'Controller' 中构造函数的参数 0 需要一个找不到的 'service' 类型的 bean。不工作：添加注释，组件扫描

Question

我正在尝试在我的项目中使用服务和 DTO（尝试了解它们是什么以及应该如何使用它们）。首先，我只有控制器、模型和存储库。后端按预期工作。然后，我想我会使用 DTO 和服务将客户端与 repo 连接起来。但后来我的应用程序无法运行。

项目结构：

MovieController：

package movie_API.movie.controllers;

import movie_API.movie.services.MovieService;
import movie_API.movie.services.beans.MovieDTO;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

import javax.validation.Valid;

@Controller
//@RequestMapping("/something") <- if you want a general something before the other resources
public class MovieController {

    private final MovieService movieService;

    public MovieController(MovieService movieService) {
        this.movieService = movieService;
        System.out.println("build controller");
    }

    @GetMapping("/movies")
    public String movies(Model model) {
        System.out.println("before getting in");
        movieService.showMovies(model);
        System.out.println("after getting in");

        return "movie/movies-all";
    }
 }

Movie模型+相应的构造函数和getter和setter：

package movie_API.movie.models;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Movie {

    private String id;
    private String metascore;
    private String title;
    private String year;
    private String description;
    private String genreId;

MovieRepository：

package movie_API.movie.repositories;

import movie_API.movie.models.Movie;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.ArrayList;
import java.util.List;

@Repository
public interface MovieRepository extends JpaRepository<Movie, String> {

    default ArrayList<String> getGenreNames(List<Movie> movies, GenreRepository genreRepository) {
        ArrayList<String> genreNames = new ArrayList<>();
        String genreIdInMovie;
        String genreName;
        for (Movie m : movies) {
            genreIdInMovie = m.getGenreId();
            genreName = genreRepository.findById(genreIdInMovie).get().getName();
            genreNames.add(genreName);
        }
        return genreNames;
    }
}

电影服务：

package movie_API.movie.services;

import movie_API.movie.models.Movie;
import movie_API.movie.repositories.GenreRepository;
import movie_API.movie.repositories.MovieRepository;
import movie_API.movie.services.beans.MovieDTO;
import org.jvnet.hk2.annotations.Service;
import org.springframework.ui.Model;

import java.util.List;

@Service
public class MovieService {

    private final MovieRepository movieRepository;
    private final GenreRepository genreRepository;
    private List<Movie> movies;
    private Movie movie;

    public MovieService(MovieRepository movieRepository, GenreRepository genreRepository) {
        this.movieRepository = movieRepository;
        this.genreRepository = genreRepository;
    }

    public void showMovies(Model m) {

        m.addAttribute("allMovies", getMovies());
        m.addAttribute("allGenres", getGenreNames());

    }
}

MovieDTO + 对应的构造函数和getter和setter：

package movie_API.movie.services.beans;

import java.io.Serializable;

public class MovieDTO implements Serializable {

    private static final long serialVersionUID = -8040351309785589042L;

    private String id;
    private String metascore;
    private String title;
    private String year;
    private String description;
    private String genreId;

MovieApplication：

package movie_API.movie;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MovieApplication {

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

}

问题是我收到一个错误，说没有没有名为 MovieService 的 bean。

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-08-03 14:41:28.664 ERROR 3504 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in movie_API.movie.controllers.MovieController required a bean of type 'movie_API.movie.services.MovieService' that could not be found.


Action:

Consider defining a bean of type 'movie_API.movie.services.MovieService' in your configuration.


Process finished with exit code 1

研究了这件事后，我发现推荐了几个解决方案：

• 显然，它没有从包中读取bean，因此我尝试通过更改为@SpringBootApplication(scanBasePackages={"movie_API.movie.services"})来专门要求它扫描组件服务。从某种意义上说，这很有效，因为我不再收到“无法启动”错误。但现在的问题是控制器不再被访问。所有调用都由“404 Not found”返回，并且我放入控制器中的打印没有被调用。我尝试将所有包放入列表中，但返回“启动失败”错误。
• 另一个解决方案是仔细检查 MovieRepository 和 MovieService 是否具有注释 @Repository 和 @Service。这些最初也存在，所以没有帮助。
• 我还尝试使 MovieController 中的 MovieService 位于构造函数之外并自动装配。还是同样的问题（没有 bean）。

Answer 1

您在 MovieService 类中导入了错误的服务注释。你应该导入的是：import org.springframework.stereotype.Service;