Spring @Autowired教程 · ZetCode 中文系列教程

# Spring `@Autowired`教程 > 原文： [http://zetcode.com/spring/autowired/](http://zetcode.com/spring/autowired/) Spring `@Autowired`教程展示了如何使用`@Autowired`注解在 Spring 应用中注入依赖项。 Spring 是用于创建企业应用的流行 Java 应用框架。 ## Spring `@Autowired` `@Autowired`注解标记将由 Spring 的依赖项注入工具自动装配的构造器，字段，设置器方法或配置方法。它是 JSR-330 `@Inject`注解的替代方法。 ## Spring `@Autowired`示例应用使用`@Autowired`注入依赖项。依赖关系是一个返回单词的服务对象。 ```java pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ └───service │ │ WordService.java │ └───resources │ logback.xml └───test └───java ``` 这是项目结构。 `pom.xml` ```java <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>springautowired</artifactId> <version>1.0-SNAPSHOT</version> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> <spring-version>5.1.3.RELEASE</spring-version> </properties> <dependencies> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.2.3</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring-version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring-version}</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>exec-maven-plugin</artifactId> <version>1.6.0</version> <configuration> <mainClass>com.zetcode.Application</mainClass> </configuration> </plugin> </plugins> </build> </project> ``` 在`pom.xml`文件中，我们具有基本的 Spring 依赖项`spring-core`，`spring-context`和日志记录`logback-classic`依赖项。 `exec-maven-plugin`用于在命令行上从 Maven 执行 Spring 应用。 `resources/logback.xml` ```java <?xml version="1.0" encoding="UTF-8"?> <configuration> <logger name="org.springframework" level="ERROR"/> <logger name="com.zetcode" level="INFO"/> <appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <Pattern>%d{HH:mm:ss.SSS} %blue(%-5level) %magenta(%logger{36}) - %msg %n </Pattern> </encoder> </appender> <root> <level value="INFO" /> <appender-ref ref="consoleAppender" /> </root> </configuration> ``` `logback.xml`是 Logback 日志库的配置文件。 `com/zetcode/service/WordService.java` ```java package com.zetcode.service; import org.springframework.stereotype.Service; import java.util.List; import java.util.Random; @Service public class WordService { private final List<String> words = List.of("pen", "sky", "rock", "forest", "falcon", "eagle"); public List<String> all() { return words; } public String randomWord() { return words.get(new Random().nextInt(words.size())); } } ``` `WordService`类带有`@Service`注解。 Spring 在组件扫描的帮助下将其注册为托管 Bean。稍后将此服务对象与`@Autowired`一起注入`Application`中。 `com/zetcode/Application.java` ```java package com.zetcode; import com.zetcode.service.WordService; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.AnnotationConfigApplicationContext; import org.springframework.context.annotation.ComponentScan; import org.springframework.stereotype.Component; @Component @ComponentScan(basePackages="com.zetcode") public class Application { private static final Logger logger = LoggerFactory.getLogger(Application.class); @Autowired private WordService wordService; public static void main(String[] args) { var ctx = new AnnotationConfigApplicationContext(Application.class); var bean = ctx.getBean(Application.class); bean.run(); ctx.close(); } public void run() { logger.info("{}", wordService.randomWord()); logger.info("{}", wordService.randomWord()); var words = wordService.all(); words.stream().forEach(word -> logger.info("{}", word)); } } ``` 使用`WordService`使用输出字注解应用。服务依赖项与`@Autowired`一起注入`Application`中。 ```java @Autowired private WordService wordService; ``` 这称为场注入。 > **注意**：虽然字段注入简短而有趣，但通常建议使用构造器注入或设置器注入。 ```java $ mvn -q exec:java 17:15:34.504 INFO com.zetcode.Application - falcon 17:15:34.507 INFO com.zetcode.Application - eagle 17:15:34.508 INFO com.zetcode.Application - pen 17:15:34.508 INFO com.zetcode.Application - sky 17:15:34.509 INFO com.zetcode.Application - rock 17:15:34.509 INFO com.zetcode.Application - forest 17:15:34.510 INFO com.zetcode.Application - falcon 17:15:34.510 INFO com.zetcode.Application - eagle ``` 我们运行该应用。在本教程中，我们使用`@Autowired`在 Spring 中注入了依赖项。您可能也对这些相关教程感兴趣： [Spring `@Bean`注解教程](/spring/bean/)， [Spring `@ComponentScan`教程](/spring/componentscan/)， [Java 教程](/lang/java/)或列出[所有 Spring 教程](/all/#spring)。