decorator patter

report.tex

@@ -465,7 +465,7 @@ pattern).  A manual search in the source code produced the following results:
 
 \textit{Pattern4J} found many instances of the adapter pattern, however all but
 one were shown to be false positives by checking the documentation and the code
-using each allegied adaptee.  The matches found are reported and commented
+using each alleged adaptee.  The matches found are reported and commented
 below. Matches are shown in the \textit{[Adapter] $\leftarrow$ [Adaptee]}
 format.
 
@@ -497,16 +497,64 @@ format.
 \end{description}
 
 \subsection{TBD Decorator Pattern}
-Decorator pattern lets you dynamically change the behavior of an object at run
+Decorator pattern lets you dynamically change the behaviour of an object at run
-time by wrapping them in an object of a decorator class.
+time by wrapping them in an object of a decorator class. 
+\textit{Pattern4J} found two instances of the decorator patter, 
+however we are probably in a case of ambiguity because in the documentation of the \textbf{util.JsonParserDelegate}
+is stated that the patter used is a delegation pattern.
+\begin{lstlisting}[language=java,label={lst:jsonparserdelegate}, caption={}]
+/**
+ * Helper class that implements
+ * <a href="http://en.wikipedia.org/wiki/Delegation_pattern">delegation pattern</a> 
+ * for {@link JsonParser},
+ * to allow for simple overridability of basic parsing functionality.
+ * The idea is that any functionality to be modified can be simply
+ * overridden; and anything else will be delegated by default.
+ */
+\end{lstlisting}
+The decorator patter is similar to the delegation patter and the delegation patter is similar to the proxy patter,
+in-fact the delegation patter is also known as ''proxy chains``.
+We have a mismatch in this case because the decorato pattern uses a lot the delegation pattern to accomplish its task,
+so thats why we have a misclassification signalling the decorator pattern and not the proxy patter.
 
 \begin{description}
-  \item[JsonGenerator]
+  \item[util.JsonParserDelegate]
-   TBD
+  is clearly a false positive because the developer stated explicitly the design patter used for the class.
-  \item[JsonParser]
+  This class extends the \textbf{JsonParser} and fully implements the delegation patter.
-  TBD
+  \item[util.JsonGeneratorDelegate]
+  there is no clear statement by the developer if the used designed pattern is different from the one detected by the tool,
+  but we can make an assumption by looking on the authors contribution to the file.
+  \begin{lstlisting}[language=bash, caption={Display the number of commits on a file and sort it by the number of commits.},label=lst:gitcommand]
+  git shortlog -n -s -- $filename$
+  \end{lstlisting}
+  Using the command presente in Listing \ref{lst:gitcommand} we can see the number of authors of a single file 
+  and the result is sorted by the number of commits.
+  By running the command on \textbf{util.JsonParserDelegate} and \textbf{util.JsonGeneratorDelegate} we can clearly see that the top contributor to the file is the same for both the classes, the out-put of the command are presented for the classes in Listing \ref{lst:gitcommandparser} and Listing \ref{lst:gitcommandgenerator}.
+  \begin{lstlisting}[caption={Command of Listing \ref{lst:gitcommand} executed on util.JsonParserDelegate class},label=lst:gitcommandparser]
+  git shortlog -n -s -- JsonParserDelegate.java 
+   33  Tatu Saloranta
+    3  Tatu
+    1  Andrey Somov
+    1  LokeshN
+  \end{lstlisting}
+  \begin{lstlisting}[caption={Command of Listing \ref{lst:gitcommand} executed on util.JsonGeneratorDelegate class}, label=lst:gitcommandgenerator]
+   git shortlog -n -s -- JsonGeneratorDelegate.java 
+   38  Tatu Saloranta
+    2  Cowtowncoder
+    1  Andrey Somov
+    1  Logan Widick
+    1  Martin Steiger
+    1  Oleksandr Poslavskyi
+    1  Q.P.Liu
+    1  Volkan Yaz${\i}$c${\i}$
+  \end{lstlisting}
+  Is more an empirical assumption, we can do a deeper analysis looking at the statistics of modified lines, 
+  but in general the structure of the \textbf{util.JsonGeneratorDelegate} is very similar to the one in \textbf{util.JsonParserDelegate}, 
+  so is more probable that is a false positive.
+  This class extend the \textbf{JsonGenerator} class and it is implementing the delegate patter with a modification.
+  In the constructor of the class we have a boolean parameter \textit{delegateCopyMethods}, 
+  it is used in \textbf{writeObject, writeTree, copyCurrentEvent, copyCurrentStructure} methods to signal if delegate the function call to the delegator or to the super class. 
 \end{description}
-Only in Pattern4J
 
 \subsection{TBD Bridge Pattern}
 TBD