SpringブートWebアプリケーション：throwing java.lang.IllegalStateException：この応答にgetOutputStream（）が既に呼び出されています。

Question

SpringブートWebアプリケーションでは、java.lang.IllegalStateException: getOutputStream()がこの応答にすでに呼び出されています。

は、私は私のクラスにアクセスしようとすると

@Entity 
public class Book { 
    @Id 
    @GeneratedValue 
    private Long id; 
    private String isbn; 
    private String title; 
    private String description; 
    @ManyToOne 
    private Author author; 
    @ManyToOne 
    private Publisher publisher; 
    @ManyToMany 
    private List<Reviewer> reviewers; 

    protected Book() { 
    } 

    public Book(String isbn, String title, Author author, Publisher publisher) { 
     this.isbn = isbn; 
     this.title = title; 
     this.author = author; 
     this.publisher = publisher; 
    } 

    public Long getId() { 
     return id; 
    } 

    public void setId(Long id) { 
     this.id = id; 
    } 

    public String getIsbn() { 
     return isbn; 
    } 

    public void setIsbn(String isbn) { 
     this.isbn = isbn; 
    } 

    public String getTitle() { 
     return title; 
    } 
} 

とテストクラス

public class StartupRunner implements CommandLineRunner { 
    protected final Log logger = LogFactory.getLog(getClass()); 

    @Autowired 
    private BookRepository bookRepository; 

    @Autowired 
    private AuthorRepository authorRepository; 

    @Autowired 
    private PublisherRepository publisherRepository; 

    @Override 
    public void run(String... args) throws Exception { 
     logger.info("Number of books: " + bookRepository.count()); 
     Author author = new Author("Alex", "Antonov"); 
     author = authorRepository.save(author); 
     Publisher publisher = new Publisher("Packt"); 
     publisher = publisherRepository.save(publisher); 
     Book book = new Book("978-1-78528-415-1", "Spring Boot Recipes", author, publisher); 
     bookRepository.save(book); 
    } 

    @Scheduled(initialDelay = 1000, fixedRate = 10000) 
    public void run() { 

     logger.info("Number of books: " + bookRepository.count()); 
    } 

} 

メインクラス

public class StartupRunner implements CommandLineRunner { 
    protected final Log logger = LogFactory.getLog(getClass()); 

    @Autowired 
    private BookRepository bookRepository; 

    @Autowired 
    private AuthorRepository authorRepository; 

    @Autowired 
    private PublisherRepository publisherRepository; 

    @Override 
    public void run(String... args) throws Exception { 
     logger.info("Number of books: " + bookRepository.count()); 
     Author author = new Author("Alex", "Antonov"); 
     author = authorRepository.save(author); 
     Publisher publisher = new Publisher("Packt"); 
     publisher = publisherRepository.save(publisher); 
     Book book = new Book("978-1-78528-415-1", "Spring Boot Recipes", author, publisher); 
     bookRepository.save(book); 
    } 

    @Scheduled(initialDelay = 1000, fixedRate = 10000) 
    public void run() { 

     logger.info("Number of books: " + bookRepository.count()); 
    } 

} 

のように見える@ManyToOne, @ManyToMany, のORMの関係でメモリデータベースh2を持っていますデータhttp://localhost:8080/books/978-1-78528-415-1 例外をスローする

Answer 1

理想的なソリューションではありませんが、マッピングされた子に賢明なフェッチタイプを追加した後、私は私の仕事を得ることができました。 fetch=FetchType.EAGER）

@ManyToMany (fetch=FetchType.EAGER) 
private List<Reviewer> reviewers;