I really need your help guys .... I am trying to make a java program connects to mysql database, and I used to connect with localhost by xampp and its working fine with this code ...
public class myConnection {
public static Connection getconnection(){
Connection con = null;
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://localhost/test?serverTimezone=Turkey","root","");
} catch (Exception e) {
System.out.println(e.getMessage());
}
return con;
}
}
but now I just bought an online server and made a new datebase Inside it but I have no Idea how to connect my program with it I tried a lot and I searched for many hours but I couldnt find anything about that... this is my database
and this is the code I am trying to use but I always get Communications link failure ..
public static Connection getconnection(){
Connection con = null;
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://mysql.bravehost.com/afkodb_3483514","username","password");
} catch (Exception e) {
System.out.println(e.getMessage());
}
return con;
}
Related
import java.sql.*;
public class Driver {
public static void main(String[] args) {
try {
Connection myConn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb?autoReconnect=true&useSSL=false",
"root", "password");
Statement myStamement = myConn.createStatement();
ResultSet myRs = myStamement.executeQuery("SELECT * FROM table1");
while(myRs.next()) {
System.out.println("I GOT SOMETHING FROM DATABASE");
System.out.println(myRs.getString("id"));
}
}
catch (Exception exc) {
exc.printStackTrace();
}
}
}
and I have setup my SQL server and can see the same query in mySQL workbench here:
enter image description here
It doesn't give me an error connecting to the database else it would go to catch.
It returns an empty ResultSet else it would go into while loop once.
There is data in my database that I can see from using same command in photo photo.
I have main page index.jsp. from jsp page requset has been sent to database.But database connection is not happening.Its not giving any error and its giving blank page.Even I have added mysql connector.jar to library file.am using tomcatserver. Can anybody please help me what is the problem.Here is the complete code
disply.java
public class MyDb {
Connection con;
public Connection getcon() {
try {
Class.forName("com.mysql.jdbc.Driver");
DriverManager.getConnection("jdbc:mysql://localhost:3306/studentinfo", "root", "adminuser");
} catch (ClassNotFoundException ex) {
Logger.getLogger(MyDb.class.getName()).log(Level.SEVERE, null, ex);
} catch (SQLException ex) {
Logger.getLogger(MyDb.class.getName()).log(Level.SEVERE, null, ex);
}
return con;
}
}
You have to assign the Connection Object to the connection returned from the DriverManager
Connection con = null;
....
con = DriverManager.getConnection("jdbc:mysql......
So I have setup my code like so
public static Connection getConnection() {
try {
String dbURL = "jdbc:sqlserver://localhost:1433;databaseName=HRDB;
String user = "sa";
String pass = "r";
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection conn = DriverManager.getConnection(dbURL, user, pass);
return conn;
} catch (ClassNotFoundException c) {
return null;
} catch (SQLException s) {
System.out.println(s.toString());
return null;
}
}
However, when I try to connect to the database I get the following exceptions.
com.microsoft.sqlserver.jdbc.SQLServerException: The driver could not establish a secure connection to SQL Server by using Secure Sockets Layer (SSL) encryption. Error: "java.lang.RuntimeException: Could not generate DH keypair".
I'm developping a RESTful API with Jersey and MySQL.
I'm actually using the JDBC driver to connect to the database and I create a new connection everytime I want to acess it. As it clearly is a memory leakage, I started to implement the ServletContextClassclass but I don't know how to call the method when I need to get the result of a SQL query.
Here is how I did it wrong:
DbConnection.java
public class DbConnection {
public Connection getConnection() throws Exception {
try {
String connectionURL = "jdbc:mysql://root:port/path";
Connection connection = null;
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(connectionURL, "root", "password");
return connection;
}
catch (SQLException e) {
throw e;
}
}
}
DbData.java
public ArrayList<Product> getAllProducts(Connection connection) throws Exception {
ArrayList<Product> productList = new ArrayList<Product>();
try {
PreparedStatement ps = connection.prepareStatement("SELECT id, name FROM product");
ResultSet rs = ps.executeQuery();
while (rs.next()) {
Product product = new Product();
product.setId(rs.getInt("id"));
product.setName(rs.getString("name"));
productList.add(product);
}
return productList;
} catch (Exception e) {
throw e;
}
}
Resource.java
#GET
#Path("task/{taskId}")
#Consumes(MediaType.APPLICATION_JSON)
public Response getInfos(#PathParam("taskId") int taskId) throws Exception {
try {
DbConnection database= new DbConnection();
Connection connection = database.getConnection();
Task task = new Task();
DbData dbData = new DbData();
task = dbData.getTask(connection, taskId);
return Response.status(200).entity(task).build();
} catch (Exception e) {
throw e;
}
}
Here is where I ended up trying to implement the new class:
ServletContextClass.java
public class ServletContextClass implements ServletContextListener {
public Connection getConnection() throws Exception {
try {
String connectionURL = "jdbc:mysql://root:port/path";
Connection connection = null;
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(connectionURL, "root", "password");
return connection;
} catch (SQLException e) {
throw e;
}
}
public void contextInitialized(ServletContextEvent arg0) {
System.out.println("ServletContextListener started");
DbConnection database = new DbConnection();
try {
Connection connection = database.getConnection();
} catch (Exception e) {
e.printStackTrace();
}
}
public void contextDestroyed(ServletContextEvent arg0) {
System.out.println("ServletContextListener destroyed");
//con.close ();
}
}
But problem is, I don't know what to do next. Any help? Thanks
You need to set the Connection variable as an attribute of the ServletContext. Also, I would recommend using connection as a static class variable so you can close it in the contextDestroyed method.
You can retrieve the connection attribute in any of your servlets later on for doing your DB operations.
public class ServletContextClass implements ServletContextListener {
public static Connection connection;
public Connection getConnection(){
try {
String connectionURL = "jdbc:mysql://root:port/path";
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(connectionURL, "root", "password");
} catch (SQLException e) {
// Do something
}
}
public void contextInitialized(ServletContextEvent arg0) {
System.out.println("ServletContextListener started");
getConnection();
arg0.getServletContext().setAttribute("connection", connection);
}
public void contextDestroyed(ServletContextEvent arg0) {
System.out.println("ServletContextListener destroyed");
try{
if(connection != null){
connection.close();
}
}catch(SQLException se){
// Do something
}
}
}
Finally access your connection attribute inside your Servlet (Resource). Make sure you pass #Context ServletContext to your Response method so you can access your context attributes.
#GET
#Path("task/{taskId}")
#Consumes(MediaType.APPLICATION_JSON)
public Response getInfos(#PathParam("taskId") int taskId, #Context ServletContext context) throws Exception {
try {
Connection connection = (Connection) context.getAttribute("connection");
Task task = new Task();
DbData dbData = new DbData();
task = dbData.getTask(connection, taskId);
return Response.status(200).entity(task).build();
} catch (Exception e) {
throw e;
}
}
Now that we have solved your current issue, we need to know what can go wrong with this approach.
Firstly, you are only creating one connection object which will be used everywhere. Imagine multiple users simultaneously accessing your API, the single connection will be shared among all of them which will slow down your response time.
Secondly, your connection to DB will die after sitting idle for a while (unless you configure MySql server not to kill idle connections which is not a good idea), and when you try to access it, you will get SQLExceptions thrown all over. This can be solved inside your servlet, you can check if your connection is dead, create it again, and then update the context attribute.
The best way to go about your Mysql Connection Pool will be to use a JNDI resource. You can create a pool of connections which will be managed by your servlet container. You can configure the pool to recreate connections if they go dead after sitting idle. If you are using Tomcat as your Servlet Container, you can check this short tutorial to get started with understanding the JNDI connection pool.
hi i am doing an jsp project. and i deploy my project on apache tomcat. i use mysql as databese.
when i deploy project on remote server it is run good. but after some hours it gives me sql error. then i go back my apache server and start projecet again it run and after some hours it gives me same sql error again. i dont know the problem. is that caused from my java connection code or it is about mysql server. can some one tell me why it gives me sql error.?
public class ConnectionManager {
private String className = "com.mysql.jdbc.Driver";
private String userName ="username";
private String password = "password";
private String url = "jdbc:mysql://localhost:3306/database?useUnicode=true&characterEncoding=utf-8";
/**
* #uml.property name="connectionInstance"
* #uml.associationEnd
*/
private static ConnectionManager connectionInstance = null;
public ConnectionManager(){
}
public static synchronized ConnectionManager getInstance() {
if(connectionInstance == null) {
connectionInstance = new ConnectionManager();
}
return connectionInstance;
}
public Connection getConnection(){
Connection conn = null;
try {
Class.forName(className);
conn = DriverManager.getConnection (url, userName, password);
System.out.println("Connection Established");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
MySQL has a default connection timeout of 8 hours. So this means that you've kept a SQL connection open for too long. Your code suggests that you're creating only one connection on application's startup and reusing it application wide. This is very bad. This is not threadsafe.
You need to change your code so that you're not declaring and storing the SQL Connection as a static or instance variable anywhere in your code. Instead, it should be declared, created and closed within the shortest possible scope. Preferably within the very same method block as where you're executing the SQL query.
Here's a minor rewrite of your ConnectionManager which does the job properly:
public class ConnectionManager {
private static final String DRIVER = "com.mysql.jdbc.Driver";
private static final String USERNAME ="username";
private static final String PASSWORD = "password";
private static final String URL = "jdbc:mysql://localhost:3306/database?useUnicode=true&characterEncoding=utf-8";
static {
try {
Class.forName(DRIVER);
}
catch (ClassNotFoundException e) {
throw new ExceptionInInitializerError(DRIVER + " missing in classpath!", e);
}
}
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(URL, USERNAME, PASSWORD);
}
}
Use it as follows:
public class SomeDAO {
public SomeEntity find(Long id) throws SQLException {
Connection connection = null;
// ...
try {
connection = ConnectionManager.getConnection();
// ...
}
finally {
// ...
if (connection != null) try { connection.close(); } catch(SQLException ignore) {}
}
return someEntity;
}
To improve connecting performance, use a connection pool instead of DriverManager.
See also:
Show JDBC ResultSet in HTML in JSP page using MVC and DAO pattern
Are you closing connections properly after using them.