Adding java. Serializable — This is equivalent to adding types. There will be no values in the stream for this class so its fields will be initialized to default values. If the no-arg constructor is not available, the InvalidClassException is thrown. Changing the access to a field — The access modifiers public, package, protected, and private have no effect on the ability of serialization to assign values to the fields.
Changing a field from static to non-static or transient to non transient — When relying on default serialization to compute the serializable fields, this change is equivalent to adding a field to the class. The new field will be written to the stream but earlier classes will ignore the value since serialization will not assign values to static or transient fields. Do not change the value of this field in future versions, unless you are knowingly making changes to the class which will render it incompatible with old serialized objects.
If needed, follow above given guidelines. If constructors make defensive copies for mutable object fields, so must readObject. No static or transient fields undergo default serialization. Extendable classes should not be Serializable, unless necessary. Inner classes should rarely, if ever, implement Serializable. Container classes should usually follow the style of Hashtable, which implements Serializable by storing keys and values, as opposed to a large hash table data structure.
Sample class following serialization best practices package staticTest; import java. Serializable; import java. StringCharacterIterator; import java. Serialization and deserialization example package serializationTest; import java.
FileInputStream; import java. FileOutputStream; import java. IOException; import java. ObjectInputStream; import java. ObjectOutputStream; import java. Calendar; import java. Let us know if you liked the post. Java deep copy using in-memory serialization.
Thanks a bunch. Can you check the readObject method again. It is not returning anything. Return type is void. Are we on same page? Can you please elaborate? Can you give some real time examples where the concept of serialization is applied Reply. Good Explanation and example great work Lokesh. Excellent program. Thanks Rajendra for musical words!! Hi Lokesh, Can you please tell us how can we control the fields to be serialized with the help of readObject.
Individual bytes and arrays of bytes are read with the methods of InputStream. Except for serializable fields, primitive data is read from block-data records. ObjectInputStream can be extended to utilize customized information in the stream about classes or to replace objects that have been deserialized.
Refer to the resolveClass and resolveObject method descriptions for details. Each object that acts as a container implements an interface which allows primitives and objects to be stored in or retrieved from it. These interfaces are the ObjectOutput and ObjectInput interfaces which:. To be stored in an Object Stream, each object must implement either the Serializable or the Externalizable interface:.
When a class is declared Serializable, the serializable state of the object is defined by serializable fields by name and type plus optional data. Optional data can only be written explicitly by the writeObject method of a Serializable class.
Optional data can be read by the Serializable class' readObject method or serialization will skip unread optional data. When a class is declared Externalizable, the data that is written to the stream by the class itself defines the serialized state. The class must specify the order, types, and meaning of each datum that is written to the stream.
The class must handle its own evolution, so that it can continue to read data written by and write data that can be read by previous versions. The class must coordinate with the superclass when saving and restoring data. The location of the superclasses data in the stream must be specified. The designer of a Serializable class must ensure that the information saved for the class is appropriate for persistence and follows the serialization-specified rules for interoperability and evolution.
Running this example produces the following output. Note: The procedures described here are for binding a serializable object in a directory service that follows the schema defined in RFC These procedures might not be generally applicable to other naming and directory services that support binding a serializable object with a specified codebase.
When a serialized object is bound in the directory as shown in the previous example, applications that read the serialized object from the directory must have access to the class definitions necessary to deserialize the object. Alternatively, you can record a codebase with the serialized object in the directory, either when you bind the object or subsequently by adding an attribute by using DirContext.
You can use any attribute to record this codebase and have your application read that attribute from the directory and use it appropriately. Or you can use the "javaCodebase" attribute specified in. In the latter case, Oracle's LDAP service provider will automatically use the attribute to load the class definitions as needed. The following example resembles the one for binding a java.
It differs in that it uses a user-defined Serializable class, Flower , and supplies a "javaCodebase" attribute that contains the location of Flower 's class definition. Here's the code that does the binding. When you run this example , you must supply the URL of the location at which the class file Flower.
For example, if Flower.
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