feat:完成自定义类加载器的自定义加载逻辑 (#3)

merge

Author: XianReallyHot-ZZH

src/main/java/club/shengsheng/MyClassLoader.java

@@ -1,9 +1,74 @@
 package club.shengsheng;
 
 
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+
 /**
  * @author gongxuanzhangmelt@gmail.com
  **/
 public class MyClassLoader extends ClassLoader {
 
+    /**
+     * 重写findClass方法，让其查找我们指定路径下的class文件，并完成定义加载
+     *
+     * @param name
+     * @return
+     * @throws ClassNotFoundException
+     */
+    @Override
+    protected Class<?> findClass(String name) throws ClassNotFoundException {
+        // 1、读取项目根目录中的加密.class文件，获取class文件的字节数组
+        String projectDir = System.getProperty("user.dir"); // 获取项目根目录
+        String filePath = projectDir + File.separator + "加密.class";
+        byte[] classBytes = readClassFile(filePath);
+
+        if (classBytes == null) {
+            throw new ClassNotFoundException("无法加载类：" + name);
+        }
+
+        // 2、解密字节数组，并返回解密后的字节数组。解密规则：每个字节减1
+        classBytes = decryptClassBytes(classBytes);
+
+        return defineClass(name, classBytes, 0, classBytes.length);
+    }
+
+    private byte[] decryptClassBytes(byte[] classBytes) {
+        for (int i = 0; i < classBytes.length; i++) {
+            classBytes[i] = (byte) (classBytes[i] - 1);
+        }
+        return classBytes;
+    }
+
+    /**
+     * 读取class文件到字节数组
+     *
+     * @param filePath class文件路径
+     * @return 字节数组 或 null
+     */
+    private byte[] readClassFile(String filePath) {
+        File file = new File(filePath);
+        if (!file.exists()) {
+            System.err.println("文件不存在: " + filePath);
+            return null;
+        }
+
+        try (FileInputStream fis = new FileInputStream(file);
+             ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+
+            byte[] buffer = new byte[1024];
+            int bytesRead;
+            while ((bytesRead = fis.read(buffer)) != -1) {
+                baos.write(buffer, 0, bytesRead);
+            }
+            return baos.toByteArray();
+
+        } catch (IOException e) {
+            e.printStackTrace();
+            return null;
+        }
+    }
+
 }