运行时的Java注释

Question

存在以下类，该类由预定义的UUID组成，该UUID描述数据库的可能实例。

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"); 
} 

这些值被接收为一个密钥对值槽web服务：然后将它们付诸HashMap中。

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

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

当我收到的UUID我知道我创造的一个实例预定义的类，然后得到的在预定义类，即提出的注解：

Annotation[] annon = field.getDeclaredAnnotations(); 

现在我需要检查这些注释agains，我从网络服务得到了值，即“00112233445566778899”和“一些VirtualCompnayName“在运行时

这可能吗？ 我是例如覆盖JSR 303

中特别有趣，不久，为什么我有这样的结构： 的DAO，@Repository类有不同的结构，即

接触

contact_attrbute

contact_attibute_type

其中databse“contact_attibute_type”是指“公司”和“电话”。第二个表，即“contact_attrbute”意味着“公司”和“电话”的实际值。

现在，我需要一种方法来验证这些值，然后再将它们写入休眠状态，因此我得到“public UUID phone”，然后尝试将这些约束应用于从用户获得的实际值，即“+00112233445566778899 ”。

Answer 1

我会发布完整的代码，我拿出来验证你的测试用例（包括简单的可执行演示）：

注释：

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(); 
} 

预定义类：

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; 
    } 
} 

迭代通过声明字段并检查其注释和字段/值映射的验证程序类：

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; 
    } 
} 

最后但并非最不重要一个简单的演示：

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