structural pattern draft done

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Claudio Maggioni 2022-10-18 11:14:17 +02:00
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@ -70,16 +70,16 @@ instead, as it is the previous LTS version.
An XML dump of the \textit{Pattern4j} analysis results are included in the An XML dump of the \textit{Pattern4j} analysis results are included in the
submission as the file \texttt{analysis.xml}. submission as the file \texttt{analysis.xml}.
\subsection{Singleton pattern}
Lots of false positives for the Singleton pattern. Example,
com.fasterxml.jackson.core.sym.Name1 has a package private constructor and a
public static final instance of it, but reading the documentation the class
represents (short) JSON string literals and therefore is clearly
initialized by client code.
(com.fasterxml.jackson.core omitted for brevity)
\subsection{Comments} \begin{description}
\begin{itemize}
\item Lots of false positives for the Singleton pattern. Example,
com.fasterxml.jackson.core.sym.Name1 has a package private constructor and a
public static final instance of it, but reading the documentation the class
represents (short) JSON string literals and therefore is clearly
initialized by client code.
\begin{description}
\item[sym.Name1, JsonLocation, DefaultIndenter, \item[sym.Name1, JsonLocation, DefaultIndenter,
util.DefaultPrettyPrinter\$FixedSpaceIndenter] not a singleton (detected util.DefaultPrettyPrinter\$FixedSpaceIndenter] not a singleton (detected
cause of "convenient" default instance given as static final field), the cause of "convenient" default instance given as static final field), the
@ -92,8 +92,77 @@ submission as the file \texttt{analysis.xml}.
\item[util.InternCache, io.CharTypes\$AltEscapes] \item[util.InternCache, io.CharTypes\$AltEscapes]
actual singleton, thread-unsafe initialization actual singleton, thread-unsafe initialization
\item[io.ContentReference] like above, but constructor is protected \item[io.ContentReference] like above, but constructor is protected
\end{description} \end{description}
\item TBD
\end{itemize} \subsection{Abstract Factory Pattern}
\textit{Pattern4} detects only two instances of the abstract factory pattern:
\begin{description}
\item[TokenStreamFactory] which indeed is a factory for \textbf{JsonParser} and
\textbf{JsonGenerator} objects, although two overloaded factory methods
exist on this class (one for each class) catering for different combination of
arguments. A concrete implementation of this factory is included in the form
of the \textbf{JsonFactory} class, although other modules may add additional
implementations to cater for different encodings (like the
\texttt{jackson-dataformat-xml} module for XML);
\item[TSFBuilder] which is also a factory for concrete implementations of
\textbf{TokenStreamFactory} to allow slight changes in the serialization and
deserialization rules (e.g. changing the quote character used in JSON keys
from \texttt{"} to \texttt{'}). Like \textbf{TokenStreamFactory}, this class
is only implemented by one class, namely \textbf{JsonFactoryBuilder}, whitin
the scope of this module. And as mentioned previously, this abstract factory
is also likely to be extended by concrete implementations in other
\textit{Jackson} modules.
\end{description}
\subsection{Builder Pattern}
The builder pattern does not seem to be analyzed by
\textit{Pattern4}, as the analysis output does not mention the pattern, even
just to report that no instances of it have been found (as it is the case with
other patterns, e.g. the observer pattern). A manual search in the source code
produced the following results:
\begin{description}
\item[TSFBuilder] is also a builder other than an abstract factory. As mentioned
previously, this class allows to alter slightly the serialization and
deserialization rules used to build outputtting \textbf{JsonFactory}
objects. Each rule is represented by an object or enum instance implementing
the \textbf{util.JacksonFeature} interface. \texttt{TSFBuilder} then
provides several overloaded methods to enable and disable features
represented by the interface. Enabled features are stored in several
bitmask \texttt{protected int} fields, which are then directly accessed by
the constructor of the \textbf{TokenStreamFactory} concrete implementation
to build;
\item[JsonFactoryBuilder] an concrete factory implementation of
\textbf{TSFBuilder} that builds \textbf{JsonFactory} instances;
\item[util.ByteArrayBuilder] provides facilities to build \texttt{byte[]} objects
of varying length, akin to \textbf{StringBuilder} building \textbf{String}
objects. This is not a strict implementation of the builder pattern per se
(as Java arrays do not have a ``real'' constructor),
but it is nevertheless included since the features it exposes (namely
dynamic sizing while building) are decoupled by the underlying (fixed-size)
array representation.
\end{description}
Structural patterns provide flexible ways of combining and connecting components.
- abstract factory
- singleton
- builder
Creational patterns deal with object creation mechanisms in situations where directly using constructors is inconvenient.
- adapter
- bridge
- composite
- facade
- proxy
Behavioral patterns provides way of coordinating object behavior without increasing coupling too much.
- command
- observer
- strategy
- template method
- visitor
\end{document} \end{document}