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1.什么是springboot自动装配？

自动装配是springboot的核心，一般提到自动装配就会和springboot联系在一起。实际上 Spring Framework 早就实现了这个功能。Spring Boot 只是在其基础上，通过 SPI 的方式，做了进一步优化。

SpringBoot 定义了一套接口规范，这套规范规定：SpringBoot 在启动时会扫描外部引用 jar 包中的META-INF/spring.factories文件，将文件中配置的类型信息加载到 Spring 容器（此处涉及到 JVM 类加载机制与 Spring 的容器知识），并执行类中定义的各种操作。对于外部 jar 来说，只需要按照 SpringBoot 定义的标准，就能将自己的功能装置进 SpringBoot

2.springboot注解：
@EnableAutoConfiguration：扫包范围默认当前类。
@ComponentScan(" “) 扫包范围默认当前类所在的整个包下面所有类。
扫包范围大于@EnableAutoConfiguration，@ComponentScan(” ")依赖于@EnableAutoConfiguration启动程序。
@EnableAutoConfiguration
@ComponentScan("第三方包 ")
app.run()
@SpringBootApplication 扫包范围同级包和当前包。
@SpringBootApplication 底层等同于@EnableAutoConfiguration+@ComponentScan。不扫描第三方包

3.springboot整合mybatisplus实现增删改查

1.首先导入相关依赖

   <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>com.spring4all</groupId>
            <artifactId>swagger-spring-boot-starter</artifactId>
            <version>1.9.1.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>swagger-bootstrap-ui</artifactId>
            <version>1.7.8</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </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>

2.创建数据表并添加数据

DROP TABLE IF EXISTS `category`;
CREATE TABLE `category`  (
  `cid` varchar(32) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NOT NULL,
  `cname` varchar(50) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`cid`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb3 COLLATE = utf8mb3_general_ci ROW_FORMAT = DYNAMIC;

-- ----------------------------
-- Records of category
-- ----------------------------
INSERT INTO `category` VALUES ('c001', '家电');
INSERT INTO `category` VALUES ('c002', '鞋服');
INSERT INTO `category` VALUES ('c003', '化妆品');
INSERT INTO `category` VALUES ('c004', '汽车');

-- ----------------------------
-- Table structure for products
-- ----------------------------
DROP TABLE IF EXISTS `products`;
CREATE TABLE `products`  (
  `pid` varchar(32) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NOT NULL,
  `pname` varchar(50) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NULL DEFAULT NULL,
  `price` int NULL DEFAULT NULL,
  `flag` varchar(2) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NULL DEFAULT NULL,
  `category_id` varchar(32) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`pid`) USING BTREE,
  INDEX `category_id`(`category_id`) USING BTREE,
  CONSTRAINT `products_ibfk_1` FOREIGN KEY (`category_id`) REFERENCES `category` (`cid`) ON DELETE RESTRICT ON UPDATE RESTRICT
) ENGINE = InnoDB CHARACTER SET = utf8mb3 COLLATE = utf8mb3_general_ci ROW_FORMAT = DYNAMIC;

-- ----------------------------
-- Records of products
-- ----------------------------
INSERT INTO `products` VALUES ('p001', '小
米电视 机', 5000, '1', 'c001');
INSERT INTO `products` VALUES ('p002', '格
力空调', 3000, '1', 'c001');
INSERT INTO `products` VALUES ('p003', '美
的冰箱', 4500, '1', 'c001');
INSERT INTO `products` VALUES ('p004', '篮
球鞋', 800, '1', 'c002');
INSERT INTO `products` VALUES ('p005', '运
动裤', 200, '1', 'c002');
INSERT INTO `products` VALUES ('p006', 'T
恤', 300, '1', 'c002');
INSERT INTO `products` VALUES ('p009', '篮球', 188, '1', 'c002');

3.在项目中创建如下目录

4.在resources下创建application.propertis并配置数据源

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql:///springboot

#日志
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

mybatis.mapper-locations=classpath:mapper/*.xml

5.在pojo下创建实体类

package com.azy.pojo;

import java.io.Serializable;

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;

/**
 * products
 * @author 
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@TableName(value = "products")
public class Products implements Serializable {
    @TableId(type = IdType.AUTO)
    private String pid;

    public Products(String pid, String pname, Integer price) {
        this.pid = pid;
        this.pname = pname;
        this.price = price;
    }

    private String pname;

    private Integer price;

    private String flag;

    private String category_id;
    @TableField(exist = false)
    private Category category;

    private static final long serialVersionUID = 1L;
}

6.在dao层下创建ProductDao这个接口,由于mybatisplus封装了单表的增删改查，所有只需继承BaseMapper这个接口就ok

package com.azy.dao;

import com.azy.pojo.Products;

import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import org.apache.ibatis.annotations.Param;

/**
 * @ fileName:ProductsDao
 * @ description:
 * @ author:Azy
 * @ createTime:2023/4/11 18:57
 * @ version:1.0.0
 */
public interface ProductsDao extends BaseMapper<Products> {
    IPage<Products> findPage(IPage<Products> iPage, @Param("ew") Wrapper<Products> wrapper);
}

7.在resources下面的mapper下创建ProductsDao.xml

<?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.azy.dao.ProductsDao">
    <resultMap id="ProductsMap" type="com.azy.pojo.Products" autoMapping="true">
        <id property="pid" column="pid" jdbcType="VARCHAR"/>
        <result property="pname" column="pname" jdbcType="VARCHAR"/>
        <result property="price" column="price" jdbcType="INTEGER"/>
        <result property="flag" column="flag" jdbcType="VARCHAR"/>
        <result property="category_id" column="category_id" jdbcType="VARCHAR"/>
        <association property="category" javaType="com.azy.pojo.Category" autoMapping="true">
            <id column="cid" property="cid" jdbcType="VARCHAR"/>
            <result property="cname" column="cname" jdbcType="VARCHAR"/>
        </association>
    </resultMap>

    <select id="findPage" resultType="com.azy.pojo.Products" resultMap="ProductsMap">
        select *
        from products p
        join category c
        on p.category_id=c.cid
        <if test="ew!=null">
            <where>
                 ${ew.sqlSegment}
            </where>
        </if>
    </select>

</mapper>

8.在test包下的测试类中测试

package com.azy;

import com.azy.dao.ProductsDao;
import com.azy.dao.UserDao;
import com.azy.pojo.Products;
import com.azy.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

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

@SpringBootTest
class DemoApplicationTests {
    @Resource
    private UserDao userDao;
    @Test
    void contextLoads() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.likeRight("name","_z");
        wrapper.or();
        wrapper.between("age",10,20);
        wrapper.orderByDesc("age");
        wrapper.select("name","age");
        List<User> users = userDao.selectList(wrapper);
        users.forEach(System.out::println);
    }
    @Test
    public void delete(){
        System.out.println(userDao.deleteById(5));
    }
    @Test
    public void insert(){
        User user = new User();
        user.setAge(18);
        user.setName("cxk");
        user.setEmail("123@qq.com");
        System.out.println(userDao.insert(user));
    }
    @Test
    public void update(){
        User user = new User();
        user.setAge(19);
        user.setName("azy");
        user.setEmail("321@qq.com");
        user.setId(6L);
        System.out.println(userDao.updateById(user));
    }
    @Test
    public void selectById(){
        System.out.println(userDao.selectById(4));
    }
    @Test
    public void testPage(){
        Page<User> page = new Page<>(1, 3);//current:当前第几页 size：每页显示条数
        userDao.selectPage(page,null);//把查询分页的结构封装到page对象中
        System.out.println("当前页的记录"+page.getRecords());//获取当前页的记录
        System.out.println("获取总页数"+page.getPages());//获取当前页的总页数
        System.out.println("获取总条数"+page.getTotal());//获取当前页的记录
    }

//    ==============================================================
    @Resource
    private ProductsDao productsDao;
    @Test
    public void testQueryProductById(){
        System.out.println(productsDao.selectById("p008"));
    }

    @Test
    public void testDelete(){
        System.out.println(productsDao.deleteById("p008"));
    }

    @Test
    public void testInsert(){
        Products products = new Products();
        products.setPname("滑板鞋");
        products.setFlag("2");
        products.setPrice(8888);
        products.setCategory_id("c002");
        products.setPid("p009");
        System.out.println(productsDao.insert(products));
    }
    @Test
    public void testUpdate(){
        Products products = new Products();
        products.setPname("篮球");
        products.setFlag("1");
        products.setPrice(188);
        products.setCategory_id("c002");
        products.setPid("p009");
        System.out.println(productsDao.updateById(products));
    }
    @Test
    public void testProductsPage(){
        Page<Products> page = new Page<>(1, 3);//current:当前第几页 size：每页显示条数
        productsDao.selectPage(page,null);//把查询分页的结构封装到page对象中
        System.out.println("当前页的记录"+page.getRecords());//获取当前页的记录
        System.out.println("获取总页数"+page.getPages());//获取当前页的总页数
        System.out.println("获取总条数"+page.getTotal());//获取当前页的记录
    }
    @Test
    public void testProductsPage2(){
        Page<Products> page=new Page<>(1,3);
        QueryWrapper<Products> wrapper=new QueryWrapper<>();
        wrapper.gt("price",1000);
        productsDao.findPage(page,wrapper);
        System.out.println("当前页的记录"+page.getRecords());//获取当前页的记录
        System.out.println("获取总页数"+page.getPages());//获取当前页的记录
        System.out.println("获取总条数"+page.getTotal());//获取当前页的记录
    }
}

9.最后运行测试类

测试完成