Time: 2024-04-08 14:21:19
Author: Jackasher

Ajax-2

今天学的是,基于JSON格式的数据交换,浏览器自带JSON对象,JSON对象可以调用方法把字符串转为JSON对象,从而可以以JS中的属性访问方式访问

_String = ajax.responseText
var jsonObject = JSON.parse(_String)

如果需要连接数据库,我们需要把数据库的信息封装成对象,然后使用阿里巴巴提供的fastjson转化成JSON格式的字符串

String _String = JSON.toJSONString(_Object)
our.print(_String)

总体来说是这样

package com.example.ajax;

import com.alibaba.fastjson2.JSON;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.junit.Test;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

@WebServlet("/request3")
public class Servlet4 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<User> users = new ArrayList<>();
        User jack = new User("jack","casio233.");
        users.add(jack);
//        String jsonString = JSON.toJSONString(jack);
//        System.out.println(jsonString);
        PrintWriter out = resp.getWriter();

        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
//        out.print(jsonString);
        try (Connection root = DriverManager.getConnection("jdbc:mysql://localhost:3306/jack", "root", "casio233.");) {
            Statement statement = root.createStatement();

            String sql = "select * from users";
            ResultSet resultSet = statement.executeQuery(sql);
            while(resultSet.next()){
                String username = resultSet.getString("username");
                String password = resultSet.getString("password");
                users.add(new User(username, password));
            }
            String jsonString = JSON.toJSONString(users);
            out.print(jsonString);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }


    }
}