How do you connect to a MySQL database in Java?
When I try, I get
java.sql.SQLException: No suitable driver found for jdbc:mysql://database/table
at java.sql.DriverManager.getConnection(DriverManager.java:689)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
Or
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
Or
java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
Here's a step by step explanation how to install MySQL and JDBC and how to use it:
Download and install the MySQL server. Just do it the usual way. Remember the port number whenever you've changed it. It's by default 3306.
Download the JDBC driver and put in classpath, extract the ZIP file and put the containing JAR file in the classpath. The vendor-specific JDBC driver is a concrete implementation of the JDBC API (tutorial here).
If you're using an IDE like Eclipse or Netbeans, then you can add it to the classpath by adding the JAR file as Library to the Build Path in project's properties.
If you're doing it "plain vanilla" in the command console, then you need to specify the path to the JAR file in the -cp or -classpath argument when executing your Java application.
java -cp .;/path/to/mysql-connector.jar com.example.YourClass
The . is just there to add the current directory to the classpath as well so that it can locate com.example.YourClass and the ; is the classpath separator as it is in Windows. In Unix and clones : should be used.
Create a database in MySQL. Let's create a database javabase. You of course want World Domination, so let's use UTF-8 as well.
CREATE DATABASE javabase DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci;
Create a user for Java and grant it access. Simply because using root is a bad practice.
CREATE USER 'java'#'localhost' IDENTIFIED BY 'password';
GRANT ALL ON javabase.* TO 'java'#'localhost' IDENTIFIED BY 'password';
Yes, java is the username and password is the password here.
Determine the JDBC URL. To connect the MySQL database using Java you need an JDBC URL in the following syntax:
jdbc:mysql://hostname:port/databasename
hostname: The hostname where MySQL server is installed. If it's installed at the same machine where you run the Java code, then you can just use localhost. It can also be an IP address like 127.0.0.1. If you encounter connectivity problems and using 127.0.0.1 instead of localhost solved it, then you've a problem in your network/DNS/hosts config.
port: The TCP/IP port where MySQL server listens on. This is by default 3306.
databasename: The name of the database you'd like to connect to. That's javabase.
So the final URL should look like:
jdbc:mysql://localhost:3306/javabase
Test the connection to MySQL using Java. Create a simple Java class with a main() method to test the connection.
String url = "jdbc:mysql://localhost:3306/javabase";
String username = "java";
String password = "password";
System.out.println("Connecting database...");
try (Connection connection = DriverManager.getConnection(url, username, password)) {
System.out.println("Database connected!");
} catch (SQLException e) {
throw new IllegalStateException("Cannot connect the database!", e);
}
If you get a SQLException: No suitable driver, then it means that either the JDBC driver wasn't autoloaded at all or that the JDBC URL is wrong (i.e. it wasn't recognized by any of the loaded drivers). Normally, a JDBC 4.0 driver should be autoloaded when you just drop it in runtime classpath. To exclude one and other, you can always manually load it as below:
System.out.println("Loading driver...");
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Driver loaded!");
} catch (ClassNotFoundException e) {
throw new IllegalStateException("Cannot find the driver in the classpath!", e);
}
Note that the newInstance() call is not needed here. It's just to fix the old and buggy org.gjt.mm.mysql.Driver. Explanation here. If this line throws ClassNotFoundException, then the JAR file containing the JDBC driver class is simply not been placed in the classpath.
Note that you don't need to load the driver everytime before connecting. Just only once during application startup is enough.
If you get a SQLException: Connection refused or Connection timed out or a MySQL specific CommunicationsException: Communications link failure, then it means that the DB isn't reachable at all. This can have one or more of the following causes:
IP address or hostname in JDBC URL is wrong.
Hostname in JDBC URL is not recognized by local DNS server.
Port number is missing or wrong in JDBC URL.
DB server is down.
DB server doesn't accept TCP/IP connections.
DB server has run out of connections.
Something in between Java and DB is blocking connections, e.g. a firewall or proxy.
To solve the one or the other, follow the following advices:
Verify and test them with ping.
Refresh DNS or use IP address in JDBC URL instead.
Verify it based on my.cnf of MySQL DB.
Start the DB.
Verify if mysqld is started without the --skip-networking option.
Restart the DB and fix your code accordingly that it closes connections in finally.
Disable firewall and/or configure firewall/proxy to allow/forward the port.
Note that closing the Connection is extremely important. If you don't close connections and keep getting a lot of them in a short time, then the database may run out of connections and your application may break. Always acquire the Connection in a try-with-resources statement. Or if you're not on Java 7 yet, explicitly close it in finally of a try-finally block. Closing in finally is just to ensure that it get closed as well in case of an exception. This also applies to Statement, PreparedStatement and ResultSet.
That was it as far the connectivity concerns. You can find here a more advanced tutorial how to load and store fullworthy Java model objects in a database with help of a basic DAO class.
Using a Singleton Pattern for the DB connection is a bad approach. See among other questions: Is it safe to use a static java.sql.Connection instance in a multithreaded system?. This is a #1 starters mistake.
DriverManager is a fairly old way of doing things. The better way is to get a DataSource, either by looking one up that your app server container already configured for you:
Context context = new InitialContext();
DataSource dataSource = (DataSource) context.lookup("java:comp/env/jdbc/myDB");
or instantiating and configuring one from your database driver directly:
MysqlDataSource dataSource = new MysqlDataSource();
dataSource.setUser("scott");
dataSource.setPassword("tiger");
dataSource.setServerName("myDBHost.example.org");
and then obtain connections from it, same as above:
Connection conn = dataSource.getConnection();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT ID FROM USERS");
...
rs.close();
stmt.close();
conn.close();
Initialize database constants
Create constant properties database username, password, URL and drivers, polling limit etc.
// init database constants
// com.mysql.jdbc.Driver
private static final String DATABASE_DRIVER = "com.mysql.cj.jdbc.Driver";
private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
private static final String MAX_POOL = "250"; // set your own limit
Initialize Connection and Properties
Once the connection is established, it is better to store for reuse purpose.
// init connection object
private Connection connection;
// init properties object
private Properties properties;
Create Properties
The properties object hold the connection information, check if it is already set.
// create properties
private Properties getProperties() {
if (properties == null) {
properties = new Properties();
properties.setProperty("user", USERNAME);
properties.setProperty("password", PASSWORD);
properties.setProperty("MaxPooledStatements", MAX_POOL);
}
return properties;
}
Connect the Database
Now connect to database using the constants and properties initialized.
// connect database
public Connection connect() {
if (connection == null) {
try {
Class.forName(DATABASE_DRIVER);
connection = DriverManager.getConnection(DATABASE_URL, getProperties());
} catch (ClassNotFoundException | SQLException e) {
// Java 7+
e.printStackTrace();
}
}
return connection;
}
Disconnect the database
Once you are done with database operations, just close the connection.
// disconnect database
public void disconnect() {
if (connection != null) {
try {
connection.close();
connection = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
Everything together
Use this class MysqlConnect directly after changing database_name, username and password etc.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
public class MysqlConnect {
// init database constants
private static final String DATABASE_DRIVER = "com.mysql.cj.jdbc.Driver";
private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
private static final String MAX_POOL = "250";
// init connection object
private Connection connection;
// init properties object
private Properties properties;
// create properties
private Properties getProperties() {
if (properties == null) {
properties = new Properties();
properties.setProperty("user", USERNAME);
properties.setProperty("password", PASSWORD);
properties.setProperty("MaxPooledStatements", MAX_POOL);
}
return properties;
}
// connect database
public Connection connect() {
if (connection == null) {
try {
Class.forName(DATABASE_DRIVER);
connection = DriverManager.getConnection(DATABASE_URL, getProperties());
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace();
}
}
return connection;
}
// disconnect database
public void disconnect() {
if (connection != null) {
try {
connection.close();
connection = null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
How to Use?
Initialize the database class.
// !_ note _! this is just init
// it will not create a connection
MysqlConnect mysqlConnect = new MysqlConnect();
Somewhere else in your code ...
String sql = "SELECT * FROM `stackoverflow`";
try {
PreparedStatement statement = mysqlConnect.connect().prepareStatement(sql);
... go on ...
... go on ...
... DONE ....
} catch (SQLException e) {
e.printStackTrace();
} finally {
mysqlConnect.disconnect();
}
This is all :) If anything to improve edit it! Hope this is helpful.
String url = "jdbc:mysql://127.0.0.1:3306/yourdatabase";
String user = "username";
String password = "password";
// Load the Connector/J driver
Class.forName("com.mysql.jdbc.Driver").newInstance();
// Establish connection to MySQL
Connection conn = DriverManager.getConnection(url, user, password);
Here's the very minimum you need to get data out of a MySQL database:
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection conn = DriverManager.getConnection
("jdbc:mysql://localhost:3306/foo", "root", "password");
Statement stmt = conn.createStatement();
stmt.execute("SELECT * FROM `FOO.BAR`");
stmt.close();
conn.close();
Add exception handling, configuration etc. to taste.
you need to have mysql connector jar in your classpath.
in Java JDBC API makes everything with databases. using JDBC we can write Java applications to
1. Send queries or update SQL to DB(any relational Database)
2. Retrieve and process the results from DB
with below three steps we can able to retrieve data from any Database
Connection con = DriverManager.getConnection(
"jdbc:myDriver:DatabaseName",
dBuserName,
dBuserPassword);
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM Table");
while (rs.next()) {
int x = rs.getInt("a");
String s = rs.getString("b");
float f = rs.getFloat("c");
}
You can see all steps to connect MySQL database from Java application here. For other database, you just need to change the driver in first step only. Please make sure that you provide right path to database and correct username and password.
Visit http://apekshit.com/t/51/Steps-to-connect-Database-using-JAVA
MySQL JDBC Connection with useSSL.
private String db_server = BaseMethods.getSystemData("db_server");
private String db_user = BaseMethods.getSystemData("db_user");
private String db_password = BaseMethods.getSystemData("db_password");
private String connectToDb() throws Exception {
String jdbcDriver = "com.mysql.jdbc.Driver";
String dbUrl = "jdbc:mysql://" + db_server +
"?verifyServerCertificate=false" +
"&useSSL=true" +
"&requireSSL=true";
System.setProperty(jdbcDriver, "");
Class.forName(jdbcDriver).newInstance();
Connection conn = DriverManager.getConnection(dbUrl, db_user, db_password);
Statement statement = conn.createStatement();
String query = "SELECT EXTERNAL_ID FROM offer_letter where ID =" + "\"" + letterID + "\"";
ResultSet resultSet = statement.executeQuery(query);
resultSet.next();
return resultSet.getString(1);
}
Short and Sweet code.
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Driver Loaded");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/testDB","root","");
//Database Name - testDB, Username - "root", Password - ""
System.out.println("Connected...");
} catch(Exception e) {
e.printStackTrace();
}
For SQL server 2012
try {
String url = "jdbc:sqlserver://KHILAN:1433;databaseName=testDB;user=Khilan;password=Tuxedo123";
//KHILAN is Host and 1433 is port number
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
System.out.println("Driver Loaded");
conn = DriverManager.getConnection(url);
System.out.println("Connected...");
} catch(Exception e) {
e.printStackTrace();
}
Connection I was using some time ago, it was looking like the easiest way, but also there were recommendation to make there if statement- exactly
Connection con = DriverManager.getConnection(
"jdbc:myDriver:DatabaseName",
dBuserName,
dBuserPassword);
if (con != null){
//..handle your code there
}
Or something like in that way :)
Probably there's some case, while getConnection can return null :)
HOW
To set up the Driver to run a quick sample
1. Go to https://dev.mysql.com/downloads/connector/j/, get the latest version of Connector/J
2. Remember to set the classpath to include the path of the connector jar file.
If we don't set it correctly, below errors can occur:
No suitable driver found for jdbc:mysql://127.0.0.1:3306/msystem_development
java.lang.ClassNotFoundException: com.mysql.jdbc:Driver
To set up the CLASSPATH
Method 1: set the CLASSPATH variable.
export CLASSPATH=".:mysql-connector-java-VERSION.jar"
java MyClassFile
In the above command, I have set the CLASSPATH to the current folder and mysql-connector-java-VERSION.jar file. So when the java MyClassFile command executed, java application launcher will try to load all the Java class in CLASSPATH.
And it found the Drive class => BOOM errors was gone.
Method 2:
java -cp .:mysql-connector-java-VERSION.jar MyClassFile
Note: Class.forName("com.mysql.jdbc.Driver"); This is deprecated at this moment 2019 Apr.
Hope this can help someone!
MySql JDBC Connection:
Class.forName("com.mysql.jdbc.Driver");
Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/DatabaseName","Username","Password");
Statement stmt=con.createStatement();
stmt = con.createStatement();
ResultSet rs=stmt.executeQuery("Select * from Table");
Short Code
public class DB {
public static Connection c;
public static Connection getConnection() throws Exception {
if (c == null) {
Class.forName("com.mysql.jdbc.Driver");
c =DriverManager.getConnection("jdbc:mysql://localhost:3306/DATABASE", "USERNAME", "Password");
}
return c;
}
// Send data TO Database
public static void setData(String sql) throws Exception {
DB.getConnection().createStatement().executeUpdate(sql);
}
// Get Data From Database
public static ResultSet getData(String sql) throws Exception {
ResultSet rs = DB.getConnection().createStatement().executeQuery(sql);
return rs;
}
}
Download JDBC Driver
Download link (Select platform independent): https://dev.mysql.com/downloads/connector/j/
Move JDBC Driver to C Drive
Unzip the files and move to C:\ drive. Your driver path should be like C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19
Run Your Java
java -cp "C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19.jar" testMySQL.java
testMySQL.java
import java.sql.*;
import java.io.*;
public class testMySQL {
public static void main(String[] args) {
// TODO Auto-generated method stub
try
{
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con=DriverManager.getConnection(
"jdbc:mysql://localhost:3306/db?useSSL=false&useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC","root","");
Statement stmt=con.createStatement();
ResultSet rs=stmt.executeQuery("show databases;");
System.out.println("Connected");
}
catch(Exception e)
{
System.out.println(e);
}
}
}
I am using play java 2.5.
I have created a database with following java code.
public OnStartup() throws SQLException {
//demo create database with java code
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/?user=root&password=12345678");
Statement s = con.createStatement();
int Result = s.executeUpdate("CREATE DATABASE recruit3");
}
Module:
public class OnStartupModule extends AbstractModule {
#Override
public void configure() {
bind(OnStartup.class).asEagerSingleton();
}
}
application.conf:
play.modules {
enabled += "be.objectify.deadbolt.java.DeadboltModule"
enabled += modules.CustomDeadboltHook
enabled += modules.OnStartupModule
}
default.driver=com.mysql.jdbc.Driver
default.url="jdbc:mysql://localhost:3306/recruit3"
default.username=root
default.password="12345678"
My question is, why running the web-app creating
error Cannot connect to database [default]
How to fix that, if I don't want to create the database with mysql workbench.
Any suggestion or cannot do this, please tell me.
Thanks for advance.
As well as moving your database keys to the db.default namespace, you should be injecting Database into OnStartup to access the database configured with those properties.
First, add Play's JDBC support to build.sbt.
libraryDependencies += javaJdbc
If you're already running activator, make sure you use the reload command to pick up the changes to the build.
Update your application.conf to place the database configuration into the correct namespace.
db {
default {
driver=com.mysql.jdbc.Driver
url="jdbc:mysql://localhost:3306/recruit3"
username=root
password="12345678"
}
}
Finally, update OnStartup to receive a Database object that will be injected by Play.
import javax.inject.Inject;
import play.db.Database;
public class OnStartup {
#Inject
public OnStartup(final Database db) throws SQLException {
db.withConnection((Connection conn) -> {
final Statement s = con.createStatement();
return s.executeUpdate("CREATE DATABASE recruit3");
});
}
}
This allows you to configure the database one time, in application.conf, instead of hard-coding DB configuration into a class.
You can find more information here.
Your database keys start with default instead of db.default. The correct syntax is something like this:
db {
default {
driver=com.mysql.jdbc.Driver
url="jdbc:mysql://localhost:3306/recruit3"
username=root
password="12345678"
}
}
You already made your class as eager singleton, so it should work
I'm trying to use dapper with mysql in .net core 1.0. I'm using this mysql connector: https://github.com/bgrainger/MySqlConnector
I know the connector is in alpha but I was wondering if anyone had a similar issue when using it together with dapper.
This is my simple model:
public List<GeneralModel> GetAllLists()
{
try
{
using (DbConnection connection = new MySqlConnection("Server=localhost;Database=lists;Uid=Unnamed;Pwd=lol;"))
{
return connection.Query<GeneralModel>("SELECT * FROM lists.general").ToList();
}
}
catch (Exception)
{
throw;
}
}
And this is the controller:
public IActionResult Index()
{
GeneralModel GenRepo = new GeneralModel();
return View(GenRepo.GetAllLists());
}
When I go to the index page for the first time, it works. If I refresh, I get an "Access denied for user...". I have no idea what could be causing the error. I don't think the problem is in my code.
Edit:
I guess the problem is in the connector, since this also returns the error after a refresh:
List<GeneralModel> lists = new List<GeneralModel>();
using (DbConnection connection = new MySqlConnection("Server=localhost;Database=lists;Uid=Unnamed;Pwd=lol;"))
{
using (DbCommand myCommand = connection.CreateCommand())
{
myCommand.CommandText = "SELECT * FROM lists.general";
connection.Open();
using (DbDataReader myReader = myCommand.ExecuteReader())
{
while (myReader.Read())
{
GeneralModel tmpGen = new GeneralModel();
tmpGen.name = myReader["name"].ToString();
tmpGen.description = myReader["description"].ToString();
tmpGen.language = myReader["language "].ToString();
lists.Add(tmpGen);
}
}
connection.Close();
}
}
return lists;
This bug was caused by MySqlConnector not correctly handling the fast path for a COM_CHANGE_USER packet.
MySQL Server (versions 5.6 and 5.7) doesn't appear to immediately accept the user's credentials, but always returns an Authentication Method Switch Request Packet. MariaDB (which you are using) does implement the fast path and immediately returns an OK packet.
The connector has now been updated to handle this response and should stop throwing the spurious "Access Denied" exceptions. The fix is in 0.1.0-alpha09.
I use something like this for my application
MySqlConnection cnn = new MySqlConnection("Server=myServerAddress;" +
"Database=myDataBase;" +
"Uid=myUsername;" +
"Pwd=myPassword;");
And this changes everytime because we deploy databases with our application.
It works fine. I type in using(new connection(cnn)){ query... } and go.
And I've got it working with a dataset using a connection defined in the windows ODBC datasouce administrator.
But I'm curious, is there a way to use visual studio's dataset items using the my local test db and then change the connection of the dataset at runtime? Even better, can I use c# to programmatically add the ODBC data source at runtime?
Usually a connection string is loaded from the application exe.config file present in the same folder of the application. This connection string could be defined using the Settings tab in the project properties.
Right click on Properties of your project
Select the Settings tab (confirm the creation if you have no
settings)
Click on the ComboBox in the column type and select Connection String
Give a symbolic name to your connection
Type the connection string in the Value column (Examples at
connectionstrings.com)
Now in your project files you should have the file app.config (that becomes yourapp.exe.config) where there is a section like this
<configuration>
<connectionStrings>
<add name="MyAppConnection"
connectionString="Server=myServerAddress;Database=myDB;Uid=user;Pwd=pass;" />
</connectionStrings>
</configuration
At this point you read it in the program using
string conString = ConfigurationManager
.ConnectionStrings["MyAppConnection"]
.ConnectionString;
Instead in a dynamic situation where you want to build yourself the connection string during runtime (from user inputs, your own configuration files and so on) then you could leverage the functionality of the class MySqlConnectionStringBuilder
MySqlConnectionStringBuilder msb = new MySqlConnectionStringBuilder();
msb.Server = "localhost";
msb.Port = 3306;
msb.UserID = "root";
msb.Password = "xxx";
msb.Database = "test";
MySqlConnection cnn = new MySqlConnection(msb.ConnectionString);
cnn.Open();
Of course, these literal values could be substituted by your own variables.
The documentation of this class is surprising difficult to find. The best docs are the one of the Sql Server equivalent. It is interesting that you could read a static connection string from your config file and then change only the property needed.
string conString = ConfigurationManager
.ConnectionStrings["MyAppConnection"]
.ConnectionString;
MySqlConnectionStringBuilder msb = new MySqlConnectionStringBuilder(conString);
msb.Database = "AnotherDB";
MySqlConnection cnn = new MySqlConnection(msb.ConnectionString);
Application connection string cannot be changed at runtime.
User settings can be changed.
Assuming you are using an application setting-property named "MyConnectionString" which holds the connection string for the entire application.
On your main Program class create a global string:
internal static string Prconnstring;
Create and save this settings.cs file:
namespace MYSOLUTIONORPROJECTNAME.Properties
{
// (Not sure where I found this solution some time ago)
// This class allows you to handle specific events on the settings class:
// The SettingChanging event is raised before a setting's value is changed.
// The PropertyChanged event is raised after a setting's value is changed.
// The SettingsLoaded event is raised after the setting values are loaded.
// The SettingsSaving event is raised before the setting values are saved.
internal sealed partial class Settings
{
public Settings()
{
// // To add event handlers for saving and changing settings, uncomment the lines below:
//
// this.SettingChanging += this.SettingChangingEventHandler;
//
// this.SettingsSaving += this.SettingsSavingEventHandler;
//
}
private void SettingChangingEventHandler(object sender, System.Configuration.SettingChangingEventArgs e)
{
// Add code to handle the SettingChangingEvent event here.
}
private void SettingsSavingEventHandler(object sender, System.ComponentModel.CancelEventArgs e)
{
// Add code to handle the SettingsSaving event here.
}
public override object this[string propertyName]
{
get
{
if (propertyName == "MyConnectionString")
{
return Program.Prconnstring;
}
else
{
return base[propertyName];
}
}
set
{
base[propertyName] = value;
}
}
}
}
Before calling-opening any object that uses the connection string (examples include Forms that use datasets or other classes that use datasets created on the development enviroment) create your new connection string by any means you think. (Example: You might want to use as user name in the connection string the current user. Create the connection string using the info provided form the environment.)
Program.Prconnstring = thenewruntimeconnectionstring.
Now whenever the application tries to get MyConnectionString (which is hardcoded in the myapplicationname.config and cannot be changed) instead gets the new thenewruntimeconnectionstring you provided to Program.Prconnstring.
Be aware that the development connection string will be available-visible to final user, since it is just a text file. If you do not want this, you can change that file (will be a file named NAMEOFMYAPPLICATION.exe.config) during deployment, since the connection string hardcoded there, will be of no use for the running app. Do not delete it, just change.
Your connection string will be stored in your App.config (or c# equivalent). Say it's called MyConnectionString. Just add My.Settings("MyConnectionString")="[your new connection string]" to your entry point to change to database binding at runtime. E.g:
Public Sub New()
' This call is required by the designer.
InitializeComponent()
My.Settings("MyConnectionString") = "server=remotedb.uk;user id=MainUser;password=2jdi38edhnche73g;database=mainDb;persistsecurityinfo=True;allowuservariables=True;defaultcommandtimeout=480;characterset=utf8mb4"
End Sub
I am developing an AIR mobile application. I am using Sqlite as my local database. Now I have to maintain some datas in a centralised database which has located in remote server ie., i have to push some data to remote database from my mobile application as well as retreieve.
My questions are
Can I use sqlite as centralised database?
How can I connect to the database located in server.
Thanks in Advance.
I'll try to sum up the answer for this question. SQLite is not designed to be a service and therefore can not be used as a remote database, unless you only need to read from it.
If you only need it for reading data you can download it from the server, save as a file and then use it as a local database. This method is better explained here: Link
But if you want to use it for writing as well as reading you'll have a lot of problems with concurrency and data usage, so using a SQLite database is not an option here. Better explained here: Link
The correct way of doing this is having a backend (server script or server program), which listens to your requests and acts according to them.
For example if you want to authenticate user you can send something like this to the server:
username: "Gio"
password: "123"
action: "login"
In Actionscript 3 call would look like this:
import flash.net.URLVariables;
import flash.net.URLRequest;
import flash.net.URLLoader;
import flash.events.IOErrorEvent;
import flash.events.Event;
import flash.net.URLRequestMethod;
// create a URLLoader to POST data to the server
var loader:URLLoader = new URLLoader();
// server address where your script is listening
var request:URLRequest = new URLRequest("http://example.com");
// create and set the variables passed to the server script
var params:URLVariables = new URLVariables();
params.username = "Gio";
params.password = "123";
params.action = "login";
request.data = params;
// set the request type to POST as it's more secure and can hold more data
request.method = URLRequestMethod.POST;
loader.addEventListener(Event.COMPLETE, onPostComplete);
loader.addEventListener(IOErrorEvent.IO_ERROR, onPostFailed);
loader.load(request);
function onPostFailed(e:Event):void
{
// happens if the server is unreachable
trace("I/O Error when sending a POST request");
}
function onPostComplete(e:Event):void
{
// loader.data will hold the response received from the server
trace(e.target.data);
}
On the server side I'd recommend using PHP as it's easier to learn, simple and works great with MySQL.
In PHP you'd have something like this to handle the request:
<?php
$host="localhost"; // Host name
$username=""; // Mysql username
$password=""; // Mysql password
$db_name="test"; // Database name
$tbl_name="members"; // Table name
// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
// username and password sent from form
if($_POST['action'] == "login")
{
$receivedUsername=$_POST['username'];
$receivedPassword=$_POST['password'];
$sql="SELECT * FROM $tbl_name WHERE username='$receivedUsername' and password='$receivedPassword'";
$result=mysql_query($sql);
// Mysql_num_row is counting table row
$count=mysql_num_rows($result);
// If result matched $receivedUsername and $receivedPassword, table row must be 1 row
if($count==1){
echo "Authentication success";
}
else {
echo "Wrong Username or Password";
}
}
?>
This will seem a little complicated at first, but it's not of a big deal actually. You'll have to read more on PHP and how to setup it as I can't fit all the details in this post.
I using AMFPHP in serverside.
In Flash You call service on server:
_net_connection = new NetConnection();
_net_connection.addEventListener(NetStatusEvent.NET_STATUS, connectionStatusHandler);
_net_connection.connect(_server_url);
_responder = new Responder(loginResult, null);
_net_connection.call("userSerivce2/login", _responder, _user_login, _user_passwword);
private function loginResult(result_object:Object):void {
save_log('loginResult (' + result_object.status + ")");
//rest of code
}
responder - is function in AS3 you will execute after call
userSerivce2/login - class userSerivce2, method login
you add responder (_responder) and additional arguments like _user_login, _user_passwword, in this case.
server PHP:
public function login($user_name, $user_password) {
//SELECT blablabla
try {
if ($logged) {
$this->call_result['status'] = 0;
throw new mysqli_sql_exception("Pomyślnie zalogowano.");
} else {
$this->call_result['status'] = 3;
throw new mysqli_sql_exception("Błąd logowania. Wprowadź poprawny login, oraz hasło.");
}
} catch(Exception $e) {
$this->call_result['error_message'] = $e->getMessage();
return $this->call_result;
}
return $this->call_result; //method will return object
}