java.lang.nullpointerexception

[AxOpO]

Boa tarde, estou a elaborar um login e surgiu-me este erro "java.lang.nullpointerexception", como o posso resolver?

O código é:

Classe login:

public class Login extends javax.swing.JFrame {

Connection conn = null;
ResultSet rset = null;
PreparedStatement pstmt = null;
private DaoHelper daoHelper;
/**
 * Creates new form Logi
 */
public Logi() throws SQLException {
	initComponents();
	DaoHelper daoHelper = new DaoHelper();

}


private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {										
	// TODO add your handling code here:
	String sql = "Select * from log where nome = ? and senha = ?";
	try{
	   conn = daoHelper.getConnectionFromContext();
	   pstmt = conn.prepareStatement(sql);
	   pstmt.setString(1, txtNome.getText());
	   pstmt.setString(2, txtPass.getText());

	   rset = pstmt.getGeneratedKeys();

	   if(rset.next()){
		   JOptionPane.showMessageDialog(null, "Entrou");
		   Main m = new Main();
		   m.setVisible(true);
	   }

	   else{
		   JOptionPane.showMessageDialog(null, "Dados ");
	   }

	}catch(Exception e){
		 JOptionPane.showMessageDialog(null, e);
	}

}										

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
	/* Set the Nimbus look and feel */
	//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
	/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
	 * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
	 */
	try {
		for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
			if ("Nimbus".equals(info.getName())) {
				javax.swing.UIManager.setLookAndFeel(info.getClassName());
				break;
			}
		}
	} catch (ClassNotFoundException ex) {
		java.util.logging.Logger.getLogger(Logi.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
	} catch (InstantiationException ex) {
		java.util.logging.Logger.getLogger(Logi.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
	} catch (IllegalAccessException ex) {
		java.util.logging.Logger.getLogger(Logi.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
	} catch (javax.swing.UnsupportedLookAndFeelException ex) {
		java.util.logging.Logger.getLogger(Logi.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
	}
	//</editor-fold>

	/* Create and display the form */
	java.awt.EventQueue.invokeLater(new Runnable() {
		public void run() {
			try {
				new Logi().setVisible(true);
			} catch (SQLException ex) {
				Logger.getLogger(Logi.class.getName()).log(Level.SEVERE, null, ex);
			}
		}
	});
}

Classe de conexão a base de dados:

public class DaoHelper {

private static final ThreadLocal<Connection> context = new ThreadLocal<Connection>();


/**
* Fornece conex�o a BD
* @return
* @throws SQLException
*/

public Connection getConnection() throws SQLException{

Connection conn = null;

try {
Class.forName("com.mysql.jdbc.Driver");

conn = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/ipss", "root", "");

} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

return conn;

}

public void beginTransaction() throws SQLException{

Connection conn = getConnection();
conn.setAutoCommit(false);
context.set(conn);
}

public void endTransaction() throws SQLException {
commit ( getConnectionFromContext() );
releaseTransaction();
}

public void releaseTransaction () throws SQLException {
Connection conn = getConnectionFromContext();
release(conn);
context.remove();
}

public void rollbackTransaction () {
Connection conn;
try {
conn = getConnectionFromContext();
rollback(conn);
release(conn);
} catch (SQLException e) {
e.printStackTrace();
}

context.remove();
}

public void commit (Connection conn) throws SQLException {
conn.commit();
}

public void rollback (Connection conn) throws SQLException{
if (conn != null) conn.rollback();
}


public Connection getConnectionFromContext() throws SQLException{
Connection conn = context.get();
if (conn == null) throw new SQLException("Transac��o invalida");
if (conn.isClosed()) throw new SQLException("Transac��o invalida, Conex�o fechada :S");

return conn;
}

public <T> void executeQuery (String query
 , QueryMapping<T> queryMapping) throws SQLException {

executeQuery(getConnection(), query, queryMapping);

}

public <T> void executeQuery (Connection conn, String query
  , QueryMapping<T> queryMapping) throws SQLException {
Statement stmt = null;
ResultSet rset = null;
try{
stmt = conn.createStatement();
rset = stmt.executeQuery(query);
queryMapping.mapping(rset);

} finally{
release(rset);
release(stmt);
}
}

public <T> void executePreparedQuery (String query
, QueryMapping<T> queryMapping
, Object... params) throws SQLException {

executePreparedQuery(getConnection(), query, queryMapping, params);
}

public <T> void executePreparedQuery (Connection conn
, String query
, QueryMapping<T> queryMapping
, Object... params) throws SQLException {

PreparedStatement pstmt = conn.prepareStatement (query);
ResultSet rset = null;

try{
pstmt = conn.prepareStatement (query);
populatePreparedStatement(pstmt, params);
rset = pstmt.executeQuery();
queryMapping.mapping(rset);

} finally{
release(rset);
release(pstmt);
}

}

public long executePreparedUpdateAndReturnGeneratedKeys (Connection conn, String query, Object... params) throws SQLException {

PreparedStatement pstmt = null;
ResultSet rset = null;
long result = 01;
try{
pstmt = conn.prepareStatement(query, PreparedStatement.RETURN_GENERATED_KEYS);

populatePreparedStatement(pstmt, params);

pstmt.executeUpdate();
rset = pstmt.getGeneratedKeys();

if(rset.next()) result = rset.getLong(1);
} finally{
release (pstmt);
release (rset);
}
return result;
}

public void populatePreparedStatement(PreparedStatement pstmt,
Object... params) throws SQLException {
int i = 0;
for (Object param : params){
pstmt.setObject( ++i,  param);
}
}

public long executePreparedUpdateAndReturnGeneratedKeys ( String query
, Object... params) throws SQLException {

return executePreparedUpdateAndReturnGeneratedKeys (getConnectionFromContext()
, query
, params);
}

public void executePreparedUpdate (String query, Object... params) throws SQLException {
executePreparedUpdate(getConnectionFromContext(), query, params);
}


public void executePreparedUpdate (Connection conn, String query, Object... params) throws SQLException {

PreparedStatement pstmt = null;
try{
pstmt = conn.prepareStatement(query);
populatePreparedStatement(pstmt, params);
pstmt.executeUpdate();
} finally{
release (pstmt);

}
}



public void release (Statement stmt){
if(stmt != null) return;
try {
stmt.close();
} catch (SQLException e) { }
}

public void release (Connection conn){
if(conn != null) return;
try {
conn.close();
} catch (SQLException e) { }
}

public void release (ResultSet rset){
if(rset != null) return;
try {
rset.close();
} catch (SQLException e) { }
}

public void releaseAll (Connection conn, Statement stmt){
release(stmt);
release(conn);
}

public void releaseAll (Connection conn, Statement stmt, ResultSet rset){
release(rset);
releaseAll(conn,stmt);
}


}

[lusitan]

Duvido que alguém te ajude.

Em que linha é o erro?

E que tal investigares se tudo está bem na linha anterior ao erro?

Demora menos tempo a fazer o debug que escrever o post...

Fica a dica!

[AxOpO]

Obrigado pela dica 😉 MAs já fiz isso!!!

[I-NOZex]

Duvido que alguém te ajude.

Em que linha é o erro?