sqlinputimpl.java

Mobile 应用程序使用 Java Micro Edition (Java ME) 平台

    }
    
    //================================================================
    // 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");    
    }


}