用户登录系统对用户信息的增删改查的后端实现

package lab1_3; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class Person { public static void person_Increase(Connection con,String username,String name,String age,String telenumber) throws SQLException { boolean flag=false; Statement sta; sta=con.createStatement(); String sql="select * from users"; ResultSet rs=sta.executeQuery(sql); while(rs.next()){ if(rs.getString(1).equals(username)) { sta=con.createStatement(); String sql1; if(age.equals("")) { if(telenumber.equals("")) { sql1="insert into person (username,name) values('"+username+"','"+name+"')"; } else {sql1="insert into person (username,name,teleno) values('"+username+"','"+name+"','"+telenumber+"')";} } else{ if(telenumber.equals("")) { sql1="insert into person (username,name,age) values('"+username+"','"+name+"','"+age+"')"; } else {sql1="insert into person values('"+username+"','"+name+"','"+age+"','"+telenumber+"')";} } sta.executeUpdate(sql1); flag=true; break; } } rs.close(); if(!flag) { System.out.printf("Insert person failed!\n"); } } public static void delete_person(Connection con,String username) throws SQLException { Statement sta; sta=con.createStatement(); String sql="select * from person"; ResultSet rs=sta.executeQuery(sql); while(rs.next()){ if(rs.getString(1).equals(username)) { sta=con.createStatement(); String sql1="delete from person where username='"+username+"'"; //SQL语句 sta.executeUpdate(sql1); } } rs.close(); } public static void Update_data(Connection con,String username,String name,String age,String telenumber) throws SQLException { Statement sta; sta=con.createStatement(); String sql="select * from person"; ResultSet rs=sta.executeQuery(sql); int flag=0; while(rs.next()){ if(rs.getString(1).equals(username)) { if(name.equals("")) name=rs.getString(2); if(age.equals("")&&(rs.getString(3)!=null)) age=rs.getString(3); if(telenumber.equals("")&&(rs.getString(4)!=null)) telenumber=rs.getString(4); sta=con.createStatement(); String sql1; if(age.equals("")) { if(telenumber.equals("")) { sql1="update person set name='"+name+"' where username='"+username+"'"; }else { sql1="update person set name='"+name+"',teleno='"+telenumber+"' where username='"+username+"'"; } }else { if(telenumber.equals("")) { sql1="update person set name='"+name+"',age='"+age+"' where username='"+username+"'"; }else { sql1="update person set name='"+name+"',age='"+age+"',teleno='"+telenumber+"' where username='"+username+"'"; } } sta.executeUpdate(sql1); //将sql语句上传至数据库执行 flag=1; } } if(flag==0) { sql="select * from users"; rs=sta.executeQuery(sql); boolean flag1=false; while(rs.next()){ if(rs.getString(1).equals(username)) { flag1=true; break; } } if(!flag1) {User.users_Increase(con, username, "888888");} Person.person_Increase(con, username, name, age, telenumber); } rs.close(); } }