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<title>OTL 4.0, Example 206 (otl_exception, derived from a base class)</title>
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<h1>OTL 4.0, Example 206</h1>
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<h1>(otl_exception, derived from a base class, MS SQL Server)</h1>
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<h1>
Example 206 (otl_exception, derived from a base class, MS SQL Server)</h1>
This example demonstrates how to derive otl_exception from a base
class,
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 char* getErrorMessage(void) const<br> {<br> return "";<br> }<br><br>};<br><br>#define <a
href="otl3_compile.htm#OTL_ODBC_MSSQL_2005">OTL_ODBC_MSSQL_2005</a> // Compile OTL 4/ODBC, MS SQL 2005<br>//#define OTL_ODBC // Compile OTL 4/ODBC. Uncomment this when used with MS SQL 7.0/ 2000<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 code; \<br> } \<br> \<br> virtual char* getErrorMessage(void) const \<br> { \<br> return (char*)msg; \<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/tiger@mssql"); // connect to MS 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 MS 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>
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