i'm trying to create a desktop application using corba and java swing for graphical interface.
As you know , in CORBA we have to make the principal methods like: connecting to the database ,calculations... in the server ,so i have created a method in a server class for connecting to the database.
The java class method is the one shown bellow:
public void connect_db(){
// TODO Auto-generated method stub
JTextField txtUsername = FrameLogin.txtUsername;
JPasswordField pwd= FrameLogin.pwd;
JLabel lblLoginMessage= FrameLogin.lblLoginMessage;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection conn =(Connection)DriverManager.getConnection("jdbc:mysql://localhost:3306/utilisateurs","root", "Mrayhana123");
Statement stm = conn.createStatement();
String sql="select * from etudiant where username='"+txtUsername+"' and pwd='"+pwd+"'";
ResultSet result = stm.executeQuery(sql);
if(result.next()){
lblLoginMessage.setText("you are connected");
lblLoginMessage.setForeground(Color.GREEN);
}
else {
lblLoginMessage.setText("Incorrect username or password!");
lblLoginMessage.setForeground(Color.RED);
}
} catch(Exception e){
//System.out.println("not connected to database");
e.printStackTrace();
}
}
And i have called it in the client class which contain the graphical interface by the following way:
public static JTextField txtUsername;
public static JPasswordField pwd;
public static JLabel lblLoginMessage = new JLabel("");
pnlBtnlogin.addMouseListener(new MouseAdapter() {
#Override
String username = txtUsername.getText();
String pwd= pwd.getText();
try {
SraCorbaImpl sci = new SraCorbaImpl();
sci.connect_db();
} catch(Exception e1){
//System.out.println("not connected to database");
e1.printStackTrace();
}
But the result always shows me Incorrect username or password! even though I type a username and a password which are in the database.
THANK YOU FOR HELPING ME
According to your comment, I understand that you are successfully connecting to the database but your query is not returning any rows.
If the code in your question is your actual code, then you are passing a JTextField to your [SQL] query and not the text of the JTextField. Likewise with the password. You are passing the JPasswordField and not the actual password.
Try the below code.
public void connect_db(){
JTextField txtUsername = FrameLogin.txtUsername;
JPasswordField pwd= FrameLogin.pwd;
JLabel lblLoginMessage= FrameLogin.lblLoginMessage;
try {
// Class.forName("com.mysql.cj.jdbc.Driver"); <- not required
Connection conn =(Connection)DriverManager.getConnection("jdbc:mysql://localhost:3306/utilisateurs","root", "Mrayhana123");
Statement stm = conn.createStatement();
String sql="select * from etudiant where username='"+txtUsername.getText()+"' and pwd='"+pwd.getText()+"'"; // Change here.
ResultSet result = stm.executeQuery(sql);
if(result.next()){
lblLoginMessage.setText("you are connected");
lblLoginMessage.setForeground(Color.GREEN);
}
else {
lblLoginMessage.setText("Incorrect username or password!");
lblLoginMessage.setForeground(Color.RED);
}
} catch(Exception e){
//System.out.println("not connected to database");
e.printStackTrace();
}
Because you are using string concatenation, the toString of JTextField is being inserted into your SQL string.
Consider using a PreparedStatement instead.
String sql="select * from etudiant where username=? and pwd=?";
PreparedStatement ps = conn.prepareStatement(sql);
ps.setString(1, txtUsername.getText());
ps.setString(2, pwd.getText());
In that case, if you omit the .getText(), the code will not compile.
Related
I want to use a MySQL with JDBC in a loop, because I have to poll a table frequently for new data which comes in from other clients. But even if I close the ResultSet, the connection and the statement, is the old result at the next round still there. I cannot get a new result, unless I restart the program. What is my mistake?
I condensed the code for the necessary.
import java.sql.*;
public class Eventmgr {private static String in_text;
private static String in_typ;
private static Connection connection;
private static String URL = "jdbc:mysql://xxx.xxx.x.x:3306/xxxx";
private static String username = "xxx";
private static String password = "xxx";
public static void start() throws SQLException {
while(loop_count > 0) {
if (loop == false) {
loop_count = loop_count -1;}
connection = DriverManager.getConnection(URL, username, password);
Statement stmt = connection.createStatement();
ResultSet rs = stmt.executeQuery("select id, nummer, text, typ from inbox order by id asc limit 1") ;
while(rs.next()) {
in_id = rs.getString("id");
in_nummer = rs.getString("nummer");
in_text = rs.getString("text");
in_typ = rs.getString("typ");}
connection.close();
stmt.close();
rs.close();
System.out.println("still running");
}
}
}
Anybody has an idea what my problem is?
Thanks in advance
I am stupid, and it was my mistake...
The problem is. I check on the variable "in_id" and if there is no new result "while(rs.next())" dont deliver a new value, so I need to reset that variable with "in_id = null;" at the end of the loop.
Now it works...
#Override
public void start(Stage primaryStage) throws Exception{
try{
String fxmlName;
Connection con = DriverManager.getConnection("url","root","password");
Statement st = con.createStatement();
String qry = "select UpdateT from schema.update";
ResultSet rs = st.executeQuery(qry);
fxmlName = rs.getString("UpdateT");
// System.out.println(fxmlName);
st.close();
Parent root = FXMLLoader.load(getClass().getResource(fxmlName));
primaryStage.setScene(new Scene(root));
primaryStage.initStyle(StageStyle.UNDECORATED);
primaryStage.show();
}
catch (Exception e){
System.out.println(e);
}
}
Hey guys this is my code and its my first time on stack overflow and why I am getting this exception?
java.sql.SQLException: Before start of result set
UPDATE is a reserved word, so your DB objects should not use it. You can:
change the table name (i 'd prefer this)
use quotes every time to refer to that table
From groovy script in SoapUI I need to connect to a mysql database to perform some queries. The problem is that due to security reasons no external access is possible.
Therefore it is required to get an ssh access (like a tunnel) and invoke mysql locally.
Initially I was reading the below project properties and then connect to mysql:
ServerUrl=jdbc:mysql://10.255.255.122:3306/db
ServerDbUser=user
ServerDbPwd=password
ServerDriver=com.mysql.jdbc.Driver
def url=testRunner.testCase.testSuite.project.getPropertyValue("ServerUrl")
def usr=testRunner.testCase.testSuite.project.getPropertyValue("ServerDbUser")
def pwd=testRunner.testCase.testSuite.project.getPropertyValue("ServerDbPwd")
def driver=testRunner.testCase.testSuite.project.getPropertyValue("ServerDriver")
com.eviware.soapui.support.GroovyUtils.registerJdbcDriver(driver)
sqlServer = Sql.newInstance(url, usr, pwd, driver)`
But this didn't work so now it is required to establish first a ssh connection to the server with the IP 10.255.255.122 and then open the mysql connection locally. So I guess the Server Url will change to:
ServerUrl=jdbc:mysql://127.0.0.1:3306/db
But I don't know how to set first the ssh connection to the server.
Can someone help me with this?
Thanks.
Have a look at http://forum.soapui.org/viewtopic.php?t=15400 and connect to remote mysql database through ssh using java
It will give you an idea about implementing it in soapUI.
Below is the code by Ripon Al Wasim which is available as an answer at the stackoverflow link mentioned above
package mypackage;
import java.sql.*;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
public class UpdateMySqlDatabase {
static int lport;
static String rhost;
static int rport;
public static void go(){
String user = "ripon";
String password = "wasim";
String host = "myhost.ripon.wasim";
int port=22;
try
{
JSch jsch = new JSch();
Session session = jsch.getSession(user, host, port);
lport = 4321;
rhost = "localhost";
rport = 3306;
session.setPassword(password);
session.setConfig("StrictHostKeyChecking", "no");
System.out.println("Establishing Connection...");
session.connect();
int assinged_port=session.setPortForwardingL(lport, rhost, rport);
System.out.println("localhost:"+assinged_port+" -> "+rhost+":"+rport);
}
catch(Exception e){System.err.print(e);}
}
public static void main(String[] args) {
try{
go();
} catch(Exception ex){
ex.printStackTrace();
}
System.out.println("An example for updating a Row from Mysql Database!");
Connection con = null;
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://" + rhost +":" + lport + "/";
String db = "testDB";
String dbUser = "wasim";
String dbPasswd = "riponalwasim123";
try{
Class.forName(driver);
con = DriverManager.getConnection(url+db, dbUser, dbPasswd);
try{
Statement st = con.createStatement();
String sql = "UPDATE MyTableName " +
"SET email = 'ripon.wasim#smile.com' WHERE email='peace#happy.com'";
int update = st.executeUpdate(sql);
if(update >= 1){
System.out.println("Row is updated.");
}
else{
System.out.println("Row is not updated.");
}
}
catch (SQLException s){
System.out.println("SQL statement is not executed!");
}
}
catch (Exception e){
e.printStackTrace();
}
}
}
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.
I am trying to determine if I am actually using JDBC connection pooling. After doing some research, the implementation almost seems too easy. Easier than a regular connection in fact so i'd like to verify.
Here is my connection class:
public class DatabaseConnection {
Connection conn = null;
public Connection getConnection() {
BasicDataSource bds = new BasicDataSource();
bds.setDriverClassName("com.mysql.jdbc.Driver");
bds.setUrl("jdbc:mysql://localhost:3306/data");
bds.setUsername("USERNAME");
bds.setPassword("PASSWORD");
try{
System.out.println("Attempting Database Connection");
conn = bds.getConnection();
System.out.println("Connected Successfully");
}catch(SQLException e){
System.out.println("Caught SQL Exception: " + e);
}
return conn;
}
public void closeConnection() throws SQLException {
conn.close();
}
}
Is this true connection pooling? I am using the connection in another class as so:
//Check data against database.
DatabaseConnection dbConn = new DatabaseConnection();
Connection conn;
ResultSet rs;
PreparedStatement prepStmt;
//Query database and check username/pass against table.
try{
conn = dbConn.getConnection();
String sql = "SELECT * FROM users WHERE username=? AND password=?";
prepStmt = conn.prepareStatement(sql);
prepStmt.setString(1, user.getUsername());
prepStmt.setString(2, user.getPassword());
rs = prepStmt.executeQuery();
if(rs.next()){ //Found Match.
do{
out.println("UserName = " + rs.getObject("username") + " Password = " + rs.getObject("password"));
out.println("<br>");
} while(rs.next());
} else {
out.println("Sorry, you are not in my database."); //No Match.
}
dbConn.closeConnection(); //Close db connection.
}catch(SQLException e){
System.out.println("Caught SQL Exception: " + e);
}
Assuming that it's the BasicDataSource is from DBCP, then yes, you are using a connection pool. However, you're recreating another connection pool on every connection acquirement. You are not really pooling connections from the same pool. You need to create the connection pool only once on application's startup and get every connection from it. You should also not hold the connection as an instance variable. You should also close the connection, statement and resultset to ensure that the resources are properly closed, also in case of exceptions. Java 7's try-with-resources statement is helpful in this, it will auto-close the resources when the try block is finished.
Here's a minor rewrite:
public final class Database {
private static final BasicDataSource dataSource = new BasicDataSource();
static {
dataSource.setDriverClassName("com.mysql.jdbc.Driver");
dataSource.setUrl("jdbc:mysql://localhost:3306/data");
dataSource.setUsername("USERNAME");
dataSource.setPassword("PASSWORD");
}
private Database() {
//
}
public static Connection getConnection() throws SQLException {
return dataSource.getConnection();
}
}
(this can if necessary be refactored as an abstract factory to improve pluggability)
and
private static final String SQL_EXIST = "SELECT * FROM users WHERE username=? AND password=?";
public boolean exist(User user) throws SQLException {
boolean exist = false;
try (
Connection connection = Database.getConnection();
PreparedStatement statement = connection.prepareStatement(SQL_EXIST);
) {
statement.setString(1, user.getUsername());
statement.setString(2, user.getPassword());
try (ResultSet resultSet = preparedStatement.executeQuery()) {
exist = resultSet.next();
}
}
return exist;
}
which is to be used as follows:
try {
if (!userDAO.exist(username, password)) {
request.setAttribute("message", "Unknown login. Try again.");
request.getRequestDispatcher("/WEB-INF/login.jsp").forward(request, response);
} else {
request.getSession().setAttribute("user", username);
response.sendRedirect("userhome");
}
} catch (SQLException e) {
throw new ServletException("DB error", e);
}
In a real Java EE environement you should however delegate the creation of the DataSource to the container / application server and obtain it from JNDI. In case of Tomcat, see also for example this document: http://tomcat.apache.org/tomcat-6.0-doc/jndi-resources-howto.html
Doesn't seem like it's pooled. You should store the DataSource in DatabaseConnection instead of creating a new one with each getConnection() call. getConnection() should return datasource.getConnection().
Looks like a DBCP usage. If so, then yes. It's already pooled. And here is the default pool property value of the DBCP.
/**
* The default cap on the number of "sleeping" instances in the pool.
* #see #getMaxIdle
* #see #setMaxIdle
*/
public static final int DEFAULT_MAX_IDLE = 8;
/**
* The default minimum number of "sleeping" instances in the pool
* before before the evictor thread (if active) spawns new objects.
* #see #getMinIdle
* #see #setMinIdle
*/
public static final int DEFAULT_MIN_IDLE = 0;
/**
* The default cap on the total number of active instances from the pool.
* #see #getMaxActive
*/
public static final int DEFAULT_MAX_ACTIVE = 8;
As a follow up to BalusC's solution, below is an implementation that I can be used within an application that requires more than one connection, or in a common library that would not know the connection properties in advance...
import org.apache.commons.dbcp.BasicDataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.concurrent.ConcurrentHashMap;
public final class Database {
private static final ConcurrentHashMap<String, BasicDataSource> dataSources = new ConcurrentHashMap();
private Database() {
//
}
public static Connection getConnection(String connectionString, String username, String password) throws SQLException {
BasicDataSource dataSource;
if (dataSources.containsKey(connectionString)) {
dataSource = dataSources.get(connectionString);
} else {
dataSource = new BasicDataSource();
dataSource.setDriverClassName("com.mysql.jdbc.Driver");
dataSource.setUrl(connectionString);
dataSource.setUsername(username);
dataSource.setPassword(password);
dataSources.put(connectionString, dataSource);
}
return dataSource.getConnection();
}
}