@GetMapping("/{id}") 泛型用不了

泛型是 Java 语言的一个特性，用于在编译时期提供类型安全检查。在你提供的 `@GetMapping("/{id}")` 注解中，并不包含泛型的使用。

`@GetMapping("/{id}")` 是 Spring Framework 提供的注解，用于将 HTTP GET 请求映射到指定的处理方法上。其中的 `{id}` 表示一个路径参数，用于接收请求中的 id 值。

如果你想在方法中使用泛型，可以在方法的参数类型或返回值类型上进行泛型声明。例如：

@GetMapping("/{id}")
public ResponseEntity<Student> getStudentById(@PathVariable Long id) {
    // 根据 id 查询学生信息
    Student student = studentService.findById(id);

    // 返回包含学生信息的 ResponseEntity
    return ResponseEntity.ok(student);
}

在上述示例中，`ResponseEntity<Student>` 使用了泛型，表示返回的响应体中包含一个 Student 对象。

相关问题

import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.*; import java.util.List; @RestController @RequestMapping("/transportation") public class TransportationController<TransportationRepository> { @Autowired private TransportationRepository transportationRepository; @PostMapping("/create") public ResponseEntity<?> createTransportation(@RequestBody TransportationDto transportationDto) { Transportation transportation = new Transportation(); transportation.setFrom(transportationDto.getFrom()); transportation.setTo(transportationDto.getTo()); transportation.setDepartureTime(transportationDto.getDepartureTime()); transportation.setArrivalTime(transportationDto.getArrivalTime()); transportationRepository.save(transportation); return ResponseEntity.ok("Transportation created successfully"); } @GetMapping("/all") public ResponseEntity<?> getAllTransportations() { List<Transportation> transportations = transportationRepository.findAll(); return ResponseEntity.ok(transportations); } @GetMapping("/{id}") public ResponseEntity<?> getTransportationById(@PathVariable Long id) { Transportation transportation = transportationRepository.findById(id).orElse(null); if (transportation == null) { return ResponseEntity.notFound().build(); } return ResponseEntity.ok(transportation); } }这段代码中所有transportationDto的方法报错，比如Cannot resolve method 'getFrom' in 'TransportationDto'，请帮我修改

根据报错信息来看，TransportationDto中缺少getFrom等方法，所以需要在TransportationDto中添加相应的getter方法，例如：

public class TransportationDto {
    private String from;
    private String to;
    private LocalDateTime departureTime;
    private LocalDateTime arrivalTime;

    public String getFrom() {
        return from;
    }

    public void setFrom(String from) {
        this.from = from;
    }

    public String getTo() {
        return to;
    }

    public void setTo(String to) {
        this.to = to;
    }

    public LocalDateTime getDepartureTime() {
        return departureTime;
    }

    public void setDepartureTime(LocalDateTime departureTime) {
        this.departureTime = departureTime;
    }

    public LocalDateTime getArrivalTime() {
        return arrivalTime;
    }

    public void setArrivalTime(LocalDateTime arrivalTime) {
        this.arrivalTime = arrivalTime;
    }
}

同时，TransportationController中依赖的TransportationRepository需要声明泛型类型，例如：

@RestController
@RequestMapping("/transportation")
public class TransportationController {
    @Autowired
    private TransportationRepository transportationRepository;

    @PostMapping("/create")
    public ResponseEntity<?> createTransportation(@RequestBody TransportationDto transportationDto) {
        Transportation transportation = new Transportation();
        transportation.setFrom(transportationDto.getFrom());
        transportation.setTo(transportationDto.getTo());
        transportation.setDepartureTime(transportationDto.getDepartureTime());
        transportation.setArrivalTime(transportationDto.getArrivalTime());
        transportationRepository.save(transportation);
        return ResponseEntity.ok("Transportation created successfully");
    }

    @GetMapping("/all")
    public ResponseEntity<?> getAllTransportations() {
        List<Transportation> transportations = transportationRepository.findAll();
        return ResponseEntity.ok(transportations);
    }

    @GetMapping("/{id}")
    public ResponseEntity<?> getTransportationById(@PathVariable Long id) {
        Transportation transportation = transportationRepository.findById(id).orElse(null);
        if (transportation == null) {
            return ResponseEntity.notFound().build();
        }
        return ResponseEntity.ok(transportation);
    }
}

希望这能够帮助到你。

如果用spring框架,result后面还要加泛型吗

在使用 Spring 框架时，返回值的泛型可选，取决于具体的需求和使用场景。如果你需要在控制器方法中返回一个对象，可以直接指定对象类型作为返回值类型，而不需要使用泛型。例如：

@GetMapping("/user/{id}")
public User getUser(@PathVariable Long id) {
    return userService.getUserById(id);
}

如果你需要返回一个集合类型，可以指定集合类型的泛型。例如：

@GetMapping("/users")
public List<User> getUsers() {
    return userService.getAllUsers();
}

需要注意的是，如果你在返回值中使用了泛型，Spring 框架会根据泛型类型自动进行序列化和反序列化。因此，在使用泛型时，需要确保序列化和反序列化的正确性。