java入门笔记四（springboot框架博客系统开发1）

实践出真知，先码一个博客系统先,参考https://juejin.cn/post/6844903823966732302。

1 使用IDEA新建项目->Spring Initializr->下一步,填写组/包名字->下一步选择依赖。(Developer Tools钩上Spring Boot Devtools和 Lombok,

Web钩上Spring Web,SQL钩上MySQL Driver)->下一步填写项目目录即可完成创建。

2 配置MyBatis-Plus用于数据库链接参考https://mp.baomidou.com/guide/，首先添加依赖，更新。

修改src/main/resources/application.properties改名application.yml

# DataSource Config
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/blog?useUnicode=true&useSSL=false&characterEncoding=utf8&serverTimezone=Asia/Shanghai
    username: root
    password: 123
mybatis-plus:
  mapper-locations: classpath*:/mapper/**Mapper.xml

3 打开navicat，输入sql语句执行，建表。

CREATE TABLE `m_user`(
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`username` varchar(64) DEFAULT NULL,
`avatar` varchar(255) DEFAULT NULL,
`email` varchar(64) DEFAULT NULL,
`password` varchar(64) DEFAULT NULL,
`status` int(5) NOT NULL,
`created` datetime DEFAULT NULL,
`last_login` datetime DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `UK_USERNAME` (`username`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
CREATE TABLE `m_blog`(
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`user_id` bigint(20) NOT NULL,
`title` varchar(255) NOT NULL,
`description` varchar(255) NOT NULL,
`content` longtext,
`created` datetime NOT NULL ON UPDATE CURRENT_TIMESTAMP,
`status` tinyint(4) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8mb4;
INSERT INTO `blog`.`m_user` (`id`, `username`, `avatar`, `email`, `password`, `status`, `created`, `last_login`) VALUES ('1', 'markerhub', 'https://image-1300566513.cos.ap-guangzhou.myqcloud.com/upload/images/5a9f48118166308daba8b6da7e466aab.jpg', NULL, '96e79218965eb72c92a549dd5a330112', '0', '2020-04-20 10:44:01', NULL);

3 引入spring-boot-starter-freemarker用于给前端发送模版

4 MyBatis-Plus有一个分页插件PaginationInterceptor，开启mapper接口扫描，添加分页插件，通过@mapperScan注解指定要变成

实现类的接口所在的包，然后包下面的所有接口在编译之后都会生成相应的实现类。

项目新增类com.blog.config.MybatisPlusConfig插入配置

package com.blog.config;

import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Configuration
@EnableTransactionManagement
@MapperScan("com.blog.mapper")
public class MybatisPlusConfig {
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
        return paginationInterceptor;
    }
}

5 项目创建CodeGenerator类自动生成表对应的controller/entity/mapper/service文件夹下对应表代码。

6 测试一下写个接口。

package com.blog.controller;


import com.blog.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

/**
 * <p>
 *  前端控制器
 * </p>
 *
 * @author 关注公众号：MarkerHub
 * @since 2021-02-15
 */
@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    UserService userService;

    @GetMapping("/index")
    public Object index(){
        return  userService.getById(1l);
    }

}

7 运行项目打开浏览器输入网址http://localhost:8080/user/index获取到了用户单条信息

8 封装接口返回类。新建类common.lang.Result,代码如下

package com.blog.common.lang;

import lombok.Data;

import java.io.Serializable;

@Data
public class Result implements Serializable {

    private int code;
    private String msg;
    private Object data;

    public static Result succ(int code,String msg,Object data){
        Result res=new Result();
        res.setCode(code);
        res.setData(data);
        res.setMsg(msg);
        return  res;
    }
    public static Result succ(Object data){
        return  succ(200,"success",data);
    }
    public static Result fail(int code,String msg,Object data){
        Result res=new Result();
        res.setCode(code);
        res.setData(data);
        res.setMsg(msg);
        return  res;
    }
    public static Result fail(String msg){
        return  succ(400,msg,null);
    }
}

然后修改接口方法直接返回Result类型即可 

错误列表备注

1 未找到项目org.springframework.boot:spring-boot-starter-parent2.4.2 ,重新maven下载改为版本2.2.6.RELEASE。