Mybatis plus案例

前言

• 当表名为user时，会多生成2个实体类
  
  
• 正常情况下生成的类
  
• 测试是否可以直接在当前mybatis代码生成器的项目中开发
  
• 启动项目后测试，发现当前项目只能用来生成代码
  
• 即使项目添加所需的开发依赖，启动项目后依然无法找到接口path，或者报依赖冲突的错误
  
• 解决方案，参考gitee/chnx/cloud/seata/seata01项目重新构建一个项目，将生成的代码复制到新项目中
• 案例要求

# 使用代码生成器生成代码
# 工具类：返回对象工具类、分页对象工具类
# 使用分页、分页连接查询
# 传入参数为对象、集合、集合对象

案例一

• 使用mybatis代码生成器生成代码
• 使用的mybatis代码生成器项目案例是gitee/chenx/mybatis-geneator
• 未使用该方式开发的原因：

# 在该代码生成器项目中生成代码后，无法直接在该项目上继续开发
# 将生成的代码复制到1个新建的项目，需修改每个类的路径，已经违背了使用代码生成器的初衷

案例二

• 案例地址
• 使用mybatis plus代码生成器生成代码
• 首先参考案例二生成代码
• 生成代码后，将pom.xml中的依赖删除，将application.properties中的配置删除，并重命名为application.yml
• 注释掉测试类中的main方法
• 之后参考构建mybatis plus项目
• 将maven配置为3.6.1或IDE自带的maven，否者某些依赖无法导入
• 导入如下依赖

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    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3.1</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>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.2.6</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.73</version>
        </dependency>
        <!-- 以下为代码生成器中的依赖 -->
        <!-- freemarker模板和velocity模板依赖，后面配置的时候会2选其1 -->
        <dependency>
            <groupId>org.freemarker</groupId>
            <artifactId>freemarker</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.velocity</groupId>
            <artifactId>velocity-engine-core</artifactId>
            <version>2.1</version>
        </dependency>
        <!-- swagger -->
        <dependency>
            <groupId>io.swagger</groupId>
            <artifactId>swagger-annotations</artifactId>
            <version>1.5.20</version>
        </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>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <version>3.1.0</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.22.1</version>
                <configuration>
                    <skipTests>true</skipTests>
                </configuration>
            </plugin>
        </plugins>
    </build>

• 编写yml

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server:
  port: 8080

spring:
  application:
    name: mybatisplus
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://192.168.0.102:3306/dbtest?characterEncoding=utf-8&serverTimezone=UTC
    username: root
    password: 123456
  mvc:
    view:
      suffix: ".html"

mybatis:
  configuration:
    map-underscore-to-camel-case: true
  mapperLocations: classpath:mapper/*.xml

logging:
  level:
    com:
      chnq:
        mybatisplus: debug

• 配置启动类

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

@SpringBootApplication
@MapperScan("com.chnq.mybatisplus.mapper")
public class MybatisplusApplication {

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

}

• 编写mybatis plus 配置类

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import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;
 
@EnableTransactionManagement
@Configuration
@MapperScan("com.chnq.mybatisdemo.mapper")
public class MybatisPlusConfig {
 
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
 
}

• 检查实体类中的注解配置
• 检查mapper层注解
• 检查service层注解，并注入mapper
• 检查controller层注解，并注入mapper、service
• 在controller层调用mapper对象和service对象中的方法进行测试

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@RestController
@RequestMapping("/user")
public class UserController {

    @Resource
    UserService userService;

    @Resource
    UserMapper userMapper;

    // 测试
    // 调用service层接口查询所有
    @GetMapping("/getUsers")
    public String getUserList(){
        List<User> user = userService.list();
        System.out.println(user);
        return RespResult.success("获取成功！", user);
    }

    // 调用mapper层接口查询所有
    @GetMapping("/getUsers2")
    @ResponseBody
    public String getUserTest(){
        List<User> users = userMapper.selectList(null);
        users.forEach(user-> System.out.println("user = " + user));
        return RespResult.success("获取成功！", users);
    }

}

• 在service层和controller层注入对象时，无法注入，是因为之前使用代码生成器的依赖被删除了，之后重新配置了mybatis plus开发所需的依赖，导致还有缓存

• 解决方案参考
  

• 配置工具类

• 编写req

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import lombok.Data;
import java.io.Serializable;
import java.math.BigDecimal;

@Data
public class UserBookReq implements Serializable {
    private static final long serialVersionUID = 1L;

    // 用户名
    private String username;

    // 性别
    private String sex;

    // 书名
    private String bookname;

    // 作者
    private String author;

    // 价格
    private BigDecimal price;

    // 当前页
    private int pageNum = 1;

    // 每页条数
    private int pageSize = 5;

}

• 编写resp

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import com.fasterxml.jackson.annotation.JsonFormat;
import lombok.Data;
import java.io.Serializable;
import java.math.BigDecimal;
import java.util.Date;

@Data
public class UserBookResp implements Serializable {
    private static final long serialVersionUID = 1L;

    private Integer uId;

    private String username;

    private String password;

    private String sex;

    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date birthday;

    private Integer bId;

    private String bookname;

    private String author;

    private BigDecimal price;

}

• 编写mapper

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@Mapper
public interface UserMapper extends BaseMapper<User> {

    // 连接查询
    List<User> findUser();

    // 分页查询
    List<User> findUsers();

    // 分页连接查询
    List<UserBookResp> getUserBook(UserBookReq userBookReq);

}

• 编写mapper.xml

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<?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.chnq.mybatisplus.mapper.UserMapper">

    <!-- 连接查询 -->
    <select id="findUser" resultType="com.chnq.mybatisplus.entity.User">
        select u.id, u.username, u.password, u.sex, u.birthday, b.id, b.bookname, b.author, b.price from user u inner join book b on u.username = b.author;
    </select>
    <!-- 连接查询：第3条开始的3条数据 -->
    <select id="findUsers" resultType="com.chnq.mybatisplus.entity.User">
        SELECT * FROM user LIMIT 2,3;
    </select>

    <!-- 分页连接查询 -->
    <select id="getUserBook" resultType="com.chnq.mybatisplus.resp.UserBookResp">
        select u.id, u.username, u.password, u.sex, u.birthday, b.id, b.bookname, b.author, b.price
        from user u inner join book b on u.username = b.author
        where
        <if test="username != null">
            u.username = #{username}
        </if>
        <if test="sex != null">
            or u.sex = #{sex}
        </if>
        <if test="bookname != null">
            or b.bookname = #{bookname}
        </if>
        <if test="author != null">
            or b.author = #{author}
        </if>
        <if test="price != null">
            or b.price = #{price}
        </if>
        <if test="pageNum !=null and pageSize != null">
            limit #{pageNum}, #{pageSize}
        </if>
    </select>

</mapper>

• 编写service

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public interface UserService extends IService<User> {

    // 连接查询
    List<User> findUser();

    // 分页查询
    List<User> findUsers();

    // 分页连接查询
    List<UserBookResp> getUserBook(UserBookReq userBookReq);

}

• 编写service实现类

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@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

    @Resource
    private UserMapper userMapper;

    @Override
    public List<User> findUser() {
        return userMapper.findUser();
    }

    @Override
    public List<User> findUsers() {
        return userMapper.findUsers();
    }

    @Override
    public List<UserBookResp> getUserBook(UserBookReq userBookReq) {
        return userMapper.getUserBook(userBookReq);
    }

}

• 编写controller

点击查看详情

@RestController
@RequestMapping("/user")
public class UserController {

    @Resource
    UserMapper userMapper;

    // 连接查询
    @GetMapping("/userList")
    @ResponseBody
    public String UserList(){
        List<User> users = userMapper.findUser();
        users.forEach(user-> System.out.println("user = " + user));
        return RespResult.success("获取成功！", users);
    }

    // 分页查询
    @GetMapping("/usersList")
    @ResponseBody
    public String UsersList(){
        List<User> users = userMapper.findUsers();
        users.forEach(user-> System.out.println("user = " + user));
        return RespResult.success("获取成功！", users);
    }

    // 分页连接查询
    @RequestMapping(value = "/listAll", method = RequestMethod.POST)
    public List<UserBookResp> listAll(@RequestBody UserBookReq req){
        return userService.getUserBook(req);
    }

}

• 测试