S04L02 - 构造函数注入

### Chinese Translation

html


精通Spring中的Constructor Injection：全面指南
目录

简介 - 第1页
理解Constructor Injection - 第3页

什么是Constructor Injection？ - 第3页
Constructor Injection的好处 - 第4页


实现Constructor Injection - 第6页

设置类 - 第6页
创建构造函数 - 第8页
配置Spring Beans - 第10页
使用Qualifiers - 第12页


实际示例 - 第14页

逐步实现 - 第14页
代码解释 - 第16页
运行应用程序 - 第18页


结论 - 第20页
附加资源 - 第21页


简介
在Spring Framework领域中，依赖注入是创建灵活且可维护应用程序的基石。在各种类型的依赖注入中，Constructor Injection因其强制不可变性和确保依赖项不会被未初始化而备受推崇。
本电子书深入探讨了constructor injection的概念，引导初学者和具有基本知识的开发人员通过其实现和优势。通过本指南的学习，您将对如何在Spring项目中有效使用constructor injection以提升代码质量和可管理性有了扎实的理解。

理解Constructor Injection
什么是Constructor Injection？
Constructor Injection是一种依赖注入形式，其中依赖项通过构造函数提供给类。类不再自行创建其依赖项，而是由外部实体（通常是Spring容器）注入。这种方法确保在类实例化时所有必要的依赖项都已具备，促进了明确且显式的依赖结构。
Constructor Injection的好处

不可变性：依赖项可以声明为final，确保在对象创建后保持不变。
明确的依赖关系：所有必需的依赖项都在构造函数中列出，使理解类所依赖的内容更加容易。
增强的可测试性：通过允许依赖项被模拟或存根，简化了单元测试。
减少样板代码：最小化了setter方法的需求，导致代码更清洁且更易维护。


实现Constructor Injection
设置类
要实现constructor injection，首先需要定义代表应用程序组件的类。例如，考虑两个类：V6Engine和V8Engine，它们都实现了Engine接口。
示例：




		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


创建构造函数
在上面的示例中，V6Engine具有默认构造函数和参数化构造函数。默认构造函数将引擎类型设置为“Unknown Engine”，而参数化构造函数允许指定自定义引擎类型。
步骤：

默认构造函数：使用默认值初始化属性。
参数化构造函数：允许在对象创建时注入特定值。

配置Spring Beans
在AppConfig类中配置Spring Beans，定义如何实例化和连接Beans。
示例：




		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
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						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


使用Qualifiers
当存在多个相同类型的Beans时，Qualifiers帮助Spring确定注入哪个Bean。这是通过依赖类中的@Qualifier注解实现的。
示例：




		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
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						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		



实际示例
逐步实现

定义Engine接口：

    



		
		
			
			
Java
			
			public interface Engine {
    String getType();
}
			
				
					
				
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						public interface Engine {
    String getType();
}
					
				
			
		


  
在V6Engine中实现Engine接口：

    



		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


  
在AppConfig中配置Beans：

    



		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
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						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


  
在Corolla类中注入依赖项：

    



		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
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						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		


  
运行应用程序：

    



		
		
			
			
Java
			
			@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
			
				
					
				
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						@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
					
				
			
		


  

代码解释

Engine接口：定义引擎类型的契约。
V6Engine类：使用默认和参数化构造函数实现了Engine接口。
AppConfig类：配置了两个Bean，unknownEngine和v6Engine，代表不同的引擎类型。
Corolla类：通过使用@Qualifier注解指定使用哪个引擎Bean，展示了constructor injection。
App类：初始化Spring应用程序上下文并检索Corolla Bean以启动引擎。

运行应用程序
当您运行应用程序时，Corolla类使用通过构造函数注入的v6Engine Bean。输出将是：




		
		
			
			
Java
			
			Engine Type: V6 Engine
			
				
					
				
					1
				
						Engine Type: V6 Engine
					
				
			
		


这确认了constructor injection成功地将所需的Engine实现注入到Corolla类中。

结论
Constructor injection是Spring Framework中一种强大的技术，促进了代码的清洁、可维护性和可测试性。通过在对象创建时强制提供必要的依赖项，它确保类保持不可变并且不受意外副作用的影响。
实现constructor injection涉及在类中定义明确的构造函数，适当配置Beans，以及在存在多个Bean实例时使用Qualifiers。本指南提供了掌握constructor injection的逐步方法，配以实际示例和代码解释。
在您的Spring项目中采用constructor injection不仅将提升代码质量，还将简化依赖管理，导致更强大和可扩展的应用程序。
SEO关键词：Constructor Injection, Spring Framework, Dependency Injection, Spring Beans, Immutability, Spring Configuration, @Autowired, @Qualifier, Spring Boot, Dependency Management, Spring Application, Java Spring, Spring Tutorial, Spring Dependency Injection, Spring Best Practices

附加资源

Spring Framework 文档
Baeldung：Spring中的依赖注入
Spring Boot 官方指南
Joshua Bloch的《Effective Java》第三版

注意：本文由AI生成。

### Hindi Translation

html


Spring में Constructor Injection में महारत: एक व्यापक गाइड
सामग्री सूची

परिचय - पृष्ठ 1
Constructor Injection को समझना - पृष्ठ 3

Constructor Injection क्या है? - पृष्ठ 3
Constructor Injection के लाभ - पृष्ठ 4


Constructor Injection को लागू करना - पृष्ठ 6

क्लास सेटअप करना - पृष्ठ 6
Constructors बनाना - पृष्ठ 8
Spring Beans कॉन्फ़िगर करना - पृष्ठ 10
Qualifiers का उपयोग करना - पृष्ठ 12


व्यावहारिक उदाहरण - पृष्ठ 14

स्टेप-बाय-स्टेप कार्यान्वयन - पृष्ठ 14
कोड व्याख्या - पृष्ठ 16
एप्लिकेशन चलाना - पृष्ठ 18


निष्कर्ष - पृष्ठ 20
अतिरिक्त संसाधन - पृष्ठ 21


परिचय
Spring Framework के क्षेत्र में, dependency injection लचीले और रखरखाव योग्य अनुप्रयोग बनाने के लिए एक कोना स्तंभ के रूप में मौजूद है। विभिन्न प्रकार के dependency injection में, Constructor Injection अपनी अपरिवर्तनीयता को लागू करने की क्षमता और यह सुनिश्चित करने के लिए अत्यधिक मूल्यांकित है कि dependencies अनियमित नहीं रहे।
यह ईबुक constructor injection की अवधारणा में गहराई से उतरती है, शुरुआती और मूल ज्ञान वाले डेवलपर्स को इसके कार्यान्वयन और लाभों के माध्यम से मार्गदर्शन करती है। इस गाइड के अंत तक, आपके पास अपने Spring प्रोजेक्ट्स में constructor injection का प्रभावी ढंग से उपयोग करने की ठोस समझ होगी, जिससे कोड की गुणवत्ता और प्रबंध्यता में सुधार होगा।

Constructor Injection को समझना
Constructor Injection क्या है?
Constructor Injection dependency injection का एक रूप है जहां dependencies को एक class के constructor के माध्यम से प्रदान किया जाता है। class अपने dependencies को स्वयं बनाने के बजाय, इन्हें एक बाहरी इकाई, आमतौर पर Spring container, द्वारा इंजेक्ट किया जाता है। यह दृष्टिकोण यह सुनिश्चित करता है कि class के इंस्टैंसिएट होने पर सभी आवश्यक dependencies उपलब्ध हों, जिससे एक स्पष्ट और स्पष्ट dependency संरचना को बढ़ावा मिलता है।
Constructor Injection के लाभ

अपरिवर्तनीयता: dependencies को final के रूप में घोषित किया जा सकता है, जिससे वे ऑब्जेक्ट निर्माण के बाद अपरिवर्तित रहते हैं।
स्पष्ट Dependencies: सभी आवश्यक dependencies constructor में सूचीबद्ध होती हैं, जिससे यह समझना आसान हो जाता है कि एक class किस पर निर्भर है।
बेहतर परीक्षण योग्यता: dependencies को mock या stub करने की अनुमति देकर unit testing को आसान बनाता है।
कम बायलरप्लेट: setter methods की आवश्यकता को कम करता है, जिससे कोड साफ-सुथरा और अधिक रखरखाव योग्य बनता है।


Constructor Injection को लागू करना
क्लास सेटअप करना
constructor injection लागू करने के लिए, अपने अनुप्रयोग के घटकों का प्रतिनिधित्व करने वाले classes को परिभाषित करना शुरू करें। उदाहरण के लिए, दो classes पर विचार करें: V6Engine और V8Engine, जो दोनों Engine इंटरफेस को लागू करते हैं।
उदाहरण:




		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


Constructors बनाना
उपरोक्त उदाहरण में, V6Engine के पास डिफ़ॉल्ट constructor और parameterized constructor दोनों हैं। डिफ़ॉल्ट constructor engine type को "Unknown Engine" पर सेट करता है, जबकि parameterized constructor कस्टम engine type को निर्दिष्ट करने की अनुमति देता है।
कदम:

डिफ़ॉल्ट Constructor: गुणों को डिफ़ॉल्ट मानों के साथ प्रारंभ करता है।
Parameterized Constructor: ऑब्जेक्ट निर्माण के दौरान विशिष्ट मानों को इंजेक्ट करने की अनुमति देता है।

Spring Beans कॉन्फ़िगर करना
Spring Beans को AppConfig class में कॉन्फ़िगर किया जाता है, जहां आप परिभाषित करते हैं कि beans कैसे instantiate और wired किए जाएं।
उदाहरण:




		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
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						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


Qualifiers का उपयोग करना
जब एक ही प्रकार के कई beans मौजूद होते हैं, तो qualifiers Spring को यह निर्धारित करने में मदद करते हैं कि कौन सा bean inject किया जाना है। यह निर्भर क्लास में @Qualifier annotation का उपयोग करके प्राप्त किया जाता है।
उदाहरण:




		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
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						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		



व्यावहारिक उदाहरण
स्टेप-बाय-स्टेप कार्यान्वयन

Engine इंटरफेस को परिभाषित करें:

    



		
		
			
			
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			public interface Engine {
    String getType();
}
			
				
					
				
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						public interface Engine {
    String getType();
}
					
				
			
		


  
V6Engine में Engine इंटरफेस को लागू करें:

    



		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


  
AppConfig में Beans कॉन्फ़िगर करें:

    



		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
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						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


  
Corolla क्लास में dependencies inject करें:

    



		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
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						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		


  
एप्लिकेशन चलाएं:

    



		
		
			
			
Java
			
			@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
			
				
					
				
					1
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8
				
						@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
					
				
			
		


  

कोड व्याख्या

Engine इंटरफेस: engine types के लिए अनुबंध को परिभाषित करता है।
V6Engine क्लास: default और parameterized constructors के साथ Engine इंटरफेस को लागू करता है।
AppConfig क्लास: दो beans, unknownEngine और v6Engine, को कॉन्फ़िगर करता है, जो विभिन्न engine types का प्रतिनिधित्व करते हैं।
Corolla क्लास: @Qualifier annotation का उपयोग करके कौन सा engine bean उपयोग करना है, यह निर्दिष्ट करके constructor injection का प्रदर्शन करता है।
App क्लास: Spring application context को initialize करता है और engine शुरू करने के लिए Corolla bean को प्राप्त करता है।

एप्लिकेशन चलाना
जब आप एप्लिकेशन चलाते हैं, तो Corolla क्लास constructor के माध्यम से injected v6Engine bean का उपयोग करती है। आउटपुट होगा:




		
		
			
			
Java
			
			Engine Type: V6 Engine
			
				
					
				
					1
				
						Engine Type: V6 Engine
					
				
			
		


यह पुष्टि करता है कि constructor injection ने सफलतापूर्वक इच्छित Engine implementation को Corolla क्लास में inject किया है।

निष्कर्ष
Constructor injection Spring Framework में एक शक्तिशाली तकनीक है जो स्वच्छ, रखरखाव योग्य और परीक्षण योग्य कोड को बढ़ावा देती है। ऑब्जेक्ट निर्माण के समय आवश्यक dependencies को प्रदान करने को लागू करके, यह सुनिश्चित करता है कि classes अपरिवर्तनीय रहें और अनपेक्षित साइड इफेक्ट्स से मुक्त रहें।
Constructor injection को लागू करना आपके classes में स्पष्ट constructors को परिभाषित करना, beans को उपयुक्त रूप से कॉन्फ़िगर करना, और Qualifiers का उपयोग करना शामिल है जब कई bean instances मौजूद होते हैं। इस गाइड ने constructor injection में महारत हासिल करने के लिए एक चरण-दर-चरण दृष्टिकोण प्रदान किया है, जिसमें व्यावहारिक उदाहरण और कोड व्याख्याएं शामिल हैं।
अपने Spring प्रोजेक्ट्स में constructor injection को अपनाने से न केवल कोड की गुणवत्ता में सुधार होगा बल्कि dependency प्रबंधन को भी सरल किया जाएगा, जिससे अधिक मजबूत और स्केलेबल अनुप्रयोग बनेंगे।
SEO Keywords: Constructor Injection, Spring Framework, Dependency Injection, Spring Beans, Immutability, Spring Configuration, @Autowired, @Qualifier, Spring Boot, Dependency Management, Spring Application, Java Spring, Spring Tutorial, Spring Dependency Injection, Spring Best Practices

अतिरिक्त संसाधन

Spring Framework दस्तावेज़ीकरण
Baeldung: Spring में Dependency Injection
Spring Boot आधिकारिक गाइड
Joshua Bloch की Effective Java तीसरा संस्करण

ध्यान दें: यह लेख AI द्वारा जेनरेट किया गया है।

### Korean Translation

html


Spring에서 Constructor Injection 마스터하기: 종합 가이드
목차

소개 - 1페이지
Constructor Injection 이해하기 - 3페이지

Constructor Injection이란? - 3페이지
Constructor Injection의 장점 - 4페이지


Constructor Injection 구현하기 - 6페이지

클래스 설정하기 - 6페이지
생성자 만들기 - 8페이지
Spring Beans 구성하기 - 10페이지
Qualifier 활용하기 - 12페이지


실제 예제 - 14페이지

단계별 구현 - 14페이지
코드 설명 - 16페이지
애플리케이션 실행하기 - 18페이지


결론 - 20페이지
추가 자료 - 21페이지


소개
Spring Framework 분야에서는, dependency injection이 유연하고 유지 보수 가능한 애플리케이션을 만드는 데 핵심적인 역할을 합니다. 다양한 종류의 dependency injection 중에서, Constructor Injection은 불변성을 강제하고 의존성이 초기화되지 않은 상태로 남지 않도록 보장하는 능력 덕분에 높이 평가받고 있습니다.
이 전자책은 constructor injection의 개념을 깊이 있게 다루며, 초보자와 기본 지식을 가진 개발자들이 이를 구현하고 그 이점을 이해하도록 안내합니다. 이 가이드를 통해 Spring 프로젝트에서 constructor injection을 효과적으로 사용하는 방법에 대한 확고한 이해를 갖추게 되어, 코드 품질과 관리성을 향상시킬 수 있을 것입니다.

Constructor Injection 이해하기
Constructor Injection이란?
Constructor Injection은 클래스의 생성자를 통해 의존성을 제공하는 dependency injection의 한 형태입니다. 클래스가 자신의 의존성을 생성하는 대신, 외부 엔티티(일반적으로 Spring 컨테이너)에 의해 주입됩니다. 이 접근 방식은 클래스가 인스턴스화될 때 모든 필요한 의존성이 제공되도록 보장하여 명확하고 명시적인 의존성 구조를 촉진합니다.
Constructor Injection의 장점

불변성: 의존성을 final로 선언할 수 있어 객체 생성 후 변경되지 않도록 보장합니다.
명확한 의존성: 필요한 모든 의존성이 생성자에 나열되어 클래스가 무엇에 의존하는지 쉽게 이해할 수 있습니다.
개선된 테스트 용이성: 의존성을 mock 또는 stub할 수 있어 단위 테스트가 용이합니다.
보일러플레이트 코드 감소: setter 메서드의 필요성을 최소화하여 코드가 더 깔끔하고 유지 보수하기 쉬워집니다.


Constructor Injection 구현하기
클래스 설정하기
constructor injection을 구현하려면, 애플리케이션의 구성 요소를 나타내는 클래스를 정의하는 것부터 시작합니다. 예를 들어, Engine 인터페이스를 구현하는 두 클래스인 V6Engine과 V8Engine을 고려해보세요.
예시:




		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
					1
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


생성자 만들기
위의 예시에서, V6Engine은 기본 생성자와 매개변수가 있는 생성자 모두를 가지고 있습니다. 기본 생성자는 엔진 타입을 "Unknown Engine"으로 설정하고, 매개변수가 있는 생성자는 사용자 지정 엔진 타입을 지정할 수 있습니다.
단계:

기본 생성자: 기본 값으로 속성을 초기화합니다.
매개변수가 있는 생성자: 객체 생성 시 특정 값을 주입할 수 있게 합니다.

Spring Beans 구성하기
Spring Beans는 AppConfig 클래스에서 구성되며, 여기서 beans가 어떻게 인스턴스화되고 연결되는지 정의합니다.
예시:




		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
					1
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						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


Qualifier 활용하기
같은 타입의 여러 beans가 존재할 때, Qualifiers는 Spring이 어떤 bean을 주입할지 결정하는 데 도움을 줍니다. 이는 의존 클래스에서 @Qualifier 애노테이션을 사용하여 달성됩니다.
예시:




		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
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						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		



실제 예제
단계별 구현

Engine 인터페이스 정의하기:

    



		
		
			
			
Java
			
			public interface Engine {
    String getType();
}
			
				
					
				
					1
2
3
				
						public interface Engine {
    String getType();
}
					
				
			
		


  
V6Engine에서 Engine 인터페이스 구현하기:

    



		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
					1
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


  
AppConfig에서 Beans 구성하기:

    



		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
					1
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						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


  
Corolla 클래스에 의존성 주입하기:

    



		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
					1
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						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		


  
애플리케이션 실행하기:

    



		
		
			
			
Java
			
			@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
			
				
					
				
					1
2
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8
				
						@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
					
				
			
		


  

코드 설명

Engine 인터페이스: 엔진 타입에 대한 계약을 정의합니다.
V6Engine 클래스: 기본 및 매개변수가 있는 생성자를 사용하여 Engine 인터페이스를 구현합니다.
AppConfig 클래스: 두 개의 beans인 unknownEngine과 v6Engine을 구성하여 다양한 엔진 타입을 나타냅니다.
Corolla 클래스: @Qualifier 애노테이션을 사용하여 어떤 엔진 bean을 사용할지 지정함으로써 constructor injection을 보여줍니다.
App 클래스: Spring 애플리케이션 컨텍스트를 초기화하고 Corolla bean을 가져와 엔진을 시작합니다.

애플리케이션 실행하기
애플리케이션을 실행하면, Corolla 클래스는 생성자를 통해 주입된 v6Engine bean을 사용합니다. 출력은 다음과 같습니다:




		
		
			
			
Java
			
			Engine Type: V6 Engine
			
				
					
				
					1
				
						Engine Type: V6 Engine
					
				
			
		


이는 constructor injection이 원하는 Engine 구현을 Corolla 클래스에 성공적으로 주입했음을 확인시켜줍니다.

결론
Constructor injection은 Spring Framework에서 깨끗하고 유지 관리 가능하며 테스트 가능한 코드를 촉진하는 강력한 기술입니다. 객체 생성 시 필요한 dependencies를 제공함으로써, 클래스가 불변성을 유지하고 의도하지 않은 부작용으로부터 자유로울 수 있도록 보장합니다.
Constructor injection을 구현하려면 클래스에 명확한 생성자를 정의하고, beans를 적절하게 구성하며, 여러 bean 인스턴스가 존재할 때 qualifiers를 활용해야 합니다. 이 가이드는 실제 예제와 코드 설명을 포함하여 constructor injection을 숙달하기 위한 단계별 접근 방식을 제공합니다.
Spring 프로젝트에서 constructor injection을 도입하면 코드 품질이 향상될 뿐만 아니라 dependency 관리를 단순화하여 더욱 견고하고 확장 가능한 애플리케이션을 구축할 수 있게 됩니다.
SEO 키워드: Constructor Injection, Spring Framework, Dependency Injection, Spring Beans, Immutability, Spring Configuration, @Autowired, @Qualifier, Spring Boot, Dependency Management, Spring Application, Java Spring, Spring Tutorial, Spring Dependency Injection, Spring Best Practices

추가 자료

Spring Framework 문서
Baeldung: Spring에서의 Dependency Injection
Spring Boot 공식 가이드
Joshua Bloch의 Effective Java 3판

참고: 이 기사는 AI에 의해 생성되었습니다.

### Portuguese Translation

html


Dominando Constructor Injection no Spring: Um Guia Abrangente
Índice

Introdução - Página 1
Entendendo Constructor Injection - Página 3

O que é Constructor Injection? - Página 3
Benefícios do Constructor Injection - Página 4


Implementando Constructor Injection - Página 6

Configurando as Classes - Página 6
Criando Construtores - Página 8
Configurando Spring Beans - Página 10
Utilizando Qualifiers - Página 12


Exemplo Prático - Página 14

Implementação Passo a Passo - Página 14
Explicação do Código - Página 16
Executando a Aplicação - Página 18


Conclusão - Página 20
Recursos Adicionais - Página 21


Introdução
No âmbito do Spring Framework, a injeção de dependência é uma pedra angular para a criação de aplicações flexíveis e fáceis de manter. Entre os vários tipos de injeção de dependência, a Constructor Injection é altamente respeitada por sua capacidade de impor imutabilidade e garantir que as dependências não fiquem não inicializadas.
Este eBook aprofunda-se no conceito de constructor injection, guiando iniciantes e desenvolvedores com conhecimentos básicos através de sua implementação e benefícios. Ao final deste guia, você terá uma compreensão sólida de como utilizar efetivamente a constructor injection em seus projetos Spring para melhorar a qualidade e a gerenciabilidade do código.

Entendendo Constructor Injection
O que é Constructor Injection?
Constructor Injection é uma forma de injeção de dependência onde as dependências são fornecidas a uma classe através de seu construtor. Em vez de a classe criar suas próprias dependências, elas são injetadas por uma entidade externa, tipicamente o Spring container. Essa abordagem assegura que todas as dependências necessárias estejam disponíveis quando a classe é instanciada, promovendo uma estrutura de dependência clara e explícita.
Benefícios do Constructor Injection

Imutabilidade: As dependências podem ser declaradas como finais, garantindo que permaneçam inalteradas após a criação do objeto.
Dependências Claras: Todas as dependências requeridas são listadas no construtor, tornando mais fácil entender de que uma classe depende.
Testabilidade Aprimorada: Facilita testes unitários mais simples permitindo que as dependências sejam mockadas ou stubadas.
Redução de Boilerplate: Minimiza a necessidade de métodos setter, levando a um código mais limpo e mais fácil de manter.


Implementando Constructor Injection
Configurando as Classes
Para implementar constructor injection, comece definindo as classes que representam os componentes da sua aplicação. Por exemplo, considere duas classes: V6Engine e V8Engine, ambas implementando a interface Engine.
Exemplo:




		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
					1
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3
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5
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


Criando Construtores
No exemplo acima, V6Engine possui tanto um construtor padrão quanto um construtor parametrizado. O construtor padrão define o tipo de engine como "Unknown Engine", enquanto o construtor parametrizado permite especificar um tipo de engine personalizado.
Passos:

Construtor Padrão: Inicializa propriedades com valores padrão.
Construtor Parametrizado: Permite a injeção de valores específicos durante a criação do objeto.

Configurando Spring Beans
Os Spring Beans são configurados na classe AppConfig, onde você define como os beans são instanciados e conectados.
Exemplo:




		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
					1
2
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9
10
11
12
13
				
						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


Utilizando Qualifiers
Quando existem múltiplos beans do mesmo tipo, qualifiers ajudam o Spring a determinar qual bean injetar. Isso é alcançado usando a anotação @Qualifier na classe dependente.
Exemplo:




		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
					1
2
3
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5
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7
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9
10
11
12
13
14
				
						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		



Exemplo Prático
Implementação Passo a Passo

Definir a Interface Engine:

    



		
		
			
			
Java
			
			public interface Engine {
    String getType();
}
			
				
					
				
					1
2
3
				
						public interface Engine {
    String getType();
}
					
				
			
		


  
Implementar a Interface Engine em V6Engine:

    



		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
					1
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


  
Configurar Beans em AppConfig:

    



		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
				
						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


  
Injetar Dependências na Classe Corolla:

    



		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
				
						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		


  
Executar a Aplicação:

    



		
		
			
			
Java
			
			@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
			
				
					
				
					1
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5
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8
				
						@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
					
				
			
		


  

Explicação do Código

Interface Engine: Define o contrato para os tipos de engine.
Classe V6Engine: Implementa a interface Engine com construtores padrão e parametrizados.
Classe AppConfig: Configura dois beans, unknownEngine e v6Engine, representando diferentes tipos de engine.
Classe Corolla: Demonstra constructor injection especificando qual bean de engine usar via anotação @Qualifier.
Classe App: Inicializa o contexto da aplicação Spring e recupera o bean Corolla para iniciar a engine.

Executando a Aplicação
Ao executar a aplicação, a classe Corolla utiliza o bean v6Engine injetado através do construtor. A saída será:




		
		
			
			
Java
			
			Engine Type: V6 Engine
			
				
					
				
					1
				
						Engine Type: V6 Engine
					
				
			
		


Isso confirma que o constructor injection injetou com sucesso a implementação desejada de Engine na classe Corolla.

Conclusão
Constructor injection é uma técnica poderosa no Spring Framework que promove código limpo, fácil de manter e testável. Ao impor a provisão das dependências necessárias no momento da criação do objeto, garante que as classes permaneçam imutáveis e livres de efeitos colaterais indesejados.
Implementar constructor injection envolve definir construtores claros em suas classes, configurar beans apropriadamente e utilizar qualifiers quando múltiplas instâncias de bean existirem. Este guia forneceu uma abordagem passo a passo para dominar constructor injection, completa com exemplos práticos e explicações de código.
Adoção do constructor injection em seus projetos Spring não apenas melhorará a qualidade do código, mas também simplificará o gerenciamento de dependências, levando a aplicações mais robustas e escaláveis.
SEO Keywords: Constructor Injection, Spring Framework, Dependency Injection, Spring Beans, Immutability, Spring Configuration, @Autowired, @Qualifier, Spring Boot, Dependency Management, Spring Application, Java Spring, Spring Tutorial, Spring Dependency Injection, Spring Best Practices

Recursos Adicionais

Documentação do Spring Framework
Baeldung: Inversão de Controle e Dependency Injection no Spring
Guia Oficial do Spring Boot
Effective Java de Joshua Bloch (3ª Edição)

Nota: Este artigo foi gerado por IA.

### Spanish Translation

html


Dominando Constructor Injection en Spring: Una Guía Integral
Tabla de Contenidos

Introducción - Página 1
Entendiendo Constructor Injection - Página 3

¿Qué es Constructor Injection? - Página 3
Beneficios de Constructor Injection - Página 4


Implementando Constructor Injection - Página 6

Configurando las Clases - Página 6
Creando Constructores - Página 8
Configurando Spring Beans - Página 10
Utilizando Qualifiers - Página 12


Ejemplo Práctico - Página 14

Implementación Paso a Paso - Página 14
Explicación del Código - Página 16
Ejecutando la Aplicación - Página 18


Conclusión - Página 20
Recursos Adicionales - Página 21


Introducción
En el ámbito de Spring Framework, la inyección de dependencias se erige como una piedra angular para crear aplicaciones flexibles y mantenibles. Entre los diversos tipos de inyección de dependencias, Constructor Injection es altamente valorada por su capacidad para imponer inmutabilidad y asegurar que las dependencias no queden sin inicializar.
Este eBook profundiza en el concepto de constructor injection, guiando a principiantes y desarrolladores con conocimientos básicos a través de su implementación y beneficios. Al final de esta guía, tendrás una comprensión sólida de cómo utilizar efectivamente constructor injection en tus proyectos Spring para mejorar la calidad y la manejabilidad del código.

Entendiendo Constructor Injection
¿Qué es Constructor Injection?
Constructor Injection es una forma de inyección de dependencias donde las dependencias se proporcionan a una clase a través de su constructor. En lugar de que la clase cree sus propias dependencias, estas son inyectadas por una entidad externa, típicamente el contenedor Spring. Este enfoque asegura que todas las dependencias necesarias estén disponibles cuando se instancia la clase, promoviendo una estructura de dependencias clara y explícita.
Beneficios de Constructor Injection

Inmutabilidad: Las dependencias pueden declararse como finales, asegurando que permanezcan sin cambios después de la creación del objeto.
Dependencias Claras: Todas las dependencias requeridas se listan en el constructor, facilitando la comprensión de en qué depende una clase.
Mejor Testabilidad: Facilita las pruebas unitarias permitiendo que las dependencias sean mockeadas o stubbed.
Reducción de Código Boilerplate: Minimiza la necesidad de métodos setter, llevando a un código más limpio y fácil de mantener.


Implementando Constructor Injection
Configurando las Clases
Para implementar constructor injection, comienza definiendo las clases que representan los componentes de tu aplicación. Por ejemplo, considera dos clases: V6Engine y V8Engine, ambas implementando la interfaz Engine.
Ejemplo:




		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


Creando Constructores
En el ejemplo anterior, V6Engine tiene tanto un constructor por defecto como uno parametrizado. El constructor por defecto establece el tipo de motor en "Unknown Engine", mientras que el constructor parametrizado permite especificar un tipo de motor personalizado.
Pasos:

Constructor por Defecto: Inicializa las propiedades con valores predeterminados.
Constructor Parametrizado: Permite inyectar valores específicos durante la creación del objeto.

Configurando Spring Beans
Los Spring Beans se configuran en la clase AppConfig, donde defines cómo se instancian y conectan los beans.
Ejemplo:




		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
					1
2
3
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13
				
						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


Utilizando Qualifiers
Cuando existen múltiples beans del mismo tipo, los qualifiers ayudan a Spring a determinar qué bean inyectar. Esto se logra utilizando la anotación @Qualifier en la clase dependiente.
Ejemplo:




		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
					1
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						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		



Ejemplo Práctico
Implementación Paso a Paso

Definir la Interfaz Engine:

    



		
		
			
			
Java
			
			public interface Engine {
    String getType();
}
			
				
					
				
					1
2
3
				
						public interface Engine {
    String getType();
}
					
				
			
		


  
Implementar la Interfaz Engine en V6Engine:

    



		
		
			
			
Java
			
			public class V6Engine implements Engine {
    private String type;

    public V6Engine() {
        this.type = "Unknown Engine";
    }

    public V6Engine(String type) {
        this.type = type;
    }

    @Override
    public String getType() {
        return type;
    }
}
			
				
					
				
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						public class V6Engine implements Engine {
    private String type;
 
    public V6Engine() {
        this.type = "Unknown Engine";
    }
 
    public V6Engine(String type) {
        this.type = type;
    }
 
    @Override
    public String getType() {
        return type;
    }
}
					
				
			
		


  
Configurar Beans en AppConfig:

    



		
		
			
			
Java
			
			@Configuration
public class AppConfig {

    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }

    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
			
				
					
				
					1
2
3
4
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13
				
						@Configuration
public class AppConfig {
 
    @Bean(name = "unknownEngine")
    public Engine engineType() {
        return new V6Engine();
    }
 
    @Bean(name = "v6Engine")
    public Engine v6Engine() {
        return new V6Engine("V6 Engine");
    }
}
					
				
			
		


  
Inyectar Dependencias en la Clase Corolla:

    



		
		
			
			
Java
			
			@Component
public class Corolla {

    private Engine engine;

    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }

    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
			
				
					
				
					1
2
3
4
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14
				
						@Component
public class Corolla {
 
    private Engine engine;
 
    @Autowired
    public Corolla(@Qualifier("v6Engine") Engine engine) {
        this.engine = engine;
    }
 
    public void startEngine() {
        System.out.println("Engine Type: " + engine.getType());
    }
}
					
				
			
		


  
Ejecutar la Aplicación:

    



		
		
			
			
Java
			
			@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
			
				
					
				
					1
2
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5
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8
				
						@SpringBootApplication
public class App {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(App.class, args);
        Corolla corolla = context.getBean(Corolla.class);
        corolla.startEngine();
    }
}
					
				
			
		


  

Explicación del Código

Interfaz Engine: Define el contrato para los tipos de motor.
Clase V6Engine: Implementa la interfaz Engine con constructores por defecto y parametrizados.
Clase AppConfig: Configura dos beans, unknownEngine y v6Engine, que representan diferentes tipos de motor.
Clase Corolla: Demuestra constructor injection especificando cuál bean de motor usar mediante la anotación @Qualifier.
Clase App: Inicializa el contexto de la aplicación Spring y recupera el bean Corolla para iniciar el motor.

Ejecutando la Aplicación
Al ejecutar la aplicación, la clase Corolla utiliza el bean v6Engine inyectado a través del constructor. La salida será:




		
		
			
			
Java
			
			Engine Type: V6 Engine
			
				
					
				
					1
				
						Engine Type: V6 Engine
					
				
			
		


Esto confirma que constructor injection inyectó exitosamente la implementación deseada de Engine en la clase Corolla.

Conclusión
Constructor injection es una técnica poderosa en Spring Framework que promueve un código limpio, mantenible y testeable. Al imponer la provisión de dependencias necesarias en el momento de la creación del objeto, asegura que las clases permanezcan inmutables y libres de efectos secundarios no deseados.
Implementar constructor injection implica definir constructores claros en tus clases, configurar beans apropiadamente y utilizar qualifiers cuando existan múltiples instancias de bean. Esta guía ha proporcionado un enfoque paso a paso para dominar constructor injection, completa con ejemplos prácticos y explicaciones de código.
Adoptar constructor injection en tus proyectos Spring no solo mejorará la calidad del código, sino que también simplificará la gestión de dependencias, llevando a aplicaciones más robustas y escalables.
SEO Keywords: Constructor Injection, Spring Framework, Dependency Injection, Spring Beans, Immutability, Spring Configuration, @Autowired, @Qualifier, Spring Boot, Dependency Management, Spring Application, Java Spring, Spring Tutorial, Spring Dependency Injection, Spring Best Practices

Recursos Adicionales

Documentación de Spring Framework
Baeldung: Inversión de Control e Inyección de Dependencias en Spring
Guía Oficial de Spring Boot
Effective Java de Joshua Bloch (3ª Edición)

Nota: Este artículo fue generado por IA.