package org.example.io;
import java.io.Serializable;
//類通過實現 java.io.Serializable 接口以啓用其序列化功能。
public class Person implements Serializable {
//通過id來判斷類是否改變
private static final long serialVersionUID = 3;
private transient String name;
//不需要序列化的成員變量
private int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + "]";
}
}
0xACED:根據協議文檔的約定,由於所有二進制流(文件)都需要在流的頭部約定魔數(magic number=STREAM_MAGIC),既java object 序列化後的流的魔數約定爲ACED;
0x0005:然後是流協議版本是short類型(2字節)並且值爲5,則十六進制值爲0005;
java byte型長度爲1字節,所以0x73 0x72直接對應到字節流上,0x73(TC_OBJECT)代表這是一個對象,0x72(TC_CLASSDESC)代表這個之後開始是對類的描述.
接着類長度,我也不知道爲啥是15
類全限定名
序列化id
0x02:表示可以序列化
0001:表示只有一個字段
49:表示int類型
0003:字段名長度
接着字段名
0x78:該塊定義的序列化流結束了
0x70是NULL,沒有超類了.
00000002:表示字段值
ObjectInputStream
public ObjectInputStream(InputStream in) throws IOException {
//校驗是否是子類
verifySubclass();
bin = new BlockDataInputStream(in);
handles = new HandleTable(10);
vlist = new ValidationList();
serialFilter = ObjectInputFilter.Config.getSerialFilter();
enableOverride = false;
//驗證魔數和版本號
readStreamHeader();
bin.setBlockDataMode(true);
}
protected void readStreamHeader()
throws IOException, StreamCorruptedException
{
short s0 = bin.readShort();
short s1 = bin.readShort();
//魔數,用來描述這個文件到底啥類型,ACED
if (s0 != STREAM_MAGIC ||
//class版本號,0005
s1 != STREAM_VERSION) {
throw new StreamCorruptedException(
String.format("invalid stream header: %04X%04X", s0, s1));
}
}
反序列化
//讀取輸入流數據,返回一個對象
public final Object readObject()
throws IOException, ClassNotFoundException
{
//爲true,則調用readObjectOverride(),調用子類覆蓋方法
if (enableOverride) {
return readObjectOverride();
}
// if nested read, passHandle contains handle of enclosing object
int outerHandle = passHandle;
try {
//加載對象
Object obj = readObject0(false);
handles.markDependency(outerHandle, passHandle);
ClassNotFoundException ex = handles.lookupException(passHandle);
if (ex != null) {
throw ex;
}
if (depth == 0) {
vlist.doCallbacks();
}
return obj;
} finally {
passHandle = outerHandle;
if (closed && depth == 0) {
clear();
}
}
}
protected Object readObjectOverride()
throws IOException, ClassNotFoundException
{
return null;
}
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++;
totalObjectRefs++;
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));
case TC_ENUM:
return checkResolve(readEnum(unshared));
//0x73 則新建對象
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);
}
}
private Object readOrdinaryObject(boolean unshared)
throws IOException
{
if (bin.readByte() != TC_OBJECT) {
throw new InternalError();
}
//獲取類的描述
ObjectStreamClass desc = readClassDesc(false);
desc.checkDeserialize();
Class<?> cl = desc.forClass();
if (cl == String.class || cl == Class.class
|| cl == ObjectStreamClass.class) {
throw new InvalidClassException("invalid class descriptor");
}
Object obj;
try {
obj = desc.isInstantiable() ? desc.newInstance() : null;
} catch (Exception ex) {
throw (IOException) new InvalidClassException(
desc.forClass().getName(),
"unable to create instance").initCause(ex);
}
passHandle = handles.assign(unshared ? unsharedMarker : obj);
ClassNotFoundException resolveEx = desc.getResolveException();
if (resolveEx != null) {
handles.markException(passHandle, resolveEx);
}
if (desc.isExternalizable()) {
readExternalData((Externalizable) obj, desc);
} else {
//填充字段數據
readSerialData(obj, desc);
}
handles.finish(passHandle);
if (obj != null &&
handles.lookupException(passHandle) == null &&
desc.hasReadResolveMethod())
{
Object rep = desc.invokeReadResolve(obj);
if (unshared && rep.getClass().isArray()) {
rep = cloneArray(rep);
}
if (rep != obj) {
// Filter the replacement object
if (rep != null) {
if (rep.getClass().isArray()) {
filterCheck(rep.getClass(), Array.getLength(rep));
} else {
filterCheck(rep.getClass(), -1);
}
}
handles.setObject(passHandle, obj = rep);
}
}
return obj;
}
private ObjectStreamClass readClassDesc(boolean unshared)
throws IOException
{
byte tc = bin.peekByte();
ObjectStreamClass descriptor;
switch (tc) {
case TC_NULL:
descriptor = (ObjectStreamClass) readNull();
break;
case TC_REFERENCE:
descriptor = (ObjectStreamClass) readHandle(unshared);
break;
case TC_PROXYCLASSDESC:
descriptor = readProxyDesc(unshared);
break;
//0x72 對類的描述
case TC_CLASSDESC:
descriptor = readNonProxyDesc(unshared);
break;
default:
throw new StreamCorruptedException(
String.format("invalid type code: %02X", tc));
}
return descriptor;
}
private ObjectStreamClass readNonProxyDesc(boolean unshared)
throws IOException
{
if (bin.readByte() != TC_CLASSDESC) {
throw new InternalError();
}
ObjectStreamClass desc = new ObjectStreamClass();
int descHandle = handles.assign(unshared ? unsharedMarker : desc);
passHandle = NULL_HANDLE;
ObjectStreamClass readDesc = null;
try {
//讀取類的說明
readDesc = readClassDescriptor();
} catch (ClassNotFoundException ex) {
throw (IOException) new InvalidClassException(
"failed to read class descriptor").initCause(ex);
}
Class<?> cl = null;
ClassNotFoundException resolveEx = null;
bin.setBlockDataMode(true);
final boolean checksRequired = isCustomSubclass();
try {
if ((cl = resolveClass(readDesc)) == null) {
resolveEx = new ClassNotFoundException("null class");
} else if (checksRequired) {
ReflectUtil.checkPackageAccess(cl);
}
} catch (ClassNotFoundException ex) {
resolveEx = ex;
}
// Call filterCheck on the class before reading anything else
filterCheck(cl, -1);
skipCustomData();
try {
totalObjectRefs++;
depth++;
desc.initNonProxy(readDesc, cl, resolveEx, readClassDesc(false));
} finally {
depth--;
}
handles.finish(descHandle);
passHandle = descHandle;
return desc;
}
protected ObjectStreamClass readClassDescriptor()
throws IOException, ClassNotFoundException
{
ObjectStreamClass desc = new ObjectStreamClass();
desc.readNonProxy(this);
return desc;
}
填充字段值
private void readSerialData(Object obj, ObjectStreamClass desc)
throws IOException
{
ObjectStreamClass.ClassDataSlot[] slots = desc.getClassDataLayout();
for (int i = 0; i < slots.length; i++) {
ObjectStreamClass slotDesc = slots[i].desc;
if (slots[i].hasData) {
if (obj == null || handles.lookupException(passHandle) != null) {
defaultReadFields(null, slotDesc); // skip field values
} else if (slotDesc.hasReadObjectMethod()) {
ThreadDeath t = null;
boolean reset = false;
SerialCallbackContext oldContext = curContext;
if (oldContext != null)
oldContext.check();
try {
curContext = new SerialCallbackContext(obj, slotDesc);
bin.setBlockDataMode(true);
slotDesc.invokeReadObject(obj, this);
} catch (ClassNotFoundException ex) {
/*
* In most cases, the handle table has already
* propagated a CNFException to passHandle at this
* point; this mark call is included to address cases
* where the custom readObject method has cons'ed and
* thrown a new CNFException of its own.
*/
handles.markException(passHandle, ex);
} finally {
do {
try {
curContext.setUsed();
if (oldContext!= null)
oldContext.check();
curContext = oldContext;
reset = true;
} catch (ThreadDeath x) {
t = x; // defer until reset is true
}
} while (!reset);
if (t != null)
throw t;
}
/*
* defaultDataEnd may have been set indirectly by custom
* readObject() method when calling defaultReadObject() or
* readFields(); clear it to restore normal read behavior.
*/
defaultDataEnd = false;
} else {
//填充值
defaultReadFields(obj, slotDesc);
}
if (slotDesc.hasWriteObjectData()) {
skipCustomData();
} else {
bin.setBlockDataMode(false);
}
} else {
if (obj != null &&
slotDesc.hasReadObjectNoDataMethod() &&
handles.lookupException(passHandle) == null)
{
slotDesc.invokeReadObjectNoData(obj);
}
}
}
}
private void defaultReadFields(Object obj, ObjectStreamClass desc)
throws IOException
{
Class<?> cl = desc.forClass();
if (cl != null && obj != null && !cl.isInstance(obj)) {
throw new ClassCastException();
}
//獲取讀取數據長度
int primDataSize = desc.getPrimDataSize();
if (primVals == null || primVals.length < primDataSize) {
primVals = new byte[primDataSize];
}
//讀取數據
bin.readFully(primVals, 0, primDataSize, false);
//賦值
if (obj != null) {
desc.setPrimFieldValues(obj, primVals);
}
int objHandle = passHandle;
ObjectStreamField[] fields = desc.getFields(false);
Object[] objVals = new Object[desc.getNumObjFields()];
int numPrimFields = fields.length - objVals.length;
for (int i = 0; i < objVals.length; i++) {
ObjectStreamField f = fields[numPrimFields + i];
objVals[i] = readObject0(f.isUnshared());
if (f.getField() != null) {
handles.markDependency(objHandle, passHandle);
}
}
if (obj != null) {
desc.setObjFieldValues(obj, objVals);
}
passHandle = objHandle;
}
讀取類描述以及屬性
void readNonProxy(ObjectInputStream in)
throws IOException, ClassNotFoundException
{
//獲取類全限定名
name = in.readUTF();
//讀取之後8個字節,獲取序列化id
suid = Long.valueOf(in.readLong());
isProxy = false;
//0002:表示可序列化
byte flags = in.readByte();
hasWriteObjectData =
((flags & ObjectStreamConstants.SC_WRITE_METHOD) != 0);
hasBlockExternalData =
((flags & ObjectStreamConstants.SC_BLOCK_DATA) != 0);
externalizable =
((flags & ObjectStreamConstants.SC_EXTERNALIZABLE) != 0);
boolean sflag =
((flags & ObjectStreamConstants.SC_SERIALIZABLE) != 0);
if (externalizable && sflag) {
throw new InvalidClassException(
name, "serializable and externalizable flags conflict");
}
serializable = externalizable || sflag;
isEnum = ((flags & ObjectStreamConstants.SC_ENUM) != 0);
if (isEnum && suid.longValue() != 0L) {
throw new InvalidClassException(name,
"enum descriptor has non-zero serialVersionUID: " + suid);
}
//讀取2個字節,代表了類中域的個數
int numFields = in.readShort();
if (isEnum && numFields != 0) {
throw new InvalidClassException(name,
"enum descriptor has non-zero field count: " + numFields);
}
fields = (numFields > 0) ?
new ObjectStreamField[numFields] : NO_FIELDS;
//遍歷序列化字段
for (int i = 0; i < numFields; i++) {
//讀取字段類型
char tcode = (char) in.readByte();
//獲取字段名,內部會先讀取字段的長度,然後讀取長度的字節也就是字段名稱了
String fname = in.readUTF();
String signature = ((tcode == 'L') || (tcode == '[')) ?
in.readTypeString() : new String(new char[] { tcode });
try {
fields[i] = new ObjectStreamField(fname, signature, false);
} catch (RuntimeException e) {
throw (IOException) new InvalidClassException(name,
"invalid descriptor for field " + fname).initCause(e);
}
}
computeFieldOffsets();
}