運行時的Java註釋

Question

存在以下類，該類由預定義的UUID組成，該UUID描述數據庫的可能實例。

public class Predefined { 
    @NotNull 
    @Size(min = 1, max = 25) 
    public UUID phone = UUID.fromString("47b58767-c0ad-43fe-8e87-c7dae489a4f0"); 

    @NotNull 
    @Size(min = 1, max = 40) 
    public UUID company = UUID.fromString("f9a1e8f4-b8c0-41f2-a626-49c11da8d5c2"); 
} 

這些值被接收爲一個密鑰對值槽web服務：然後將它們付諸HashMap中。

47b58767-c0ad-43fe-8e87-c7dae489a4f0 = 00112233445566778899

f9a1e8f4-b8c0-41f2-a626-49c11da8d5c2 = someVirtualCompnayName

當我收到的UUID我知道我創造的一個實例預定義的類，然後得到的在預定義類，即提出的註解：

Annotation[] annon = field.getDeclaredAnnotations(); 

現在我需要檢查這些註釋agains，我從網絡服務得到了值，即「00112233445566778899」和「一些VirtualCompnayName「在運行時

這可能嗎？ 我是例如覆蓋JSR 303

中特別有趣，不久，爲什麼我有這樣的結構： 的DAO，@Repository類有不同的結構，即

接觸

contact_attrbute

contact_attibute_type

其中databse「contact_attibute_type」是指「公司」和「電話」。第二個表，即「contact_attrbute」意味着「公司」和「電話」的實際值。

現在，我需要一種方法來驗證這些值，然後再將它們寫入休眠狀態，因此我得到「public UUID phone」，然後嘗試將這些約束應用於從用戶獲得的實際值，即「+00112233445566778899 」。

Answer 1

我會發布完整的代碼，我拿出來驗證你的測試用例（包括簡單的可執行演示）：

註釋：

package annotations; 

import java.lang.annotation.ElementType; 
import java.lang.annotation.Retention; 
import java.lang.annotation.RetentionPolicy; 
import java.lang.annotation.Target; 

@Target({ElementType.FIELD }) 
@Retention(RetentionPolicy.RUNTIME) 
public @interface NotNull 
{ 

} 

import java.lang.annotation.ElementType; 
import java.lang.annotation.Retention; 
import java.lang.annotation.RetentionPolicy; 
import java.lang.annotation.Target; 

@Target({ElementType.FIELD }) 
@Retention(RetentionPolicy.RUNTIME) 
public @interface Size 
{ 
    int min() default 0; 
    int max(); 
} 

預定義類：

public class Predefined 
{ 
    @NotNull 
    @Size(min = 1, max = 25) 
    public UUID phone; 

    @NotNull 
    @Size(min = 1, max = 40) 
    public UUID company; 

    public Predefined(UUID phone, UUID company) 
    { 
     this.phone = phone; 
     this.company = company; 
    } 
} 

迭代通過聲明字段並檢查其註釋和字段/值映射的驗證程序類：

public class PredefinedValidator 
{ 
    public boolean validate(Predefined predefined, Map<UUID, String> mappings) 
    { 
     if (predefined == null) 
      return false; 

     for (Field field :predefined.getClass().getDeclaredFields()) 
     { 
      if (field.getType().equals(UUID.class)) 
      { 
       try 
       { 
        Annotation[] annotations = field.getDeclaredAnnotations(); 
        UUID uuid = (UUID)field.get(predefined); 
        if (!this.validateField(uuid, annotations, mappings)) 
         return false; 
       } 
       catch (IllegalArgumentException | IllegalAccessException ex) 
       { 
        Logger.getLogger(PredefinedValidator.class.getName()).log(Level.SEVERE, null, ex); 
       } 
      } 
     } 
     return true; 
    } 

    private boolean validateField(UUID field, Annotation[] annotations, Map<UUID, String> mapping) 
    { 
     boolean containsSize = false; 
     boolean containsNotNull = false; 
     int minSize = -1; 
     int maxSize = -1; 

     // fetch which annotations are available for the provided field 
     for (Annotation annotation : annotations) 
     { 
      if (annotation instanceof Size) 
      { 
       containsSize = true; 
       Size size = (Size)annotation; 
       minSize = size.min(); 
       maxSize = size.max(); 
      } 
      else if (annotation instanceof NotNull) 
       containsNotNull = true; 
     } 

     // check if the provided value is null and an annotatition for @NotNull 
     // is set 
     if (field == null && containsNotNull) 
      return false; 

     if (containsSize) 
     { 
      // get the value of the mapped UUID which we are going to validate 
      String value = mapping.get(field); 
      if (value == null && containsNotNull) 
       return false; 
      else if (value == null) 
       return true; 

      // check if the length of the value matches 
      if (value.length() <= minSize || value.length() >= maxSize) 
       return false; 
     } 

     // passed all tests 
     return true; 
    } 
} 

最後但並非最不重要一個簡單的演示：

public static void main(String ... args) 
{ 
    Map<UUID, String> mappings = new HashMap<>(); 
    mappings.put(UUID.fromString("47b58767-c0ad-43fe-8e87-c7dae489a4f0"), "+00112233445566778899"); 
    mappings.put(UUID.fromString("f9a1e8f4-b8c0-41f2-a626-49c11da8d5c2"), "someVirtualCompnayName");  

    Predefined predefined = new Predefined(
      UUID.fromString("47b58767-c0ad-43fe-8e87-c7dae489a4f0"), 
      UUID.fromString("f9a1e8f4-b8c0-41f2-a626-49c11da8d5c2")); 
    Predefined predefined2 = new Predefined(
      UUID.randomUUID(), 
      UUID.fromString("f9a1e8f4-b8c0-41f2-a626-49c11da8d5c2")); 
    Predefined predefined3 = new Predefined(
      null, 
      UUID.fromString("f9a1e8f4-b8c0-41f2-a626-49c11da8d5c2")); 
    PredefinedValidator validator = new PredefinedValidator(); 

    System.out.println("predefined is valid: "+validator.validate(predefined, mappings)); 
    System.out.println("predefined is valid: "+validator.validate(predefined2, mappings)); 
    System.out.println("predefined is valid: "+validator.validate(predefined3, mappings)); 

    mappings.put(UUID.fromString("f9a1e8f4-b8c0-41f2-a626-49c11da8d5c2"), "someVirtualCompnayNamesomeVirtualCompnayNamesomeVirtualCompnayNamesomeVirtualCompnayName"); 
    System.out.println("predefined is valid: "+validator.validate(predefined, mappings)); 
} 

HTH