Zas Save

What is ZAS

• ZAS（Zhou’s Adaptor of Sql）is being developed based on the MYSQL Client/Server Protocol
• ZAS is a C++ library that used by applications to access MYSQL databases
• ZAS can translate SQL syntax automatically

Features

• Cross platforms: 32/64 bit processors supports, linux and windows supports
• Cross languages: you may use ZAS with c++, java, python
• Provides OTLV4-compatible interfaces
• Provides automatically SQL syntax translations that is transparent to upper applications
• Supports most SQL syntaxs in ORACLE/MYSQL
• Good performance in SQL syntax analyzing
• The underlying MYSQL Client/Server Protocol is being optimized
• Conceals complexities of MYSQL Client/Server Protocol
• Good extensibility
• Being tested over a year and runs steadily

Structure

• Connection String processor: processes the DB connection strings including Oracle TNS and traditional DSN format
• Protocol Management(the MYSQLC libray) provides:
  1. implementations of the MYSQL Client/Server Protocol
  2. fully support for the prepare and query mode
  3. API compatibilities with libmysqlclient
• SQL Syntax Engine: performs SQL syntax analyzing/checking/translations
• OTLV4 Compatible API: provides a set of c++ classes that compatible with OTLV4 libraries

Process Flow

• First of all, the application should call rlogon() to parse connection strings and to do database login
• Second, the application should call open() to initialize the SQL and translate it
• Third, the application should input enough place holder values to execute the statement
• Last, fetching the result
• Further more, one can reopen a new SQL or execute the old one again

Connection String Handling

• When login, the connection string is passed to the connection string processor which will test the inputed string
  1. if it’s TNS format, the processor will parse the TNS file for login informations
  2. if it’s DSN format, the processor will parse it directly
  3. otherwise, throws C++ exception

the SQL Syntax Engine

• when a SQL is inputed, it would be processed by a hard-coding parser and be translated to a syntax tree
• if no errors, the tree will be scaned for syntax errors
• if everythings’ ok, the tree will be scaned again for translation points to being translated to MYSQL-style syntax
• then, all place-holders within the tree will be processed
• last, the tree will be serialized to string form and passed to output

The MYSQLC library

• The library provides the following functionalities: database login, SQL execution, result fetching, protocol compression, connection maintainance
• The protocol compression invokes the deflate algorithm from zlib
• The library employs the ping protocol to maintain the database connection
• To execute a SQL statement, the application may use query mode with which all place holder values are embeded within the SQL statement string that will be sent to server by a single com_query request, here’s the diagram:

• The application may also execute SQL under prepare mode. The SQL execution progress is seperated into 2 requests:
  1. the primordial SQL statement is sent to server by com_stmt_prepare to prepare resources and do checkings at server side
  2. the place-holder value list are embeded into the com_stmt_execute request to initiate the SQL execution progress, and the binary/string/blob type place-holders values should be sent by com_send_long_data requests especially, Here’s the diagram:

Compiling and Installing

• Simply do make clean install under source root directory
• The libzas.a, libzas.so, and zas wrapper library will be generated
• Link the .a or .so library to your c++ applications
• Load the wrapper library into your java/python applications

Roadmap

• src: core of zas library
• tests: test cases of zas
• win: vss project files of zas under windows
• wrapper: library classes for java/python that encapsulates APIs onto ZAS

Wrappers

• both java and python wrappers load a c library named libcwpr that encapsulates a set of usage with ZAS APIs. see wrapper/cwpr.c for more details
• in java wrapper, it calls libcwpr methods with JNI interfaces
• in python wrapper, it dynamically loads the libcwpr

HOWTO

In c++, one should access MYSQL with ZAS like this:

 /* initialize connection object and login to database with MYSQL driver */
 zas_connect cnn(tnsFilePath,dal_mysql) ;
 /* initialize stream object with SQL-prepare mode */
 zas_stream stream(cnn,true);
 
 /* initialize the ORACLE-style SQL */
 stream.open(0,"select id,nvl(name),price from test_db.test_tbl "
        "where id>=:f1<unsigned int> and id<:f2<int,in>");
 
 /* insert place holders and execute the SQL */
 streams<<1;
 streams<<5;
 
 /* fetch results */
 while (!streams[strs].eof()) {
  int id=0;
  char name[256] = "";
  float point = 0.0;
  long size = 0L;
  
  streams>>id ;
  streams>>name ;
  streams>>point ;
  streams>>size ;
  streams.flush();
  printd("%d: name %s, point %f, size %ld\n",
    id, name, point, size);
}

In java, one should set correct 'CLASSPATH' of ZAS java wrapper class and play like this:

public class test_cases {

  public static void main(String[] args) throws Exception {

    /* initialize instance of zas.class and do initializations with it */
    zas mz = (zas)Class.forName("zas").newInstance();

    /* login to MYSQL */
    mz.login("localhost",3306,"root","123","");

    /* initialize the ORACLE-style SQL */
    mz.prepare("select id,nvl(name),price,size from test_db.test_tbl where id<:f1<int>");

    /* insert placeholder and execute SQL */
    mz.insertInt(10);

    /* fetch results */
    while (!mz.isEof()) {
      Integer id = 0;
      String name = "" ;
      Double price = 0.0;
      Long size = 0L; 

      id = mz.fetchInt();
      name = mz.fetchStr();
      price = mz.fetchDouble();
      size = mz.fetchLong();
      System.out.println(id + ": name: " + name + ", point: " + 
        price + ", size: " + size + "\n");
    }   

  }
}

In python, one should load ZAS python wrapper class and play like this:

# path of ZAS python wrapper class
sys.path.append(zasPythonWrapperPath)

# load the wrapper class
from python.zas import *

def main():

  # do initializations
  mz = zas()

  # login to database
  if mz.login("localhost",3306,"root","123","")!=0 :
    print("login fail\n")
    exit(-1)

  # initialize the ORACLE-style SQL
  if mz.prepare('select nvl(id),name,price,size from test_db.test_tbl where id <:f1<int>')!=0 :
    print("prepare fail\n")
    exit(-1)

  # insert placeholder and execute SQL
  if mz.insert_int(10)!=0 :
    exit(-1)

  # fetch results
  while mz.is_eof()==0 :
    id = mz.fetch_int()
    name = mz.fetch_str()
    price = mz.fetch_double()
    size = mz.fetch_long()
    print("{0}: name: {1}, point: {2}, size: {3}\n".format(id,name,price,size))