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JDBC connection in Java with Eclipse ( when a method calling a method)

I'm trying to connect to my DB using JDBC. I wanted to make a method for connection and another method for selecting data. I am getting a red line in Eclipse on the 'Connection con = connectDB();' part. ( See also attached) Cany anyone give me advice?
public class DBJdbc {
//Statement stmt = null;
// connecting to DB
public void connectDB() {
//Connection con = null;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://****/SAC?useSSL=false&serverTimezone=UTC", "***", "***");
}
catch(SQLException e) {
e.printStackTrace();
}
catch(ClassNotFoundException e) {
e.printStackTrace();
}
}
// a method for selecting DB
public static void select() {
//connectDB();
String sql = "SELECT * from SAC_SUR";
try(Connection con = connectDB(); // I'm getting a red line here)
PreparedStatement pstmt = con.prepareStatement(sql)){
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery(sql);
while(rs.next()) {
int id = rs.getInt(1);
String name = rs.getString(2);
System.out.println("Id = " + id + "name = " + name);
} //while
} catch(SQLException e) {
System.out.println(e.getMessage());
}
}
red line here!!!

connectDB() method is of void type and not returning anything but when you are calling the method, you are assigning it to variable con. So you need to change the return type of connectDb to the Connection type.
public Connection connectDB() {
Connection con = null;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://****/SAC?useSSL=false&serverTimezone=UTC", "***", "***");
}
catch(SQLException e) {
e.printStackTrace();
}
catch(ClassNotFoundException e) {
e.printStackTrace();
}
return con;
}

You are trying to call non-static method into the static area, which is not allowed in Java. So I made this method static and returning the database connection.
Please update the below method into your code. It will resolve your problem.
public static Connection connectDB() {
Connection con = null;
try {
Class.forName("com.mysql.cj.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://****/SAC?useSSL=false&serverTimezone=UTC", "", "");
} catch(SQLException e) {
e.printStackTrace();
} catch(ClassNotFoundException e) {
e.printStackTrace();
}
return con;
}

Null pointer exception after initialize

private static String dbURL = "jdbc:mysql://localhost:3306/mydb";
private static String username = "secret";
private static String password = "secret";
private static Connection conn = null;
public static void initDbConnection(){
try {
conn = DriverManager.getConnection(dbURL, username, password);
Class.forName("com.mysql.jdbc.Driver");
} catch (SQLException e1) {
e1.printStackTrace();
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public static void test3(){
initDbConnection();
try{
String sql = "SELECT * FROM Products";
Statement statement = conn.createStatement();
ResultSet result = statement.executeQuery(sql);
while (result.next()){
String name = result.getString("name");
System.out.println(name);
}
}
catch (SQLException ex) {
ex.printStackTrace();
}
}
Why I'm getting null pointer exception on conn even though I called the initDbConnection() on test3() ? How will I elimate this problem?

Class.forName("com.mysql.jdbc.Driver");
should be the first line. As this load the mysql driver in the memory. Then you will acquire the connection.
So it should be
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(dbURL, username, password);
} catch (SQLException e1) {
e1.printStackTrace();
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}

Java DB Connection Manager Best Practice

I have a connection manager code as follows:
public class ConnectionManager {
private final String driverName = "com.mysql.jdbc.Driver";
private final String connectionUrl = "jdbc:mysql://localhost:3306/student";
private final String userName = "root";
private final String userPass = "root";
private Connection con = null;
public ConnectionManager() {
try {
Class.forName(driverName);
} catch (ClassNotFoundException e) {
System.out.println(e.toString());
}
}
public Connection createConnection() {
try {
con = DriverManager.getConnection(connectionUrl, userName, userPass);
} catch (SQLException e) {
e.printStackTrace();
}
return con;
}
public void closeConnection() {
try {
this.con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
How can I improve this? I am thinking the following improvement:
) create a connection.properties. What is the best way to implement this? Should I put it the call of the property file on a singleton?
) Make the connection singleton.
Thank you.

If it's for a real application you'd better use a connection pool like this http://commons.apache.org/proper/commons-dbcp/.

can't get connection to database through java class

i'm trying to establish connection with mysql database through file properties and then run the information from servlet. my Connection class looks like this:
public class pageDao {
private Connection connection;
private Statement statement;
private pageDao() {
Properties prop = new Properties();
try {
//Class.forName("oracle.jdbc.driver.OracleDriver");
//Class.forName("org.gjt.mm.mysql.Driver");
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException cnfe) {
System.out.println("Error loading driver: " +cnfe);
}
try {
try {
//load a properties file
prop.load(new FileInputStream("config.properties"));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
String db = prop.getProperty("database");
String dbuser = prop.getProperty("dbuser");
String dbpassword = prop.getProperty("dbpassword");
connection = DriverManager.getConnection(db,dbuser,dbpassword);
} catch (SQLException e) {
e.printStackTrace();
}
}
private static pageDao thisDao;
public static pageDao gedDao()
{
if(thisDao == null)
thisDao = new pageDao();
return thisDao;
}
public PageData getPage(String id)
{
PageData data = new PageData();
try {
statement = connection.createStatement();
ResultSet rs = statement.executeQuery("select * from pages where id='"+id+"'");
if(rs.next())
{
data.setId(rs.getString("id"));
data.setParentid(rs.getString("parentid"));
data.setTitle(rs.getString("title"));
data.setTitle4menu(rs.getString("title4menu"));
data.setKeywords(rs.getString("keywords"));
data.setDescription(rs.getString("description"));
data.setMaintext(rs.getString("maintext"));
}
else
return null;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return data;
}
when i run it, it doesn't show the mistake that connection wasn't established, but when it gets to the
public PageData getPage(String id) {
PageData data = new PageData();
try {
statement = connection.createStatement();
it throws java.lang.NullPointerException.
can anybody help me out with that?

there is no issue with code.
check your passing parameter ...
check sample
private Connection getConnection() {
try {
String dbUrl = "jdbc:mysql://localhost:3306/projectmining";
Class.forName("com.mysql.jdbc.Driver");
return DriverManager.getConnection(dbUrl, "root", "admin");
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}

Returning the Connection from JDBC into a main method of Java?

Is it possible to return the type Connection?
And use it as a method passed by reference through out the program?
I find it makes the database interaction a lot easier if it is passed as a method.
public static Connection database(String database, String username, String password) {
String url = "jdbc:postgresql:" + database;
//LOAD DRIVER
try {
Class.forName("org.postgresql.Driver");
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}
//CONNECT TO DATABASE
try {
Connection conn = DriverManager.getConnection(url, username, password);
return conn;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
public static void main(String[] args) {
db = database("java_jdbc", "admin", "fake_password_1234");
}

You can do that.
Just remember to invoke close() on the connection to release its resources when done.

package mySystem;
import java.sql.*;
import javax.swing.*;
public class MySqlConnector {
Connection conn = null;
public static Connection ConnectDB() {
try {
Class.forName("com.mysql.jdbc.Driver"); //register jdbc driver
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/inventory_db", "root", "");
// JOptionPane.showMessageDialog(null, "Connected to db");
return conn;
} catch (Exception e) {
JOptionPane.showMessageDialog(null, e);
return null;
}
}
}