SQLDelete.java

package org.cdlib.xtf.saxonExt.sql;

import net.sf.saxon.expr.Expression;
import net.sf.saxon.expr.SimpleExpression;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.instruct.Executable;
import net.sf.saxon.om.Item;
import net.sf.saxon.style.ExtensionInstruction;
import net.sf.saxon.trans.SaxonErrorCode;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.ObjectValue;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
* An sql:delete element in the stylesheet.
*/
public class SQLDelete extends ExtensionInstruction 
{
  Expression connection;
  Expression table;
  Expression where;

  public void prepareAttributes()
    throws XPathException 
  {
    String connectAtt = getAttributeList().getValue("", "connection");
    if (connectAtt == null)
      reportAbsence("connection");
    connection = makeExpression(connectAtt);

    String tableAtt = attributeList.getValue("", "table");
    if (tableAtt == null)
      reportAbsence("table");
    table = makeAttributeValueTemplate(tableAtt);

    String whereAtt = attributeList.getValue("", "where");
    if (whereAtt == null)
      reportAbsence("where");
    where = makeAttributeValueTemplate(whereAtt);
  }

  public void validate()
    throws XPathException 
  {
    super.validate();
    connection = typeCheck("connection", connection);
    table = typeCheck("table", table);
    where = typeCheck("where", where);
  }

  public Expression compile(Executable exec)
    throws XPathException 
  {
    return new DeleteInstruction(connection, table, where);
  }

  private static class DeleteInstruction extends SimpleExpression 
  {
    public static final int CONNECTION = 0;
    public static final int TABLE = 1;
    public static final int WHERE = 2;

    public DeleteInstruction(Expression connection, Expression table,
                             Expression where) 
    {
      Expression[] sub = { connection, table, where };
      setArguments(sub);
    }

    /**
     * A subclass must provide one of the methods evaluateItem(), iterate(), or process().
     * This method indicates which of the three is provided.
     */
    public int getImplementationMethod() {
      return Expression.EVALUATE_METHOD;
    }

    public String getExpressionType() {
      return "sql:delete";
    }

    public Item evaluateItem(XPathContext context)
      throws XPathException 
    {
      // Construct the SQL statement.
      String dbTab = arguments[TABLE].evaluateAsString(context);
      String dbWhere = arguments[WHERE].evaluateAsString(context);

      StringBuffer statement = new StringBuffer(120);
      statement.append("DELETE FROM " + dbTab + " WHERE " + dbWhere);

      // Prepare the SQL statement (only do this once)
      Item conn = arguments[CONNECTION].evaluateItem(context);
      if (!(conn instanceof ObjectValue &&
          ((ObjectValue)conn).getObject() instanceof Connection)) 
      {
        dynamicError("Value of connection expression is not a JDBC Connection",
                     SaxonErrorCode.SXSQ0001, context);
      }
      Connection connection = (Connection)((ObjectValue)conn).getObject();
      PreparedStatement ps = null;

      @SuppressWarnings("unused")
      int nDeleted = -1;

      try 
      {
        ps = connection.prepareStatement(statement.toString());
        nDeleted = ps.executeUpdate();
        if (!connection.getAutoCommit()) {
          connection.commit();
        }
      }
      catch (SQLException ex) {
        dynamicError("(SQL DELETE) " + ex.getMessage(), SaxonErrorCode.SXSQ0004, context);
      }
      finally {
        if (ps != null) 
        {
          try {
            ps.close();
          }
          catch (SQLException ignore) {
          }
        }
      }

      // Return nothing, so that it's not necessary to re-route the result.
      return null;
    }
  }
}

//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay.
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Additional Contributor(s): Martin Haye
//
// Acknowledgements:
//
// A significant amount of new and/or modified code in this module
// was made possible by a grant from the Andrew W. Mellon Foundation,
// as part of the Melvyl Recommender Project.
//