小编Nir*_*ani的帖子

我如何在Kafka Streams API中使用.groupby和多个约束.与下面的Java 8 Streams API示例相同

public void twoLevelGrouping(List<Person> persons) {
     final Map<String, Map<String, List<Person>>> personsByCountryAndCity = persons.stream().collect(
         groupingBy(Person::getCountry,
            groupingBy(Person::getCity)
        )
    );
    System.out.println("Persons living in London: " + personsByCountryAndCity.get("UK").get("London").size());
}

我正在使用 Web API 2.0 的实体框架工作 我试图将 Author Book 查询到自定义对象。

对象是：

public class AuthorBooks
{
    public Author Author;
    public List<BookDetail> BookDetails;

    public AuthorBooks() {
        Author = new Author();
        BookDetails = new List<BookDetail>();
    }
}

public class BookDetail
{
    public BookDetail()
    {
        Book = new Book();
        Category = new Category();
        SubCategory = new SubCategory();

    }

    public Book Book { get; set; }
    public Category Category { get; set; }
    public SubCategory SubCategory { get; set; }


}

这里 Book、Author、Category 和 SubCategory 是实体 …