1 课堂解析
2 代码演练
2.1 枚举类单例解决序列化破坏demo
2.2 枚举类单例解决序列化破坏原理
2.3 枚举类单例解决反射攻击demo
2.4 枚举类单例解决反射攻击原理
3 jad的使用
3.1 网址：
1 课堂解析
2 代码演练
2.1 枚举类单例解决序列化破坏demo
枚举类：
package com.geely.design.pattern.creational.singleton; /**
* 这个类是enum类型
*/
public enum EnumInstance {
INSTANCE;
private Object data;
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
/**
* Java类中的静态变量在程序运行期间，其内存空间对所有该类的对象实例而言是共享的，有些时候可以认为是全局变量。
* 因此在某些时候为了节省系统内存开销、共享资源，可以将类中的一些变量声明为静态变量!
*
* 最最主要的原因，单例模式外部类不能new出对象，要使用该方法只能是静态的
*
* 最终返回的肯定是本类，所以该方法的类型为EnumInstance
*/
public static EnumInstance getInstane(){
return INSTANCE;
} }
测试类：
package com.geely.design.pattern.creational.singleton; import java.io.*;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException; public class Test {
/**
* 序列化代码演练
* 将 HungrySingleton对象放入文件，再从文件读取该对象，还是同一个对象吗？
* 实际应用：在从文件存入后读取，用equals时需要注意（equals比较的是hash码）
*
* @param args
*/
public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
try {
//将singleton对象写入到输出流中
EnumInstance instance = EnumInstance.getInstane();
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("singleton_file"));
oos.writeObject(instance); //从输入流中读取到该对象
File file = new File("singleton_file");
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
EnumInstance instance2 = (EnumInstance) ois.readObject();
System.out.println(instance);
System.out.println(instance2);
System.out.println(instance == instance2);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} }
}
打印日志：
"C:\Program Files\Java\jdk1.7.0_79\bin\java.exe" "-javaagent:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\lib\idea_rt.jar=42967:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.7.0_79\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jce.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfxrt.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\resources.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\rt.jar;F:\xiangmu3\Xin\Idea\design_pattern\target\classes" com.geely.design.pattern.creational.singleton.Test
INSTANCE
INSTANCE
true Process finished with exit code 0
2.2 枚举类单例解决序列化破坏原理
ObjectInputStream
/**
* Underlying readObject implementation.
*/
private Object readObject0(boolean unshared) throws IOException {
boolean oldMode = bin.getBlockDataMode();
if (oldMode) {
int remain = bin.currentBlockRemaining();
if (remain > 0) {
throw new OptionalDataException(remain);
} else if (defaultDataEnd) {
/*
* Fix for 4360508: stream is currently at the end of a field
* value block written via default serialization; since there
* is no terminating TC_ENDBLOCKDATA tag, simulate
* end-of-custom-data behavior explicitly.
*/
throw new OptionalDataException(true);
}
bin.setBlockDataMode(false);
} byte tc;
while ((tc = bin.peekByte()) == TC_RESET) {
bin.readByte();
handleReset();
} depth++;
try {
switch (tc) {
case TC_NULL:
return readNull(); case TC_REFERENCE:
return readHandle(unshared); case TC_CLASS:
return readClass(unshared); case TC_CLASSDESC:
case TC_PROXYCLASSDESC:
return readClassDesc(unshared); case TC_STRING:
case TC_LONGSTRING:
return checkResolve(readString(unshared)); case TC_ARRAY:
return checkResolve(readArray(unshared));
/*
* 注意：读取enum
*
*/
case TC_ENUM:
return checkResolve(readEnum(unshared)); case TC_OBJECT:
return checkResolve(readOrdinaryObject(unshared)); case TC_EXCEPTION:
IOException ex = readFatalException();
throw new WriteAbortedException("writing aborted", ex); case TC_BLOCKDATA:
case TC_BLOCKDATALONG:
if (oldMode) {
bin.setBlockDataMode(true);
bin.peek(); // force header read
throw new OptionalDataException(
bin.currentBlockRemaining());
} else {
throw new StreamCorruptedException(
"unexpected block data");
} case TC_ENDBLOCKDATA:
if (oldMode) {
throw new OptionalDataException(true);
} else {
throw new StreamCorruptedException(
"unexpected end of block data");
} default:
throw new StreamCorruptedException(
String.format("invalid type code: %02X", tc));
}
} finally {
depth--;
bin.setBlockDataMode(oldMode);
}
} /**
* Reads in and returns enum constant, or null if enum type is
* unresolvable. Sets passHandle to enum constant's assigned handle.
*/
private Enum readEnum(boolean unshared) throws IOException {
if (bin.readByte() != TC_ENUM) {
throw new InternalError();
} ObjectStreamClass desc = readClassDesc(false);
if (!desc.isEnum()) {
throw new InvalidClassException("non-enum class: " + desc);
} int enumHandle = handles.assign(unshared ? unsharedMarker : null);
ClassNotFoundException resolveEx = desc.getResolveException();
if (resolveEx != null) {
handles.markException(enumHandle, resolveEx);
} String name = readString(false);//通过readString方法获取到枚举对象的名称
Enum en = null;
Class cl = desc.forClass();
if (cl != null) {
try {
en = Enum.valueOf(cl, name);//通过类型和名称获取到枚举常量，枚举中的name是唯一的，并且对应一个枚举常量，所以拿到的肯定是唯一的对象。
} catch (IllegalArgumentException ex) {
throw (IOException) new InvalidObjectException(
"enum constant " + name + " does not exist in " +
cl).initCause(ex);
}
if (!unshared) {
handles.setObject(enumHandle, en);
}
} handles.finish(enumHandle);
passHandle = enumHandle;
return en;
}
2.3 枚举类单例解决反射攻击demo
枚举类：(同2.1)
package com.geely.design.pattern.creational.singleton; /**
* 这个类是enum类型
*/
public enum EnumInstance {
INSTANCE;
private Object data;
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
/**
* Java类中的静态变量在程序运行期间，其内存空间对所有该类的对象实例而言是共享的，有些时候可以认为是全局变量。
* 因此在某些时候为了节省系统内存开销、共享资源，可以将类中的一些变量声明为静态变量!
*
* 最最主要的原因，单例模式外部类不能new出对象，要使用该方法只能是静态的
*
* 最终返回的肯定是本类，所以该方法的类型为EnumInstance
*/
public static EnumInstance getInstane(){
return INSTANCE;
} }
测试类：
package com.geely.design.pattern.creational.singleton; import java.io.*;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException; public class Test { /**
* 序列化代码演练
* 将 HungrySingleton对象放入文件，再从文件读取该对象，还是同一个对象吗？
* 实际应用：在从文件存入后读取，用equals时需要注意（equals比较的是hash码）
*
* @param args
*/
public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
/*try {
//将singleton对象写入到输出流中
EnumInstance instance = EnumInstance.getInstane();
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("singleton_file"));
oos.writeObject(instance); //从输入流中读取到该对象
File file = new File("singleton_file");
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
EnumInstance instance2 = (EnumInstance) ois.readObject();
System.out.println(instance);
System.out.println(instance2);
System.out.println(instance == instance2);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}*/ Class objectClass = EnumInstance.class;
Constructor constructor = objectClass.getDeclaredConstructor();
constructor.setAccessible(true);
}
}
打印结果：
"C:\Program Files\Java\jdk1.7.0_79\bin\java.exe" "-javaagent:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\lib\idea_rt.jar=43086:D:\java\devolopKit\idea\anZh\IntelliJ IDEA Community Edition 2018.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.7.0_79\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jce.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jfxrt.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\resources.jar;C:\Program Files\Java\jdk1.7.0_79\jre\lib\rt.jar;F:\xiangmu3\Xin\Idea\design_pattern\target\classes" com.geely.design.pattern.creational.singleton.Test
Exception in thread "main" java.lang.NoSuchMethodException: com.geely.design.pattern.creational.singleton.EnumInstance.<init>()
at java.lang.Class.getConstructor0(Class.java:2892)
at java.lang.Class.getDeclaredConstructor(Class.java:2058)
at com.geely.design.pattern.creational.singleton.Test.main(Test.java:148) Process finished with exit code 1
反射有参对象：
package com.geely.design.pattern.creational.singleton; import java.io.*;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException; public class Test {
/**
* 序列化代码演练
* 将 HungrySingleton对象放入文件，再从文件读取该对象，还是同一个对象吗？
* 实际应用：在从文件存入后读取，用equals时需要注意（equals比较的是hash码）
*
* @param args
*/
public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
/*try {
//将singleton对象写入到输出流中
EnumInstance instance = EnumInstance.getInstane();
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("singleton_file"));
oos.writeObject(instance); //从输入流中读取到该对象
File file = new File("singleton_file");
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
EnumInstance instance2 = (EnumInstance) ois.readObject();
System.out.println(instance);
System.out.println(instance2);
System.out.println(instance == instance2);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}*/ Class objectClass = EnumInstance.class;
Constructor constructor = objectClass.getDeclaredConstructor(String.class,int.class);
constructor.setAccessible(true);
EnumInstance enumInstance = (EnumInstance) constructor.newInstance("dd",123); }
}
打印结果：
Exception in thread "main" java.lang.IllegalArgumentException: Cannot reflectively create enum objects
at java.lang.reflect.Constructor.newInstance(Constructor.java:521)
at com.geely.design.pattern.creational.singleton.Test.main(Test.java:150) Process finished with exit code 1
2.4 枚举类单例解决反射攻击原理
Enum.java
只有有参构造器
protected Enum(String name, int ordinal) {
this.name = name;
this.ordinal = ordinal;
}
Constructor.java
/**
* Uses the constructor represented by this {@code Constructor} object to
* create and initialize a new instance of the constructor's
* declaring class, with the specified initialization parameters.
* Individual parameters are automatically unwrapped to match
* primitive formal parameters, and both primitive and reference
* parameters are subject to method invocation conversions as necessary.
*
* <p>If the number of formal parameters required by the underlying constructor
* is 0, the supplied {@code initargs} array may be of length 0 or null.
*
* <p>If the constructor's declaring class is an inner class in a
* non-static context, the first argument to the constructor needs
* to be the enclosing instance; see section 15.9.3 of
* <cite>The Java™ Language Specification</cite>.
*
* <p>If the required access and argument checks succeed and the
* instantiation will proceed, the constructor's declaring class
* is initialized if it has not already been initialized.
*
* <p>If the constructor completes normally, returns the newly
* created and initialized instance.
*
* @param initargs array of objects to be passed as arguments to
* the constructor call; values of primitive types are wrapped in
* a wrapper object of the appropriate type (e.g. a {@code float}
* in a {@link java.lang.Float Float})
*
* @return a new object created by calling the constructor
* this object represents
*
* @exception IllegalAccessException if this {@code Constructor} object
* is enforcing Java language access control and the underlying
* constructor is inaccessible.
* @exception IllegalArgumentException if the number of actual
* and formal parameters differ; if an unwrapping
* conversion for primitive arguments fails; or if,
* after possible unwrapping, a parameter value
* cannot be converted to the corresponding formal
* parameter type by a method invocation conversion; if
* this constructor pertains to an enum type.
* @exception InstantiationException if the class that declares the
* underlying constructor represents an abstract class.
* @exception InvocationTargetException if the underlying constructor
* throws an exception.
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails.
*/
@CallerSensitive
public T newInstance(Object ... initargs)
throws InstantiationException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, null, modifiers);
}
}
if ((clazz.getModifiers() & Modifier.ENUM) != 0)//如果目标类是枚举类型，抛出异常
throw new IllegalArgumentException("Cannot reflectively create enum objects");
ConstructorAccessor ca = constructorAccessor; // read volatile
if (ca == null) {
ca = acquireConstructorAccessor();
}
return (T) ca.newInstance(initargs);
3 jad的使用
3.1 网址：
https://varaneckas.com/jad/
