/*
 * @(#)SQLInputImpl.java	1.7 06/08/06
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.sql.rowset.serial;

import java.sql.*;
import javax.sql.*;
import java.io.*;
import java.math.*;
import java.util.Map;

/**
 * An input stream used for custom mapping user-defined types (UDTs).
 * An <code>SQLInputImpl</code> object is an input stream that contains a
 * stream of values that are the attributes of a UDT.
 * <p>
 * This class is used by the driver behind the scenes when the method 
 * <code>getObject</code> is called on an SQL structured or distinct type 
 * that has a custom mapping; a programmer never invokes
 * <code>SQLInputImpl</code> methods directly. They are provided here as a 
 * convenience for those who write <code>RowSet</code> implementations.
 * <P>
 * The <code>SQLInputImpl</code> class provides a set of
 * reader methods analogous to the <code>ResultSet</code> getter
 * methods.  These methods make it possible to read the values in an
 * <code>SQLInputImpl</code> object.
 * <P>
 * The method <code>wasNull</code> is used to determine whether the
 * the last value read was SQL <code>NULL</code>.
 * <P>When the method <code>getObject</code> is called with an
 * object of a class implementing the interface <code>SQLData</code>,
 * the JDBC driver calls the method <code>SQLData.getSQLType</code>
 * to determine the SQL type of the UDT being custom mapped. The driver
 * creates an instance of <code>SQLInputImpl</code>, populating it with the
 * attributes of the UDT.  The driver then passes the input
 * stream to the method <code>SQLData.readSQL</code>, which in turn
 * calls the <code>SQLInputImpl</code> reader methods
 * to read the attributes from the input stream.
 * @see java.sql.SQLData
 */
public class SQLInputImpl implements SQLInput {

    /**
     * <code>true</code> if the last value returned was <code>SQL NULL</code>;
     * <code>false</code> otherwise.
     */
    private boolean lastValueWasNull;
    
    /**
     * The current index into the array of SQL structured type attributes
     * that will be read from this <code>SQLInputImpl</code> object and 
     * mapped to the fields of a class in the Java programming language.
     */
    private int idx;

    /**
     * The array of attributes to be read from this stream.  The order
     * of the attributes is the same as the order in which they were
     * listed in the SQL definition of the UDT.
     */
    private Object attrib[];

    /**
     * The type map to use when the method <code>readObject</code>
     * is invoked. This is a <code>java.util.Map</code> object in which
     * there may be zero or more entries.  Each entry consists of the
     * fully qualified name of a UDT (the value to be mapped) and the 
     * <code>Class</code> object for a class that implements
     * <code>SQLData</code> (the Java class that defines how the UDT
     * will be mapped).
     */
    private Map map;


    /**
     * Creates an <code>SQLInputImpl</code> object initialized with the
     * given array of attributes and the given type map. If any of the
     * attributes is a UDT whose name is in an entry in the type map,
     * the attribute will be mapped according to the corresponding
     * <code>SQLData</code> implementation.
     *
     * @param attributes an array of <code>Object</code> instances in which
     *        each element is an attribute of a UDT. The order of the 
     *        attributes in the array is the same order in which
     *        the attributes were defined in the UDT definition.
     * @param map a <code>java.util.Map</code> object containing zero or more
     *        entries, with each entry consisting of 1) a <code>String</code>
     *        giving the fully
     *        qualified name of the UDT and 2) the <code>Class</code> object
     *        for the <code>SQLData</code> implementation that defines how
     *        the UDT is to be mapped
     * @throws SQLException if the <code>attributes</code> or the <code>map</code>
     *        is a <code>null</code> value
     */
  
    public SQLInputImpl(Object[] attributes, Map<String,Class<?>> map) 
        throws SQLException 
    {        
        if ((attributes == null) || (map == null)) {
            throw new SQLException("Cannot instantiate a SQLInputImpl " +
            "object with null parameters");
        }        
        // assign our local reference to the attribute stream
        attrib = attributes;
        // init the index point before the head of the stream
        idx = -1;
        // set the map
        this.map = map;
    }
        

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object 
     * as an <code>Object</code> in the Java programming language.
     *
     * @return the next value in the input stream 
     *         as an <code>Object</code> in the Java programming language
     * @throws SQLException if the read position is located at an invalid
     *         position or if there are no further values in the stream
     */
    private Object getNextAttribute() throws SQLException {
        if (++idx >= attrib.length) {
            throw new SQLException("SQLInputImpl exception: Invalid read " + 
				   "position");
        } else {
            return attrib[idx];
        }
    }


    //================================================================
    // Methods for reading attributes from the stream of SQL data.
    // These methods correspond to the column-accessor methods of
    // java.sql.ResultSet.
    //================================================================

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object as
     * a <code>String</code> in the Java programming language.
     * <p>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code>
     * implementation.
     * <p>
     * @return the next attribute in this <code>SQLInputImpl</code> object; 
     *     if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *     position or if there are no further values in the stream.
     */
    public String readString() throws SQLException {

        String attrib = (String)getNextAttribute();   
        
        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object as
     * a <code>boolean</code> in the Java programming language.
     * <p>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code>
     * implementation.
     * <p>
     * @return the next attribute in this <code>SQLInputImpl</code> object; 
     *     if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *     position or if there are no further values in the stream.
     */
    public boolean readBoolean() throws SQLException {

        Boolean attrib = (Boolean)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return false;
        } else {
            lastValueWasNull = false;
            return attrib.booleanValue();
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object as
     * a <code>byte</code> in the Java programming language.
     * <p>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code>
     * implementation.
     * <p>
     * @return the next attribute in this <code>SQLInputImpl</code> object; 
     *     if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *     position or if there are no further values in the stream
     */
    public byte readByte() throws SQLException {
        Byte attrib = (Byte)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return (byte)0;
        } else {
            lastValueWasNull = false;
            return attrib.byteValue();
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object 
     * as a <code>short</code> in the Java programming language.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public short readShort() throws SQLException {
        Short attrib = (Short)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return (short)0;
        } else {
            lastValueWasNull = false;
            return attrib.shortValue();
        }
    }
    
    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object 
     * as an <code>int</code> in the Java programming language.     
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public int readInt() throws SQLException {
        Integer attrib = (Integer)getNextAttribute();
        
        if (attrib == null) {
            lastValueWasNull = true;
            return (int)0;
        } else {
            lastValueWasNull = false;
            return attrib.intValue();
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object
     * as a <code>long</code> in the Java programming language.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public long readLong() throws SQLException {
        Long attrib = (Long)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return (long)0;
        } else {
            lastValueWasNull = false;
            return attrib.longValue();
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object
     * as a <code>float</code> in the Java programming language.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public float readFloat() throws SQLException {
        Float attrib = (Float)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return (float)0;
        } else {
            lastValueWasNull = false;
            return attrib.floatValue();
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object
     * as a <code>double</code> in the Java programming language.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public double readDouble() throws SQLException {
        Double attrib = (Double)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return (double)0;
        } else {
            lastValueWasNull = false;
            return attrib.doubleValue();
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object 
     * as a <code>java.math.BigDecimal</code>.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public java.math.BigDecimal readBigDecimal() throws SQLException {
        java.math.BigDecimal attrib = (java.math.BigDecimal)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }
    
    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object
     * as an array of bytes.
     * <p>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public byte[] readBytes() throws SQLException {
        byte[] attrib = (byte[])getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> as 
     * a <code>java.sql.Date</code> object.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type; this responsibility is delegated
     * to the UDT mapping as defined by a <code>SQLData</code> implementation.
     * <P>
     * @return the next attribute in this <code>SQLInputImpl</code> object;
     *       if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     *       position or if there are no more values in the stream 
     */
    public java.sql.Date readDate() throws SQLException {
        java.sql.Date attrib = (java.sql.Date)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object as
     * a <code>java.sql.Time</code> object.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return the attribute; if the value is <code>SQL NULL</code>, return
     * <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream. 
     */
    public java.sql.Time readTime() throws SQLException {
        java.sql.Time attrib = (java.sql.Time)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object as 
     * a <code>java.sql.Timestamp</code> object.
     *
     * @return the attribute; if the value is <code>SQL NULL</code>, return
     * <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream. 
     */
    public java.sql.Timestamp readTimestamp() throws SQLException {
        java.sql.Timestamp attrib = (java.sql.Timestamp)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Retrieves the next attribute in this <code>SQLInputImpl</code> object
     * as a stream of Unicode characters.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return the attribute; if the value is <code>SQL NULL</code>, return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.
     */
    public java.io.Reader readCharacterStream() throws SQLException {
        java.io.Reader attrib = (java.io.Reader)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Returns the next attribute in this <code>SQLInputImpl</code> object
     * as a stream of ASCII characters.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return the attribute; if the value is <code>SQL NULL</code>, 
     * return <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.
     */
    public java.io.InputStream readAsciiStream() throws SQLException {
        java.io.InputStream attrib = (java.io.InputStream)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }
    
    /**
     * Returns the next attribute in this <code>SQLInputImpl</code> object
     * as a stream of uninterpreted bytes.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return the attribute; if the value is <code>SQL NULL</code>, return 
     * <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.
     */
    public java.io.InputStream readBinaryStream() throws SQLException {
        java.io.InputStream attrib = (java.io.InputStream)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }        
    }
    
    //================================================================
    // Methods for reading items of SQL user-defined types from the stream.
    //================================================================
    
    /**
     * Retrieves the value at the head of this <code>SQLInputImpl</code>
     * object as an <code>Object</code> in the Java programming language.  The
     * actual type of the object returned is determined by the default 
     * mapping of SQL types to types in the Java programming language unless
     * there is a custom mapping, in which case the type of the object
     * returned is determined by this stream's type map.
     * <P>
     * The JDBC technology-enabled driver registers a type map with the stream 
     * before passing the stream to the application.
     * <P>
     * When the datum at the head of the stream is an SQL <code>NULL</code>,
     * this method returns <code>null</code>.  If the datum is an SQL
     * structured or distinct type with a custom mapping, this method
     * determines the SQL type of the datum at the head of the stream, 
     * constructs an object of the appropriate class, and calls the method 
     * <code>SQLData.readSQL</code> on that object. The <code>readSQL</code>
     * method then calls the appropriate <code>SQLInputImpl.readXXX</code> 
     * methods to retrieve the attribute values from the stream.
     *
     * @return the value at the head of the stream as an <code>Object</code>
     *         in the Java programming language; <code>null</code> if
     *         the value is SQL <code>NULL</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.
     */
    public Object readObject() throws SQLException {
        Object attrib = (Object)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            if (attrib instanceof Struct) {
                Struct s = (Struct)attrib;
                // look up the class in the map
                Class c = (Class)map.get(s.getSQLTypeName());
                if (c != null) {
                    // create new instance of the class
                    SQLData obj = null;
                    try {
                        obj = (SQLData)c.newInstance();
                    } catch (java.lang.InstantiationException ex) {
                        throw new SQLException("Unable to instantiate: " +
                                               ex.getMessage());
                    } catch (java.lang.IllegalAccessException ex) {
                        throw new SQLException("Unable to instantiate: " +
                                               ex.getMessage());
                    }
                    // get the attributes from the struct
                    Object attribs[] = s.getAttributes(map);
                    // create the SQLInput "stream"
                    SQLInputImpl sqlInput = new SQLInputImpl(attribs, map);
                    // read the values...
                    obj.readSQL(sqlInput, s.getSQLTypeName());
                    return (Object)obj;
                } 
            } 
            return (Object)attrib;
        }
    }
    
    /**
     * Retrieves the value at the head of this <code>SQLInputImpl</code> object
     * as a <code>Ref</code> object in the Java programming language. 
     *
     * @return a <code>Ref</code> object representing the SQL 
     *         <code>REF</code> value at the head of the stream; if the value
     *         is <code>SQL NULL</code> return <code>null</code>
     * @throws SQLException if the read position is located at an invalid 
     *         position; or if there are no further values in the stream.     
     */
    public Ref readRef() throws SQLException {
        Ref attrib = (Ref)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Retrieves the <code>BLOB</code> value at the head of this
     * <code>SQLInputImpl</code> object as a <code>Blob</code> object
     * in the Java programming language.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return a <code>Blob</code> object representing the SQL 
     *         <code>BLOB</code> value at the head of this stream; 
     *         if the value is <code>SQL NULL</code>, return
     *         <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.
     */
    public Blob readBlob() throws SQLException {
        Blob attrib = (Blob)getNextAttribute();
        
        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Retrieves the <code>CLOB</code> value at the head of this
     * <code>SQLInputImpl</code> object as a <code>Clob</code> object
     * in the Java programming language.
     * <P>    
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return a <code>Clob</code> object representing the SQL 
     *         <code>CLOB</code> value at the head of the stream; 
     *         if the value is <code>SQL NULL</code>, return
     *         <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.
     */
    public Clob readClob() throws SQLException {

        Clob attrib = (Clob)getNextAttribute();
        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Reads an SQL <code>ARRAY</code> value from the stream and
     * returns it as an <code>Array</code> object in the Java programming 
     * language.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return an <code>Array</code> object representing the SQL
     *         <code>ARRAY</code> value at the head of the stream; *
     *         if the value is <code>SQL NULL</code>, return
     *         <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.

     */
    public Array readArray() throws SQLException {
        Array attrib = (Array)getNextAttribute();

        if (attrib == null) {
            lastValueWasNull = true;
            return null;
        } else {
            lastValueWasNull = false;
            return attrib;
        }
    }

    /**
     * Ascertains whether the last value read from this 
     * <code>SQLInputImpl</code> object was <code>null</code>.
     * 
     * @return <code>true</code> if the SQL value read most recently was 
     *         <code>null</code>; otherwise, <code>false</code>; by default it
     *         will return false
     * @throws SQLException if an error occurs determining the last value
     *         read was a <code>null</code> value or not; 
     */
    public boolean wasNull() throws SQLException {
        return lastValueWasNull;
    }
    
    /**     
     * Reads an SQL <code>DATALINK</code> value from the stream and
     * returns it as an <code>URL</code> object in the Java programming 
     * language.
     * <P>
     * This method does not perform type-safe checking to determine if the
     * returned type is the expected type as this responsibility is delegated
     * to the UDT mapping as implemented by a <code>SQLData</code>
     * implementation.
     *
     * @return an <code>URL</code> object representing the SQL
     *         <code>DATALINK</code> value at the head of the stream; *
     *         if the value is <code>SQL NULL</code>, return
     *         <code>null</code>
     * @throws SQLException if the read position is located at an invalid
     * position; or if there are no further values in the stream.
     */
    public java.net.URL readURL() throws SQLException {
        throw new SQLException("Operation not supported");    
    }

    //---------------------------- JDBC 4.0 -------------------------

    /**
     * Reads an SQL <code>NCLOB</code> value from the stream and returns it as a
     * <code>Clob</code> object in the Java programming language.
     *
     * @return a <code>NClob</code> object representing data of the SQL <code>NCLOB</code> value
     * at the head of the stream; <code>null</code> if the value read is
     * SQL <code>NULL</code>
     * @exception SQLException if a database access error occurs
     */
     public NClob readNClob() throws SQLException {
        throw new UnsupportedOperationException("Operation not supported");    
    }

    /**
     * Reads the next attribute in the stream and returns it as a <code>String</code>
     * in the Java programming language. It is intended for use when
     * accessing  <code>NCHAR</code>,<code>NVARCHAR</code>
     * and <code>LONGNVARCHAR</code> columns.
     *
     * @return the attribute; if the value is SQL <code>NULL</code>, returns <code>null</code>
     * @exception SQLException if a database access error occurs
     */
    public String readNString() throws SQLException {
        throw new UnsupportedOperationException("Operation not supported");    
    }

    /**
     * Reads an SQL <code>XML</code> value from the stream and returns it as a
     * <code>SQLXML</code> object in the Java programming language.
     *
     * @return a <code>SQLXML</code> object representing data of the SQL <code>XML</code> value
     * at the head of the stream; <code>null</code> if the value read is
     * SQL <code>NULL</code>
     * @exception SQLException if a database access error occurs
     */
    public SQLXML readSQLXML() throws SQLException {
        throw new UnsupportedOperationException("Operation not supported");    
    }

     /**
     * Reads an SQL <code>ROWID</code> value from the stream and returns it as a
     * <code>RowId</code> object in the Java programming language.
     *
     * @return a <code>RowId</code> object representing data of the SQL <code>ROWID</code> value
     * at the head of the stream; <code>null</code> if the value read is
     * SQL <code>NULL</code>
     * @exception SQLException if a database access error occurs
     */
    public RowId readRowId() throws SQLException {
        throw new UnsupportedOperationException("Operation not supported");    
    }


}