Jakarta Bean Validation：如何为CreditTransfer的sender设置条件地址约束

现有类结构 #

public class CreditTransfer {
  private String messageId;
  private Party sender;
  private Party receiver;
  private BigDecimal amount;

  //getters and setters
}
public class Party {
  private String name;
  private PostalAddress address;
  private Account account;

  //getters and setters
}

问题描述 #

是否可以在不给Party类添加全局字段约束的前提下，仅对CreditTransfer类中的sender嵌套对象验证其address属性必须为null，而receiver的address属性则必须非null？直接在Party类的address字段标注@Null会导致所有Party实例的address都必须为null，无法满足receiver的要求。

可行方案 #

方案一：分组验证（推荐） #

通过分组验证可以实现差异化规则，且无需修改Party类的全局约束：

1. 在Party类中为address字段添加分组约束，并定义对应的分组接口：

import jakarta.validation.constraints.Null;
import jakarta.validation.constraints.NotNull;

public class Party {
  private String name;
  
  // 仅在SenderValidationGroup分组下要求address为null
  @Null(groups = SenderValidationGroup.class)
  // 仅在ReceiverValidationGroup分组下要求address非null
  @NotNull(groups = ReceiverValidationGroup.class)
  private PostalAddress address;
  
  private Account account;

  //getters and setters
  
  // 定义两个验证分组接口
  public interface SenderValidationGroup {}
  public interface ReceiverValidationGroup {}
}

2. 在CreditTransfer类中，对sender和receiver字段开启嵌套验证，并指定对应的验证分组：

import jakarta.validation.Valid;
import jakarta.validation.groups.ConvertGroup;
import jakarta.validation.groups.Default;

public class CreditTransfer {
  private String messageId;
  
  @Valid
  // 将默认分组转换为SenderValidationGroup，验证sender的address必须为null
  @ConvertGroup(from = Default.class, to = Party.SenderValidationGroup.class)
  private Party sender;
  
  @Valid
  // 将默认分组转换为ReceiverValidationGroup，验证receiver的address必须非null
  @ConvertGroup(from = Default.class, to = Party.ReceiverValidationGroup.class)
  private Party receiver;
  
  private BigDecimal amount;

  //getters and setters
}

这种方式不会给Party类添加全局约束，仅在CreditTransfer的不同字段验证时应用对应规则，完全满足需求。

方案二：类内方法级验证 #

如果不想修改Party类，也可以直接在CreditTransfer内通过方法验证实现规则：

import jakarta.validation.Valid;
import jakarta.validation.constraints.AssertTrue;

public class CreditTransfer {
  private String messageId;
  
  @Valid
  private Party sender;
  
  @Valid
  private Party receiver;
  
  private BigDecimal amount;

  // 验证sender的address必须为null
  @AssertTrue(message = "sender的address必须为null")
  public boolean isSenderAddressNull() {
    return sender == null || sender.getAddress() == null;
  }

  // 验证receiver的address必须非null
  @AssertTrue(message = "receiver的address不能为空")
  public boolean isReceiverAddressNotNull() {
    return receiver != null && receiver.getAddress() != null;
  }

  //getters and setters
}

这种方式无需改动Party类，直接在CreditTransfer内部完成差异化验证。

内容的提问来源于stack exchange，提问作者Federico