start.sping.io代码研读及二次开发

水深无声 2023-01-10 14:44 33阅读 0赞

>    Spring是Java开发者的圣经，[https://spring.io][https_spring.io]官网作为布道场。开发者几乎能在上面找到关于Spring的一切信息，当然也包括官方推荐项目代码规范。其中[https://start.spring.io][https_start.spring.io]既是官方的手脚架工程，也常被初学者用来生成入门工程。这个站点也是一个开源Spring项目，颇有些自举的骄傲（Git也有这种骄傲）。国内大厂某云平台也发布了定制化版本。

## 相关资源 ##

### 项目列表 ###

*  [initializr][]
 *  [start.spring.io][]

### 官网文档 ###

*  [Spring Initializr Reference Guide][]

## 本地构建 ##

国内很多开发者会构建本地版本作为加速镜像，这也是[start.spring.io][]项目最常用的功能。

这项目带有[https://start.spring.io][https_start.spring.io]前端界面的配置化[Spring Initializr][initializr] 实例。包含下列模块：

*  start-client: 前端界面
 *  start-site: 后端基础服务和元数据配置
 *  start-site-verification: 元数据测试用例

执行`./mvnw clean install`生成**target/start-site-exec.jar**即可运行。值得借鉴的是`frontend-maven-plugin`插件，通过maven插件来代替shell脚本，更显规范。

<plugin>
    	<groupId>com.github.eirslett</groupId>
    	<artifactId>frontend-maven-plugin</artifactId>
    	<executions>
    		<execution>
    			<id>install node and yarn</id>
    			<goals>
    				<goal>install-node-and-yarn</goal>
    			</goals>
    			<configuration>
    				<nodeVersion>v12.13.0</nodeVersion>
    				<yarnVersion>v1.22.4</yarnVersion>
    			</configuration>
    		</execution>
    		<execution>
    			<id>yarn install</id>
    			<goals>
    				<goal>yarn</goal>
    			</goals>
    		</execution>
    		<execution>
    			<id>yarn build</id>
    			<goals>
    				<goal>yarn</goal>
    			</goals>
    			<configuration>
    				<arguments>build</arguments>
    			</configuration>
    		</execution>
    	</executions>
    </plugin>

`start-client`项目会将静态资源打包成`start-client-0.0.1-SNAPSHOT.jar`，然后被`start-site`项目引入。

## 代码研读 ##

拜读官方文档可知，[start.spring.io][]项目只是门面，[initializr][]才是里子。[initializr文档][initializr 1]介绍项目结构：

*  **initializr-actuator**: optional module to provide additional information and statistics on project generation.
 *  **initializr-bom**: provides a Bill of Materials for easier dependency management in your project.
 *  **initializr-docs**: documentation.
 *  **initializr-generator**: core project generation library.
 *  **initializr-generator-spring**: optional module defining the conventions for a typical Spring Boot project. Can be reused or replaced by your own conventions.
 *  **initializr-generator-test**: test infrastructure for project generation.
 *  **initializr-metadata**: metadata infrastructure for various aspects of the project.
 *  **initializr-service-sample**: showcases a basic custom instance.
 *  **initializr-version-resolver**: optional module to extract version numbers from an arbitrary POM.
 *  **initializr-web**: web endpoints for third party clients.

为了了解生成原理，主要看 **initializr-generator** and **initializr-generator-spring** 。**initializr-generator**中的`ProjectGenerator`类是项目生成的单元。

public <T> T generate(ProjectDescription description, ProjectAssetGenerator<T> projectAssetGenerator)
    		throws ProjectGenerationException { 
    	try (ProjectGenerationContext context = this.contextFactory.get()) { 
    		registerProjectDescription(context, description);
    		registerProjectContributors(context, description);
    		this.contextConsumer.accept(context);
    		context.refresh();
    		try { 
    			return projectAssetGenerator.generate(context);
    		}
    		catch (IOException ex) { 
    			throw new ProjectGenerationException("Failed to generate project", ex);
    		}
    	}
    }

首先在`/src/main/resources/META-INF/spring.factories`文件注册配置文件，然后通过`@ProjectGenerationConfiguration`注解扫描获取配置，然后遍历执行其中的配置项生成代码。

### 二次开发 ###

官方文档预留了丰富的扩展接口，详见[6.1.1节][6.1.1]。具体实现就是追加或重写配置文件，对于应用级开发直接在[start.spring.io][https_start.spring.io]项目内开发。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg_size_16_color_FFFFFF_t_70_pic_center]

### 关键代码 ###

*  FcsGenerationConfiguration.java

@ProjectGenerationConfiguration
    public class FcsGenerationConfiguration { 
    	@Bean
    	public FcsContributor fcsContributor(ProjectDescription description,TemplateRenderer templateRenderer) { 
    		return new FcsContributor(description, templateRenderer);
    	}
    }

*  FcsContributor.java

public class FcsContributor implements ProjectContributor { 
    	
    	private final ProjectDescription description;
    	private final TemplateRenderer templateRenderer;
    	private final String SOURCE_PATH = "src/main/java/";
    	
    	public FcsContributor(ProjectDescription description, TemplateRenderer templateRenderer) { 
    		this.description = description;
    		this.templateRenderer = templateRenderer;
    	}
    
    	@Override
    	public void contribute(Path projectRoot) throws IOException { 
    		Map<String, Object> data = new HashMap<>();
    		String groupId = description.getGroupId();
    		String artifactId = description.getArtifactId();
    		data.put("groupId", groupId);
    		data.put("artifactId", artifactId);
    		
            Path file = Files.createFile(projectRoot.resolve("README.md"));
            String pre = SOURCE_PATH + groupId.replace(".", "/") + "/" + artifactId;
            Files.createDirectories(projectRoot.resolve(pre+"/controller/"));
            Path codeFile = Files.createFile(projectRoot.resolve(pre+"/controller/DemoController.java"));
            String code = this.templateRenderer.render("code/DemoController.java", data);
            try (
            	PrintWriter writer = new PrintWriter(Files.newBufferedWriter(file));
            	PrintWriter codeWriter = new PrintWriter(Files.newBufferedWriter(codeFile));
            ) { 
                writer.println("README");
                codeWriter.print(code);
            }
    	}
    }

### 生成效果 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg_size_16_color_FFFFFF_t_70_pic_center 1]

## 总结 ##

*  [start.spring.io][]作为手脚架工程虽说用的次数不多，但作为一个技术风向标值得Java开发者关注。
 *  其打包构建方式，为后续构建流水线提供一个选项。
 *  易于二次开发适配团队的开发风格（配置Maven私有仓库更佳），利于统一团队内的开发架构。

[https_spring.io]: https://spring.io/
[https_start.spring.io]: https://start.spring.io
[initializr]: https://github.com/spring-io/initializr
[start.spring.io]: https://github.com/spring-io/start.spring.io
[Spring Initializr Reference Guide]: https://docs.spring.io/initializr/docs/current-SNAPSHOT/reference/html/
[initializr 1]: https://docs.spring.io/initializr/docs/current-SNAPSHOT/reference/html/#configuration-guide
[6.1.1]: https://docs.spring.io/initializr/docs/current-SNAPSHOT/reference/html/#initializr-generator-project
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