教你如何写springboot接口

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="Http://Maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-WEB</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.1</version>
        </dependency>

        <dependency>
            <groupId>Mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&useSSL=false&characterEncoding=utf8&serverTimezone=Asia/Shanghai
    username: root
    passWord: 123456
server:
  port: 8001

package com.example.demo.entity;

import lombok.Data;

@Data
public class User {
    private Integer id;
    private String name;
    private String address;
    private Integer age;
    private String sex;
    private String phone;

}

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.16.10</version>
    <scope>provided</scope>
</dependency>

package com.example.demo.mapper;

import com.example.demo.entity.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;

import java.util.List;

public interface UserMapper {

    @Select("select * from user")
    List<User> findAll();

    @Update("INSERT INTO `user` (`name`, `address`, `age`, `sex`, `phone`) VALUES (#{name},#{address},#{age},#{sex},#{phone});")
    @Transactional
    void save(User user);


    @Update("update user set name=#{name} , address=#{address}, age=#{age}, sex=#{sex},phone=#{phone} where id =#{id}")
    @Transactional
    void updateById(User user);


    @Delete("delete from user where id =#{id}")
    @Transactional
    void deleteById(Long id);

    @Select("select * from user where id =#{id}")
    User findById(Long id);


    @Select("select * from user limit #{offset},#{pageSize}")
    List<User> findByPage(Integer offset, Integer pageSize);

    @Select("select count(id) from user")
    Integer countUser();
}

package com.example.demo.controller;

import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import com.example.demo.vo.Page;
import org.apache.ibatis.annotations.Delete;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;
import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {
    
    @Resource
    UserMapper userMapper;
    @GetMapping
    public List<User> getUser() {
        return userMapper.findAll();
    }

    @PostMapping
    public String addUser(@RequestBody User user){
        //把前端传过来的数据转化为user实体类的对象插入到数据库中
        userMapper.save(user);
        return "success";


    }
    @PutMapping
    public String updateUser(@RequestBody User user){
        userMapper.updateById(user);
        return "success";
    }

    @DeleteMapping("/{id}")  //一一对相应的关系
    public String deleteUser(@PathVariable("id") Long id){
        //注解是循序JSON回传带有id
        userMapper.deleteById(id);
        return "success";
    }
    @GetMapping("/{id}")  //把返回的结果 返回出来 包装成一个user对象
    public User findById(@PathVariable("id") Long id){
        //注解是循序json回传带有id
        return userMapper.findById(id);
    }

    @GetMapping("/page")
    public Page<User> findByPage(@RequestParam(defaultValue = "1") Integer pageNum,
                                 @RequestParam(defaultValue = "10") Integer pageSize) {
        Integer offset = (pageNum - 1) * pageSize;
        List<User> userData = userMapper.findByPage(offset, pageSize);
        Page<User> page = new Page<>();
        page.setData(userData);

        Integer total = userMapper.countUser();
        page.setTotal(total);
        page.setPageNum(pageNum);
        page.setPageSize(pageSize);
        return page;
    }

}