Difference between revisions of ""Simple" Factory (padrão de desenho)"

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(→‎Utilizando Informação de Tipos em Tempo de Execução)
(→‎Utilização de Método Independente da Linguagem)
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== Utilização de Método Independente da Linguagem ==
 
== Utilização de Método Independente da Linguagem ==
  
 +
<java5>
 +
        public void readImportFile(String name) throws IOException {
 +
                BufferedReader reader = new BufferedReader(new FileReader(name));
 +
                String line;
 +
                while ((line = reader.readLine()) != null) {
 +
                        String[] fields = line.split("\\|");
 +
                        try {
 +
                                registerFromFields(fields);
 +
                        } catch (UnknownDataException e) {
 +
                                System.err.printf("WARNING: unknown data %s\n", e.getMessage());
 +
                                e.printStackTrace();
 +
                        } catch (PublicationExistsException e) {
 +
                                e.printStackTrace();
 +
                        } catch (UnknownAgentException e) {
 +
                                e.printStackTrace();
 +
                        } catch (ClientExistsException e) {
 +
                                e.printStackTrace();
 +
                        } catch (InvalidIdentifierException e) {
 +
                                e.printStackTrace();
 +
                        }
 +
                }
 +
                reader.close();
 +
        }
 +
</java5>
  
 +
<java5>
 +
        public void registerFromFields(String[] fields) throws UnknownDataException,
 +
                        PublicationExistsException, UnknownAgentException, ClientExistsException,
 +
                        InvalidIdentifierException {
 +
                // Regular expression pattern to match an agent.
 +
                Pattern patAgent = Pattern.compile("^(PERSON|ORGANIZATION)");
 +
                // Regular expression pattern to match a message.
 +
                Pattern patMessage = Pattern.compile("^(MESSAGE)");
 +
                // Regular expression pattern to match a publication.
 +
                Pattern parPublication = Pattern.compile("^(IMAGE|NOTE|URI)");
 +
                // Regular expression pattern to match a publication.
 +
                Pattern parConnection = Pattern.compile("^(CONNECTION)");
 +
 +
                if (patAgent.matcher(fields[0]).matches()) {
 +
                        registerAgent(fields);
 +
                } else if (patMessage.matcher(fields[0]).matches()) {
 +
                        registerMessage(fields);
 +
                } else if (parPublication.matcher(fields[0]).matches()) {
 +
                        registerPublication(fields);
 +
                } else if (parConnection.matcher(fields[0]).matches()) {
 +
                        registerConnection(fields);
 +
                } else {
 +
                        throw new UnknownDataException(fields[0]);
 +
                }
 +
        }
 +
</java5>
 +
 +
<java5>
 +
        /**
 +
        * @param fields
 +
        *            0 - type; 1 - id/null; 2 - agent; other - pub-specific
 +
        * @throws PublicationExistsException
 +
        *            we throw it because we may be called from outside (i.e., we
 +
        *            are not responsible for communicating the problem to the
 +
        *            end-user)
 +
        * @throws UnknownAgentException
 +
        *            we throw it because we may be called from outside (i.e., we
 +
        *            are not responsible for communicating the problem to the
 +
        *            end-user)
 +
        * @throws UnknownDataException
 +
        *            we throw it because we may be called from outside (i.e., we
 +
        *            are not responsible for communicating the problem to the
 +
        *            end-user)
 +
        */
 +
        public void registerPublication(String... fields) throws PublicationExistsException,
 +
                        UnknownAgentException, UnknownDataException {
 +
                int pubId = (fields[1] != null) ? Integer.parseInt(fields[1]) : getUUID();
 +
                int agtId = Integer.parseInt(fields[2]);
 +
                if (fields[0].equals("IMAGE")) {
 +
                        Image image = new Image(pubId, fields[3], fields[4]);
 +
                        Agent owner = fetchAgent(agtId);
 +
                        owner.addPublication(pubId, image);
 +
                        setLastUUID(pubId);
 +
                        changed();
 +
                } else if (fields[0].equals("NOTE")) {
 +
                        TextNote note = new TextNote(pubId, fields[3], fields[4]);
 +
                        Agent owner = fetchAgent(agtId);
 +
                        owner.addPublication(pubId, note);
 +
                        setLastUUID(pubId);
 +
                        changed();
 +
                } else if (fields[0].equals("URI")) {
 +
                        URI uri = new URI(pubId, fields[3], fields[4]);
 +
                        Agent owner = fetchAgent(agtId);
 +
                        owner.addPublication(pubId, uri);
 +
                        setLastUUID(pubId);
 +
                        changed();
 +
                } else {
 +
                        throw new UnknownDataException(fields[0]);
 +
                }
 +
        }
 +
</java5>
 +
 +
<java5>
 +
        /**
 +
        * Format: type|id-or-null|name|email|phone
 +
        *
 +
        * @param fields
 +
        * @throws ClientExistsException
 +
        *            we throw it because we may be called from outside (i.e., we
 +
        *            are not responsible for communicating the problem to the
 +
        *            end-user)
 +
        * @throws UnknownDataException
 +
        *            we throw it because we may be called from outside (i.e., we
 +
        *            are not responsible for communicating the problem to the
 +
        *            end-user)
 +
        */
 +
        @SuppressWarnings("nls")
 +
        public void registerAgent(String... fields) throws ClientExistsException, UnknownDataException {
 +
                int id = (fields[1] != null) ? Integer.parseInt(fields[1]) : getUUID();
 +
                if (fields[0].equals("PERSON")) {
 +
                        Person person = new Person(id, fields[2], fields[3], fields[4]);
 +
                        addAgent(id, person);
 +
                        setLastUUID(id);
 +
                        changed();
 +
                } else if (fields[0].equals("ORGANIZATION")) {
 +
                        Organization organization = new Organization(id, fields[2], fields[3], fields[4]);
 +
                        addAgent(id, organization);
 +
                        setLastUUID(id);
 +
                        changed();
 +
                } else {
 +
                        throw new UnknownDataException(fields[0]);
 +
                }
 +
        }
 +
</java5>
 +
 +
<java5>
 +
        /**
 +
        * This method DOES NOT check message permissions when registering messages
 +
        * with agents inboxes/outboxes. It must be private.
 +
        *
 +
        * @param fields
 +
        * @throws UnknownAgentException
 +
        * @throws UnknownDataException
 +
        * @throws InvalidIdentifierException
 +
        */
 +
        @SuppressWarnings("nls")
 +
        private void registerMessage(String... fields) throws UnknownAgentException,
 +
                        UnknownDataException, InvalidIdentifierException {
 +
                if (fields[0].equals("MESSAGE")) {
 +
                        int msgId = Integer.parseInt(fields[1]);
 +
                        Sender sender = fetchAgent(Integer.parseInt(fields[2]));
 +
                        List<Recipient> recipients = new ArrayList<Recipient>();
 +
                        for (String recipientId : fields[3].split(",")) {
 +
                                Recipient recipient = fetchAgent(Integer.parseInt(recipientId));
 +
                                recipients.add(recipient);
 +
                        }
 +
                        assertValidIdentifier(msgId);
 +
                        EmailMessage message = new EmailMessage(msgId, fields[2], sender, fields[3],
 +
                                        recipients, fields[4], fields[5], "", null);
 +
                        sendMessage(message);
 +
                        setLastUUID(msgId);
 +
                        changed();
 +
                } else {
 +
                        throw new UnknownDataException(fields[0]);
 +
                }
 +
        }
 +
</java5>
 +
 +
=== Connections between agents ===
 +
 +
Unrelated exceptions that are detected in this function are simply forwarded.
 +
 +
<java5>
 +
        private void registerConnection(String[] fields) throws NumberFormatException,
 +
                        UnknownAgentException, UnknownDataException {
 +
                if (fields[0].equals("CONNECTION")) {
 +
                        Agent a1 = fetchAgent(Integer.parseInt(fields[1]));
 +
                        Agent a2 = fetchAgent(Integer.parseInt(fields[2]));
 +
                        boolean a1Accepting = (Integer.parseInt(fields[3]) != 0);
 +
                        boolean a2Accepting = (Integer.parseInt(fields[4]) != 0);
 +
                        a1.addConnection(new Connection(a1, a2, a1Accepting, a2Accepting));
 +
                        a2.addConnection(new Connection(a2, a1, a2Accepting, a1Accepting));
 +
                        changed();
 +
                } else {
 +
                        throw new UnknownDataException(fields[0]);
 +
                }
 +
        }
 +
</java5>
  
 
== Utilização de Informação de Tipos em Tempo de Execução ==
 
== Utilização de Informação de Tipos em Tempo de Execução ==

Revision as of 12:10, 14 November 2013

Programação com Objectos
Introduction
Creation and Destruction
Inheritance & Composition
Abstraction & Polymorphism
Code Organization
Java Topics
Inner Classes
Enumerations
Data Structures
Exceptions
Input/Output
RTTI
Other Topics
JUnit Tests
UML Topics
Design Patterns
"Simple" Factory
Composite & Visitor
Command
Strategy & State
Template Method
Observer
Abstract Factory
Decorator & Adapter
Façade (aka Facade)

O padrão "simple" factory fornece uma forma de criar objectos a partir de uma descrição externa.

O processo de criação de objectos a partir de texto é um processo semelhante à compilação e implica interpretar esse texto e construir a semântica.

Utilização de Método Independente da Linguagem

<java5> 

       public void readImportFile(String name) throws IOException {
               BufferedReader reader = new BufferedReader(new FileReader(name));
               String line;
               while ((line = reader.readLine()) != null) {
                       String[] fields = line.split("\\|");
                       try {
                               registerFromFields(fields);
                       } catch (UnknownDataException e) {
                               System.err.printf("WARNING: unknown data %s\n", e.getMessage());
                               e.printStackTrace();
                       } catch (PublicationExistsException e) {
                               e.printStackTrace();
                       } catch (UnknownAgentException e) {
                               e.printStackTrace();
                       } catch (ClientExistsException e) {
                               e.printStackTrace();
                       } catch (InvalidIdentifierException e) {
                               e.printStackTrace();
                       }
               }
               reader.close();
       }

</java5>

<java5> 

       public void registerFromFields(String[] fields) throws UnknownDataException,
                       PublicationExistsException, UnknownAgentException, ClientExistsException,
                       InvalidIdentifierException {
               // Regular expression pattern to match an agent.
               Pattern patAgent = Pattern.compile("^(PERSON|ORGANIZATION)");
               // Regular expression pattern to match a message.
               Pattern patMessage = Pattern.compile("^(MESSAGE)");
               // Regular expression pattern to match a publication.
               Pattern parPublication = Pattern.compile("^(IMAGE|NOTE|URI)");
               // Regular expression pattern to match a publication.
               Pattern parConnection = Pattern.compile("^(CONNECTION)");

               if (patAgent.matcher(fields[0]).matches()) {
                       registerAgent(fields);
               } else if (patMessage.matcher(fields[0]).matches()) {
                       registerMessage(fields);
               } else if (parPublication.matcher(fields[0]).matches()) {
                       registerPublication(fields);
               } else if (parConnection.matcher(fields[0]).matches()) {
                       registerConnection(fields);
               } else {
                       throw new UnknownDataException(fields[0]);
               }
       }

</java5>

<java5> 

       /**
        * @param fields
        *            0 - type; 1 - id/null; 2 - agent; other - pub-specific
        * @throws PublicationExistsException
        *             we throw it because we may be called from outside (i.e., we
        *             are not responsible for communicating the problem to the
        *             end-user)
        * @throws UnknownAgentException
        *             we throw it because we may be called from outside (i.e., we
        *             are not responsible for communicating the problem to the
        *             end-user)
        * @throws UnknownDataException
        *             we throw it because we may be called from outside (i.e., we
        *             are not responsible for communicating the problem to the
        *             end-user)
        */
       public void registerPublication(String... fields) throws PublicationExistsException,
                       UnknownAgentException, UnknownDataException {
               int pubId = (fields[1] != null) ? Integer.parseInt(fields[1]) : getUUID();
               int agtId = Integer.parseInt(fields[2]);
               if (fields[0].equals("IMAGE")) {
                       Image image = new Image(pubId, fields[3], fields[4]);
                       Agent owner = fetchAgent(agtId);
                       owner.addPublication(pubId, image);
                       setLastUUID(pubId);
                       changed();
               } else if (fields[0].equals("NOTE")) {
                       TextNote note = new TextNote(pubId, fields[3], fields[4]);
                       Agent owner = fetchAgent(agtId);
                       owner.addPublication(pubId, note);
                       setLastUUID(pubId);
                       changed();
               } else if (fields[0].equals("URI")) {
                       URI uri = new URI(pubId, fields[3], fields[4]);
                       Agent owner = fetchAgent(agtId);
                       owner.addPublication(pubId, uri);
                       setLastUUID(pubId);
                       changed();
               } else {
                       throw new UnknownDataException(fields[0]);
               }
       }

</java5>

<java5> 

       /**
        * Format: type|id-or-null|name|email|phone
        * 
        * @param fields
        * @throws ClientExistsException
        *             we throw it because we may be called from outside (i.e., we
        *             are not responsible for communicating the problem to the
        *             end-user)
        * @throws UnknownDataException
        *             we throw it because we may be called from outside (i.e., we
        *             are not responsible for communicating the problem to the
        *             end-user)
        */
       @SuppressWarnings("nls")
       public void registerAgent(String... fields) throws ClientExistsException, UnknownDataException {
               int id = (fields[1] != null) ? Integer.parseInt(fields[1]) : getUUID();
               if (fields[0].equals("PERSON")) {
                       Person person = new Person(id, fields[2], fields[3], fields[4]);
                       addAgent(id, person);
                       setLastUUID(id);
                       changed();
               } else if (fields[0].equals("ORGANIZATION")) {
                       Organization organization = new Organization(id, fields[2], fields[3], fields[4]);
                       addAgent(id, organization);
                       setLastUUID(id);
                       changed();
               } else {
                       throw new UnknownDataException(fields[0]);
               }
       }

</java5>

<java5> 

       /**
        * This method DOES NOT check message permissions when registering messages
        * with agents inboxes/outboxes. It must be private.
        * 
        * @param fields
        * @throws UnknownAgentException
        * @throws UnknownDataException
        * @throws InvalidIdentifierException
        */
       @SuppressWarnings("nls")
       private void registerMessage(String... fields) throws UnknownAgentException,
                       UnknownDataException, InvalidIdentifierException {
               if (fields[0].equals("MESSAGE")) {
                       int msgId = Integer.parseInt(fields[1]);
                       Sender sender = fetchAgent(Integer.parseInt(fields[2]));
                       List<Recipient> recipients = new ArrayList<Recipient>();
                       for (String recipientId : fields[3].split(",")) {
                               Recipient recipient = fetchAgent(Integer.parseInt(recipientId));
                               recipients.add(recipient);
                       }
                       assertValidIdentifier(msgId);
                       EmailMessage message = new EmailMessage(msgId, fields[2], sender, fields[3],
                                       recipients, fields[4], fields[5], "", null);
                       sendMessage(message);
                       setLastUUID(msgId);
                       changed();
               } else {
                       throw new UnknownDataException(fields[0]);
               }
       }

</java5>

Connections between agents

Unrelated exceptions that are detected in this function are simply forwarded.

<java5> 

       private void registerConnection(String[] fields) throws NumberFormatException,
                       UnknownAgentException, UnknownDataException {
               if (fields[0].equals("CONNECTION")) {
                       Agent a1 = fetchAgent(Integer.parseInt(fields[1]));
                       Agent a2 = fetchAgent(Integer.parseInt(fields[2]));
                       boolean a1Accepting = (Integer.parseInt(fields[3]) != 0);
                       boolean a2Accepting = (Integer.parseInt(fields[4]) != 0);
                       a1.addConnection(new Connection(a1, a2, a1Accepting, a2Accepting));
                       a2.addConnection(new Connection(a2, a1, a2Accepting, a1Accepting));
                       changed();
               } else {
                       throw new UnknownDataException(fields[0]);
               }
       }

</java5>

Utilização de Informação de Tipos em Tempo de Execução

Neste caso, apresenta-se a criação dinâmica de objectos de um determinado tipo, a partir de descrições textuais desses objectos.

Este exemplo utiliza informação de tipos em tempo de execução. Note-se que este tipo de abordagem apenas é possível em linguagens que providenciem este tipo de informação em tempo de execução, como é o caso do Java.

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