嵌入式Linux之我行,主要讲述和总结了本人在学习嵌入式linux中的每个步骤。一为总结经验,二希望能给想入门嵌入式Linux的朋友提供方便。如有错误之处,谢请指正。
一、开发环境
- 主 机:Fedora 9
- 编译器:arm-linux-gcc-3.4.1
- 编辑器: Eclipse
- 开发板:Mini2440
- 数据库:sqlite-3.6.16.tar.gz
二、示例代码
本示例代码是嵌入式CGI WEB应用程序中的一部分,主要实现了用户的登录和用户的验证功能。代码结构分为三层,分别是数据库操作层、数据访问层、业务逻辑层。
- 数据库操作层
sqlitedb.h
/* ============================================================================ Name : sqlitedb.h Author : Huang Gang Version : 1.0.0 Date : 21/07/2009 Copyright : (C) 2009 XXXXXXXX LTD Description : Revision History : ============================================================================ */ #ifndef SQLITEDB_H_ #define SQLITEDB_H_
#include <sqlite3.h> //这个是移植sqlite数据库时编译生成的头文件,在移植篇里提到过 #include <stdio.h> #include <string>
using namespace std;
/* *数据集类 */ class Result { public: Result(); ~Result(); int getRowNum(); //获取数据集行数
int getColNum(); //获取数据集列数
int getResultNum(); //获取数据集记录行数
char *getAt(int r, int c); //获取数据集一条记录
friend class SQLiteDB; private: int row; int col; char **result; };
class SQLiteDB { public: SQLiteDB(); ~SQLiteDB(); bool openDB(const char *db_name); //打开数据库
bool execute(const char *sql); //执行SQL语句,无返回记录的
Result* executeSelect(const char *sql); //执行SQL语句,有返回记录的
bool closeDB(); //关闭数据库
private: sqlite3 *pDB; char *pErrMsg; };
#endif /*SQLITEDB_H_*/
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sqlitedb.cpp
/* ============================================================================ Name : sqlitedb.cpp Author : Huang Gang Version : 1.0.0 Date : 21/07/2009 Copyright : (C) 2009 XXXXXXXX LTD Description : Revision History : ============================================================================ */ #include "sqlitedb.h"
Result::Result() { row = 0; col = 0; result = NULL; }
Result::~Result() { sqlite3_free_table(result); }
int Result::getRowNum() { return row + 1; }
int Result::getColNum() { return col; }
int Result::getResultNum() { return row; }
char *Result::getAt(int r, int c) { if(r <= row + 1 && c <= col) { return result[r * col + c]; } else { return NULL; } }
SQLiteDB::SQLiteDB() { pDB = NULL; pErrMsg = NULL; }
SQLiteDB::~SQLiteDB() { if(pDB != NULL) { this->closeDB(); } }
bool SQLiteDB::openDB(const char *db_name) { int res = 0; res = sqlite3_open(db_name, &pDB); if(res != SQLITE_OK) { return false; } return true; }
bool SQLiteDB::execute(const char *sql) { if(pDB == NULL) { return false; } sqlite3_exec(pDB, sql, 0, 0, &pErrMsg); if(pErrMsg != NULL) { pErrMsg = NULL; return false; } return true; }
Result* SQLiteDB::executeSelect(const char *sql) { if(pDB == NULL) { return NULL; } Result *rs = new Result(); sqlite3_get_table(pDB, sql, &rs->result, &rs->row, &rs->col, &pErrMsg); if(pErrMsg != NULL) { pErrMsg = NULL; return NULL; } return rs; }
bool SQLiteDB::closeDB() { int res = 0; if(pDB != NULL) { res = sqlite3_close(pDB); if(res == SQLITE_BUSY) { return false; } } return true; }
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2. 数据访问层
user_DAL.h
/* ============================================================================ Name : user_DAL.h Author : Huang Gang Version : 1.0.0 Date : 29/07/2009 Copyright : (C) 2009 XXXXXXXX LTD Description : Revision History : ============================================================================ */ #ifndef USER_DAL_H_ #define USER_DAL_H_
#include <sstream> #include <string.h> #include "sqlitedb.h" #include "system_DAL.h"
using namespace std;
#define SQLITE_DATABASE_PATH "/usr/bin/ems_service.db" //数据库路径
class User_DAL { public: User_DAL(); ~User_DAL(); bool user_Login(char *name, char *pass, const char *sid); //用户登录
int user_Validate(char *sid); //验证用户
string get_CurrentTime(); //获取系统时间
private: typedef enum { LOG_OFF = 0, LOG_ON = 1 } USER_STATE; //用户登录状态
SQLiteDB sqliteDB; };
#endif /*USER_DAL_H_*/
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user_DAL.cpp
/* ============================================================================ Name : user_DAL.cpp Author : Huang Gang Version : 1.0.0 Date : 29/07/2009 Copyright : (C) 2009 XXXXXXXX LTD Description : Revision History : ============================================================================ */ #include "user_DAL.h"
User_DAL::User_DAL(){}
User_DAL::~User_DAL(){}
bool User_DAL::user_Login(char *name, char *pass, const char *sid) { bool ret = false; Result *result = NULL; ostringstream sql; sql << "SELECT id FROM SystemUsers WHERE name = '" << name << "' AND pass = '" << pass << "';";
if(!sqliteDB.openDB(SQLITE_DATABASE_PATH)) { return false; } result = sqliteDB.executeSelect((sql.str()).c_str());
if(result->getResultNum() > 0) { sql << "UPDATE SystemUsers SET state = " << LOG_ON << ", time = '" << get_CurrentTime() << "', sid = '" << sid << "' WHERE name = '" << name << "';"; ret = sqliteDB.execute((sql.str()).c_str()); } sqliteDB.closeDB(); return ret; }
int User_DAL::user_Validate(char *sid) { int ret = 0; Result *result = NULL; ostringstream sql; sql << "SELECT time FROM SystemUsers WHERE sid = '" << sid << "' AND state = " << LOG_ON << ";"; if(!sqliteDB.openDB(SQLITE_DATABASE_PATH)) { return 0; } result = sqliteDB.executeSelect((sql.str()).c_str()); if(result->getResultNum() > 0) { System_DAL system_DAL; int session_timeout = system_DAL.get_SessionTimeout(); if(session_timeout > 0) { char *login_time = result->getAt(1, 0); string curr_time = get_CurrentTime(); struct tm* tmp_time = (struct tm*)malloc(sizeof(struct tm)); strptime(login_time, "%Y-%m-%d %H:%M:%S", tmp_time); time_t login_t = mktime(tmp_time); strptime(curr_time.c_str(), "%Y-%m-%d %H:%M:%S", tmp_time); time_t curr_t = mktime(tmp_time); int dif_t = static_cast<int> (difftime(curr_t, login_t) / 60); if(session_timeout > dif_t) { sql << "UPDATE SystemUsers SET time = '" << get_CurrentTime() << "' WHERE sid = '" << sid << "' AND state = " << LOG_ON << ";"; sqliteDB.execute((sql.str()).c_str());
ret = 1; } else { sql << "UPDATE SystemUsers SET state = " << LOG_OFF << " WHERE sid = '" << sid << "' AND state = " << LOG_ON << ";"; sqliteDB.execute((sql.str()).c_str()); ret = -1; } } else { ret = 1; } } sqliteDB.closeDB(); return ret; }
string User_DAL::get_CurrentTime() { char s[32]; time_t t = time(0); strftime(s, sizeof(s), "%Y-%m-%d %H:%M:%S", localtime(&t)); return s; }
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3. 业务逻辑层
user_manage.h
/* ============================================================================ Name : user_manage.h Author : Huang Gang Version : 1.0.0 Date : 29/07/2009 Copyright : (C) 2009 XXXXXXXX LTD Description : Revision History : ============================================================================ */ #ifndef USER_MANAGE_H_ #define USER_MANAGE_H_
#include "md5.h" #include "parse.h" #include "user_DAL.h"
class User_Manage { public: User_Manage(); ~User_Manage(); void user_login(Parse list); bool user_validate(Parse list); private: User_DAL user_DAL; };
extern User_Manage user_manage;
#endif /*USER_MANAGE_H_*/
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user_manage.cpp
/* ============================================================================ Name : user_manage.cpp Author : Huang Gang Version : 1.0.0 Date : 29/07/2009 Copyright : (C) 2009 XXXXXXXX LTD Description : Revision History : ============================================================================ */ #include "user_manage.h"
User_Manage user_manage;
User_Manage::User_Manage(){}
User_Manage::~User_Manage(){}
/* * 功能:系统用户登录 * 参数: 客户端传来的查询字符串 * 返回:无 */ void User_Manage::user_login(Parse list) { char *name = list.get_item_n("name"); char *pass = list.get_item_n("pass"); string sid = MD5Encode((string(name) + string(user_DAL.get_CurrentTime())).c_str()); bool login = user_DAL.user_Login(name, pass, sid.c_str());
if(login) { //用户登录成功,跳转到主页并返回Session ID printf("window.location.href='index.html?sid=%s';", sid.c_str()); } else { //用户登录失败 printf("用户名或密码错误!"); } }
/* * 功能:验证系统登录用户 * 参数: 客户端传来的查询字符串 * 返回:是否通过 */ bool User_Manage::user_validate(Parse list) { char *sid = list.get_item_n("sid"); int state = user_DAL.user_Validate(sid);
if(state == 0) { //用户没有登录,跳转到登录页 printf("parent.window.location.href='login.html';"); return false; } else if(state == -1) { //用户登录后长时间没操作Session超时 printf("parent.window.location.href='error.html';"); return false; } else { //用户验证通过 return true; } }
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三、结束语
从示例代码看,sqlite数据库在嵌入式中的应用是非常的简单,跟在Windows下开发Windows应用程序没两样。这里值得一提的是三层结构思想即这里的数据库操作层、数据访问层、业务逻辑层,这使得应用程序的条理和效率更高。通过本篇,相信你已对sqlite数据库的应用有了一定的了解。
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