# transactor.hxx

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    00001 /*-------------------------------------------------------------------------
    00002  *
    00003  *   FILE
    00004  *      pqxx/transactor.hxx
    00005  *
    00006  *   DESCRIPTION
    00007  *      definition of the pqxx::transactor class.
    00008  *   pqxx::transactor is a framework-style wrapper for safe transactions
    00009  *   DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/transactor instead.
    00010  *
    00011  * Copyright (c) 2001-2006, Jeroen T. Vermeulen <jtv@xs4all.nl>
    00012  *
    00013  * See COPYING for copyright license.  If you did not receive a file called
    00014  * COPYING with this source code, please notify the distributor of this mistake,
    00015  * or contact the author.
    00016  *
    00017  *-------------------------------------------------------------------------
    00018  */
    00019 #include "pqxx/compiler-public.hxx"
    00020 #include "pqxx/compiler-internal-pre.hxx"
    00021
    00022 #include "pqxx/connection_base"
    00023 #include "pqxx/transaction"
    00024
    00025
    00026 /* Methods tested in eg. self-test program test001 are marked with "//[t1]"
    00027  */
    00028
    00029 namespace pqxx
    00030 {
    00031
    00033
    00062 template<typename TRANSACTION=transaction<read_committed> >
    00063   class transactor :
    00064     public PGSTD::unary_function<TRANSACTION, void>
    00065 {
    00066 public:
    00067   explicit transactor(const PGSTD::string &TName="transactor") :        //[t4]
    00068     m_Name(TName) { }
    00069
    00071
    00082   void operator()(TRANSACTION &T);                                      //[t4]
    00083
    00084   // Overridable member functions, called by connection_base::perform() if an
    00085   // attempt to run transaction fails/succeeds, respectively, or if the
    00086   // connection is lost at just the wrong moment, goes into an indeterminate
    00087   // state.  Use these to patch up runtime state to match events, if needed, or
    00088   // to report failure conditions.
    00089
    00091
    00099   void on_abort(const char[]) throw () {}                               //[t13]
    00100
    00102
    00106   void on_commit() {}                                                   //[t6]
    00107
    00109
    00120   void on_doubt() throw () {}                                           //[t13]
    00121
    00122   // TODO: Rename Name()--is there a compatible way?
    00124   PGSTD::string Name() const { return m_Name; }                         //[t13]
    00125
    00126 private:
    00127   PGSTD::string m_Name;
    00128 };
    00129
    00130
    00131 }
    00132
    00133
    00134 template<typename TRANSACTOR>
    00135 inline void pqxx::connection_base::perform(const TRANSACTOR &T,
    00136                                            int Attempts)
    00137 {
    00138   if (Attempts <= 0) return;
    00139
    00140   bool Done = false;
    00141
    00142   // Make attempts to perform T
    00143   // TODO: Differentiate between db-related exceptions and other exceptions?
    00144   do
    00145   {
    00146     --Attempts;
    00147
    00148     // Work on a copy of T2 so we can restore the starting situation if need be
    00149     TRANSACTOR T2(T);
    00150     try
    00151     {
    00152       typename TRANSACTOR::argument_type X(*this, T2.Name());
    00153       T2(X);
    00154       X.commit();
    00155       Done = true;
    00156     }
    00157     catch (const in_doubt_error &)
    00158     {
    00159       // Not sure whether transaction went through or not.  The last thing in
    00160       // the world that we should do now is retry.
    00161       T2.on_doubt();
    00162       throw;
    00163     }
    00164     catch (const PGSTD::exception &e)
    00165     {
    00166       // Could be any kind of error.
    00167       T2.on_abort(e.what());
    00168       if (Attempts <= 0) throw;
    00169       continue;
    00170     }
    00171     catch (...)
    00172     {
    00173       // Don't try to forge ahead if we don't even know what happened
    00174       T2.on_abort("Unknown exception");
    00175       throw;
    00176     }
    00177
    00178     T2.on_commit();
    00179   } while (!Done);
    00180 }
    00181
    00182
    00183 #include "pqxx/compiler-internal-post.hxx"