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Chapter 11 The java.io Package |
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Chapter 11 The java.io Package |
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java.io.Externalizable
java.io.Serializable
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New as of JDK 1.1
The Externalizable interface is an extension of the Serializable interface. Whereas a Serializable object is automatically saved and loaded (in most cases), an Externalizable object has sole responsibility for saving and loading its state via the writeExternal() and readExternal() methods. If a class implements the Externalizable interface, it must handle any versioning issues that occur.
The methods of Externalizable are public, which can pose a security risk. If security is a concern, Externalizable objects should not write or read sensitive information, or the Serializable interface should be used instead.
public abstract interface java.io.Externalizable
extends java.io.Serializable {
// Methods
public abstract void readExternal(ObjectInput in);
public abstract void writeExternal(ObjectOutput out);
}
public abstract void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
The object input stream to use.
If the class of the object being deserialized cannot be found.
If any kind of I/O error occurs.
This method reads an object from the given stream. This method has full responsibility for restoring the object's state. The implementation of readExternal() should read data in the format that is written out by writeExternal(). In general, an implementation should call methods of DataInput to read primitive types and methods of ObjectInput to read objects, strings, and arrays.
public abstract void writeExternal(ObjectOutput out) throws IOException
The object output stream to use.
If any kind of I/O error occurs.
This method writes an object to the given stream. This method has full responsibility for saving the object's state. The implementation of writeExternal() should write data in the format that is read by readExternal(). In general, an implementation should call methods of DataOutput to write primitive types and methods of ObjectOutput to write objects, strings, and arrays.
ClassNotFoundException, DataInput, DataOutput, IOException, ObjectInput, ObjectOutput, Serializable
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