Catch MySQL error in c++

问题

In C++, I am using mysql.h libraries and I do not manage to catch MySQL errors (for example, failure to insert due to conflict in primary key).

I have tried

#include <mysql.h>
// ...
try{
    res = mysql_perform_query(conn, sqlIn);
} catch (...) {
// ...
}

but it still does not avoid aborting with:

MySQL query error : Duplicate entry

I am running the compiled c++ program using PuTTy interface and as the program aborts, it reproduces MySQL's error (regardless of whether I use TRY CATCH or not).
I have not found any reference to specific exception codes for MySQL use with catch statement.

Apparently, C++ (using this library mysql.h) does not catch MySQL callback errors even with the "blanket" syntax (catch (...)). Since this syntax should catch ALL exceptions, yet doesn't in this case, I am at a loss to understand what is happening here. How can I catch the SQL exceptions?

回答1:

The mysql C library does not throw any excptions; it merely, like most other C libraries, sets up error info in a common place ( like errno ) and returns a status. Its up to your client code to check the return and throw an error/exception.

If you need an easy fix for your problem, try mysql++ (AKA mysqlpp). It is a piece of software that I can vouch for; solid as a rock! http://tangentsoft.net/mysql++/

回答2:

Try using some c++ wrapper around the mysql C library. e.g. http://mysqlcppapi.sourceforge.net/

C doesnt throw exceptions you have to check via mysql_errorno function.

回答3:

I wont suggest Mysql C++ libraries for two reasons 1.It is difficult to get support. 2.Slow compared to Mysql C library

you can use mysql_error() and mysql_errno() API's to know the errors and manually through exceptions

回答4:

as per kingstonian's suggestion, i used the mysql++ wrapper around mysql (for installation in ubuntu, see my recipe answering another SO question)

the code below was used to test error handling, where a duplicate value was inserted in the key (Id_Target = 9). adapt to your own needs, using the appropriate insert for your DB structure.

#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include </usr/include/mysql++/mysql++.h>


// sudo g++ -o /temp/zdelMySQLpp01c $(mysql_config --cflags) /home/ubuntu/zdelMySQLpp01c.cpp $(mysql_config --cflags --libs) -l pthread -std=c++0x -g -L/usr/lib/mysql -lmysqlclient -lmysqlpp

using namespace mysqlpp;
using namespace std;

//MySQL type
struct connection_details {
        char *server;
        char *user;
        char *password;
        char *database;
};

int main(int argv, char** argc){

// MySQL connection (global)
struct connection_details mysqlD;
mysqlD.server = (char *)"localhost";  // where the mysql database is
mysqlD.user = (char *)"root";       // the root user of mysql   
mysqlD.password = (char *)"XXXXXX"; // the password of the root user in mysql
mysqlD.database = (char *)"test";   // the databse to pick

// connect to the mysql database
mysqlpp::Connection conn(false);
if (conn.connect(mysqlD.database, mysqlD.server, mysqlD.user, mysqlD.password)) {
    //printf("ALOALO funcionou conexao\n");
    mysqlpp::Query query = conn.query("INSERT INTO test.target (Id_Target, Ds_Target, Ds_Target_Name, Ds_Target_PWD, Ds_Target_Email, Ds_Target_Icon) VALUES ('9', 'test', 'name', 'pass', 'email', NULL)");
        if (mysqlpp::StoreQueryResult res = query.store()) {
                cout << "We have:" << endl;
                for (size_t i = 0; i < res.num_rows(); ++i) {
                    cout << '\t' << res[i][0] << endl;
                }
        } else {
                cerr << "Failed to get item list: " << query.error() << endl;
                return 1;
    }
        return 0;
}
}

来源：https://stackoverflow.com/questions/12609104/catch-mysql-error-in-c

标签

c++

exception-handling

mysql-error-1062