SpringBoot入门：开发自定义的Spring-Boot-Starter

1、starter命名规范

spring提供的starter：

• spring-boot-starter-xxx-x.y.z.jar

• spring-boot-xxx-autoconfigure-x.y.z.jar

第三方提供的starter：

• xxx-spring-boot-starter-x.y.z.jar

2、动手制作自定义Spring-Boot-Starter的步骤

1、新建项目，引入依赖
引入spring-boot-starter、spring-boot-autoconfigure、第三方jar，如果需要生成配置元信息，加入spring-boot-configuration-processor

2、编写功能实现类
3、编写自动配置类
4、在resources/META-INF/spring.factories中配置自动装配类
5、打包
这里我们使用jsoup抓取网页信息为例，制作一个starter。

项目结构：

2.1、新建maven项目，引入依赖

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.3.RELEASE</version>
    <relativePath /> 
</parent>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-autoconfigure</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-configuration-processor</artifactId>
        <optional>true</optional>
    </dependency>

    <dependency>
        <groupId>org.jsoup</groupId>
        <artifactId>jsoup</artifactId>
        <version>1.11.3</version>
    </dependency>

</dependencies>

2.2、编写功能实现类

编写实现抓取网页内容的类

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
 
public class CrawlPageClient {
 
    private String pageUrl;
 
    private CrawlPageClient() {
    }
 
    public CrawlPageClient(String pageUrl) {
        this.pageUrl = pageUrl;
    }
 
    public static CrawlPageClient of(String pageUrl) {
        return new CrawlPageClient(pageUrl);
    }
 
    public String getPageUrl() {
        return pageUrl;
    }
 
    public PageInfo getPageInfo() {
        PageInfo pageInfo = new PageInfo();
        try {
            Document doc = Jsoup.connect(pageUrl).get();
            pageInfo.setUrl(pageUrl);
            pageInfo.setTitle(doc.title());
            pageInfo.setContent(doc.html());
            return pageInfo;
        } catch (Exception e) {
            e.printStackTrace();
        }
 
        return null;
    }
}

网页信息类

public class PageInfo {
    private String url;
    private String title;
    private String content;
 
    public String getUrl() {
        return url;
    }
 
    public void setUrl(String url) {
        this.url = url;
    }
 
    public String getTitle() {
        return title;
    }
 
    public void setTitle(String title) {
        this.title = title;
    }
 
    public String getContent() {
        return content;
    }
 
    public void setContent(String content) {
        this.content = content;
    }
}

2.3、编写自动配置类

import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
@Configuration
@EnableConfigurationProperties( {PageProperties.class })
public class CrawlAutoConfigure {
 
    @Bean
    public CrawlPageClient create(PageProperties pageProperties) {
        return CrawlPageClient.of(pageProperties.getPageUrl());
    }
}

页面配置类，配置前缀：crawl

import org.springframework.boot.context.properties.ConfigurationProperties;
 
@ConfigurationProperties(prefix = PageProperties.CRAWL_PREFIX)
public class PageProperties {
 
    public static final String CRAWL_PREFIX = "crawl";
 
    private String pageUrl = "http://www.baidu.com";
 
    public String getPageUrl() {
        return pageUrl;
    }
 
    public void setPageUrl(String pageUrl) {
        this.pageUrl = pageUrl;
    }
}

默认抓取百度的页面内容

2.4、在resources/META-INF/spring.factories中配置自动装配类

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
cn.river.springboot.CrawlAutoConfigure

2.5、打包

打成jar包: crawl-spring-boot-starter-1.0.jar，maven依赖信息：

<dependency>
    <groupId>cn.river.springboot</groupId>
    <artifactId>crawl-spring-boot-starter</artifactId>
    <version>1.0</version>
</dependency>

3、测试自定义starter

最后，新建测试项目测试自定义的starter。

引入依赖：

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.3.RELEASE</version>
    <relativePath />
</parent>

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

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

    <!-- spring-boot crawl -->
    <dependency>
        <groupId>cn.river.springboot</groupId>
        <artifactId>crawl-spring-boot-starter</artifactId>
        <version>1.0</version>
    </dependency>

</dependencies>

新建测试类：

import cn.river.springboot.CrawlPageClient;
import cn.river.springboot.PageInfo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
@RequestMapping("crawl")
public class CrawlController {
 
    @Autowired
    private CrawlPageClient crawlPageClient;
 
    @GetMapping("")
    @ResponseBody
    public PageInfo crawlPageInfo() {
        StringBuilder pageBuilder = new StringBuilder();
        pageBuilder.append("抓取到").append(crawlPageClient.getPageUrl())
                .append("网页的信息<br/>").append(crawlPageClient.getPageInfo());
        System.out.println(crawlPageClient.getPageInfo());
        return crawlPageClient.getPageInfo();
    }
}

运行程序，浏览器输入：http://127.0.0.1:8080/crawl

默认看到的是百度网页的信息：

我们在application.properties配置中加入以下配置：

crawl.page-url=https://www.csdn.net

抓取网页改成csdn的，再次运行程序，访问内容如下：

4、总结

本文简单介绍如何开发自定义的Spring-Boot-Starter，通过添加依赖自动完成功能导入，使用起来很方便，大家也可以自己动手实现自定义的starter。