webjars 是很方便，方式很多時候我們也需要讀取內容，ClassGraph 是一個高效的classpath 以及模組掃描器
如果查看了webjars 提供的webjars-locator 內部實現也是基於此工具的，但是weebjars 預設提供的功能缺少
內容讀取的能力，我們可以基於ClassGraph提供讀取檔案內容的能力

參考webjars 專案

webjars實際上就是利用了web 容器對於META-INF/resources下資原始檔的自動載入處理，製作一個webjars 就是打包
資源到這個路徑下

• 專案結構

• 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.dalong-web</groupId>
 

  <artifactId>webjars</artifactId>

  <version>1.0-SNAPSHOT</version>

  <properties>

    <java.version>1.8</java.version>

    <package-version>1.0</package-version>

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

    <destinationDir>${project.build.outputDirectory}/META-INF/resources/webjars/dalongdemo/${package-version}</destinationDir>

  </properties>

  <build>

    <resources>

      <resource>

        <directory>${project.basedir}/src/main/resources</directory>

        <targetPath>${destinationDir}</targetPath>

      </resource>

    </resources>

  </build>

</project>

• 構建

mvn clean package install

webjars 引用以及讀取內容

• 專案結構

  就是基於spring start 的web 專案，很簡單

• 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">

  <modelVersion>4.0.0</modelVersion>

  <parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>2.3.1.RELEASE</version>

    <relativePath/> <!-- lookup parent from repository -->

  </parent>

  <groupId>com.dalong</groupId>

  <artifactId>wbjarsapps</artifactId>

  <version>0.0.1-SNAPSHOT</version>

  <name>wbjarsapps</name>

  <description>Demo project for Spring Boot</description>

​

  <properties>

    <java.version>1.8</java.version>

  </properties>

​

  <dependencies>

    <dependency>

      <groupId>org.springframework.boot</groupId>

      <artifactId>spring-boot-starter-web</artifactId>

    </dependency>

​

    <dependency>

      <groupId>io.micrometer</groupId>

      <artifactId>micrometer-registry-prometheus</artifactId>

      <scope>runtime</scope>

    </dependency>

    <dependency>

      <groupId>org.springframework.boot</groupId>

      <artifactId>spring-boot-starter-test</artifactId>

      <scope>test</scope>

      <exclusions>

        <exclusion>

          <groupId>org.junit.vintage</groupId>

          <artifactId>junit-vintage-engine</artifactId>

        </exclusion>

      </exclusions>

    </dependency>

    <dependency>

      <groupId>com.dalong-web</groupId>

      <artifactId>webjars</artifactId>

      <version>1.0-SNAPSHOT</version>

    </dependency>

    <dependency>

      <groupId>io.github.classgraph</groupId>

      <artifactId>classgraph</artifactId>

      <version>4.8.87</version>

    </dependency>

  </dependencies>

  <build>

    <plugins>

      <plugin>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-maven-plugin</artifactId>

      </plugin>

    </plugins>

  </build>

</project>

• 入口

package com.dalong.wbjarsapps;

​

import io.github.classgraph.ClassGraph;

import io.github.classgraph.Resource;

import io.github.classgraph.ScanResult;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.http.HttpHeaders;

import org.springframework.http.HttpStatus;

import org.springframework.http.ResponseEntity;

import org.springframework.util.MultiValueMap;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

​

import java.nio.charset.StandardCharsets;

import java.util.ArrayList;

import java.util.List;

​

@SpringBootApplication

@RestController

public class WbjarsappsApplication {

  public static void main(String[] args) {

    SpringApplication.run(WbjarsappsApplication.class, args);

   }

  @RequestMapping(value = {"/r"})

  public Object listResources() {

     List<String> resultContents = new ArrayList<>();

     ClassGraph classGraph =new ClassGraph();

     try (ScanResult scanResult = classGraph.acceptPaths("META-INF/resources/webjars").scan()) {

      scanResult.getResourcesWithExtension(".js").forEachByteArrayIgnoringIOException((Resource res, byte[] content) -> {

        resultContents.add(new String(content, StandardCharsets.UTF_8));

       });

     }

     MultiValueMap<String,String> headers =new HttpHeaders();

     headers.add("content-type","text/js");

     return new ResponseEntity(resultContents.get(0),headers,HttpStatus.OK);

   }

}

說明

以上是一個簡單的內容讀取，實際上我們基於webjars 的多版本能力可以靈活的用來進行配置管理（比如配置系統，我們可以靈活的管理）
同時結合ClassGraph強大高效的classpath 掃描能力，我們可以增強系統的擴充套件能力

參考資料

https://github.com/classgraph/classgraph
https://www.webjars.org/