public class Connect {

    private final String URL = "jdbc:mysql://localhost:3306/gregs_list?" +
        "useUnicode=true&useSSL=true&useJDBCCompliantTimezoneShift=true" +
        "&useLegacyDatetimeCode=false&serverTimezone=UTC";
    private final String USERNAME = "root";
    private final String PASSWORD = "root";

    private Connection connection;

    public Connection getConnect(){
        try {
            connection = DriverManager.
                getConnection(URL, USERNAME, PASSWORD);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }
}

public class ServletGlobal extends HttpServlet {
private Connect connect;
protected void doPost(HttpServletRequest request, HttpServletResponseresponse)
        throws ServletException, IOException {
    doGet(request, response);
}

protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    try(Connection connection = connect.getConnect();
        PreparedStatement prt = connection.prepareStatement("SELECT * FROM user");
        ResultSet rs = prt.executeQuery()) {

        while (rs.next()){
            System.out.println(rs.getInt("user_id"));
            System.out.println(rs.getString("user_name"));
            System.out.println(rs.getInt("user_age"));
            System.out.println(rs.getInt("user_salary"));
        }

    } catch (SQLException e) {
        e.printStackTrace();
    }
}

04-Feb-2018 22:07:39.170 SEVERE [http-nio-9000-exec-6]
org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for
servlet [Servant] in context with path [] threw exception
java.lang.NullPointerException
at com.mycompany.app.logic.ServletGlobal.doGet(ServletGlobal.java:28)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)

<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
  <servlet-name>Servant</servlet-name>
  <servlet-class>com.mycompany.app.logic.ServletGlobal</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Servant</servlet-name>
<url-pattern>/rer</url-pattern>