Spring Boot 自定义starter

Spring Boot 自定义starter

Spring Boot 为大多数流程的开源项目提供了stater包，便于开发者做系统集成。同时，Spring Boot 允许开发者根据业务需要自定义stater，以方便在同一个组织中使用。在之前的公司中，自定义的starter由架构师团队开发维护，他们负责研发公司内部公共组件。

Spring Boot 自动配置机制

Spring Boot 启动时，在classpath中寻找位于 /META-INF目录下的 spring.factories 文件。Spring Boot Auto Configuration 自动装配机制根据以下几种情况确定是否进行装配

• @ConditionalOnProperty - 根据属性判断是否进行装配
• @ConditionalOnClass - 根据类名判断是否进行装配
• @ConditionalOnBean - 根据bean判断是否进行装配
• @ConditionalOnResource - 根据资源判断是否进行装配

以上注解都是 自动装配经常使用的。Spring Boot 自动注解详细介绍请参考

自定义starter

根据官网文档描述，自定义Spring Boot starter 需要包含两部分

• An auto-configure class for our library along with a properties class for custom configuration.

  自定义jar包内部，根据配置属性自动装配的class文件
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• A starter pom to bring in the dependencies of the library and the autoconfigure project.

  一个引用的starter项目，引入依赖jar包，以及自动装配其他模块
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首先创建三个模块

• starter-library - 公共的基础模块
• hello-spring-boot-starter-configure - 自动装配模块
• hello-spring-boot-starter - 外部引用模块

公共基础模块

在该模块中，定义了几个基础的类

public class Greeter {

    private GreetingConfig greetingConfig;

    public Greeter(GreetingConfig greetingConfig) {
        this.greetingConfig = greetingConfig;
    }

    public String greet(LocalDateTime localDateTime) {

        String name = greetingConfig.getProperty(USER_NAME);
        int hourOfDay = localDateTime.getHour();

        if (hourOfDay >= 5 && hourOfDay < 12) {
            return String.format("Hello %s, %s", name, greetingConfig.get(MORNING_MESSAGE));
        } else if (hourOfDay >= 12 && hourOfDay < 17) {
            return String.format("Hello %s, %s", name, greetingConfig.get(AFTERNOON_MESSAGE));
        } else if (hourOfDay >= 17 && hourOfDay < 20) {
            return String.format("Hello %s, %s", name, greetingConfig.get(EVENING_MESSAGE));
        } else {
            return String.format("Hello %s, %s", name, greetingConfig.get(NIGHT_MESSAGE));
        }
    }

    public String greet() {
        return greet(LocalDateTime.now());
    }
}
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public class GreeterConfigParams {

    public static final String USER_NAME = "user.name";
    public static final String MORNING_MESSAGE = "morning.message";
    public static final String AFTERNOON_MESSAGE = "afternoon.message";
    public static final String EVENING_MESSAGE = "evening.message";
    public static final String NIGHT_MESSAGE = "night.message";
}
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public class GreetingConfig extends Properties{

    private static final long serialVersionUID = 5662570853707247891L;

}
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自动装配模块

pom依赖

<dependency>
  <groupId>com.andy.spring.boot.custom.startergroupId>
  <artifactId>starter-libraryartifactId>
  <version>1.0-SNAPSHOTversion>
dependency>
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自动装配类

@ConfigurationProperties(prefix = "com.greeter")
@Data
@ToString
public class GreeterProperties {

    private String userName;
    private String morningMessage;
    private String afternoonMessage;
    private String eveningMessage;
    private String nightMessage;
}
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@Configuration
@ConditionalOnClass(Greeter.class)
@EnableConfigurationProperties(GreeterProperties.class)
public class GreeterAutoConfiguration {

    @Autowired
    private GreeterProperties greeterProperties;

    @Bean
    @ConditionalOnMissingBean
    public GreetingConfig greeterConfig() {

        String userName = greeterProperties.getUserName() == null
                ? System.getProperty("user.name")
                : greeterProperties.getUserName();

        // ..

        GreetingConfig greetingConfig = new GreetingConfig();
        greetingConfig.put(USER_NAME, userName);
        // ...
        return greetingConfig;
    }

    @Bean
    @ConditionalOnMissingBean
    public Greeter greeter(GreetingConfig greetingConfig) {
        return new Greeter(greetingConfig);
    }
}
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外部引用模块

该模块只包含pom文件依赖，没有任何实际的代码

<dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starterartifactId>
            <version>${spring-boot.version}version>
        dependency>
        <dependency>
            <groupId>com.andy.spring.boot.custom.startergroupId>
            <artifactId>hello-spring-boot-starter-configureartifactId>
            <version>${project.version}version>
        dependency>
        <dependency>
            <groupId>com.andy.spring.boot.custom.startergroupId>
            <artifactId>starter-libraryartifactId>
            <version>${project.version}version>
        dependency>
    dependencies>
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验证测试

添加属性

本地另外创建一个项目，在application.properties文件中增加

# 自定义 stater 配置
baeldung.greeter.userName=Baeldung
baeldung.greeter.afternoonMessage=Woha\ Afternoon
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添加依赖

在pom文件中添加

<dependency>
			<groupId>com.andy.spring.boot.custom.startergroupId>
			<artifactId>hello-spring-boot-starterartifactId>
			<version>1.0-SNAPSHOTversion>
		dependency>
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注入Bean

添加依赖后，开发者可以想使用普通bean注入一样，直接使用@Autowired注入bean

@SpringBootApplication
public class GreeterSampleApplication implements CommandLineRunner {

    @Autowired
    private Greeter greeter;

    public static void main(String[] args) {
        SpringApplication.run(GreeterSampleApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        String message = greeter.greet();
        System.out.println(message);
    }
}
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源码地址

点击这里