bean验证不使用kotlin（JSR 380）

Question

@Controller
@RequestMapping("/users")
class UserController {
    @PostMapping
    fun createUser(@Valid user: User, bindingResult: BindingResult): ModelAndView {
        return ModelAndView("someview", "user", user)
    }
}

这是用Kotlin编写的User类：

data class User(
    @field:NotEmpty
    var roles: MutableSet<@NotNull Role> = HashSet()
)

这就是测试：

@Test
internal fun shouldNotCreateNewTestWithInvalidParams() {
    mockMvc.perform(post("/users")
        .param("roles", "invalid role"))
        .andExpect(model().attributeHasFieldErrors("user",  "roles[]"))
}

无效的角色映射为NULL。

@Data // just lombok...
public class User {
    @NotEmpty
    private Set<@NotNull Role> roles = new HashSet<>();
}

private Ljava/util/Set; roles
@Ljavax/validation/constraints/NotEmpty;()
@Ljavax/validation/constraints/NotNull;() : FIELD, 0;
@Ljavax/validation/constraints/NotEmpty;() : FIELD, null

private Ljava/util/Set; roles
@Ljavax/validation/constraints/NotEmpty;()
@Lorg/jetbrains/annotations/NotNull;() // added because roles is not nullable in kotlin. this does not affect validation

这里有一个示例项目，以防您想尝试一些东西。

Answer 1

确保使用jvm Target1.8或更高版本编译kotlin代码，并通过在编译时提供-xemit-jvm-type-annotations来启用此特性。

对于Spring Boot项目，您只需进行以下更改（使用Spring Boot 2.3.3和Kotlin 1.4.0测试）：

1. In your pom set the following property:

   <properties>
       <java.version>11</java.version>
       <kotlin.version>1.4.0</kotlin.version>
   </properties>
   

   <build>
       <plugin>
           <artifactId>kotlin-maven-plugin</artifactId>
           <groupId>org.jetbrains.kotlin</groupId>
           <configuration>
               <args>
                   <arg>-Xjsr305=strict</arg>
                   <arg>-Xemit-jvm-type-annotations</arg>
               </args>
               <compilerPlugins>
                   <plugin>spring</plugin>
               </compilerPlugins>
           </configuration>
           <dependencies>
               <dependency>
                   <groupId>org.jetbrains.kotlin</groupId>
                   <artifactId>kotlin-maven-allopen</artifactId>
                   <version>${kotlin.version}</version>
               </dependency>
           </dependencies>
       </plugin>
   </build>
   

   项目示例

   import javax.validation.Constraint
   import javax.validation.Payload
   import kotlin.annotation.AnnotationTarget.ANNOTATION_CLASS
   import kotlin.annotation.AnnotationTarget.CONSTRUCTOR
   import kotlin.annotation.AnnotationTarget.FIELD
   import kotlin.annotation.AnnotationTarget.FUNCTION
   import kotlin.annotation.AnnotationTarget.TYPE_PARAMETER
   import kotlin.annotation.AnnotationTarget.VALUE_PARAMETER
   import kotlin.reflect.KClass
   
   @MustBeDocumented
   @Constraint(validatedBy = [NoNullElementsValidator::class])
   @Target(allowedTargets = [FUNCTION, FIELD, ANNOTATION_CLASS, CONSTRUCTOR, VALUE_PARAMETER, TYPE_PARAMETER])
   @Retention(AnnotationRetention.RUNTIME)
   annotation class NoNullElements(
       val message: String = "must not contain null elements",
       val groups: Array<KClass<out Any>> = [],
       val payload: Array<KClass<out Payload>> = []
   )
   

   import javax.validation.ConstraintValidator
   import javax.validation.ConstraintValidatorContext
   
   class NoNullElementsValidator : ConstraintValidator<NoNullElements, Collection<Any>> {
       override fun isValid(value: Collection<Any>?, context: ConstraintValidatorContext): Boolean {
           // null values are valid
           if (value == null) {
               return true
           }
           return value.stream().noneMatch { it == null }
       }
   }
   

   data class User(
       @field:NotEmpty
       @field:NoNullElements
       var roles: MutableSet<Role> = HashSet()
   )
   

   现在所有艰难的验证都起作用了，结果的ConstrainViolution略有不同。例如，ElementType和PropertyPath是不同的，如下所示。

   Java：

   

   科特林：