项目实战：组件扫描实现(1)-扫描类路径所有文件

 1、ComponentScan  组件扫描类

• 一下知识本人都是在Maven工程下总结的，所以目录结构会不一样
• 这个类的作用是扫描所有的classes目录下的所有的字节码文件，找到相应的类，然后找到相应类上的注解

package com.csdn.mymvc.core;
import java.io.File;
import java.util.HashMap;
import java.util.Map;
public class ComponentScan {
    public static Map beanFactory = new HashMap<>();
    static String path = null;
    static {
        //分析文件夹
        path = ComponentScan.class.getClassLoader().getResource("").getPath();
        //  /F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/
        //计算机的硬盘根目录是 / ，不论是什么操作系统。只是微软人为的分出盘符的概念
        //System.out.println(path);
        path = path.substring(1);
        //   F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/
        File rootDir = new File(path);
        //开始解析文件夹 - 组件扫描工作开始
        parseFile(rootDir);
    }

    private static void parseFile(File file) {
        if (file.exists()) {
            if (file.isDirectory()) {
                //获取所有的子目录
                File[] childFiles = file.listFiles();
                for (File childFile : childFiles) {
                      parseFile(childFile);
                }
            } else {
                String absPath = file.getAbsolutePath();
                System.out.println(absPath);
            }
        }
    }
}

• 以下是我们扫描classes文件夹下的所有字节码文件 
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\dao\FruitDao.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\dao\impl\FruitDaoImpl.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\dto\PageInfo.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\dto\PageQueryParam.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\dto\Result.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\service\FruitService.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\service\impl\FruitServiceImpl.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\servlet\FruitController.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\util\GsonUtil.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\util\RequestUtil.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\fruit\util\ResponseUtil.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\annotation\Autowire.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\annotation\Controller.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\annotation\GetMapping.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\annotation\PostMapping.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\annotation\Repository.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\annotation\RequestMapping.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\annotation\Service.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\core\ComponentScan.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\core\DispatcherServlet.class
• F:\IdeaProjects\workspace\review\pro13-fruit-DispatcherServlet\target\pro13-fruit-DispatcherServlet-1.0-SNAPSHOT\WEB-INF\classes\com\csdn\mymvc\listener\ContextLoaderListener.class

 2、获取URL路径: getResource()

URL resource = ComponentScan.class.getClassLoader().getResource("");
System.out.println(resource);
file:/F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/

• file:/F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/
• 可以发现以上路径不是我们想要的，需要去掉     file:

3、去掉 file: getPath()

String path = ComponentScan.class.getClassLoader().getResource("").getPath();
System.out.println(path);
/F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/

• /F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/
• 我们发现还是多了一个 / 斜杠，需要把 / 斜杠去掉

• 计算机的硬盘根目录是 / ，不论是什么操作系统。只是微软人为的分出盘符的概念

4、去掉斜杠 / : substring(1)

String path = ComponentScan.class.getClassLoader().getResource("").getPath();
path = path.substring(1);
System.out.println(path)
F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/

• F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/