Hibernate-如何映射表示集合的对象

Question

Sorry by the too basic question, I have no experience with Hibernate and trying to map this classes and not found an example that maps an object to another object that represents a list.

The Keywords attribute used to be a list of String, like:

List<String> keywords; 

but I encapsulate it on a class to add more specialized behavior, following the book "Clean Code" from Bob C. Martin. But I have no idea how to map it as if it had the same behavior when the list was in own class.

@Entity
@Table(name = "produtos")
public class Product {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;

    @Embedded
    private BarCode barCode;

    @ManyToOne
    private Manufacturer manufacturer;

    private String description;
    //How to map?
    private Keywords keywords;

}


public class Keywords {

    private List<String> wordList = new ArrayList<>();

    public void add(String keyword) {
        wordList.add(keyword);
    }

    public boolean contains(String keyword) {
        return wordList.contains(keyword);
    }


    public static Keywords ofPhrase(String phrase) {
        Keywords keywords = new Keywords();
        StringTokenizer tokenizer = new StringTokenizer(phrase, " ", false);
        while (tokenizer.hasMoreTokens()) {
            String t = tokenizer.nextToken();
            if (t.length() > 4 && !keywords.contains(t)) {
                keywords.add(t);
            }
        }
        return keywords;
    }

    public List<String> getWordList() {
        return wordList;
    }
}

Answer 1

Looks like you split this member into a separate class mainly in order to add the ofPhrase() static method.

I would suggest to have that method in in its own, non-JPA class, named something like KeywordTokenizer, and also to make it non-static. This will allow you to test the tokenizer logic in isolation and also to mock the ofPhrase() method when testing other classes that use it. I think Uncle Bob would endorse this too.

More generally - in my humble experience, JPA objects should be used just to define the data structure - all that JPA annotation stuff is enough complexity to merit a class of its own. Use "service" type classes such as the KeywordTokenizer suggested above to include any added logic.