SSM练习

1 框架之间的关系

1 SpringBoot为框架的框架

2 Spring(整合第三方框架 整合SpringMVC与Mybatis 与他自己的Service业务层)

3 SpringMVC:实现前后端交互

4 Mybatis/MP(实现持久化操作)

2 数据传输

用户发出请求:根据url 路径到Controller层中的找到要执行的业务(Service),根据业务在Myvatis层

根据SQL语言,在数据库中找到数据

数据由Mybatis 通过注入到Service层,在注入到Controller层,映射到对象

 3 代码的层级结构

 4 编写代码的顺序

1.编辑POJO 2.编辑Mapper接口 3.编辑Service层 4.编辑Controller

5 POM.xml(包)

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.jt</groupId>
    <artifactId>springboot_demo4</artifactId>
    <version>1.0-SNAPSHOT</version>


    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <properties>
        <java.version>1.8</java.version>
        <skipTests>true</skipTests>
    </properties>

    <!--历史: SSM 需要手动的编辑大量的配置信息
        SpringBoot 使用体系了 "开箱即用" 的思想
        -->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <!--Spring的启动器,相当于之前大量的配置文件 在内部已经将整合的配置写好了,实现拿来即用-->
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.48</version>

        </dependency>
        <dependency>
            <!--spring整合mybatis-plus 删除mybatis的包-->
            <groupId>com.baomidou</groupId>

            <artifactId>mybatis-plus-boot-starter</artifactId>

            <version>3.4.3</version>

        </dependency>

    </dependencies>

    <!--插件:
        springboot项目:在打包部署发布时,需要依赖maven 工具API
        如果不添加该插件,则直接影响项目的发布
        -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

6 application.yml

#端口配置
server:
  port: 8080

#配置源
spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql:///jt?useUnicode=true&characterEncoding=utf8&useSSL=false
    username: root
    password: root
#SpringBoot整合Mybatis-plus配置
mybatis-plus:
  type-aliases-package: com.jt.pojo
  mapper-locations: classpath:/mappers/*.xml

  #开启驼峰映射
  configuration:
    map-underscore-to-camel-case: true
#打印Sql语句 为com.jt.mapper包下的Sql执行打印日志
logging:
  level:
    com.jt.mapper: debug

7 启动类:(包扫描)

package com.jt;


import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.jt.mapper")
public class RunApp {
    public static void main(String[] args) {
        SpringApplication.run(RunApp.class, args);
    }
}

8 代码

1.POJO:User类

package com.jt.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.experimental.Accessors;

import java.io.Serializable;

@Data
@Accessors(chain = true)
@AllArgsConstructor
@NoArgsConstructor
//1 将对象与表进行关联
//规则:如果表名与对象名一致时,名称可以省略
//     如果字段名与属性名一致,则注解可以省略
//序列化接口的作用:保证对象网络传输的有效性 网络传输(不同的服务器之间传递同一个对象)
//对象与表关联
@TableName("demo_user")
public class User implements Serializable {//序列化
    @TableId(type = IdType.AUTO)             //table + 主键     //主键自增/非空/UUID /生成唯一编号
    private Integer id;
    @TableField("name")//标识属性与字段的映射
    private String name;
    @TableField("age")
    private Integer age;
    @TableField("sex")
    private String sex;
}

2.Mapper接口(由于是单表结构,使用MP操作,使用Mapper接口需要继承 BaseMapper Mapper中无代码.相对应的映射文件中也无代码)

package com.jt.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.jt.pojo.User;
import org.apache.ibatis.annotations.Mapper;

import java.util.List;
/*@Mapper//将接口交给Spring管理,spring创建对象*/
/*1 继承BaseMapper时,必须添加泛型对象
* 2 自己的方法不要与接口方法重名
* */
public interface UserMapper extends BaseMapper<User> {

}

3 UserMapper.xml文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jt.mapper.UserMapper">

</mapper>

4 UserService(业务层)

package com.jt.service;

import com.jt.pojo.User;

import java.util.List;

public interface UserService {
    List<User> findAll();
}

5 UserServiceImpl(业务层接口)

package com.jt.service;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.jt.mapper.UserMapper;
import com.jt.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;
    //查询所有的where条件,所有参数为空     QueryWrapper 只有有where条件才使用
    @Override
    public List<User> findAll() {

        return  userMapper.selectList(null);
    }
}

6 Controller(控制层)

package com.jt.controller;


import com.jt.pojo.User;
import com.jt.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
/*@Controller
@ResponseBody//将服务端的数据转化为JSON串返回*/
public class UserContruller {
    //编码规则:面向接口编程 解耦
    @Autowired
    UserService userService;
    @RequestMapping("findAll")
    public List<User> findAll(){
        return userService.findAll();
    }
}