classloader

Author: BestBurning

.gitignore

@@ -111,3 +111,7 @@ hs_err_pid*
 
 *.iml
 .idea/*
+*.project
+*.prefs
+*.classpath
+*.factorypath

java-base/src/main/java/com/di1shuai/base/jvm/ByteCode.java

@@ -0,0 +1,9 @@
+package com.di1shuai.base.jvm;
+
+/**
+ * @author: shea
+ * @date: 2021/7/13
+ * @description:
+ */
+public class ByteCode {
+}

java-base/src/main/java/com/di1shuai/base/jvm/classloader/EncriptionClassLoader.java

@@ -0,0 +1,69 @@
+package com.di1shuai.base.jvm.classloader;
+
+import java.io.*;
+
+/**
+ * @author: shea
+ * @date: 2021/7/29
+ * @description: classloader应用：
+ * 加密classloader
+ * <p>
+ *     x ^ y ^ y = x
+ * 生成class文件后进行加密
+ * 使用解密的classloader进行读取
+ */
+public class EncriptionClassLoader extends ClassLoader {
+
+
+    private static final int seed = 0B10110110;
+
+    private static final String basepath = "/Users/shea/Documents/GitRepo/mine/back-end/java-versions/java-8/target/classes/";
+//    String basepath = "/Users/shea/Documents/GitRepo/mine/back-end/java-versions/java-base/target/classes";
+
+    @Override
+    protected Class<?> findClass(String name) throws ClassNotFoundException {
+        System.out.println("======进入自定义ClassLoader - findClass =====");
+        File file = new File(basepath, name.replaceAll("\\.", "/").concat(".di1shuaiclass"));
+        try {
+            FileInputStream fileInputStream = new FileInputStream(file);
+            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+            int b = 0;
+            while ((b = fileInputStream.read()) != -1) {
+                byteArrayOutputStream.write(b ^ seed);
+            }
+            fileInputStream.close();
+            byteArrayOutputStream.close();
+            byte[] bytes = byteArrayOutputStream.toByteArray();
+            return defineClass(name, bytes, 0, bytes.length);
+        } catch (Exception e) {
+            e.printStackTrace();
+        } finally {
+            System.out.println("======结束自定义ClassLoader - findClass=====");
+        }
+        return super.findClass(name);
+    }
+
+
+    public static void main(String[] args) throws Exception {
+//        String className = "com.di1shuai.base.gc.HelloJVM";
+        String className = "com.diyishuai.java8.Student";
+        encFile(className);
+        EncriptionClassLoader encriptionClassLoader = new EncriptionClassLoader();
+        Class<?> aClass = encriptionClassLoader.loadClass(className);
+        System.out.println(aClass);
+    }
+
+    private static void encFile(String name) throws Exception {
+        File file = new File(basepath, name.replaceAll("\\.", "/").concat(".class"));
+        FileInputStream fileInputStream = new FileInputStream(file);
+        FileOutputStream fileOutputStream = new FileOutputStream(new File(basepath, name.replaceAll("\\.", "/").concat(".di1shuaiclass")));
+        int b = 0;
+        while ((b = fileInputStream.read()) != -1) {
+            fileOutputStream.write(b ^ seed);
+        }
+        fileInputStream.close();
+        fileOutputStream.close();
+    }
+
+
+}

java-base/src/main/java/com/di1shuai/base/jvm/classloader/HelloClassLoader.java

@@ -0,0 +1,51 @@
+package com.di1shuai.base.jvm.classloader;
+
+import java.io.*;
+
+/**
+ * @author: shea
+ * @date: 2021/7/29
+ * @description: 自定义类加载器
+ * 指定文件路径进行加载
+ */
+public class HelloClassLoader extends ClassLoader {
+
+    String basepath = "/Users/shea/Documents/GitRepo/mine/back-end/java-versions/java-8/target/classes/";
+//    String basepath = "/Users/shea/Documents/GitRepo/mine/back-end/java-versions/java-base/target/classes";
+
+    @Override
+    protected Class<?> findClass(String name) throws ClassNotFoundException {
+        System.out.println("======进入自定义ClassLoader - findClass =====");
+        File file = new File(basepath, name.replaceAll("\\.", "/").concat(".class"));
+        try {
+            FileInputStream fileInputStream = new FileInputStream(file);
+            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+            int b = 0;
+            while ((b = fileInputStream.read()) != -1) {
+                byteArrayOutputStream.write(b);
+            }
+            fileInputStream.close();
+            byteArrayOutputStream.close();
+            byte[] bytes = byteArrayOutputStream.toByteArray();
+            return defineClass(name, bytes, 0, bytes.length);
+        } catch (Exception e) {
+            e.printStackTrace();
+        } finally {
+            System.out.println("======结束自定义ClassLoader - findClass=====");
+        }
+        return super.findClass(name);
+    }
+
+
+    public static void main(String[] args) throws ClassNotFoundException {
+//        String className = "com.di1shuai.base.gc.HelloJVM";
+        String className = "com.diyishuai.java8.Student";
+
+        HelloClassLoader helloClassLoader = new HelloClassLoader();
+        Class<?> aClass = helloClassLoader.loadClass(className);
+        System.out.println(aClass);
+
+
+    }
+
+}

java-base/src/main/java/com/di1shuai/base/jvm/classloader/JVMClassLoader.java

@@ -0,0 +1,42 @@
+package com.di1shuai.base.jvm.classloader;
+
+/**
+ * @author: shea
+ * @date: 2021/7/28
+ * @description:
+ */
+public class JVMClassLoader {
+
+    public static void main(String[] args) {
+        // null -> Bootstrap
+        // 为什么为Null，因为Bootstrap使用C++写的，在Java中没有与之相对应的类，所以返回了空值
+        System.out.println(String.class.getClassLoader()); 
+        
+        //sun.misc.Launcher$ExtClassLoader@3d4eac69 -> Extention
+        System.out.println(sun.net.spi.nameservice.dns.DNSNameService.class.getClassLoader()); 
+        
+        //sun.misc.Launcher$AppClassLoader@6d06d69c -> App
+        System.out.println(JVMClassLoader.class.getClassLoader());
+        
+        
+        
+        //双亲委派
+        System.out.println("===================");
+        // null -> Bootstrap
+        System.out.println(sun.net.spi.nameservice.dns.DNSNameService.class.getClassLoader().getClass().getClassLoader()); 
+        // null -> Bootstrap
+        System.out.println(JVMClassLoader.class.getClassLoader().getClass().getClassLoader());
+        
+        // app -> extention -> bootstrap
+        System.out.println(JVMClassLoader.class.getClassLoader().getParent());
+        System.out.println(JVMClassLoader.class.getClassLoader().getParent().getParent());
+
+        // 范围
+        System.out.println(System.getProperty("sun.boot.class.path"));
+        System.out.println(System.getProperty("java.ext.dirs"));
+        System.out.println(System.getProperty("java.class.path"));
+
+
+    }
+
+}