保存不适用于双向 @ManyToMany

我有两个实体 ：
-Trader.java
Stockmarket.java

我正在使用@ManyToMany 注释，包含股票市场列表的交易者保存对我有用，但包含交易者列表的股票市场保存不起作用。

交易者.java

import lombok.*;

import javax.persistence.*;
import java.util.List;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "trader")
public class Trader {

    @Id
    @GeneratedValue
    @Column(name = "trader_id")
    private Long id;

    @Column(name = "trader_name")
    private String traderName;

    @ManyToMany(cascade = { CascadeType.ALL })
    @JoinTable(name = "TRADER_STOCKMARKET",
            joinColumns = { @JoinColumn(name = "trader_id") },
            inverseJoinColumns = { @JoinColumn(name = "stockmarket_id") })
    private List<Stockmarket> stockmarket;

}

股票市场.java

import lombok.*;

import javax.persistence.*;
import java.util.List;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "stockmarket")
public class Stockmarket{

    @Id
    @GeneratedValue
    @Column(name = "stockmarket_id")
    private Long id;

    @Column(name = "stockmarket_name")
    private String stockmarketName;

    @ManyToMany(mappedBy="stockmarket")
    private List<Trader> traders;

}

控制器：

（MySQL 已经有 2 个交易者和 2 个交易所。）

            Stockmarket stockmarket3 = new Stockmarket();
            stockmarket3.setStockmarketName("Marvel");
            List<Trader> allTraders = manyToManyBiService.findAllTraders();

            System.out.println("\n\n\n finally " + allTraders.toString() + "\n\n\n ");
            stockmarket3.setTraders(allTraders);

            manyToManyBiService.saveStockmarket(stockmarket3);

额外的东西，如果它们有助于解决问题

多对多BiService.java：

@Service
public class ManyToManyBiService {

    @Autowired
    StockmarketRepository stockmarketRepository;

    @Autowired
    TraderRepository traderRepository;

    public void saveTrader(Trader trader){
        traderRepository.save(trader);
    }

    public void saveStockmarket(Stockmarket stockmarket){
        stockmarketRepository.save(stockmarket);
    }

    public Stockmarket findByNameStockmarket(String name){
        return stockmarketRepository.findByStockmarketName(name);
    }

    public List<Stockmarket> findAllStockmarket(){
        return stockmarketRepository.findAll();
    }

    public List<Trader> findAllTraders(){
        return traderRepository.findAll();
    }
}

StockmarketRepository 和 TraderRepository 是扩展 CrudRepository 的接口。