Spring Boot 自定義starter

一、簡介

SpringBoot 最強大的功能就是把我們常用的場景抽取成了一個個starter（場景啟動器），我們通過引入springboot 為我提供的這些場景啟動器，我們再進行少量的配置就能使用相應的功能。即使是這樣，springboot也不能囊括我們所有的使用場景，往往我們需要自定義starter，來簡化我們對springboot的使用。

二、如何自定義starter

1.實例

如何編寫自動配置 ？

我們參照@WebMvcAutoConfiguration為例，我們看看們需要準備哪些東西，下面是WebMvcAutoConfiguration的部分代碼：

@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;
        }
    }
}

我們可以抽取到我們自定義starter時同樣需要的一些配置。

@Configuration  //指定這個類是一個配置類
@ConditionalOnXXX  //指定條件成立的情況下自動配置類生效
@AutoConfigureOrder  //指定自動配置類的順序
@Bean  //向容器中添加組件
@ConfigurationProperties  //結合相關xxxProperties來綁定相關的配置
@EnableConfigurationProperties  //讓xxxProperties生效加入到容器中

自動配置類要能加載需要將自動配置類，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,\

模式

我們參照 spring-boot-starter 我們發現其中沒有代碼：

我們在看它的pom中的依賴中有個 springboot-starter

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

我們再看看 spring-boot-starter 有個 spring-boot-autoconfigure

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-autoconfigure</artifactId>
</dependency>

關于web的一些自動配置都寫在了這里 ，所以我們有總結：

啟動器starter只是用來做依賴管理
需要專門寫一個類似spring-boot-autoconfigure的配置模塊
用的時候只需要引入啟動器starter，就可以使用自動配置了

命名規范

官方命名空間

• 前綴：spring-boot-starter-
• 模式：spring-boot-starter-模塊名
• 舉例：spring-boot-starter-web、spring-boot-starter-jdbc

自定義命名空間

• 后綴：-spring-boot-starter
• 模式：模塊-spring-boot-starter
• 舉例：mybatis-spring-boot-starter

三、自定義starter實例

我們需要先創建兩個工程 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>

    <!-- 啟動器 -->
    <dependencies>
        <!-- 引入自動配置模塊 -->
        <dependency>
            <groupId>com.gf</groupId>
            <artifactId>hello-spring-boot-starter-autoconfigurer</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>

</project>

同時刪除 啟動類、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>

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;
    }

}

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();
    }
}

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應該生效
@EnableConfigurationProperties(HelloProperties.class)
public class HelloServiceAutoConfiguration {

    @Autowired
    HelloProperties helloProperties;

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

}

5. spring.factories

在 resources 下創建文件夾 META-INF 并在 META-INF 下創建文件 spring.factories ，內容如下：

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.gf.service.HelloServiceAutoConfiguration

到這兒，我們的配置自定義的starter就寫完了 ，我們hello-spring-boot-starter-autoconfigurer、hello-spring-boot-starter 安裝成本地jar包。

三、測試自定義starter

我們創建個項目 hello-spring-boot-starter-test，來測試系我們寫的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>

        <!-- 引入自定義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>

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 + " , " );
    }

}

3. application.properties

gf.hello.prefix = hi
gf.hello.suffix = what's up man ?

我運行項目訪問 http://127.0.0.1:8080/hello/zhangsan，結果如下：

hi-zhangsan , what's up man ? 

源碼 : https://github.com/gf-huanchupk/SpringBootLearning

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