CODEWITHSUNDEEP
databasepostgresqlballerina
tutiplain
tutiplain

Reputation: 1480

Connecting postgresql with ballerina

I am trying to connect a PostgreSQL database using it. I have the following code:

import ballerina/io;
import ballerinax/java.jdbc;
import ballerina/sql;

public function main() {
    io:println("Hola mundo");

    jdbc:Client|sql:Error dbClient = 
        new("jdbc:postgresql://localhost:5432/GenteDB","gente","GenteDB123!");

    io:println(dbClient);

    sql:ExecutionResult result = 
            check dbClient->execute(`CREATE TABLE student (
                                       id INT AUTO_INCREMENT,
                                       age INT, 
                                       name VARCHAR(255), 
                                       PRIMARY KEY (id)
                                     )`);

}

This doesn't compile and I get the following error:

ERROR [main.bal:(13:23,18:45)] invalid remote method call: expected a client object, but found '(ballerinax/java.jdbc:1.4.1:Client|ballerina/sql:1.4.1:Error)'

Unfortunately, documentation is scarce, google turned up exactly 0 results for this error message (a first in my lifetime). The line with the error (check dbClient->execute...) was copied directly from ballerina's JDBC driver GitHub page. I have no idea what this error means. What am I missing? Any help will be appreciated.

Upvotes: 1

Views: 186

Answers (1)

Niveathika
Niveathika

Reputation: 1445

This is because of Ballerina Error Handling is different from other languages, For more details on error handling see Ballerina By Example: Error Handling.

To look into this specific case. When invoking execute() method dbClient may be either jdbc:Client or sql:Error. You can call the remote method only if the variable is of type jdbc:Client. You should narrow the type of the dbClient before the remote method is invoked.

if dbClient is error {
    // handle the error
} else {
    // Type of `dbClient` will be `jdbc:Client` here.
    sql:ExecutionResult result = 
                check dbClient->execute(`...`);
}

Alternatively, you can use check keyword to narrow the type as sql:Error is an error type in Ballerina.

jdbc:Client dbClient = check new("jdbc:postgresql://localhost:5432/GenteDB","gente","GenteDB123!");

For more details on handling errors with check expression see Ballerina By Example: Check Expression.

Do note, the check with return the error. Here, the main function needs to be updated as follows,

import ballerina/io;
import ballerinax/java.jdbc;
import ballerina/sql;

public function main() returns error? {
    io:println("Hola mundo");

    jdbc:Client dbClient = check new("jdbc:postgresql://localhost:5432/GenteDB","gente","GenteDB123!");

    io:println(dbClient);

    sql:ExecutionResult result = 
        check dbClient->execute(`CREATE TABLE student (
                                   id INT AUTO_INCREMENT,
                                   age INT, 
                                   name VARCHAR(255), 
                                   PRIMARY KEY (id)
                                 )`);

}

Upvotes: 2

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