Spring Boot 实现 自定义Starter

2019独角兽企业重金招聘Python工程师标准>>>

Spring Boot Starter 理解

可以认为starter是一种服务（和JS的插件类似）——使得使用某个功能的开发者不需要关注各种依赖库的处理，不需要具体的配置信息，由Spring Boot自动通过classpath路径下的类发现需要的Bean，并织入bean

开始创建自定义Starter

1:新建Maven工程

2：pom.xml

<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.bbz</groupId>
	<artifactId>spring-boot-start-hello</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>spring-boot-start-hello</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-autoconfigure</artifactId>
			<version>2.0.1.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>3.8.1</version>
			<scope>test</scope>
		</dependency>
	</dependencies>
</project>

需要引入Spring-boot-autoconfigure 自动配置，Spring-boot-autoconfigure自动配置详解地址（未完待续）

3：新建HelloServiceProperties.Class

@ConfigurationProperties(prefix = "hello")
public class HelloServiceProperties {

	private static final String MSG = "world";

	private String msg = MSG;

	public String getMsg() {
		return msg;
	}

	public void setMsg(String msg) {
		this.msg = msg;
	}

}

代码解释：@ConfigurationProperties(prefix = "hello")，读取配置文件中的hello.msg注入到属性msg中，如果配置文件中没有配置，msg默认为world

4:新建HelloService.Class

public class HelloService {
	private String msg;

	public String sayHello() {
		return "Hello" + msg;
	}

	public String getMsg() {
		return msg;
	}

	public void setMsg(String msg) {
		this.msg = msg;
	}

}

5:新建HelloServiceAutoConfiguration.class 

@Configuration
@EnableConfigurationProperties(HelloServiceProperties.class)
@ConditionalOnClass(HelloService.class)
@ConditionalOnProperty(prefix = "hello", value = "enabled", matchIfMissing = true)
public class HelloServiceAutoConfiguration {

	@Autowired
	private HelloServiceProperties helloServiceProperties;

	@Bean
	@ConditionalOnMissingBean(HelloService.class)
	public HelloService helloService() {
		HelloService helloService = new HelloService();
		helloService.setMsg(helloServiceProperties.getMsg());
		return helloService;
	}
}

代码解释：

    @Configuration用于定义配置类，可替换xml配置文件，配置spring并启动spring容器

    @EnableConfigurationProperties(HelloServiceProperties.class) 将带有@ConfigurationProperties注解的类HelloServiceProperties注入为Spring容器的Bean

    @ConditionalOnClass(HelloService.class) 当类路径下有指定的类的条件下

    @ConditionalOnProperty(prefix = "hello", value = "enabled", matchIfMissing = true)  当设置hello=enabled时，如果没有设置，默认为

   

6：新建spring.factories，在resources/META-INF/下,文件中写入

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\com.bbz.spring_boot_start_hello.HelloServiceAutoConfiguration

7:新建spring-boot项目，选择web Starter

8:spring-boot项目pom.xml 中引入

<dependency>
            <groupId>com.bbz</groupId>
            <artifactId>spring-boot-start-hello</artifactId>
            <version>0.0.1-SNAPSHOT</version>
   </dependency>

9：spring-boot项目中新建controller

@RestController
public class HelloController {
	@Autowired
	HelloService helloService;

	@RequestMapping("/")
	public String hello() {
		return helloService.sayHello();
	}

}

10:启动spring-boot项目，访问http://localhost:8080/

展示如图，可以看出spring-boot项目中已经成功引入hello-starter,可以自己试试在spring-boot项目中配置hello.msg，然后访问项目。

转载于:https://my.oschina.net/u/3905482/blog/1860264