Question

我遵循Spring指南来缓存这里 - https://spring.io/guides/gs/caching/，但我的是一个复杂的对象。

对于我的用例，我也有一个Author字段。这是我的整个Book课程。

public class Book {

    private String isbn;
    private String title;
    private Author author;

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

    public String getIsbn() {
        return isbn;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Author getAuthor() {
        return author;
    }

    public void setAuthor(Author author) {
        this.author = author;
    }

    @Override
    public String toString() {
        return String.format("Book{isbn='%s',title='%s',author=%s}", isbn, title, author);
    }
}

现在，我添加了另一种按作者ID获取书籍的方法（假设只返回一本书）。这是我的SimpleBookRepository。

@Component
public class SimpleBookRepository implements BookRepository {

    private List<Book> books;

    public SimpleBookRepository() {
        books = new ArrayList<>();
        books.add(new Book("1234", "Some book", new Author(1, "Author1")));
        books.add(new Book("4567", "Some another book", new Author(2, "Author2")));
    }

    @Override
    @Cacheable("books")
    public Book getByIsbn(String isbn) {
        simulateSlowService();
        return books.stream().filter(o -> o.getIsbn().equals(isbn)).findFirst().orElse(null);
    }

    @Override
    public Book getByAuthorId(int id) {
        simulateSlowService();
        return books.stream().filter(o -> o.getAuthor().getId() == id).findFirst().orElse(null);
    }

    // Don't do this at home
    private void simulateSlowService() {
        try {
            long time = 1000L;
            Thread.sleep(time);
        } catch (InterruptedException e) {
            throw new IllegalStateException(e);
        }
    }
}

现在，我想知道是否可以通过在缓存中查找Book来从缓存中获取Author.id个实例。

这是我的执行和预期行为。

logger.info(".... Fetching books");
logger.info("isbn-1234 -->" + bookRepository.getByIsbn("1234"));   // Gets the original object
logger.info("isbn-4567 -->" + bookRepository.getByIsbn("4567"));   // Gets the original object
logger.info("isbn-1234 -->" + bookRepository.getByIsbn("1234"));   // Should fetch from cache - WORKS FINE
logger.info("isbn-4567 -->" + bookRepository.getByIsbn("4567"));   // Should fetch from cache - WORKS FINE
logger.info("isbn-1234 -->" + bookRepository.getByIsbn("1234"));   // Should fetch from cache - WORKS FINE
logger.info("isbn-1234 -->" + bookRepository.getByIsbn("1234"));   // Should fetch from cache - WORKS FINE

logger.info(".... Fetching books by author");
logger.info("author-1 -->" + bookRepository.getByAuthorId(1));   // Should fetch from cache - NOT WORKING
logger.info("author-2 -->" + bookRepository.getByAuthorId(2));   // Should fetch from cache - NOT WORKING
logger.info("author-1 -->" + bookRepository.getByAuthorId(1));   // Should fetch from cache - NOT WORKING
logger.info("author-2 -->" + bookRepository.getByAuthorId(2));   // Should fetch from cache - NOT WORKING
logger.info("author-1 -->" + bookRepository.getByAuthorId(1));   // Should fetch from cache - NOT WORKING
logger.info("author-1 -->" + bookRepository.getByAuthorId(1));   // Should fetch from cache - NOT WORKING

有没有办法做到这一点，或者我需要另一个缓存用于此目的？

Answer 1

您不需要其他缓存。只需在getByAuthorId方法中指定要缓存该方法的方法。如果不存在，那么每次调用该方法时，Spring都会在缓存中创建一个具有关键作者ID和值Book的条目。只需将@Cacheable("books")添加到您的getByAuthorId方法即可。

现在，在books缓存中，您将拥有包含映射到图书的isbn键和author.id键的条目。

响应我正在寻找的是，如果在调用getByIsbn（）时将实例添加到缓存中，我希望能够在调用getBookByAuthorId（）时使用相同的实例我能想到的解决方案是你手动将条目添加到缓存中，如：

@Component
public class SimpleBookRepository implements BookRepository {

    // inject this bean
    private CacheManager cacheManager;

    @Override
    @Cacheable("books")
    public Book getByIsbn(String isbn) {
        simulateSlowService();
        Book b = books.stream().filter(o -> o.getIsbn().equals(isbn)).findFirst().orElse(null);

        if (b != null && b.getAuthor() != null && b.getAuthor().getId() != null) {
            Cache cache = cacheManager.getCache("books");
            cache.put(b.getAuthor().getId(), b);
        }

        return b;
    }

    // ......
}

在Spring 4中返回缓存中的嵌套对象

1 个答案: