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SpringBoot 自定义 starter

SpringBoot 最强大的功能就是把我们常用的场景抽取成了一个个starter（场景启动器），我们通过引入SpringBoot 为我提供的这些场景启动器，我们再进行少量的配置就能使用相应的功能。即使是这样，SpringBoot也不能囊括我们所有的使用场景，往往我们需要自定义starter，来简化我们对SpringBoot的使用。

二、如何自定义starter

1.实例

如何编写自动配置？

我们参照@WebMvcAutoConfiguration为例，我们看看需要准备哪些东西，下面是WebMvcAutoConfiguration的部分代码：

@Configuration
@ConditionalOnWebApplication
@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurerAdapter.class})
@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})
@AutoConfigureOrder(-2147483638)
@AutoConfigureAfter({DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class})
public class WebMvcAutoConfiguration {

	@Import({WebMvcAutoConfiguration.EnableWebMvcConfiguration.class})
    @EnableConfigurationProperties({WebMvcProperties.class, ResourceProperties.class})
    public static class WebMvcAutoConfigurationAdapter extends WebMvcConfigurerAdapter {

        @Bean
        @ConditionalOnBean({View.class})
        @ConditionalOnMissingBean
        public BeanNameViewResolver beanNameViewResolver() {
            BeanNameViewResolver resolver = new BeanNameViewResolver();
            resolver.setOrder(2147483637);
            return resolver;
        }
    }
}
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我们可以抽取到我们自定义starter时,同样需要的一些配置。

@Configuration  //指定这个类是一个配置类
@ConditionalOnXXX  //指定条件成立的情况下自动配置类生效
@AutoConfigureOrder  //指定自动配置类的顺序
@Bean  //向容器中添加组件
@ConfigurationProperties  //结合相关xxxProperties来绑定相关的配置
@EnableConfigurationProperties  //让xxxProperties生效加入到容器中

自动配置类要能加载需要将自动配置类，配置在META-INF/spring.factories中
org.springframework.boot.autoconfigure.EnableAutoConfiguration=/
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,/
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,/
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模式

我们参照 spring-boot-starter 我们发现其中没有代码：

我们在看它的pom中的依赖中有个 springboot-starter

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter</artifactId>
</dependency>
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我们再看看 spring-boot-starter 有个 spring-boot-autoconfigure

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-autoconfigure</artifactId>
</dependency>
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关于web的一些自动配置都写在了这里，所以我们有以下总结：

启动器starter只是用来做依赖管理
需要专门写一个类似spring-boot-autoconfigure的配置模块
用的时候只需要引入启动器starter，就可以使用自动配置了
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命名规范

官方命名空间

前缀：spring-boot-starter-
模式：spring-boot-starter-模块名
举例：spring-boot-starter-web、spring-boot-starter-jdbc

自定义命名空间

后缀：-spring-boot-starter
模式：模块-spring-boot-starter
举例：mybatis-spring-boot-starter

三、自定义starter实例

我们需要先创建两个工程 hello-spring-boot-starter 和 hello-spring-boot-starter-autoconfigurer

1. hello-spring-boot-starter

1.pom.xml

<?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.gf</groupId>
	<artifactId>hello-spring-boot-starter</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>hello-spring-boot-starter</name>

	<!-- 启动器 -->
	<dependencies>
		<!-- 引入自动配置模块 -->
		<dependency>
			<groupId>com.gf</groupId>
			<artifactId>hello-spring-boot-starter-autoconfigurer</artifactId>
			<version>0.0.1-SNAPSHOT</version>
		</dependency>
	</dependencies>


</project>

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同时删除启动类、resources下的文件，test文件。

2. hello-spring-boot-starter-autoconfigurer

1. pom.xml

<?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.gf</groupId>
	<artifactId>hello-spring-boot-starter-autoconfigurer</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>hello-spring-boot-starter-autoconfigurer</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.9.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<!-- 引入spring-boot-starter，所有starter的基本配合 -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>

	</dependencies>


</project>

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2. HelloProperties

package com.gf.service;

import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "gf.hello")
public class HelloProperties {

    private String prefix;
    private String suffix;

    public String getPrefix() {
        return prefix;
    }

    public void setPrefix(String prefix) {
        this.prefix = prefix;
    }

    public String getSuffix() {
        return suffix;
    }

    public void setSuffix(String suffix) {
        this.suffix = suffix;
    }

}

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3. HelloService

package com.gf.service;


public class HelloService {

    HelloProperties helloProperties;

    public HelloProperties getHelloProperties() {
        return helloProperties;
    }

    public void setHelloProperties(HelloProperties helloProperties) {
        this.helloProperties = helloProperties;
    }

    public String sayHello(String name ) {
        return helloProperties.getPrefix()+ "-" + name + helloProperties.getSuffix();
    }
}

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4. HelloServiceAutoConfiguration

package com.gf.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
@ConditionalOnWebApplication //web应该生效
@EnableConfigurationProperties(HelloProperties.class)
public class HelloServiceAutoConfiguration {

    @Autowired
    HelloProperties helloProperties;

    @Bean
    public HelloService helloService() {
        HelloService service = new HelloService();
        service.setHelloProperties( helloProperties  );
        return service;
    }


}

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5. spring.factories

在 resources 下创建文件夹 META-INF 并在 META-INF 下创建文件 spring.factories ，内容如下：

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=/
com.gf.service.HelloServiceAutoConfiguration
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到这儿，我们的配置自定义的starter就写完了，我们把 hello-spring-boot-starter-autoconfigurer、hello-spring-boot-starter 安装成本地jar包。

三、测试自定义starter

我们创建个项目 hello-spring-boot-starter-test ，来测试系我们写的stater。

1. pom.xml

<?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.gf</groupId>
	<artifactId>hello-spring-boot-starter-test</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>hello-spring-boot-starter-test</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.9.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<!-- 引入自定义starter -->
		<dependency>
			<groupId>com.gf</groupId>
			<artifactId>hello-spring-boot-starter</artifactId>
			<version>0.0.1-SNAPSHOT</version>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>


</project>

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2. HelloController

package com.gf.controller;

import com.gf.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @Autowired
    HelloService helloService;

    @GetMapping("/hello/{name}")
    public String hello(@PathVariable(value = "name") String name) {
        return helloService.sayHello( name + " , " );
    }

}

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原文 https://juejin.im/post/5c81dda6e51d4539ab383e3a

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