Lianjie.java是连接数据库的,input.jsp是表单输入数据,然后通过add.jsp向数据库添加数据。但是添加不上代码如下Lianjie.java如下:package com.example;import java.sql.*;public class Lianjie { private static final String URL="jdbc:mysql://localhost:3306/student"; private static final String USER="root"; private static final String PASSWORD=""; protected static Statement s=null; protected static ResultSet rs=null; protected static Connection conn=null; public static synchronized Connection getConnection(){ try{ Class.forName("com.mysql.jdbc.Driver"); conn=DriverManager.getConnection(URL,USER,PASSWORD); }catch (Exception e) { e.printStackTrace(); } return conn; } public static int executeUpdate(String sql){ int result=0; try { s=getConnection().createStatement(); result=s.executeUpdate(sql); } catch (Exception e) { e.printStackTrace(); } return result; } public static ResultSet executeQuery(String sql){ try { s=getConnection().createStatement(); rs=s.executeQuery(sql); } catch (Exception e) { e.printStackTrace(); } return rs; } public static PreparedStatement executePreparedStatement(String sql){ PreparedStatement ps=null; try { ps=getConnection().prepareStatement(sql); } catch (Exception e) { e.printStackTrace(); } return ps; } public static void close(){ try{ if(rs!=null) rs.close(); if(s!=null) s.close(); if(conn!=null) conn.close(); }catch (Exception e) { e.printStackTrace(); } }}input.jsp和add.jsp如下