📄 otl4_ex567.htm
字号:
<!DOCTYPE html PUBLIC "-//w3c//dtd html 4.0 transitional//en"><html><head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="Author" content="Sergei Kuchin"> <meta name="GENERATOR" content="Mozilla/4.77 [en] (Win95; U) [Netscape]"> <meta name="KeyWords" content="OTL, Oracle, ODBC, DB2, CLI, database API, C++, Template Library"> <title>OTL 4.0, Example 567 (otl_exception, derived from a baseclass, Sybase SQL Server)</title></head><body><center><h1>OTL 4.0, Example 567<br></h1></center><center><h1>(otl_exception, derived from a base class, Sybase SQL Server)</h1></center>This example demonstrates how to derive otl_exception from a baseclass,which may be part of already existing exception class hierarchy.<h2>Source Code</h2><pre>#include <iostream><br>using namespace std;<br><br>#include <stdio.h><br><br>const int BASE_EXCEPTION=1; // "Base exception" class Id.<br>const int DB_BASE_EXCEPTION=2; // "DB Base exception" class Id.<br><br>// Let's assume that the following class is the base of <br>// the system exception class hierarchy<br>class my_base_exception{<br>public:<br><br> my_base_exception(){}<br> virtual ~my_base_exception(){}<br><br> virtual int getType(void) const<br> {<br> return BASE_EXCEPTION;<br> }<br><br> virtual int getErrorCode(void) const<br> {<br> return 0;<br> }<br><br> virtual const char* getErrorMessage(void) const<br> {<br> return "";<br> }<br><br>};<br><br>#define OTL_ODBC_UNIX // Compile OTL 4.0/ODBC<br><br>// This #define connects the otl_exception class to the exception<br>// class hierarchy. <br>#define <a href="otl3_compile.htm#OTL_EXCEPTION_DERIVED_FROM">OTL_EXCEPTION_DERIVED_FROM</a> my_base_exception<br><br>// This #define defines a set of new members in the <a href="otl3_exception_class.htm">otl_exception<br></a>// class<br>#define <a href="otl3_compile.htm#OTL_EXCEPTION_HAS_MEMBERS">OTL_EXCEPTION_HAS_MEMBERS</a> \<br> virtual int getType(void) const \<br> { \<br> return DB_BASE_EXCEPTION; \<br> } \<br> \<br> virtual int getErrorCode(void) const \<br> { \<br> return this->code; \<br> } \<br> \<br> virtual const char* getErrorMessage(void) const \<br> { \<br> return reinterpret_cast<const char*>(this->msg); \<br> }<br><br><br>#include <otlv4.h> // include the OTL 4.0 header file<br><br><a href="otl3_connect_class.htm">otl_connect</a> db; // connect object<br><br>void insert()<br>// insert rows into table<br>{ <br> <a href="otl3_stream_class.htm">otl_stream</a> o(50, // buffer size<br> "insert into test_tab values(:f1<float>,:f2<char[31]>)", <br> // SQL statement<br> db // connect object<br> );<br> char tmp[32];<br><br> for(int i=1;i<=100;++i){<br> sprintf(tmp,"Name%d",i);<br> o<<(float)i<<tmp;<br> }<br>}<br><br>void select()<br>{ <br> <a href="otl3_stream_class.htm">otl_stream</a> i(50, // buffer size<br> "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",<br> // SELECT statement<br> db // connect object<br> ); <br> // create select stream<br> <br> float f1;<br> char f2[31];<br><br> i<<8<<8; // assigning :f12 = 8, :f12 = 8<br> // SELECT automatically executes when all input variables are<br> // assigned. First portion of output rows is fetched to the buffer<br><br> while(!i.eof()){ // while not end-of-data<br> <a name="incompatible"></a>i>>f2>>f1; // a typo: f2 instead of f1<br> cout<<"f1="<<f1<<", f2="<<f2<<endl;<br> }<br><br> i<<4<<4;<br> // SELECT automatically executes when all input variables are<br> // assigned. First portion of output rows is fetched to the buffer<br><br> while(!i.eof()){ // while not end-of-data<br> i>>f1>>f2;<br> cout<<"f1="<<f1<<", f2="<<f2<<endl;<br> }<br><br>}<br><br>int main()<br>{<br> <a href="otl3_connect_class.htm">otl_connect::otl_initialize</a>(); // initialize ODBC environment<br> try{<br><br> db.rlogon("scott/tigger@freetds_sybsql"); // connect to Sybase SQL Server<br><br> <a href="otl3_const_sql.htm">otl_cursor::direct_exec<br></a> (<br> db,<br> "drop table test_tab",<br> otl_exception::disabled // disable OTL exceptions<br> ); // drop table<br><br> <a href="otl3_const_sql.htm">otl_cursor::direct_exec<br></a> (<br> db,<br> "create table test_tab(f1 int, f2 varchar(30))"<br> ); // create table<br><br> insert(); // insert records into table<br> select(); // select records from table<br><br> }<br> catch(my_base_exception& ex){ // intercept the base exception<br> if(ex.getType()==DB_BASE_EXCEPTION){ <br> // "database exception" is recognized<br> // here, the otl_exception can be analyzed, or simply printed out<br> cerr<<"Database exception:"<<endl;<br> cerr<<"Code: "<<ex.getErrorCode()<<endl; // print out error code<br> cerr<<"Message: "<<ex.getErrorMessage()<<endl; // print out the error message<br> }else{<br> // otherwise, do something else<br> cerr<<"Base exception was caught..."<<endl;<br> }<br> }<br><br> db.logoff(); // disconnect from Sybase SQL Server<br><br> return 0;<br><br>}</pre><h2>Output</h2><pre>Database exception:<br>Code: 32000<br>Message: Incompatible data types in stream operation<br><br><br><hr width="100%"></pre><center><a href="otl3_examples.htm">Examples</a> <a href="otl3.htm">Contents</a><a href="home.htm">GoHome</a></center><p>Copyright © 1996, 2008, Sergei Kuchin, email: <a href="mailto:skuchin@aceweb.com">skuchin@aceweb.com</a>,<a href="mailto:skuchin@gmail.com">skuchin@gmail.com/a>.<script language="JavaScript"><!-- hide from old browsers var modDate = new Date(document.lastModified) document.write("<i> Last Updated:</i> " + (modDate.getMonth()+1) + "/" + modDate.getDate() + "/" + "0"+(modDate.getYear())%100+"."); //--> </script></a></p><p><i>Permission to use, copy,modify and redistribute this documentforany purpose is hereby granted without fee, provided that the abovecopyrightnotice appear in all copies.</i></p></body></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -