JAVA is a simple link to the Oracle database for registration and login.

// The basic information of the User, which is also the package logon judgment of the three columns in the USERINFO table; public class User {private String name; private String loginname; private String loginpsw; public String getName () {return name;} public void setName (String name) {this. name = name;} public String getLoginname () {return loginname;} public void setLoginname (String loginname) {this. loginname = loginname;} public String getLoginpsw () {return loginpsw;} public void setLoginpsw (String loginpsw) {this. loginpsw = loginpsw ;}}
// Small code block for registration and login package login judgment; import java. util. extends; public class In {public static User getUser () {User u = new User (); Using SC = new using (System. in); System. out. println ("Enter the login name"); u. setLoginname (SC. nextLine (); System. out. println ("Enter Password"); u. setLoginpsw (SC. nextLine (); return u;} public static User registerUser () {User u = new User (); Limit SC = new limit (System. in); System. out. println ("Please register username"); u. setName (SC. nextLine (); System. out. println ("Please register the login name"); u. setLoginname (SC. nextLine (); System. out. println ("Please register password"); u. setLoginpsw (SC. nextLine (); return u ;}}

// Check during login to check whether the login name and password are correct. If the login is correct, return the user name package logon judgment; import java. SQL. connection; import java. SQL. driverManager; import java. SQL. preparedStatement; import java. SQL. resultSet; import java. SQL. SQLException; public class Check {public static void checkUser (User u) {try {Class. forName ("oracle. jdbc. driver. oracleDriver ");} catch (ClassNotFoundException e) {e. printStackTrace ();} String url = "jdbc: oracle: thin: @ localhost: 1 521: orcl "; String user =" scott "; String password =" tiger "; Connection conn = null; ResultSet rs = null; PreparedStatement pst = null; string SQL = "Select name from USERINFO where loginname =? And loginpsw =? "; Try {conn = DriverManager. getConnection (url, user, password); pst = conn. prepareStatement (SQL); pst. setString (1, u. getLoginname (); pst. setString (2, u. getLoginpsw (); rs = pst.exe cuteQuery (); while (rs. next () {u. setName (rs. getString (1) ;}} catch (SQLException e) {e. printStackTrace ();} finally {try {rs. close (); pst. close (); conn. close ();} catch (SQLException e) {e. printStackTrace () ;}} if (u. getName () = null | u. getName (). isEmpty () {System. out. println ("Logon Failed");} else {System. out. println ("welcome" + u. getName () + "login ");}}}

// On the registration page, check whether there are duplicate login names. If there are duplicate login names, the registration fails. I have a few questions. I have commented out the package for login and judgment; import java. SQL. connection; import java. SQL. driverManager; import java. SQL. preparedStatement; import java. SQL. resultSet; import java. SQL. SQLException; import java. SQL. statement; public class Register {public static void registUser (User u) {try {Class. forName ("oracle. jdbc. driver. oracleDriver ");} catch (ClassNotFoundException e) {e. printStackTrace ();} String url = "jdbc: oracle: thin: @ Localhost: 1521: orcl "; String user =" scott "; String password =" tiger "; Connection conn = null; string SQL = "Insert Into USERINFO values (?,?,?) "; PreparedStatement pst = null; // judge whether the login name already exists Statement s = null; ResultSet rs = null; String SQL _ck =" Select LOGINNAME FROM USERINFO "; try {conn = DriverManager. getConnection (url, user, password); pst = conn. prepareStatement (SQL); pst. setString (1, u. getName (); pst. setString (2, u. getLoginname (); pst. setString (3, u. getLoginpsw (); // determines whether the logon name already exists. s = conn. createStatement (); rs = s.exe cuteQuery (SQL _ck); while (rs. next () {// Why is rs used. if (rs. getString ("LOGINNAME "). equals (u. getLoginname () {System. out. println ("login name already exists, registration failed" cannot begin break?else=pst.exe cuteUpdate (); System. out. println ("registered"); break ;}} catch (SQLException e) {e. printStackTrace ();} finally {try {rs. close (); pst. close (); s. close (); conn. close ();} catch (SQLException e) {e. printStackTrace ();}}}}

// Main interface /// this is the structure of the table in the database // name (user name, used for display), // loginname (login name, that is, the ID entered during login) // loginpsw (password entered during login) package logon judgment; import java. util. optional; public class Test {public static void main (String [] args) {int chos = 0; Using SC = new using (System. in); System. out. println ("\ t login press 1 \ t registration press 2"); chos = SC. nextInt (); switch (chos) {case 1: Check. checkUser (In. getUser (); break; case 2: Register. registUser (In. registerUser (); break; default: System. out. println ("enter the correct choice"); break ;}}}