Query's dinamicos.

En esta ocasión les muestro un código que sirve para crear un preparedStatement con valores de búsqueda variables, estos se pueden agregar a voluntad con la interface TreeMap , esto permite generar query's de manera dinámica a la hora de hacer consultas, pudiendo poner uno o mas parámetros sin tener que escribir excesivo código con if-else a la hora de programar, esto nos permite hacer menos código a la hora de programar busquedas en sql, y combinar criterios sin tener que pelear demasiado a la hora de codificar, el resultado del método es una sentencia preparada. la cual solo necesita ser ejecutada y para regresar el set de resultados.

/**
     * Creates a Prepared Statement Query using variable arguments for a custom search, 
     * if the query has no arguments or values the query remains 
     * the same and no search params are added, this allows to make a custom 
     * search without having to add a lot of if-else statements 
     * @param baseQuery a database query that contains no search parameters
     * @param queryParams search parameters which are pairs that contain criteria and values​​, which are added to the database query to generate a ready to run PreparedStatement
     * @param connection connection to the database open and ready for querys
     * @return returns a PreparedStatement with variable search parameters to get data ready to run
     */
public PreparedStatement setQueryParams(String baseQuery, TreeMap<String, Object> queryParams,
        Connection connection) throws SQLException {
    StringBuilder query = new StringBuilder(baseQuery);
    PreparedStatement preparedStatement = null;    
    Object[] keysObject = queryParams.keySet().toArray();
    /*we check the parameters size and if the hashmap is not empty we begin 
        to build a query using the keys for storing the values */
    if (queryParams.size() > 0) {    
        boolean first = true;
        for (Object key : keysObject) {
            if (first) {
                /*if this is the first value we add the clause "where" 
                     and set first to false so we can add the "and" clauses*/
                query.append(" where ");
                first = false;
            } else {
                query.append(" and ");
            }
            query.append( (String) key + " = ? ");
        }
    }
    /*we create a prepared statement ready for accepting parameters*/
    preparedStatement = connection.prepareStatement(query.toString());
    /*here we iterate through the values in the set and put the corresponding 
         values for each one of them in the prepared statement and add them as a 
         correct Object , the corresponding values equals the current keyset 
         order since the treemap uses the same order for the keys*/
    for (int i = 0; i < keysObject.length; i++) {
        String key = (String) keysObject[i];
        Object value = queryParams.get(key);
        if (value instanceof Integer) {
            preparedStatement.setInt(i + 1, (Integer) value);
        } else if (value instanceof Float) {
            preparedStatement.setFloat(i + 1, (Float) value);
        } else if (value instanceof Double) {
            preparedStatement.setDouble(i + 1, (Double) value);
        } else if (value instanceof String) {
            preparedStatement.setString(i + 1, (String) value);
        } else if (value instanceof Date) {
            long time = ((Date) value).getTime();
            preparedStatement.setDate(i + 1, new java.sql.Date(time));
        }
    }
    /*finally we return the prepared statement with all values set*/
    return preparedStatement;
}