The role of Mapper: automatically generate SQL statements for adding, deleting, modifying and checking, which greatly reduces the operation of a single table
Project startup class:
@SpringBootApplication
@MapperScan(basePackages = {"yiche.com.mapper"})
/*
@MapperScan仅扫描业务接口包，不能扫描本地通用Mapper接口包，
否则报java.lang.ClassCastException: sun.reflect.generics.reflectiveObjects.TypeVariableImpl
cannot be cast to java.lang.Class异常
*/
public class MapperApplication {
public static void main(String[] args){
SpringApplication.run(MapperApplication.class,args);
}
}}
application.properties configuration
#数据库
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/test
spring.datasource.username=root
spring.datasource.password=xx
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
#mybatis&&通用Mapper
#扫描实力类的所在包
mybatis.type-aliases-package=yiche.com.entity
#如果不是纯注解 mapper接口对应的.xml文件
#mybatis.mapper-locations=classpath:mapper/*.xml
#通用mapper的所在接口名称 不只是包名
mapper.mappers=yiche.com.mappers.MyMapper
#数据库
mapper.identity=MYSQL
#分页插件
#pagehelper.helperDialect=mysql
#pagehelper.reasonable=true
#pagehelper.supportMethodsArguments=true
#pagehelper.params=count=countSql
#在格式：logging.level.Mapper类的包=debug 会在控制台打印出sql语句
logging.level.yiche.com.mapper=debug
project directory
mappers is the package where the general mapper is located mapper is the package where its own mapper is located mapper inherits the general mapper
Generic mapper needs to inherit these two interfaces
Generic mapper interface
/*
Mapper接口：基本的增、删、改、查方法
MySqlMapper：针对MySQL的额外补充接口，支持批量插入*/
public interface MyMapper<T> extends Mapper<T>,MySqlMapper<T> {
}own mapper interface
@Mapper
@Component
public interface EmployeeMapper extends MyMapper<Employee>{
//在使用通用Mapper的基础上 下面的都是mybatis注解的方法
@Select("select * from employee")
List<Employee> getAll();
}Controller:
@Controller
public class EmployeeController {
@Autowired
private EmployeeMapper employeeMapper;
@RequestMapping("/test")
@ResponseBody
public String test() {
System.out.println("ok");
return "ok";
}
/*添加 employee*/
@RequestMapping("/add")
@ResponseBody
public String add() {
Employee employee = new Employee("jack", 11000.0, 22);
employeeMapper.insert(employee);
return "ok";
}
/*批量插入 employee*/
@RequestMapping("/bachAdd")
@ResponseBody
public String bachAdd() {
Employee employee = new Employee("jack", 11000.0, 22);
List<Employee> list = new ArrayList<>();
Employee e = new Employee();
/*插入五条*/
for (int i = 0; i < 5; i++) {
e.setName("cici");
e.setSalary(13000.0);
e.setAge(i + 20);
list.add(e);
}
employeeMapper.insertList(list);
return "ok";
}
/*更据唯一主键查询*/
@RequestMapping("/getById")
@ResponseBody
public Employee getById() {
//更据唯一主键 或者唯一编号的查询只返回一个结果
Employee employee = new Employee();
employee.setId(1);
employee = employeeMapper.selectOne(employee);
return employee;
}
/*更据name查询*/
@RequestMapping("/getByName")
@ResponseBody
public List<Employee> selectByName() {
//普通条件查询可含有多条件 查询name=cc age=100的employee
Employee employee = new Employee();
employee.setName("cici");
employee.setAge(100);
List<Employee> list = employeeMapper.select(employee);
return list;
}
/*更新 employee*/
@RequestMapping("/update")
@ResponseBody
public String update() {
//Selective 如果有这个值的话就更新 否则不更新
Employee employee = new Employee(1, "mm", 1.0, 1);
//根据主键更新
int i = employeeMapper.updateByPrimaryKeySelective(employee);
return i + "";
}
/*QBC查询*/
@RequestMapping("/queryByExample1")
@ResponseBody
public List<Employee> queryByExample1(){
Example example=new Example(Employee.class);
Example.Criteria criteria=example.createCriteria();
//名字中含有c的员工 传入实体类的属性值
criteria.andLike("name","%c%");
//传入criteria
return employeeMapper.selectByExample(example);
}
/*QBC查询 传入两个criterial*/
@RequestMapping("/queryByExample2")
@ResponseBody
public List<Employee> queryByExample2(){
Example example=new Example(Employee.class);
Example.Criteria criteria=example.createCriteria();
Example.Criteria criteria2=example.createCriteria();
criteria.andLike("name","%c%");
//名字中含有c的员工 传入实体类的属性值
criteria2.andLike("name","%m%");
//加入第二个criterial
example.or(criteria2);
//传入criteria
return employeeMapper.selectByExample(example);
}
/*QBC查询 去重*/
@RequestMapping("/queryByExample3")
@ResponseBody
public List<Employee> queryByExample3(){
Example example=new Example(Employee.class);
Example.Criteria criteria=example.createCriteria();
//id 大于4的员工
criteria.andGreaterThan("id","4");
//排序
example.orderBy("name").asc();
//去重
example.setDistinct(true);
//select name,age from employee
example.selectProperties("id","name","age");
//传入criteria
return employeeMapper.selectByExample(example);
}
/*以上是通用Mapper的方法*/
/*......................................................................*/
/*下面是mybatis自定义sql语句的方法*/
@RequestMapping("/getAll")
@ResponseBody
public List<Employee> getAll() {
/*select * from employee*/
return employeeMapper.getAll();
}
}pom.xml
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.0</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<!--mapper-->
<dependency>
<groupId>tk.mybatis</groupId>
<artifactId>mapper-spring-boot-starter</artifactId>
<version>1.1.0</version>
</dependency>
<!--pagehelper-->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.0.25</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>