用Ajax，json，MYSQL，前端后端语言创建一个学生管理系统吧~~

select * from messageLibrary where username=? order by id DESC limit 1;//按照字段id
降序排列(即从大到小排列),然后用limit限定查询出的记录数,后面的数字即为输出的记录数。命令的
总体功能就是：查询出最后一条记录.其中主键id必须是int类型,且要用 auto-increment修饰(自动加一)

update class set classname=?,classinfo=? where id=?;//set后面写入需
要修改的字段以及对应的修改值。where后面的条件不能使用需要进行修改的字段

insert into class (classname,classinfo) values(?,?);
//第一个括号指定需要插值的字段，第二个括号为插入的值，class
表中有一个主键id(int)，因为用了auto-increment修饰，不给它插
值时,它会自动加一

登录效果&&主页切换效果

功能展示效果

servlet代码

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import net.sf.json.JSONArray;
@WebServlet("/Controller")
public class Controller extends HttpServlet {
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Controller() {
        super();}
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		request.setCharacterEncoding("UTF-8");
		String task=request.getParameter("task");
		if(task.equals("1"))//添加班级信息响应
		{String classname=request.getParameter("classname");
		String classinfo=request.getParameter("classinfo");						
		response.setContentType("text/html;charset=UTF-8");
		if(!classname.equals("") && !classinfo.equals(""))			
		{manager.addclass(classname, classinfo);
		response.getWriter().println("😊添加成功😊");}
		else {response.getWriter().println("😒输入不能为空哦😊");}
}
		if(task.equals("2")) {//查询班级信息响应
			String classname=request.getParameter("classname");
			ArrayList> Buffer=manager.getBuffer(classname);
			if(Buffer.size()==0)
			{HashMap element=new HashMap<>();
	    	element.put("id","无该班级编号");
	    	element.put("classname", "无该班级信息");
	    	element.put("classinfo", "无该班级描述");
	    	Buffer.add(element);}
			JSONArray jsonarray=JSONArray.fromObject(Buffer);
			response.setContentType("text/html;charset=UTF-8");
			response.getWriter().println(jsonarray);
		}
		if(task.equals("3")) {//修改班级信息响应
			String classname=request.getParameter("classname1");
			String classinfo=request.getParameter("classinfo");
			String id=request.getParameter("classindex");
			manager.modify(Integer.parseInt(id), classname, classinfo);
			response.setContentType("text/html;charset=UTF-8");
			response.getWriter().println("修改成功");
		}
		if(task.equals("4")) {//删除班级信息响应
			String id=request.getParameter("classindex");
			manager.cutoff(Integer.parseInt(id));
			response.setContentType("text/html;charset=UTF-8");
			response.getWriter().println("删除成功");
		}
		if(task.equals("5")) {//给前端页面的下拉框初始化选项值(classname)
			ArrayList Buffer=manager.getclassname();
			JSONArray jsonarray=JSONArray.fromObject(Buffer);
			response.setContentType("text/html;charset=UTF-8");
			response.getWriter().println(jsonarray);
		}
		if(task.equals("6")) {//添加学生信息响应
			String studentname=request.getParameter("studentname");
			String studentindex=request.getParameter("studentindex");
			String studentsex=request.getParameter("studentsex");
			String department=request.getParameter("department");
			String studentclass=request.getParameter("studentclass");
			String location=request.getParameter("location");
			response.setContentType("text/html;charset=UTF-8");
			if(!studentname.equals("") && !studentindex.equals("") && !department.equals("") && !location.equals(""))
			{manager.addstudent(studentname, studentindex, studentsex, department, studentclass, location);
			response.getWriter().println("添加成功");}
		    else {
		    response.getWriter().println("输入不能为空哦");
		}}
		if(task.equals("7")) {//查询学生信息响应
			String studentname=request.getParameter("studentname");
			String studentindex=request.getParameter("studentindex");
			ArrayList> Buffer=manager.getBuffer(studentname, studentindex);
			if(Buffer.size()==0)
			{HashMap element=new HashMap<>();
			element.put("id","无该学生编号");
	    	element.put("studentname","无该学生姓名");
	    	element.put("studentindex","无该学生学号");
	    	element.put("studentsex","无该学生性别");
	    	element.put("department","无该学生所属学院");
	    	element.put("studentclass","无该学生所属班级");
	    	element.put("location","无该学生家庭地址");
	    	Buffer.add(element);}
			JSONArray jsonarray=JSONArray.fromObject(Buffer);
			response.setContentType("text/html;charset=UTF-8");
			response.getWriter().println(jsonarray);
		}
		if(task.equals("8")){//删除学生信息响应
			String studentname=request.getParameter("studentname");
			String studentindex=request.getParameter("studentindex");
			manager.cutoff(studentname, studentindex);
			response.setContentType("text/html;charset=UTF-8");
			response.getWriter().println("删除成功");
		}
		if(task.equals("9")) {//修改学生信息响应
			String id=request.getParameter("id");
			String studentname1=request.getParameter("studentname1");
			String studentindex1=request.getParameter("studentindex1");
			String studentsex=request.getParameter("studentsex");
			String department=request.getParameter("department");
			String studentclass=request.getParameter("studentclass");
			String location=request.getParameter("location");
			response.setContentType("text/html;charset=UTF-8");
			if(!department.equals("") && !location.equals(""))
			{manager.modify(Integer.parseInt(id), studentname1, studentindex1, studentsex, department, studentclass, location);
			response.getWriter().println("修改成功");}
		    else {
		    response.getWriter().println("输入不能为空哦");
		}}}	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

 JDBC代码

import java.sql.ResultSet;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import com.mysql.cj.xdevapi.Statement;
class manager {
	static private String driver="com.mysql.cj.jdbc.Driver";//数据库驱动类所对应的字符串
	static private String URL="jdbc:mysql://localhost:3306/mydatabase?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8";
            //URL语法格式如下
	//jdbc:mysql:是固定的写法，后面跟主机名localhost，3306是默认的MySQL端口号
	//serverTimezone=UTC是指定时区时间为世界统一时间
	//useUnicode=true是指是否使用Unicode字符集，赋值为true
	//characterEncoding=utf-8是指定字符编码格式为UTF8
	static private Connection cnt=null;
	
	static void initConnection() {//建立与数据库的连接
		try {
			Class.forName(driver);
			cnt=DriverManager.getConnection(URL,"root","941593760s");
	}
			catch(SQLException e) {
				e.printStackTrace();
			}
			catch(ClassNotFoundException e) {
				e.printStackTrace();}
			catch(Exception e) {
				e.printStackTrace();
			}}
static void addmsg(String username,String password) {//添加注册信息		
		if(cnt==null) {
			initConnection();
		}
		
		try{
			PreparedStatement ps=cnt.prepareStatement("insert into user values(?,?)");			
			ps.setString(1, username);
			ps.setString(2, password);
		    ps.executeUpdate();
			}
		catch(SQLException e) {
			e.printStackTrace();
		}
		catch(Exception e) {
			e.printStackTrace();
		}
		
	}

	static void addclass(String classname,String classinfo) {//添加班级信息			
	if(cnt==null) {
		initConnection();
	}
		try{
			PreparedStatement ps=cnt.prepareStatement("insert into class (classname,classinfo) values(?,?)");			
			ps.setString(1, classname);
			ps.setString(2, classinfo);
		    ps.executeUpdate();
			}
		catch(SQLException e) {
			e.printStackTrace();
		}
		catch(Exception e) {
			e.printStackTrace();
		}
		
	}
	static boolean examinationDL(String username,String password) {//检验登录信息(密码与用户名)是否正确		
		if(cnt==null) {
			initConnection();
		}
		try(
			PreparedStatement ps=cnt.prepareStatement("select * from user where username=? and password=?"))			
			{ps.setString(1, username);
			ps.setString(2, password);
		    ResultSet rs=ps.executeQuery();
		    if(rs.next()) {
		    	return(true);}//登录成功		   
			}		
		catch(Exception e) {
			e.printStackTrace();
		}
		return(false);
	}
	static boolean examinationZC(String username) {	//检验注册所用的用户名是否有重复	有重复返回false 无则返回true
		if(cnt==null) {
			initConnection();
		}
		try(
			PreparedStatement ps=cnt.prepareStatement("select * from user where username=?"))			
			{ps.setString(1, username);			
		    ResultSet rs=ps.executeQuery();
		    if(rs.next()) {
		    	return(false);}//有重复的的名称，请重新注册(保证数据库里面的用户名唯一)		   
			}		
		catch(Exception e) {
			e.printStackTrace();
		}
		return(true);
	}
	static ArrayList> getBuffer(String classname) {//以集合的形式返回班级信息，用于JSON数据交换
		if(cnt==null) {
			initConnection();
		}
		ArrayList> Buffer=new ArrayList<>();//在方法里面创建对象，保证线程并发安全
		try(
				PreparedStatement ps=cnt.prepareStatement("select * from class where classname=?"))			
				{		ps.setString(1, classname);					   
			ResultSet rs=ps.executeQuery();
			    while(rs.next()) {	
			    	HashMap element=new HashMap<>();//java中Map形式的数据集合对应json语法里的对象形式，即{e1，e2……}
			    	element.put("id", rs.getInt("id")+"");
			    	element.put("classname", rs.getString("classname"));
			    	element.put("classinfo", rs.getString("classinfo"));
			    	Buffer.add(element);//将Map集合作为List的元素，这种形式的集合对用于json中用数组封装集合的写法，即[{e1，e2……},{e1，e2……}……]
			    	}		   
				}		
			catch(Exception e) {
				e.printStackTrace();
			}
			return(Buffer);
	}
	static ArrayList> getBuffer(String studentname,String studentindex) {//以集合的形式返回学生信息，用于JSON数据交换
		if(cnt==null) {
			initConnection();
		}
		ArrayList> Buffer=new ArrayList<>();//在方法里面创建对象，保证线程并发安全
		try(
				PreparedStatement ps=cnt.prepareStatement("select * from student where studentname=? and studentindex=?"))			
				{		ps.setString(1, studentname);
				        ps.setString(2, studentindex);
			    ResultSet rs=ps.executeQuery();
			    if(rs.next()) {	
			    	HashMap element=new HashMap<>();
			    	element.put("id", rs.getInt("id")+"");
			    	element.put("studentname", rs.getString("studentname"));
			    	element.put("studentindex", rs.getString("studentindex"));
			    	element.put("studentsex", rs.getString("studentsex"));
			    	element.put("department", rs.getString("department"));
			    	element.put("studentclass", rs.getString("studentclass"));
			    	element.put("location", rs.getString("location"));
			    	Buffer.add(element);
			    	}		   
				}		
			catch(Exception e) {
				e.printStackTrace();
			}
			return(Buffer);
	}
	static void withdraw(String username) {//撤回消息
		if(cnt==null) {
			initConnection();
		}
		try(	PreparedStatement ps1=cnt.prepareStatement("select * from messageLibrary where username=? order by id DESC limit 1");//按照字段id降序
				//排列(即从大到小排列),然后用limit限定查询出的记录数,后面的数字即为输出的记录数。命令的总体功能就是——查询出最后一条记录。其中主键id要用 auto-increment修饰(自动加一)
				PreparedStatement ps2=cnt.prepareStatement("delete from messageLibrary where id=?"))			
				{		 ps1.setString(1, username);
			            ResultSet rs=ps1.executeQuery();
				        if(rs.next()) {
				        	int id=rs.getInt("id");
				        	ps2.setInt(1, id);
				        	ps2.executeUpdate();
				        }
			    	}		   
					
			catch(Exception e) {
				e.printStackTrace();
			}
	}
	static void modify(int id,String classname,String classinfo) {//根据唯一的编号，修改班级记录
		if(cnt==null) {
			initConnection();
		}
		try(
			PreparedStatement ps=cnt.prepareStatement("update class set classname=?,classinfo=? where id=?"))//where后面的条件不能使用需要进行修改的字段			
			{ps.setInt(3, id);
			ps.setString(1, classname);
			ps.setString(2, classinfo);
			ps.executeUpdate();}		  		   	
		catch(Exception e) {
			e.printStackTrace();
		}		
	}
	static void modify(int id,String studentname1,String studentindex1,String studentsex,String department,String studentclass,String location) {
		//根据学生id(编号)修改学生信息
		if(cnt==null) {
			initConnection();
		}
		try(
			PreparedStatement ps=cnt.prepareStatement("update student set studentname=?,studentindex=?,studentsex=?,"
					+ "department=?,studentclass=?,location=? where id=?"))			
			{
			ps.setString(1, studentname1);
			ps.setString(2, studentindex1);
			ps.setString(3, studentsex);
			ps.setString(4, department);
			ps.setString(5, studentclass);
			ps.setString(6, location);			
			ps.setInt(7, id);
			ps.executeUpdate();}		  		   	
		catch(Exception e) {
			e.printStackTrace();
		}		
	}
	static void cutoff(String studentname,String studentindex) {//根据学生姓名和学号删除学生记录
		if(cnt==null) {
			initConnection();
		}
		try(
			PreparedStatement ps=cnt.prepareStatement("delete from student where studentname=? and studentindex=?"))			
			{ps.setString(1, studentname);
			ps.setString(2, studentindex);
			ps.executeUpdate();}		  		   	
		catch(Exception e) {
			e.printStackTrace();
		}		
	}
	static void cutoff(int id) {//根据编号删除班级记录
		if(cnt==null) {
			initConnection();
		}
		try(
			PreparedStatement ps=cnt.prepareStatement("delete from class where id=?"))			
			{ps.setInt(1, id);
			ps.executeUpdate();}		  		   	
		catch(Exception e) {
			e.printStackTrace();
		}		
	}
	static void addstudent(String studentname,String studentindex,String studentsex,String department,String studentclass,String location) {//添加学生信息
		if(cnt==null) {
			initConnection();
		}
			try{
				PreparedStatement ps=cnt.prepareStatement("insert into student (studentname,studentindex,studentsex,department,"
				+ "studentclass,location) values(?,?,?,?,?,?)");			
				ps.setString(1, studentname);
				ps.setString(2, studentindex);
				ps.setString(3, studentsex);
				ps.setString(4, department);
				ps.setString(5, studentclass);
				ps.setString(6, location);
			    ps.executeUpdate();
				}
			catch(SQLException e) {
				e.printStackTrace();
			}
			catch(Exception e) {
				e.printStackTrace();
			}}
	static ArrayList getclassname() {
		if(cnt==null) {
			initConnection();
		}
		ArrayList Buffer=new ArrayList();
		try(
			PreparedStatement ps=cnt.prepareStatement("select * from class"))			
			{ResultSet rs=ps.executeQuery();		
		while(rs.next()) {
			Buffer.add(rs.getString("classname"));
		}}
		catch(Exception e) {
			e.printStackTrace();
		}
		return(Buffer);}}

前端部分代码

查询条件
学生姓名:


学生学号:


     
     



编号
学生姓名
学生学号
性别
所属学院
所属班级
家庭地址




请输入学生姓名



请输入学生学号




性别:   男
   女


请输入学生所在院系



请选择学生班级




家庭地址



          

结语：全篇未用框架，全是原生语言编写，所以看上去很臃肿。但这些都是学框架之前所必须要熟知的基础，也不可怠慢。