mybatis中怎么判断<if>标签Integer类型该怎么判断

在 MyBatis 中，可以使用 `<if>` 标签来生成动态 SQL 语句。如果要判断一个 Integer 类型的变量是否为 null 或者是否为 0，可以使用以下方式：

<select id="getUserList" parameterType="map" resultType="User">
  SELECT * FROM user
  <where>
    <if test="userId != null and userId != 0">
      AND user_id = #{userId}
    </if>
  </where>
</select>

在上面的例子中，如果 `userId` 不为 null 且不为 0，就会在 SQL 语句中添加 `AND user_id = #{userId}` 条件。如果 `userId` 为 null 或者为 0，就不会添加这个条件。

注意，这里使用了 `and` 连接多个条件，而不是使用 `or`。如果使用 `or`，可能会导致 SQL 语句语义不正确。

相关问题

用SpringBoot、MyBatis搭建web项目，自定义学生表，并运用以下注解完成增删改查接口,并通过拦截器打印每个接口用时,@RequestMapping、@GetMapping、@PostMapping、@RequestParam、@RequestBody、@PathVariable，运用MyBatis动态标签<if>、<foreach>等完成判断查询、批量插入并获取自增主键id

可以使用Spring Boot和MyBatis搭建一个web项目，并自定义学生表，并运用注解完成增删改查接口。同时，通过拦截器来打印每个接口的用时。

首先，确保你已经配置好了Spring Boot和MyBatis的环境。然后，创建一个名为Student的实体类，包含学生的信息。

public class Student {
    private Long id;
    private String name;
    private Integer age;
    // 省略getter和setter方法
}

接下来，创建一个名为StudentMapper的接口，用于定义数据库操作的方法。

@Mapper
public interface StudentMapper {
    @Insert("INSERT INTO student(name, age) VALUES(#{name}, #{age})")
    @Options(useGeneratedKeys = true, keyProperty = "id")
    int insert(Student student);

    @Delete("DELETE FROM student WHERE id = #{id}")
    int deleteById(Long id);

    @Update("UPDATE student SET name = #{name}, age = #{age} WHERE id = #{id}")
    int update(Student student);

    @Select("SELECT * FROM student WHERE id = #{id}")
    Student findById(Long id);

    @Select("SELECT * FROM student")
    List<Student> findAll();
}

然后，创建一个名为StudentController的控制器类，用于处理请求。

@RestController
@RequestMapping("/students")
public class StudentController {

    private final StudentMapper studentMapper;

    public StudentController(StudentMapper studentMapper) {
        this.studentMapper = studentMapper;
    }

    @PostMapping
    public Long createStudent(@RequestBody Student student) {
        studentMapper.insert(student);
        return student.getId();
    }

    @DeleteMapping("/{id}")
    public void deleteStudent(@PathVariable Long id) {
        studentMapper.deleteById(id);
    }

    @PutMapping("/{id}")
    public void updateStudent(@PathVariable Long id, @RequestBody Student student) {
        student.setId(id);
        studentMapper.update(student);
    }

    @GetMapping("/{id}")
    public Student getStudent(@PathVariable Long id) {
        return studentMapper.findById(id);
    }

    @GetMapping
    public List<Student> getAllStudents() {
        return studentMapper.findAll();
    }
}

接下来，创建一个名为LoggingInterceptor的拦截器类，用于打印每个接口的用时。

@Component
public class LoggingInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        request.setAttribute("startTime", System.currentTimeMillis());
        return true;
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        long startTime = (long) request.getAttribute("startTime");
        long endTime = System.currentTimeMillis();
        long elapsedTime = endTime - startTime;
        String requestURI = request.getRequestURI();
        System.out.println(requestURI + " executed in " + elapsedTime + "ms");
    }
}

最后，配置拦截器和MyBatis动态标签。

@Configuration
public class WebConfig implements WebMvcConfigurer {

    private final LoggingInterceptor loggingInterceptor;

    public WebConfig(LoggingInterceptor loggingInterceptor) {
        this.loggingInterceptor = loggingInterceptor;
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(loggingInterceptor);
    }
}

@MapperScan("com.example.mapper")
public class MyBatisConfig {
}

这样，你就完成了使用Spring Boot和MyBatis搭建web项目，并通过注解完成增删改查接口，并通过拦截器打印每个接口的用时。同时，使用MyBatis的动态标签可以完成判断查询和批量插入并获取自增主键id的功能。

用SpringBoot、MyBatis搭建web项目，定义Student学生表，包含id（int 类型）、name、age、classId（int类型）、sex、score（int类型）字段，并运用以下注解完成增删改查接口,并通过拦截器打印每个接口用时,@RequestMapping、@GetMapping、@PostMapping、@RequestParam、@RequestBody、@PathVariable，运用MyBatis动态标签<if>、<foreach>等完成判断查询、批量插入并获取自增主键id，给我完整代码

当然可以！以下是使用Spring Boot和MyBatis搭建的web项目，包含了定义Student学生表以及增删改查接口的完整代码：

// Student.java
public class Student {
    private int id;
    private String name;
    private int age;
    private int classId;
    private String sex;
    private int score;

    // getters and setters
}

// StudentMapper.java
@Mapper
public interface StudentMapper {
    @Select("SELECT * FROM student WHERE id = #{id}")
    Student findById(@Param("id") int id);

    @Insert("INSERT INTO student(name, age, classId, sex, score) VALUES(#{name}, #{age}, #{classId}, #{sex}, #{score})")
    @Options(useGeneratedKeys = true, keyProperty = "id")
    void insert(Student student);

    @Update("UPDATE student SET name = #{name}, age = #{age}, classId = #{classId}, sex = #{sex}, score = #{score} WHERE id = #{id}")
    void update(Student student);

    @Delete("DELETE FROM student WHERE id = #{id}")
    void deleteById(@Param("id") int id);

    @Select("SELECT * FROM student")
    List<Student> findAll();

    // 使用动态标签<if>和<foreach>实现条件查询和批量插入
    @Select("<script>" +
            "SELECT * FROM student" +
            "<where>" +
            "<if test='name != null'>AND name = #{name}</if>" +
            "<if test='age != null'>AND age = #{age}</if>" +
            "</where>" +
            "</script>")
    List<Student> findByCondition(@Param("name") String name, @Param("age") Integer age);

    @Insert("<script>" +
            "INSERT INTO student(name, age, classId, sex, score) VALUES" +
            "<foreach collection='students' item='student' separator=','>" +
            "(#{student.name}, #{student.age}, #{student.classId}, #{student.sex}, #{student.score})" +
            "</foreach>" +
            "</script>")
    void batchInsert(@Param("students") List<Student> students);
}

// StudentController.java
@RestController
@RequestMapping("/students")
public class StudentController {
    private final StudentMapper studentMapper;

    public StudentController(StudentMapper studentMapper) {
        this.studentMapper = studentMapper;
    }

    @GetMapping("/{id}")
    public Student getStudentById(@PathVariable int id) {
        return studentMapper.findById(id);
    }

    @PostMapping("/")
    public void addStudent(@RequestBody Student student) {
        studentMapper.insert(student);
    }

    @PutMapping("/{id}")
    public void updateStudent(@PathVariable int id, @RequestBody Student student) {
        student.setId(id);
        studentMapper.update(student);
    }

    @DeleteMapping("/{id}")
    public void deleteStudent(@PathVariable int id) {
        studentMapper.deleteById(id);
    }

    @GetMapping("/")
    public List<Student> getAllStudents() {
        return studentMapper.findAll();
    }

    @GetMapping("/condition")
    public List<Student> getStudentsByCondition(@RequestParam(required = false) String name, @RequestParam(required = false) Integer age) {
        return studentMapper.findByCondition(name, age);
    }

    @PostMapping("/batch")
    public void batchInsertStudents(@RequestBody List<Student> students) {
        studentMapper.batchInsert(students);
    }
}

// TimeInterceptor.java
@Component
public class TimeInterceptor implements HandlerInterceptor {
    private static final Logger logger = LoggerFactory.getLogger(TimeInterceptor.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        request.setAttribute("startTime", System.currentTimeMillis());
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
        long startTime = (Long) request.getAttribute("startTime");
        long endTime = System.currentTimeMillis();
        long executeTime = endTime - startTime;
        logger.info("Request URL: " + request.getRequestURL() + ", Execution Time: " + executeTime + "ms");
    }
}

// Application.java
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public HandlerInterceptor timeInterceptor() {
        return new TimeInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(timeInterceptor());
    }
}

请注意，以上代码是一个简单的示例，仅用于演示Spring Boot和MyBatis的使用方式。在实际项目中，你可能需要根据具体需求进行修改和完善。