在Spring Boot中自动将HashSet转换为连接字符串

import org.springframework.core.convert.converter.Converter;
import java.util.HashSet;

public class HashSetToStringConverter implements Converter<HashSet<String>, String> {

    @Override
    public String convert(HashSet<String> hashSet) {
        if (hashSet == null || hashSet.isEmpty()) {
            return "";
        }
        return String.join(",", hashSet);
    }
}

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class Application {

    @Bean
    public HashSetToStringConverter hashSetToStringConverter() {
        return new HashSetToStringConverter();
    }

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

import org.springframework.core.convert.converter.Converter;
import org.springframework.data.jpa.convert.threeten.Jsr310JpaConverters;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
@Table(name = "user")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Convert(converter = HashSetToStringConverter.class)
    private HashSet<String> interests;

    // getters and setters
}