NIFI-309 adding javadoc

nifi/nifi-api/src/main/java/org/apache/nifi/annotation/documentation/ReadsAttribute.java

@@ -36,6 +36,15 @@ import java.lang.annotation.Target;
 @Retention(RetentionPolicy.RUNTIME)
 @Inherited
 public @interface ReadsAttribute {
+    /**
+     * The FlowFile attribute that is being read
+     * @return
+     */
     public String attribute();
+    
+    /**
+     * The description of how the attribute is being used
+     * @return
+     */
     public String description() default "";
 }

nifi/nifi-api/src/main/java/org/apache/nifi/annotation/documentation/ReadsAttributes.java

@@ -35,5 +35,9 @@ import java.lang.annotation.Target;
 @Retention(RetentionPolicy.RUNTIME)
 @Inherited
 public @interface ReadsAttributes {
+    /**
+     * A list of attributes that may be read
+     * @return
+     */
     public ReadsAttribute[] value();
 }

nifi/nifi-api/src/main/java/org/apache/nifi/annotation/documentation/WritesAttribute.java

@@ -36,6 +36,16 @@ import java.lang.annotation.Target;
 @Retention(RetentionPolicy.RUNTIME)
 @Inherited
 public @interface WritesAttribute {
+    
+    /**
+     * The FlowFile attribute that is being created or updated
+     * @return
+     */
     public String attribute();
+    
+    /**
+     * A description of what is being written to the FlowFile attribute
+     * @return
+     */
     public String description() default "";
 }

nifi/nifi-api/src/main/java/org/apache/nifi/annotation/documentation/WritesAttributes.java

@@ -36,5 +36,9 @@ import java.lang.annotation.Target;
 @Retention(RetentionPolicy.RUNTIME)
 @Inherited
 public @interface WritesAttributes {
+    /**
+     * A list of FlowFile attributes that may be written or updated 
+     * @return
+     */
     public WritesAttribute[] value();
 }