Create a springboot framework project for the first time

1.1_ Creation steps

(1) Create a spring project

（2）

（3）

Join the engine

Just the next step

2.1_ Problems encountered during startup

(1) There is no startup icon at the beginning, just wait a while.

(2) Afterwards, the startup fails and the error ERROR 3704 is reported — [main] osbdLoggingFailureAnalysisReporter:

Because the default port is 8080, if it is already occupied, you need to change the default port number

Modification method : Modificationapplication.propertiesFile, add in the file:

server.port=8081
server.context-path=/demo

Successful startup:

(3) The next visit to http://localhost:8081/ was successful, but after a day, it didn’t work and found that it was a directory problem. You
should visit http://localhost:8081/demo

2.2_ Start response web page test

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController//响应服务器，与@RequestMapping配合使用（“@RestController配合@RequestMapping”与“@Controller配合@ResponseBody再配合@RequestMapping”效果一样）
@SpringBootApplication//声明该类是一个springboot引导类，
public class DemoApplication {
    
    

    public static void main(String[] args) {
    
    
    //run方法表示运行springboot的引导类
        SpringApplication.run(DemoApplication.class, args);
    }

    @RequestMapping
    public String hello() {
    
    
        return "hello spring boot!";
    }
}

Search in the browser: "http://localhost:8081/"

2.3_ try to connect to the database

package com.example.demo;
import java.sql.*;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController//响应服务器，与@RequestMapping配合使用（“@RestController配合@RequestMapping”与“@Controller配合@ResponseBody再配合@RequestMapping”效果一样）
@SpringBootApplication
public class DemoApplication {
    
    

    public static void main(String[] args) {
    
    
        SpringApplication.run(DemoApplication.class, args);
    }

    @RequestMapping
    public String hello()throws Exception {
    
    
        SqlOperation.main();
        ResultSet resultSet = SqlOperation.statement.executeQuery("select * from Score");
        String s;
        resultSet.next();
        s = resultSet.getString("name");
        return s;
    }
}

class SqlOperation {
    
    
    public static Connection connection = null;//定义连接数据库的对象（桥梁）
    public static String url = "jdbc:sqlserver://localhost:1433;DatabaseName=Studentinfo";
    public static Statement statement = null;//定义静态操作对象
    public static PreparedStatement preparedStatement = null;//定义动态操作对象
    public static void main() {
    
    
        try{
    
    
            //第一步加载驱动
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
            System.out.println("加载驱动成功！");
            //第二步建立连接
            connection = DriverManager.getConnection(url,"sa","shejiashuai");
            System.out.println("连接数据库成功！");
            //第三步建立操作对象
            statement = connection.createStatement();
        }catch (Exception e){
    
    
            e.printStackTrace();
            System.out.println("连接数据库失败！");
        }
    }
    public static void close(){
    
    //关闭连接
        try{
    
    
            statement.close();
            connection.close();
        }catch (Exception e){
    
    
            e.printStackTrace();
        }
    }
}