Linux下使用C/C++访问数据库

在Linux下连接MSSQL是一件很痛苦的事，因为微软同志没有提供任何接口给开发人员，大约他们认为要用MSSQL的，只可能是windows的操作系统。还好，MSSQL是从Sybase衍生出来的，有一些哥们做了一些Sybase的Linux下的连接库，这些连接库同时也能支持MSSQL，FreeTDS就是这样的一个东东。 这篇文章的受用读者，我想是那些希望在Linux或Unix下编写C或C++程序来连接MSSQL2000的兄弟们，因为我就是这样的。同时，那些写PHP的哥们也可以参考一下，当然如果你是用PHP的，你恐怕还要知道APACHE以及PHP脚本的安装，或者关于PHP自定义Module的开发，可以参考我以前写的一篇Blog（PHP5自定义Module开发）。下面开始我们的探索之旅：一、相关软件

首先我们需要FreeTDS的安装包，可以在这个地址下载到：http://ibiblio.org/pub/Linux/ALPHA/freetds/stable/freetds-stable.tgz现在的最新版是0.82其次就是大家需要自己搭建C++的开发环境了。
二、软件安装、配置
# tar zxvf freetds-stable.tgz（解压）# ./configure --prefix=/usr/local/freetds /（指定FreeTDS安装路径）
  --with-tdsver=8.0 --enable-msdblib （设置TDS版本，支持SQL Server 2000）# make # make install 将freetds的库文件所在路径配置到LD_LIBRARY_PATH参数中：
$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/freetds/lib/:
这么作的目的是为了避免加载FreeTds库文件加载不上的情况。
三、程序开发
不多说了，还是直接上代码：/*  
* SyBaseManager.h  
*  
*   Created .: Feb 18, 2009  
*         Author: Steven Wee  
*/  

#ifndef SYBASEMANAGER_H_  
#define SYBASEMANAGER_H_  

#include "../Common/CheckStringTools.h"  

#include <string>  
#include <vector>  
#include <iostream>  
#include <assert.h>  
#include <errno.h>  
#include <stdlib.h>  
#include <string.h>  

#include <sybfront.h>  
#include <sybdb.h>  

using namespace std;  

class SybaseManager  
{  
public:  
    SybaseManager(std::string hosts, std::string userName, std::string password, std::string dbName, unsigned int port);  
    ~SybaseManager();  
    /*  
      * Init SQL Server  
      * @param hosts:       Host IP address  
      * @param userName:     Login UserName  
      * @param password:     Login Password  
      * @param dbName:     Database Name  
      * @param port:           Host listen port number  
      */  
    void initConnection();  
    /*  
      * Making query from database  
      * @param mysql:     MySQL Object  
      * @param sql:           Running SQL command  
      */  
    bool runSQLCommand(std::string sql);  
    /**  
      * Destroy MySQL object  
      * @param mysql           MySQL object  
      */  
    void destroyConnection();  
    bool getConnectionStatus();  
    vector<vector<string> > getResult();  
protected:  
    void setUserName(std::string userName);  
    void setHosts(std::string hosts);  
    void setPassword(std::string password);  
    void setDBName(std::string dbName);  
    void setPort(unsigned int port);  
private:  
    bool IsConnected;  
    DBPROCESS *dbProcess;  
    vector< vector<string> > resultList;  
    unsigned int DEFAULTPORT;  
    char * HOSTS;  
    char * USERNAME;  
    char * PASSWORD;  
    char * DBNAME;  
};  

#endif /* SYBASEMANAGER_H_ */

/*  
* SyBaseManager.cpp  
*  
*   Created .: Feb 18, 2009  
*         Author: Steven Wee  
*/  
#include "SybaseManager.h"  

SybaseManager::SybaseManager(std::string hosts, std::string userName, std::string password, std::string dbName, unsigned int port)  
{  
    IsConnected = false;  
    this ->setHosts(hosts);  
    this ->setUserName(userName);  
    this ->setPassword(password);  
    this ->setDBName(dbName);  
    this ->setPort(port);  
}  

SybaseManager::~SybaseManager()  
{  
    destroyConnection();  
}  

void SybaseManager::setDBName(string dbName)  
{  
    if ( dbName.empty() )  
    {  
          std::cout << "DBName is null! Used default value: master" << std::endl;  
          this ->DBNAME = new char[5];  
          strcpy(this ->DBNAME, "master");  
    }  
    else  
    {  
          this ->DBNAME = new char[dbName.length()];  
          strcpy(this ->DBNAME, dbName.c_str());  
    }  
}  

void SybaseManager::setHosts(string hosts)  
{  
    if ( hosts.empty() )  
    {  
          std::cout << "Hosts is null! Used default value: localhost" << std::endl;  
          this ->HOSTS = new char[9];  
          strcpy(this ->HOSTS, "localhost");  
    }  
    else  
    {  
          this ->HOSTS = new char[hosts.length()];  
          strcpy(this ->HOSTS, hosts.c_str());  
    }  
}  

void SybaseManager::setPassword(string password)  
{  
    if ( password.empty() )  
    {  
          std::cout << "Password is null! Used default value: " << std::endl;  
          this ->PASSWORD = new char[1];  
          strcpy(this ->PASSWORD, "");  
    }  
    else  
    {  
          this ->PASSWORD = new char[password.length()];  
          strcpy(this ->PASSWORD, password.c_str());  
    }  
}  

void SybaseManager::setPort(unsigned int port)  
{  
    if ( port )  
    {  
          std::cout << "Port number is null! Used default value: 0" << std::endl;  
          this ->DEFAULTPORT = 0;  
    }  
    else  
    {  
          this ->DEFAULTPORT = port;  
    }  
}  

void SybaseManager::setUserName(string userName)  
{  
    if ( userName.empty() )  
    {  
          std::cout << "UserName is null! Used default value: sa" << std::endl;  
          this ->USERNAME = new char[4];  
          strcpy(this ->USERNAME, "sa");  
    }  
    else  
    {  
          this ->USERNAME = new char[userName.length()];  
          strcpy(this ->USERNAME, userName.c_str());  
    }  
}  

void SybaseManager::initConnection()  
{  
    string Charset = "UTF-8";  
    dbinit();  
    LOGINREC *loginREC = dblogin();  
    DBSETLUSER(loginREC, this ->USERNAME);  
    DBSETLPWD(loginREC, this ->PASSWORD);  
    DBSETLCHARSET(loginREC, Charset.c_str());  
    dbProcess = dbopen(loginREC, this ->HOSTS);  
    if ( dbProcess == FAIL )  
    {  
          std::cout << "Connect to SQL Server failed!" << std::endl;  
    }  
    if ( dbuse( dbProcess, this ->DBNAME ) == FAIL )  
    {  
          std::cout << "Use table failed!" << std::endl;  
    }  
}  

bool SybaseManager::runSQLCommand( string sql )  
{  
    dbcmd(dbProcess, sql.c_str());  
    if ( dbsqlexec(dbProcess) == FAIL )  
    {  
          std::cout << "Query from database failed!" << std::endl;  
    }  
    DBINT result_code;  
    vector<string> objectValue;  
    StringTools stringTools;  

    sql = stringTools.filterString(sql);  

    while ( (result_code = dbresults(dbProcess)) != NO_MORE_RESULTS )  
    {  
          struct Column  
          {  
                char* colName;  
                char* colBuffer;  
                int colType, colSize, colStatus;  
          } *columns, *pCol;  
          int nColumns;  
          int rowNo;  
          if ( result_code == SUCCEED )  
          {  
                nColumns = dbnumcols(dbProcess);  
                if ( (columns = (Column*)calloc(nColumns, sizeof(struct Column))) == NULL )  
                {  
                    std::cout << "Error at bind data" << std::endl;  
                    return false;  
                }  
                for ( pCol = columns; pCol - columns < nColumns; pCol++ )  
                {  
                    int colNo = pCol - columns + 1;  
                    pCol ->colName = dbcolname(dbProcess, colNo);  
                    pCol ->colType = dbcoltype(dbProcess, colNo);  
                    pCol ->colSize = dbcollen(dbProcess, colNo);  
                    if ( SYBCHAR != pCol ->colType )  
                    {  
                          pCol ->colSize = dbwillconvert(pCol ->colType, SYBCHAR);  
                    }  

                    if ( (pCol ->colBuffer = (char*)calloc(1, pCol ->colSize + 1)) == NULL )  
                    {  
                          std::cout << "Check column buffer error!" << std::endl;  
                          return false;  
                    }  

                    if ( dbbind(dbProcess, colNo, STRINGBIND, pCol ->colSize + 1, (BYTE*)pCol ->colBuffer) == FAIL )  
                    {  
                          std::cout << "Running dbbind() error!" << std::endl;  
                          return false;  
                    }  

                    if ( dbnullbind(dbProcess, colNo, &pCol ->colStatus) == FAIL )  
                    {  
                          std::cout << "Running dbnullbind() error!" << std::endl;  
                          return false;  
                    }  
                }  

                while ( (rowNo = dbnextrow(dbProcess)) != NO_MORE_ROWS )  
                {  
                    objectValue.clear();  
                    switch ( rowNo )  
                    {  
                    case REG_ROW:  
                          for ( pCol = columns; pCol - columns < nColumns; pCol++ )  
                          {  
                                const char* columnBuffer = pCol ->colStatus == -1 ? "NULL" : pCol ->colBuffer;  
                                objectValue.push_back(stringTools.Trim(columnBuffer));     //     std::cout << columnBuffer << std::endl;  
                          }  
                          break;  
                    case BUF_FULL:  
                          assert( rowNo != BUF_FULL );  
                          break;  
                    case FAIL:  
                          std::cout << "Get result error!" << std::endl;  
                          break;  
                    default:  
                          std::cout << "Get result ignore, row number:" << rowNo << std::endl;  
                    }  
                    this ->resultList.push_back(objectValue);  
                }  
                for ( pCol = columns; pCol - columns < nColumns; pCol++ )  
                {  
                    free( pCol ->colBuffer );  
                }  
                free( columns );  
                /*  
                if ( DBCOUNT(dbProcess) > -1 )  
                {  
                    std::cout << "Affected rows:" << DBCOUNT(dbProcess) << std::endl;  
                }  
                */  
                if ( dbhasretstat(dbProcess) == TRUE )  
                {  
                    std::cout << "Procedure returned " << dbhasretstat(dbProcess) << std::endl;  
                }  
          }  
    }  
    return true;  
}  

void SybaseManager::destroyConnection()  
{  
    dbclose(dbProcess);  
}  

bool SybaseManager::getConnectionStatus()  
{  
    return IsConnected;  
}  

vector< vector<string> > SybaseManager::getResult()  
{  
    return this ->resultList;  
}

四、修改建议
本人在以后的完善中，打算把runSQLCommand(char * sql)函数分解成两个或者三个函数，分别执行select和insert等语句。在程序中，我并没有强制要求参数必须为const，可能会出现一些安全问题。本文仅起抛砖引玉的作用，希望有高手可以指点我程序中的问题。