在开始操作之前先了解一下QueryWrapper
QueryWrapper(LambdaQueryWrapper) 和 UpdateWrapper(LambdaUpdateWrapper) 的父类 用于生成 sql 的 where 条件, entity 属性也用于生成 sql 的 where 条件
eq:等于
like:模糊查询
ne:不等于
gt:大于
lt:小于
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</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>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<!--阿里巴巴连接池 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.20</version>
</dependency>
<!--mybatis-plus依赖 -->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.3.2</version>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.1.3</version>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.15</version>
</dependency>
创建poji实体类Car
@TableName("car")//和数据库的表相对应
@Data//自动添加get/set方法
public class Car {
//主键自增
@TableId(type = IdType.AUTO)
private Integer id;
private String type;
private String brand;
private Double price;
创建Mapper接口继承BaseMapper
@Mapper
public interface AutoMapper extends BaseMapper<Car> {
}
创建ServiceImpl类
@Service
public class AutoServiceImpl implements AutoService {
@Autowired(required = false)
private AutoMapper autoMapper;
}
在serviceImpl类中查询所有方法
//查询所有
@Override
public List<Car> findAll() {
return autoMapper.selectList(null);
}
在ServiceImpl类中添加增加方法
public void addCar(Car car)
{
autoMapper.insert(car);
}
在ServiceImpl中添加根据id查询的方法
//根据id查询
@Override
public List<Car> findCarById(Integer id) {
QueryWrapper<Car> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("id",id);
return autoMapper.selectList(queryWrapper);
}