当我用MapStruct将List尝试到Dto时，出现了错误

Question

public class Account {

    private String accountId
    private List<Transaction> transactions = new ArrayList<>();

public abstract class Transaction {
    private double amount;

public class AccountEntity extends BaseEntity{
    @OneToMany
    private List<TransactionEntity> transactions;

public class TransactionEntity extends BaseEntity{
    @Id
    private String transactionId;
    private double amount;
    private String type;

    @ManyToOne
    @JoinColumn(name = "accountId", referencedColumnName = "accountNumber")
    private AccountEntity account;

@Mapper(componentModel = "spring")
public interface AccountMapper {
    
    Account AccountEntityToAccount(AccountEntity accountEntity);

    AccountEntity AccountToAccountEntity(Account account);

My AccountEntityToAccount方法出现错误，返回类型Transaction是抽象类或接口。提供非抽象/非接口结果类型或工厂方法。AccountEntityToAccount（AccountEntity AccountEntity）；

我怎样才能解决这个问题。我的事务类应该是抽象的，我无法更改抽象关键字

Answer 1

问题是

private List<Transaction> transactions = new ArrayList<>();

如果您有另一个扩展Transaction的类，则将其用于列表中的泛型。否则，Mapstuct现在应该如何为该列表创建哪个类

Answer 2

添加一个方法，从提供的事务实体中创建正确的事务。

阅读代码时，您可能希望拥有如下内容：

java prettyprint-override">Transaction fromTransactionEntity(TransactionEntity entity){
  if (entity == null){
    return null;
  }
  if ( entity.getType().equals("something") ) {
    return toSomethingTransaction(entity);
  }
  if ( entity.getType().equals("other") ) {
    return toOtherTransaction(entity);
  }
  throw new IllegalStateException("unsupported transaction found, cannot instantiate object.");
}

SomethingTransaction toSomethingTransaction(TransactionEntity entity);

OtherTransaction toOtherTransaction(TransactionEntity entity);

在另一个方向上，你可能想做同样的事情。（当 1.5.0 发布时，您可以使用@SubclassMapping，而不是手动编写当前处于 1.5.0.RC1 阶段的实例。

TransactionEntity toTransactionEntity(Transaction transaction){
  if (transaction == null){
    return null;
  }
  if (transaction instanceof SomethingTransaction){
    return fromSomethingTransaction(transaction);
  }
  if (transaction instanceof OtherTransaction){
    return toOtherTransaction(entity);
  }
  throw new IllegalStateException("unsupported transaction found, cannot store it.");
}

@Mapping( target = "type", constant = "something" )
TransactionEntity fromSomethingTransaction(SomethingTransaction transaction);

@Mapping( target = "type", constant = "other" )
TransactionEntity fromOtherTransaction(OtherTransaction transaction);