{"id":1196,"date":"2024-10-31T23:27:26","date_gmt":"2024-11-01T02:27:26","guid":{"rendered":"https:\/\/micheladrianomedeiros.com.br\/blog\/?p=1196"},"modified":"2024-10-31T23:27:27","modified_gmt":"2024-11-01T02:27:27","slug":"singleton_1","status":"publish","type":"post","link":"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/","title":{"rendered":"Singleton Padr\u00e3o"},"content":{"rendered":"<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"1024\" src=\"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-content\/uploads\/2024\/10\/DALL\u00b7E-2024-10-31-23.15.19-An-educational-graphic-illustrating-the-Singleton-design-pattern-in-software-development.-The-diagram-should-include-a-simple-flowchart-showing-the-co.jpg\" alt=\"Singleton\" class=\"wp-image-1197\" srcset=\"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-content\/uploads\/2024\/10\/DALL\u00b7E-2024-10-31-23.15.19-An-educational-graphic-illustrating-the-Singleton-design-pattern-in-software-development.-The-diagram-should-include-a-simple-flowchart-showing-the-co.jpg 1024w, https:\/\/micheladrianomedeiros.com.br\/blog\/wp-content\/uploads\/2024\/10\/DALL\u00b7E-2024-10-31-23.15.19-An-educational-graphic-illustrating-the-Singleton-design-pattern-in-software-development.-The-diagram-should-include-a-simple-flowchart-showing-the-co-300x300.jpg 300w, https:\/\/micheladrianomedeiros.com.br\/blog\/wp-content\/uploads\/2024\/10\/DALL\u00b7E-2024-10-31-23.15.19-An-educational-graphic-illustrating-the-Singleton-design-pattern-in-software-development.-The-diagram-should-include-a-simple-flowchart-showing-the-co-150x150.jpg 150w, https:\/\/micheladrianomedeiros.com.br\/blog\/wp-content\/uploads\/2024\/10\/DALL\u00b7E-2024-10-31-23.15.19-An-educational-graphic-illustrating-the-Singleton-design-pattern-in-software-development.-The-diagram-should-include-a-simple-flowchart-showing-the-co-768x768.jpg 768w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n<\/div>\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_85 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Conte\u00fado<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/#O_que_e\" >O que \u00e9?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/#Por_que_usar_o_Singleton\" >Por que usar o Singleton?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/#Aplicacoes_Comuns\" >Aplica\u00e7\u00f5es Comuns:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/#Implementacao_em_Java\" >Implementa\u00e7\u00e3o em Java:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/#Consideracoes\" >Considera\u00e7\u00f5es:<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/#Exercicio\" >Exerc\u00edcio:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/singleton_1\/#Links\" >Links<\/a><\/li><\/ul><\/nav><\/div>\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"O_que_e\"><\/span>O que \u00e9?<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">O padr\u00e3o Singleton \u00e9 um padr\u00e3o de design de cria\u00e7\u00e3o que garante que uma classe tenha apenas uma inst\u00e2ncia e fornece um ponto de acesso global a essa inst\u00e2ncia. <strong>Portanto<\/strong>, esse padr\u00e3o \u00e9 especialmente \u00fatil quando voc\u00ea precisa controlar o acesso a um recurso compartilhado, como uma configura\u00e7\u00e3o de aplicativo ou uma conex\u00e3o com um banco de dados.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Por_que_usar_o_Singleton\"><\/span>Por que usar o Singleton?<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">Existem v\u00e1rias raz\u00f5es para optar por esse padr\u00e3o. <strong>Primeiramente<\/strong>, ele oferece controle sobre recursos. Quando um recurso \u00e9 escasso ou caro para criar, como uma conex\u00e3o com um banco de dados, o Singleton permite que voc\u00ea reutilize a mesma inst\u00e2ncia. <strong>Al\u00e9m disso<\/strong>, o padr\u00e3o assegura a consist\u00eancia. Ao garantir que todas as partes do seu aplicativo acessem a mesma inst\u00e2ncia, voc\u00ea evita problemas de inconsist\u00eancia. <strong>Por \u00faltimo<\/strong>, o uso do Singleton pode facilitar os testes. Embora os Singletons apresentem desafios para testes, voc\u00ea pode substitu\u00ed-los facilmente em testes com o uso de interfaces.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Aplicacoes_Comuns\"><\/span>Aplica\u00e7\u00f5es Comuns:<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">O padr\u00e3o Singleton se aplica em v\u00e1rias situa\u00e7\u00f5es. <strong>Por exemplo<\/strong>, ele \u00e9 muito utilizado em:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Gerenciamento de Conex\u00f5es<\/strong>: Um padr\u00e3o comum em aplica\u00e7\u00f5es que precisam acessar um banco de dados. <strong>Dessa forma<\/strong>, o uso de uma \u00fanica inst\u00e2ncia para gerenciar conex\u00f5es ajuda a evitar sobrecarga e melhora a efici\u00eancia.<\/li>\n\n\n\n<li><strong>Registro de Logs<\/strong>: O uso de um Singleton para gerenciar a sa\u00edda de log permite que voc\u00ea mantenha um registro coerente e centralizado de todas as opera\u00e7\u00f5es do seu sistema. <strong>Consequentemente<\/strong>, isso facilita a identifica\u00e7\u00e3o de problemas e a an\u00e1lise de desempenho.<\/li>\n\n\n\n<li><strong>Configura\u00e7\u00f5es Globais<\/strong>: Voc\u00ea pode usar um Singleton para carregar configura\u00e7\u00f5es de um arquivo de configura\u00e7\u00e3o, garantindo que todas as partes do aplicativo acessem as mesmas configura\u00e7\u00f5es. <strong>Assim<\/strong>, voc\u00ea evita a duplica\u00e7\u00e3o de c\u00f3digo e mant\u00e9m a integridade dos dados.<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Implementacao_em_Java\"><\/span>Implementa\u00e7\u00e3o em Java:<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p class=\"wp-block-paragraph\">Aqui est\u00e1 um exemplo de como implementar o padr\u00e3o Singleton em Java:<\/p>\n\n\n\n<div class=\"wp-block-urvanov-syntax-highlighter-code-block\"><pre class=\"lang:java decode:true \" >public class Singleton {\n    \/\/ Atributo est\u00e1tico que cont\u00e9m a \u00fanica inst\u00e2ncia da classe\n    private static Singleton instance;\n\n    \/\/ Construtor privado para evitar a inst\u00e2ncia externa\n    private Singleton() {\n        \/\/ Inicializa\u00e7\u00e3o, se necess\u00e1rio\n    }\n\n    \/\/ M\u00e9todo p\u00fablico est\u00e1tico para obter a inst\u00e2ncia da classe\n    public static Singleton getInstance() {\n        if (instance == null) {\n            instance = new Singleton();\n        }\n        return instance;\n    }\n\n    \/\/ Outros m\u00e9todos da classe\n    public void showMessage() {\n        System.out.println(\"Hello from Singleton!\");\n    }\n}\n<\/pre><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">Uso:<\/p>\n\n\n\n<div class=\"wp-block-urvanov-syntax-highlighter-code-block\"><pre class=\"lang:java decode:true \" >public class Main {\n    public static void main(String[] args) {\n        \/\/ Obtendo a \u00fanica inst\u00e2ncia do Singleton\n        Singleton singleton = Singleton.getInstance();\n        singleton.showMessage();\n    }\n}\n<\/pre><\/div>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Consideracoes\"><\/span>Considera\u00e7\u00f5es:<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Thread Safety<\/strong>: A implementa\u00e7\u00e3o acima n\u00e3o \u00e9 segura em um ambiente multithread. <strong>Portanto<\/strong>, para torn\u00e1-la segura, voc\u00ea pode usar a sincroniza\u00e7\u00e3o no m\u00e9todo <code>getInstance()<\/code> ou aplicar o padr\u00e3o de inicializa\u00e7\u00e3o em campo est\u00e1tico (usando <code>enum<\/code> ou uma classe interna est\u00e1tica). Aqui est\u00e1 um exemplo de implementa\u00e7\u00e3o thread-safe:<\/li>\n<\/ul>\n\n\n\n<div class=\"wp-block-urvanov-syntax-highlighter-code-block\"><pre class=\"lang:java decode:true \" >public class Singleton {\n    private static Singleton instance;\n\n    private Singleton() {}\n\n    public static synchronized Singleton getInstance() {\n        if (instance == null) {\n            instance = new Singleton();\n        }\n        return instance;\n    }\n}\n<\/pre><\/div>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Teste<\/strong>: O uso de Singletons pode dificultar os testes. <strong>No entanto<\/strong>, para contornar isso, voc\u00ea pode usar interfaces que permitam a inje\u00e7\u00e3o de depend\u00eancias, facilitando o teste com mocks.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Exercicio\"><\/span>Exerc\u00edcio:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Tente implementar uma vers\u00e3o thread-safe do padr\u00e3o Singleton.<\/li>\n\n\n\n<li>Crie uma classe que utilize o Singleton para gerenciar um recurso, como um registro de log.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Ao entender e aplicar o padr\u00e3o Singleton, voc\u00ea estar\u00e1 mais preparado para lidar com cen\u00e1rios que exigem controle rigoroso sobre a inst\u00e2ncia de uma classe.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Links\"><\/span>Links<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/proframonsouza.com.br\/?ref=T96349914G\" target=\"_blank\" rel=\"noreferrer noopener\">Qualquer pessoa\u00a0pode aprender TI e ser aprovada<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/micheladrianomedeiros.com.br\/blog\/delegate-design-pattern\/\" target=\"_blank\" rel=\"noreferrer noopener\">Delegate Design Pattern<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>O que \u00e9? O padr\u00e3o Singleton \u00e9 um padr\u00e3o de design de cria\u00e7\u00e3o que garante que uma classe tenha apenas uma inst\u00e2ncia e fornece um ponto de acesso global a essa inst\u00e2ncia. Portanto, esse padr\u00e3o \u00e9 especialmente \u00fatil quando voc\u00ea precisa controlar o acesso a um recurso compartilhado, como uma configura\u00e7\u00e3o de aplicativo ou uma [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":1197,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18,224],"tags":[227,229,215,23,230,225,228,231,226,232],"class_list":["post-1196","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-designpatterns","category-singleton","tag-arquitetura-de-software","tag-configuracoes-globais","tag-desenvolvimento-de-software","tag-design-patterns","tag-gerenciamento-de-recursos","tag-padrao-singleton","tag-padroes-de-criacao","tag-programacao-java","tag-registro-de-logs","tag-thread-safety"],"_links":{"self":[{"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/posts\/1196","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/comments?post=1196"}],"version-history":[{"count":2,"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/posts\/1196\/revisions"}],"predecessor-version":[{"id":1199,"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/posts\/1196\/revisions\/1199"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/media\/1197"}],"wp:attachment":[{"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/media?parent=1196"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/categories?post=1196"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/micheladrianomedeiros.com.br\/blog\/wp-json\/wp\/v2\/tags?post=1196"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}