Project practice: component scanning implementation (1) – scanning all files on the class path

1. ComponentScan component scanning class

I have summarized the following knowledge under the Maven project, so the directory structure will be different

The function of this class is to scan all bytecode files in all classes directories, find the corresponding class, and then find the annotations on the corresponding class.
package com.csdn.mymvc.core;
import java.io.File;
import java.util.HashMap;
import java.util.Map;
public class ComponentScan {
    public static Map<String, Object> beanFactory = new HashMap<>();
    static String path = null;
    static {
        //Analyze folder
        path = ComponentScan.class.getClassLoader().getResource("").getPath();
        // /F:/IdeaProjects/workspace/review/pro13-fruit-DispatcherServlet/target/pro13-fruit-DispatcherServlet-1.0-SNAPSHOT/WEB-INF/classes/
        //The root directory of the computer's hard disk is /, no matter what operating system it is. It's just Microsoft's artificial concept of dividing drive letters.
        //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);
        //Start parsing the folder - component scanning begins
        parseFile(rootDir);
    }

    private static void parseFile(File file) {
        if (file.exists()) {
            if (file.isDirectory()) {
                //Get all subdirectories
                File[] childFiles = file.listFiles();
                for (File childFile : childFiles) {
                      parseFile(childFile);
                }
            } else {
                String absPath = file.getAbsolutePath();
                System.out.println(absPath);
            }
        }
    }
}
The following are all the bytecode files we scanned in the classes folder

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. Get the URL path: 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/

It can be found that the above path is not what we want, and file needs to be removed:

3. Remove 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/

We found that there is still an extra / slash and we need to remove the / slash
<strong>The root directory of your computer's hard drive is / , regardless of the operating system. It's just Microsoft's artificial concept of dividing drive letters</strong>

4. Remove the slash / : 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/

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