GenericsAdd（捕获）在Set中不能应用于（ConstraintViolation）

Question

我有以下代码：

UniqueConstraintViolation violation = new UniqueConstraintViolationImpl();
Set<? extends javax.validation.ConstraintViolation> violations = new HashSet<UniqueConstraintViolation>();
violations.add(violation);
throw new javax.validation.ConstraintViolationException(violations);

其中UniqueConstraintViolation是接口扩展javax.validation.ConstraintViolation和UniqueConstraintViolationImpl是类实现的UniqueConstraintViolation

编译时出现以下错误

java:42：错误：找不到适用于add（UniqueConstraintViolation）冲突的方法。添加（违规）；^方法集合。add（CAP#1）不适用（参数不匹配；UniqueConstraintViolation无法转换为CAP#1）方法集。如果CAP#1是新类型变量，则add（CAP#1）不适用（参数不匹配；UniqueConstraintViolation无法转换为CAP#1）：CAP#1从捕获扩展ConstraintViolation？扩展ConstraintViolation C:\workspace\zcts travel\crud rest\src\main\java\ru\zcts\crud\AbstractResource。java:43：错误：不兼容的类型：无法将集合转换为集合

                                                                ^   where CAP#1 is a fresh type-variable:
CAP#1 extends ConstraintViolation from capture of ? extends ConstraintViolation

我只是想传入javax.validation.ConstraintViolationException构造函数集合与我自己的javax.validation.ConstraintViolation的实现。

Answer 1

Set<? extends javax.validation.ConstraintViolation> violations = new HashSet<UniqueConstraintViolation>();
violations.add(violation);

您不能将null以外的任何内容添加到voilations，因为它使用？扩展javax.validation.ConstraintViolation。

阅读这里：Java数组列表泛型

Answer 2

因此，有了您的限制：

interface UniqueConstraintViolation extends ConstraintViolation<YourClass> {

}

public class UniqueConstraintViolationImpl implements UniqueConstraintViolation {
    /* your impl here */
}

这将编译：

UniqueConstraintViolation violation = new UniqueConstraintViolationImpl();

Set<UniqueConstraintViolation> violations = new HashSet<UniqueConstraintViolation>();
violations.add(violation);
throw new ConstraintViolationException(violations);