java Javax @NotNull 注释用法
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Javax @NotNull annotation usage
提问by sisanared
I have a simple method to get a list of documents for a given companyId. Here is the method:
我有一个简单的方法来获取给定companyId.这是方法：
@Override
public List<Documents> getDocumentList(@NotNull Integer companyId) {
Company company = new Company(companyId);
return this.documentRepository.findByCompany(company);
}
I wanted to use Javax validation constraints to ensure that the companyIdbeing passed in, is not null. But it seems to not have any effect, as I'm able to pass in a nullvalue, and it flows down to the findByCompanycall on the repository. I also added @Validbefore @NotNullto force validation, but that too didn't do anything.
我想使用 Javax 验证约束来确保companyId传入的不是null.但这似乎没有任何效果，因为我可以传递一个null值，并且它会向下传递到findByCompany存储库上的调用。我@Valid之前还添加@NotNull了强制验证，但这也没有做任何事情。
I could always write a couple of lines to check for a nullvalue, but wanted to use javax.validationannotations to make the code more readable and concise. Is there a way to make the annotations work on method params?
我总是可以写几行来检查一个null值，但想使用javax.validation注释来使代码更具可读性和简洁性。有没有办法让注释对方法参数起作用？
采纳答案by sisanared
To activate parameter validation, simply annotate the class with @Validated
要激活参数验证，只需使用@Validated
import org.springframework.validation.annotation.Validated;
回答by Moshe Arad
From The Java EE 6 Tutorial:
来自 Java EE 6 教程：
The Bean Validation model is supported by constraints in the form of annotations placed on a field, method, or class of a JavaBeanscomponent, such as a managed bean.
Bean 验证模型由放置在JavaBeans组件（例如托管 bean）的字段、方法或类上的注释形式的约束支持。
You should place your validation of a field related to a declared bean, something like this:
您应该对与声明的 bean 相关的字段进行验证，如下所示：
@Entity
@Table(name="users")
public class BackgammonUser {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long userId;
@Column(name="username")
@NotBlank
private String userName;
@NotBlank
private String password;
@NotNull
private Boolean enabled;
}
The BackgammonUser is considered to be a bean.
BackgammonUser 被认为是一个 bean。
回答by JavaBohne
If you @Injecta class with your method, its working as expected.
如果您@Inject使用您的方法创建一个类，它会按预期工作。
@Stateless
public class MyBean{
@Inject
TestClass test;
}
and
和
public class TestClass {
public List<Documents> getDocumentList(@NotNull Integer companyId)
{
//...
}
}
ConstraintViolationExceptionwhen you call your method with null parameter:
ConstraintViolationException当您使用空参数调用您的方法时：
WFLYEJB0034: EJB Invocation failed on component MyBean for method ...:
javax.ejb.EJBException: javax.validation.ConstraintViolationException:
1 constraint violation(s) occurred during method validation.
回答by Balasubramanian
@NotNull Annotation,
@NotNull 注解，
- A method should not return null.
- A variable (like fields, local variables, and parameters) cannot hold null value.
- 方法不应返回 null。
- 变量（如字段、局部变量和参数）不能保存空值。
