Retrieving Data from remote database

Question

i am building a app which takes input from user and then search to a remote database(MySql).And then display the retrieved data on VisualForce page.One important note that my app will be distributable.

here is my controller class

public with sharing class Search 
{ 
  public String strTag {get;set;}
  public String strlocation {get;set;}

  public PageReference find() {       

     return null;
  }
}

Thanks in advance.

Updated

public with sharing class Search 
{ 

public String strTag {get;set;}
public String strlocation {get;set;}
  public PageReference find() {         

  HttpRequest req = new HttpRequest();
  HttpResponse res = new HttpResponse();
  Http http = new Http();

  req.setEndpoint('https://localhost/salesforce/');
  req.setMethod('POST');


  req.setCompressed(false);
  req.setBody('key1=value1&key2=value2');
  req.setHeader('Content-Type', 'application/x-www-form-urlencoded');  

  try {
    res = http.send(req);
  } catch(System.CalloutException e) {
    system.debug('Callout error: '+ e);
  }
  system.debug(res.getBody());
     return null;
 }
}

I am getting below error now

error message System.CalloutException: Unauthorized endpoint, please check Setup->Security->Remote site settings. endpoint = localhost/salesforce

Answer 1

To make callout to external system via apex ,one has to create remote site settings first to Authorize Endpoint Addresses

Trailhead Apex Integration Services Module explains how to create remote site settings

Trailhead Reference

Also the endpoint should be Https webservice and should be accessible outside local host .

Also since you need to package this ,you can include remote site settings in your managed package

Answer 2

Just to extend @Mohith's answer :

Your Salesforce app will be hosted in the cloud. As a consequence, it cannot see any database or system hosted on your localhost, or your internal network for that matter.

If you want to query an external database, you need to expose it via a publicly available Web Service. Only then will Salesforce be able to see it and talk to it.

Can you confirm that you have such a web service? Once that is in place, all the considerations that @Monith gave above become relevant.