SpringBoot官方文档翻译（十七）：Spring Beans和依赖注入

SpringBoot官方文档翻译
SpringBoot官方文档翻译第三部分

17. Spring Beans and Dependency Injection（Spring Beans和依赖注入）

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You are free to use any of the standard Spring Framework     
techniques to define your beans and their injected dependencies.     
For simplicity, we often find that using @ComponentScan     
(to find your beans) and using @Autowired (to do constructor     
injection) works well.

您可以自由的使用Spring框架标注的一些技术和注解来定义您的注入依赖关系。打个比方，我们经常使用
@ComponentScan（去查找您的beans），用@Autowired（去做构造注入）。

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If you structure your code as suggested above (locating your     
application class in a root package), you can add @ComponentScan     
without any arguments. All of your application components     
(@Component, @Service, @Repository, @Controller etc.) are     
automatically registered as Spring Beans.

如果您按照以上的建议构造您的代码结构（将您的主应用类放在根包下面），您可以增加@ComponentScan注解而不需要任何参数。您所有的应用组件（@Component, @Service, @Repository, @Controller 等等）都将被自动注册为Spring Beans。

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The following example shows a @Service Bean that uses     
constructor injection to obtain a required RiskAssessor bean:

接下去的例子展示了@Service使用构造注入去获得必要的RiskAssessor bean

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package com.example.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class DatabaseAccountService implements AccountService {

	private final RiskAssessor riskAssessor;

	@Autowired
	public DatabaseAccountService(RiskAssessor riskAssessor) {
		this.riskAssessor = riskAssessor;
	}

	// ...

}

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If a bean has one constructor, you can omit the @Autowired,     
as shown in the following example:

如果一个bean有一个构造函数，您可以省略@Autowired注解，如下例子：

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@Service
public class DatabaseAccountService implements AccountService {

	private final RiskAssessor riskAssessor;

	public DatabaseAccountService(RiskAssessor riskAssessor) {
		this.riskAssessor = riskAssessor;
	}

	// ...

}

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Notice how using constructor injection lets the riskAssessor     
field be marked as final, indicating that it cannot be     
subsequently changed.

注意介绍如何使用构造注入使riskAssessor字段被标记为final，表明它不可以随后改变。

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