch (SQLException e)
    {
      pw.println("<h2>Failed to execute SQL Statement:</h2>");
      printSql(sql);
      Widget.ShowException(e, pw);
    }
  }
  
  public void query(String sql)
  {
    if (DEBUG) printSql(sql);
    try
    {
      if (r != null) r.close();
      r = s.executeQuery(sql);
    }
    catch (SQLException e)
    {
      pw.println("<h2>Failed to execute SQL Query:</h2>");
      printSql(sql);
      Widget.ShowException(e, pw);
    }
  }

  public void printSql(String sql)
  {
    pw.println("<pre style=\"background-color: #EEEEEE\">" + sql + "</pre>");
  }
  
  public void close()
  {
    try
    {  
      try
      {
        if (r != null)
        {
          r.close();
          r = null;
        }
      }
      finally
      {
        s.close();
        s = null;
      }
    }
    catch (SQLException e)
    {
      Widget.ShowException(e, pw);
    }
  }

  public static void rethrow(Throwable e)
  {  
    if (e instanceof RuntimeException)
      throw (RuntimeException) e;
    if (e instanceof Error)
      throw (Error) e;
    else // should never happen
      throw new Error("Unknown Exception caught", e);
  }
};

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