（Java）的if語句優化

Question

需要優化驗證碼：

 

import java.lang.annotation.Annotation; 
import java.lang.reflect.Method; 
import javax.ws.rs.CookieParam; 
import javax.ws.rs.FormParam; 
import javax.ws.rs.HeaderParam; 
import javax.ws.rs.MatrixParam; 
import javax.ws.rs.Path; 
import javax.ws.rs.PathParam; 
import javax.ws.rs.QueryParam; 
... 

private String valueParam(Annotation a) { 

    String value = ""; 

    if (a.annotationType() == QueryParam.class) { 
     value = ((QueryParam) a).value(); 
    } else if (a.annotationType() == PathParam.class) { 
     value = ((PathParam) a).value(); 
    } else if (a.annotationType() == CookieParam.class) { 
     value = ((CookieParam) a).value(); 
    } else if (a.annotationType() == HeaderParam.class) { 
      value = ((HeaderParam) a).value(); 
    } else if (a.annotationType() == MatrixParam.class) { 
      value = ((MatrixParam) a).value(); 
    } else if (a.annotationType() == FormParam.class) { 
      value = ((FormParam) a).value(); 
    } 

    return value; 
} 

SonarQube埋怨這種方法的複雜性。

改變並不那麼容易，因爲我們需要在獲取其值之前檢查註釋類型！

注意：陷阱位於沒有value（）方法的Annotation接口上。

P.S. ：根據此代碼對這個example（代碼示例4）

Answer 1

如果反射是一種選擇，你總是可以做這樣的事情

public class Test { 

    @PathParam("path") 
    public Response doSomething() { 
     return null; 
    } 

    public static void main(String[] args) throws Exception { 
     Method method = Test.class.getMethod("doSomething"); 
     Annotation annotation = method.getAnnotations()[0]; 
     System.out.println(getValue(annotation)); 
    } 

    private static String getValue(Annotation annotation) throws Exception { 
     Class<?> type = annotation.annotationType(); 
     if (!ANNOTATIONS.contains(type)) { 
      throw new IllegalArgumentException("..."); 
     } 
     String value = (String) type.getMethod("value").invoke(annotation); 
     return value; 
    } 

    private static final Set<Class<?>> ANNOTATIONS; 

    static { 
     Set<Class<?>> annotations = new HashSet<>(); 
     annotations.add(HeaderParam.class); 
     annotations.add(QueryParam.class); 
     annotations.add(PathParam.class); 
     annotations.add(MatrixParam.class); 
     annotations.add(CookieParam.class); 
     annotations.add(FormParam.class); 
     ANNOTATIONS = Collections.unmodifiableSet(annotations); 
    } 
}