将枚举类型用作@rolesallowed批注的值参数

我认为你使用枚举的方法不会奏效。我发现如果我更改了 STUDENT_ROLE 将最后一个示例中的字段转换为常量字符串,而不是表达式:

public enum RoleType { 
  ...
  public static final String STUDENT_ROLE = "STUDENT";
  ...
}

然而,这意味着枚举值不会在任何地方使用,因为您将在注释中使用字符串常量。

在我看来,如果你 RoleType 类只包含一组静态最终字符串常量。

为了了解您的代码没有编译的原因,我研究了 Java Language Specification (JLS)。JLS annotations 声明对于参数类型为的批注 T 价值 V ,

如果 T 是原始类型或 String , V 是常量表达式。

一 constant expression 其中包括:

窗体的限定名 类型名 . 标识符 指常量变量

和A constant variable 定义为

基本类型或类型的变量 弦 ,它是最终的,并用编译时常量表达式初始化

这个怎么样?

public enum RoleType {
    STUDENT(Names.STUDENT),
    TEACHER(Names.TEACHER),
    DEANERY(Names.DEANERY);

    public class Names{
        public static final String STUDENT = "Student";
        public static final String TEACHER = "Teacher";
        public static final String DEANERY = "Deanery";
    }

    private final String label;

    private RoleType(String label) {
        this.label = label;
    }

    public String toString() {
        return this.label;
    }
}

在注释中,你可以像

@RolesAllowed(RoleType.Names.DEANERY)
public void update(User p) { ... }

一个小问题是,对于任何修改,我们需要在两个地方进行更改。但由于它们在同一个文件中,所以不太可能丢失。作为回报,我们得到了不使用原始字符串和避免复杂机制的好处。

或者这听起来很愚蠢?:)

这里有一个使用附加接口和元注释的解决方案。我已经包含了一个实用程序类来帮助进行反射,以从一组注释中获取角色类型,并对其进行了一些测试:

/**
 * empty interface which must be implemented by enums participating in
 * annotations of "type" @RolesAllowed.
 */
public interface RoleType {
    public String toString();
}

/** meta annotation to be applied to annotations that have enum values implementing RoleType. 
 *  the value() method should return an array of objects assignable to RoleType*.
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ANNOTATION_TYPE})
public @interface RolesAllowed { 
    /* deliberately empty */ 
}

@RolesAllowed
@Retention(RetentionPolicy.RUNTIME)
@Target({TYPE, METHOD})
public @interface AcademicRolesAllowed {
    public AcademicRoleType[] value();
}

public enum AcademicRoleType implements RoleType {
    STUDENT, TEACHER, DEANERY;
    @Override
    public String toString() {
        return name();
    }
}


public class RolesAllowedUtil {

    /** get the array of allowed RoleTypes for a given class **/
    public static List<RoleType> getRoleTypesAllowedFromAnnotations(
            Annotation[] annotations) {
        List<RoleType> roleTypesAllowed = new ArrayList<RoleType>();
        for (Annotation annotation : annotations) {
            if (annotation.annotationType().isAnnotationPresent(
                    RolesAllowed.class)) {
                RoleType[] roleTypes = getRoleTypesFromAnnotation(annotation);
                if (roleTypes != null)
                    for (RoleType roleType : roleTypes)
                        roleTypesAllowed.add(roleType);
            }
        }
        return roleTypesAllowed;
    }

    public static RoleType[] getRoleTypesFromAnnotation(Annotation annotation) {
        Method[] methods = annotation.annotationType().getMethods();
        for (Method method : methods) {
            String name = method.getName();
            Class<?> returnType = method.getReturnType();
            Class<?> componentType = returnType.getComponentType();
            if (name.equals("value") && returnType.isArray()
                    && RoleType.class.isAssignableFrom(componentType)) {
                RoleType[] features;
                try {
                    features = (RoleType[]) (method.invoke(annotation,
                            new Object[] {}));
                } catch (Exception e) {
                    throw new RuntimeException(
                            "Error executing value() method in "
                                    + annotation.getClass().getCanonicalName(),
                            e);
                }
                return features;
            }
        }
        throw new RuntimeException(
                "No value() method returning a RoleType[] type "
                        + "was found in annotation "
                        + annotation.getClass().getCanonicalName());
    }

}

public class RoleTypeTest {

    @AcademicRolesAllowed({DEANERY})
    public class DeaneryDemo {

    }

    @Test
    public void testDeanery() {
        List<RoleType> roleTypes = RolesAllowedUtil.getRoleTypesAllowedFromAnnotations(DeaneryDemo.class.getAnnotations());
        assertEquals(1, roleTypes.size());
    }
}

我通过添加注释解决了这个问题 @RoleTypesAllowed 以及添加元数据源。如果只有一个枚举类型需要支持,那么这个方法非常有效。有关多个枚举类型,请参见anomolos的文章。

在下面 RoleType 是我的角色枚举。

@Documented
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface RoleTypesAllowed {
  RoleType[] value();
}

然后我在Spring中添加了以下元数据源…

@Slf4j
public class CemsRolesAllowedMethodSecurityMetadataSource
    extends AbstractFallbackMethodSecurityMetadataSource {

  protected Collection<ConfigAttribute> findAttributes(Class<?> clazz) {
    return this.processAnnotations(clazz.getAnnotations());
  }

  protected Collection<ConfigAttribute> findAttributes(Method method, Class<?> targetClass) {
    return this.processAnnotations(AnnotationUtils.getAnnotations(method));
  }

  public Collection<ConfigAttribute> getAllConfigAttributes() {
    return null;
  }

  private List<ConfigAttribute> processAnnotations(Annotation[] annotations) {
    if (annotations != null && annotations.length != 0) {
      List<ConfigAttribute> attributes = new ArrayList();

      for (Annotation a : annotations) {
        if (a instanceof RoleTypesAllowed) {
          RoleTypesAllowed ra = (RoleTypesAllowed) a;
          RoleType[] alloweds = ra.value();
          for (RoleType allowed : alloweds) {
            String defaultedAllowed = new RoleTypeGrantedAuthority(allowed).getAuthority();
            log.trace("Added role attribute: {}", defaultedAllowed);
            attributes.add(new SecurityConfig(defaultedAllowed));
          }
          return attributes;
        }
      }
    }
    return null;
  }
}