ObjectInputStream

      FileInputStream fis = new FileInputStream("t.tmp");
      ObjectInputStream ois = new ObjectInputStream(fis);

      int i = ois.readInt();
      String today = (String) ois.readObject();
      Date date = (Date) ois.readObject();

      ois.close();
 

 private void writeObject(java.io.ObjectOutputStream stream)
     throws IOException;
 private void readObject(java.io.ObjectInputStream stream)
     throws IOException, ClassNotFoundException;
 private void readObjectNoData()
     throws ObjectStreamException;
 

ObjectInputStream

ObjectInputStream (InputStream in)

创建一个从指定的InputStream读取的ObjectInputStream。 从流中读取序列化流头并进行验证。 该构造函数将阻塞，直到相应的ObjectOutputStream写入并刷新标题。

如果安装了安全管理器，则此构造函数将在覆盖ObjectInputStream.readFields或ObjectInputStream.readUnshared方法的子类的构造函数直接或间接调用时检查“enableSubclassImplementation”SerializablePermission。

Parameters
in	InputStream: input stream to read from

Throws
StreamCorruptedException	if the stream header is incorrect
IOException	if an I/O error occurs while reading stream header
SecurityException	if untrusted subclass illegally overrides security-sensitive methods
NullPointerException	if in is null

ObjectInputStream

ObjectInputStream ()

为完全重新实现ObjectInputStream的子类提供一种方法，使其不必分配此ObjectInputStream实现所使用的私有数据。

如果安装了安全管理器，则此方法首先使用 SerializablePermission("enableSubclassImplementation")权限调用安全管理器的 checkPermission方法，以确保启用子类化操作即可。

Throws
SecurityException	if a security manager exists and its checkPermission method denies enabling subclassing.
IOException

available

int available ()

返回可以不阻塞地读取的字节数。

Returns
int	the number of available bytes.

Throws
IOException	if there are I/O errors while reading from the underlying InputStream

close

void close ()

关闭输入流。 必须调用才能释放与流关联的所有资源。

Throws
IOException	If an I/O error has occurred.

defaultReadObject

void defaultReadObject ()

从这个流中读取当前类的非静态和非瞬态字段。 这只能从被反序列化的类的readObject方法中调用。 如果它被调用，它会抛出NotActiveException。

Throws
ClassNotFoundException	if the class of a serialized object could not be found.
IOException	if an I/O error occurs.
NotActiveException	if the stream is not currently reading objects.

read

int read ()

读取一个字节的数据。 如果没有可用输入，此方法将被阻止。

Returns
int	the byte read, or -1 if the end of the stream is reached.

Throws
IOException	If an I/O error has occurred.

read

int read (byte[] buf, 
                int off, 
                int len)

读入一个字节数组。 此方法将阻止，直到有些输入可用。 考虑使用java.io.DataInputStream.readFully读取'长度'字节。

Parameters
buf	byte: the buffer into which the data is read
off	int: the start offset of the data
len	int: the maximum number of bytes read

Returns
int	the actual number of bytes read, -1 is returned when the end of the stream is reached.

Throws
IOException	If an I/O error has occurred.

readBoolean

boolean readBoolean ()

读入一个布尔值。

Returns
boolean	the boolean read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readByte

byte readByte ()

读取一个8位字节。

Returns
byte	the 8 bit byte read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readChar

char readChar ()

读取一个16位字符。

Returns
char	the 16 bit char read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readDouble

double readDouble ()

读取64位双精度。

Returns
double	the 64 bit double read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readFields

ObjectInputStream.GetField readFields ()

从流中读取持久字段并使其可以按名称使用。

Returns
ObjectInputStream.GetField	the GetField object representing the persistent fields of the object being deserialized

Throws
ClassNotFoundException	if the class of a serialized object could not be found.
IOException	if an I/O error occurs.
NotActiveException	if the stream is not currently reading objects.

readFloat

float readFloat ()

读取32位浮点数。

Returns
float	the 32 bit float read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readFully

void readFully (byte[] buf)

读取字节，阻塞直到读取所有字节。

Parameters
buf	byte: the buffer into which the data is read

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readFully

void readFully (byte[] buf, 
                int off, 
                int len)

读取字节，阻塞直到读取所有字节。

Parameters
buf	byte: the buffer into which the data is read
off	int: the start offset of the data
len	int: the maximum number of bytes to read

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readInt

int readInt ()

读取32位int。

Returns
int	the 32 bit integer read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readLine

String readLine ()

此方法在API级别1中已弃用。
此方法不能正确地将字节转换为字符。 有关详细信息和备选方案，请参阅DataInputStream。

读入已由\ n，\ r，\ r \ n或EOF终止的行。

Returns
String	a String copy of the line.

Throws
IOException	if there are I/O errors while reading from the underlying InputStream

readLong

long readLong ()

读取64位长。

Returns
long	the read 64 bit long.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readObject

Object readObject ()

从ObjectInputStream中读取一个对象。 读取对象的类，类的签名以及该类及其所有超类型的非瞬态和非静态字段的值。 使用writeObject和readObject方法可以覆盖类的默认反序列化。 此对象引用的对象是传递式读取的，以便通过readObject重建对象的完全等效图形。

当其所有字段及其引用的对象完全恢复时，根对象完全恢复。 此时，对象验证回调会根据其注册的优先级顺序执行。 回调由对象注册（在readObject特殊方法中），因为它们分别被恢复。

针对InputStream和不应该反序列化的类的问题引发了异常。 所有异常对于InputStream都是致命的，并使其处于不确定状态; 调用者可以忽略或恢复流状态。

Returns
Object	the object read from the stream

Throws
ClassNotFoundException	Class of a serialized object cannot be found.
InvalidClassException	Something is wrong with a class used by serialization.
StreamCorruptedException	Control information in the stream is inconsistent.
OptionalDataException	Primitive data was found in the stream instead of objects.
IOException	Any of the usual Input/Output related exceptions.

readShort

short readShort ()

读取16位短。

Returns
short	the 16 bit short read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readUTF

String readUTF ()

以 modified UTF-8格式读取字符串。

Returns
String	the String.

Throws
IOException	if there are I/O errors while reading from the underlying InputStream
UTFDataFormatException	if read bytes do not represent a valid modified UTF-8 encoding of a string

readUnshared

Object readUnshared ()

从ObjectInputStream中读取一个“非共享”对象。 此方法与readObject相同，只是它阻止对readObject的后续调用，并且readUnshared不会返回通过此调用获取的反序列化实例的其他引用。 特别：

• If readUnshared is called to deserialize a back-reference (the stream representation of an object which has been written previously to the stream), an ObjectStreamException will be thrown.
• If readUnshared returns successfully, then any subsequent attempts to deserialize back-references to the stream handle deserialized by readUnshared will cause an ObjectStreamException to be thrown.

Deserializing an object via readUnshared invalidates the stream handle associated with the returned object. Note that this in itself does not always guarantee that the reference returned by readUnshared is unique; the deserialized object may define a readResolve method which returns an object visible to other parties, or readUnshared may return a Class object or enum constant obtainable elsewhere in the stream or through external means. If the deserialized object defines a readResolve method and the invocation of that method returns an array, then readUnshared returns a shallow clone of that array; this guarantees that the returned array object is unique and cannot be obtained a second time from an invocation of readObject or readUnshared on the ObjectInputStream, even if the underlying data stream has been manipulated.

重载此方法的ObjectInputStream子类只能在拥有“enableSubclassImplementation”SerializablePermission; 任何尝试实例化没有此权限的子类都将导致抛出SecurityException。

Returns
Object	reference to deserialized object

Throws
ClassNotFoundException	if class of an object to deserialize cannot be found
StreamCorruptedException	if control information in the stream is inconsistent
ObjectStreamException	if object to deserialize has already appeared in stream
OptionalDataException	if primitive data is next in stream
IOException	if an I/O error occurs during deserialization

readUnsignedByte

int readUnsignedByte ()

读取一个无符号的8位字节。

Returns
int	the 8 bit byte read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

readUnsignedShort

int readUnsignedShort ()

读取一个无符号的16位短路。

Returns
int	the 16 bit short read.

Throws
EOFException	If end of file is reached.
IOException	If other I/O error has occurred.

registerValidation

void registerValidation (ObjectInputValidation obj, 
                int prio)

在返回图之前注册要验证的对象。 虽然与resolveObject类似，但这些验证在整个图形重新构建后调用。 通常情况下，readObject方法会将对象注册到流中，以便当所有对象都恢复时，可以执行最后一组验证。

Parameters
obj	ObjectInputValidation: the object to receive the validation callback.
prio	int: controls the order of callbacks;zero is a good default. Use higher numbers to be called back earlier, lower numbers for later callbacks. Within a priority, callbacks are processed in no particular order.

Throws
NotActiveException	The stream is not currently reading objects so it is invalid to register a callback.
InvalidObjectException	The validation object is null.

skipBytes

int skipBytes (int len)

跳过字节。

Parameters
len	int: the number of bytes to be skipped

Returns
int	the actual number of bytes skipped.

Throws
IOException	If an I/O error has occurred.

enableResolveObject

boolean enableResolveObject (boolean enable)

启用流以允许替换从流中读取的对象。 启用后，将为每个正在反序列化的对象调用resolveObject方法。

如果 启用为真，并且安装了安全管理器，则此方法首先使用 SerializablePermission("enableSubstitution")权限调用安全管理器的 checkPermission方法，以确保允许流允许替换从流中读取的对象。

Parameters
enable	boolean: true for enabling use of resolveObject for every object being deserialized

Returns
boolean	the previous setting before this method was invoked

Throws
SecurityException	if a security manager exists and its checkPermission method denies enabling the stream to allow objects read from the stream to be replaced.

readClassDescriptor

ObjectStreamClass readClassDescriptor ()

从序列化流中读取类描述符。 当ObjectInputStream需要类描述符作为序列化流中的下一项时调用此方法。 ObjectInputStream的子类可以重写此方法以读取已用非标准格式（通过ObjectOutputStream的子类重写了writeClassDescriptor方法）编写的类描述符。 默认情况下，此方法根据对象序列化规范中定义的格式读取类描述符。

Returns
ObjectStreamClass	the class descriptor read

Throws
IOException	If an I/O error has occurred.
ClassNotFoundException	If the Class of a serialized object used in the class descriptor representation cannot be found

readObjectOverride

Object readObjectOverride ()

此方法由ObjectOutputStream的受信任子类调用，它使用受保护的无参数构造函数构造ObjectOutputStream。 该子类预计会提供修饰符“final”的重写方法。

Returns
Object	the Object read from the stream.

Throws
ClassNotFoundException	Class definition of a serialized object cannot be found.
OptionalDataException	Primitive data was found in the stream instead of objects.
IOException	if I/O errors occurred while reading from the underlying stream

readStreamHeader

void readStreamHeader ()

readStreamHeader方法用于允许子类读取和验证其自己的流标头。 它读取并验证幻数和版本号。

Throws
IOException	if there are I/O errors while reading from the underlying InputStream
StreamCorruptedException	if control information in the stream is inconsistent

resolveClass

Class<?> resolveClass (ObjectStreamClass desc)

加载与指定的流类描述等效的本地类。 子类可以实现此方法，以允许从替代源获取类。

ObjectOutputStream的相应方法是annotateClass 。 对于流中的每个唯一类，该方法只会被调用一次。 该方法可以由子类实现以使用替代的加载机制，但必须返回Class对象。 一旦返回，如果该类不是数组类，则将其serialVersionUID与序列化类的serialVersionUID进行比较，如果不匹配，则反序列化将失败并引发InvalidClassException 。

ObjectInputStream中此方法的默认实现返回调用的结果

     Class.forName(desc.getName(), false, loader)
 

where loader is determined as follows: if there is a method on the current thread's stack whose declaring class was defined by a user-defined class loader (and was not a generated to implement reflective invocations), then loader is class loader corresponding to the closest such method to the currently executing frame; otherwise, loader is null. If this call results in a ClassNotFoundException and the name of the passed ObjectStreamClass instance is the Java language keyword for a primitive type or void, then the Class object representing that primitive type or void will be returned (e.g., an ObjectStreamClass with the name "int" will be resolved to Integer.TYPE). Otherwise, the ClassNotFoundException will be thrown to the caller of this method.

Parameters
desc	ObjectStreamClass: an instance of class ObjectStreamClass

Returns
Class<?>	a Class object corresponding to desc

Throws
IOException	any of the usual Input/Output exceptions.
ClassNotFoundException	if class of a serialized object cannot be found.

resolveObject

Object resolveObject (Object obj)

此方法将允许ObjectInputStream的可信子类在反序列化过程中将一个对象替换为另一个对象。 在调用enableResolveObject之前，替换对象将被禁用。 enableResolveObject方法检查请求解析对象的流是否可信。 对可序列化对象的每个引用都传递给resolveObject。 为了确保对象的私有状态不是无意暴露的，只有受信任的流可以使用resolveObject。

该方法在读取对象之后但在从readObject返回之前调用。 默认的resolveObject方法只返回相同的对象。

当一个子类正在替换对象时，它必须确保被替换的对象与引用将被存储的每个字段兼容。 对象的类型不是字段或数组元素的类型的子类，通过引发异常来中止序列化，并且不存储该对象。

当每个对象第一次遇到时，这个方法只被调用一次。 所有后续对该对象的引用都将被重定向到新对象。

Parameters
obj	Object: object to be substituted

Returns
Object	the substituted object

Throws
IOException	Any of the usual Input/Output exceptions.

resolveProxyClass

Class<?> resolveProxyClass (String[] interfaces)

返回实现代理类描述符中指定的接口的代理类; 子类可以实现此方法从流中读取自定义数据以及动态代理类的描述符，从而允许它们为接口和代理类使用备用加载机制。

对于流中的每个唯一代理类描述符，该方法只会被调用一次。

ObjectOutputStream的相应方法是annotateProxyClass 。 对于给定的子类ObjectInputStream重写该方法中， annotateProxyClass中的相应子类方法ObjectOutputStream必须写由该方法读取的任何数据或对象。

此方法在ObjectInputStream的默认实现返回调用Proxy.getProxyClass的结果和interfaces参数中指定的接口的Class对象的列表。 每个接口名称i的Class对象是通过调用返回的值

     Class.forName(i, false, loader)
 

where loader is that of the first non- null class loader up the execution stack, or null if no non- null class loaders are on the stack (the same class loader choice used by the resolveClass method). Unless any of the resolved interfaces are non-public, this same value of loader is also the class loader passed to Proxy.getProxyClass; if non-public interfaces are present, their class loader is passed instead (if more than one non-public interface class loader is encountered, an IllegalAccessError is thrown). If Proxy.getProxyClass throws an IllegalArgumentException, resolveProxyClass will throw a ClassNotFoundException containing the IllegalArgumentException.

Parameters
interfaces	String: the list of interface names that were deserialized in the proxy class descriptor

Returns
Class<?>	a proxy class for the specified interfaces

Throws
IOException	any exception thrown by the underlying InputStream
ClassNotFoundException	if the proxy class or any of the named interfaces could not be found