JavaSE---Class.getResource与ClassLoader.getResource

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package com.an.classloadertest;
 
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
 
/**
 * @author apy
 * @description
 * @date 2022/3/9 16:44
 */
public class TestMain {
 
    private String name;
    private String job;
 
    public String getJob() {
        return job;
    }
 
    public String getName() {
        return name;
    }
 
    public void setJob(String job) {
        this.job = job;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    @Override
    public String toString() {
        return "TestMain{" +
                "name='" + name + '\'' +
                ", job='" + job + '\'' +
                '}';
    }
 
    public static void main(String[] args) throws IOException, IllegalAccessException, InstantiationException, ClassNotFoundException {
 
        // TestMain.class.getResource("/") 与 testMain.getClass().getClassLoader().getResource("") 路径一致
 
//        test();
 
//        classTest();
 
//        classLoaderTest1();
 
//        classLoaderTest();
 
//        scanPackage();
 
    }
 
    private static void scanPackage() throws IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {
 
        TestMain testMain = new TestMain();
 
        List<File> list = new ArrayList<>();
 
        final String scanPackage = "com/an/classloadertest";
 
        Enumeration<URL> urlEnumeration = testMain.getClass().getClassLoader().getResources(scanPackage);
        while (urlEnumeration.hasMoreElements()){
            URL url = urlEnumeration.nextElement();
            File file = new File(url.getFile());
            list.add(file);
        }
 
        String[] resources = list.stream().findFirst().get().list();
        for (String resource : resources){
 
            if (resource.equals("TestMain.class")){
                Class<?> testClass = Class.forName(scanPackage.replace("/", ".") + "." + resource.replace(".class", ""));
                Object newInstance = testClass.newInstance();
                System.out.println(newInstance); // TestMain{name='null', job='null'}
            }
        }
 
 
 
    }
 
    private static void classLoaderTest1() {
 
        TestMain testMain = new TestMain();
 
        System.out.println(testMain.getClass().getClassLoader().getResource(""));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/
 
        System.out.println(testMain.getClass().getClassLoader().getResource("1.properties"));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/1.properties
 
        System.out.println(testMain.getClass().getClassLoader().getResource("com/an/classloadertest/2.properties"));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/com/an/classloadertest/2.properties
 
        System.out.println(testMain.getClass().getClassLoader().getResource("com/an/classloadertest/sub/3.properties"));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/com/an/classloadertest/sub/3.properties
 
    }
 
    private static void classLoaderTest() {
 
        TestMain testMain = new TestMain();
 
        System.out.println(testMain.getClass());
        //class com.an.classloadertest.TestMain
 
        System.out.println(testMain.getClass().getClassLoader());
        //sun.misc.Launcher$AppClassLoader@18b4aac2
 
        System.out.println(testMain.getClass().getClassLoader().getResource(""));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/
 
        System.out.println(testMain.getClass().getClassLoader().getResource("/"));
        //null
    }
 
    private static void classTest() {
 
        System.out.println(TestMain.class.getResource(""));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/com/an/classloadertest/
 
        System.out.println(TestMain.class.getResource("/"));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/
 
        System.out.println(TestMain.class.getResource("2.properties"));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/com/an/classloadertest/2.properties
 
        System.out.println(TestMain.class.getResource("sub/3.properties"));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/com/an/classloadertest/sub/3.properties
 
        System.out.println(TestMain.class.getResource("/1.properties"));
        //file:/Users/an/IdeaProjects/demo/javase/target/classes/1.properties
    }
 
    private static void test() {
 
        System.out.println(TestMain.class.getResource(""));
        // file:/Users/an/IdeaProjects/demo/javase/target/classes/com/an/classloadertest/
 
        System.out.println(TestMain.class.getResource("/"));
        // file:/Users/an/IdeaProjects/demo/javase/target/classes/
 
    }
 
}