"Java Basics" "Java serialization and deserialization and serialization ID"

This morning I learned about the usefulness of Java serialization and deserialization and Serialversionuid.

The effect of serialization and deserialization:

There are two main uses for serialization of objects:
1) The object's byte sequence is permanently saved to the hard disk, usually stored in a file;
2) A sequence of bytes that transmits an object over the network.

Because there are many problems with not serializing object serialization, the introduction of serialization solves these problems.

Object serialization consists of the following steps:
1) Create an object output stream, which can wrap a different type of target output stream, such as a file output stream;
2) writes an object through the WriteObject () method of the object output stream.
The steps for deserializing an object are as follows:
1) Create an object input stream, which can wrap a different type of source input stream, such as a file input stream;
2) The object is read through the ReadObject () method of the object input stream.
Let us take a look at a corresponding example, the contents of the class are as follows:

Second, Serialversionuid effect:
Serialization preserves the uniqueness of the object in order to maintain version compatibility, that is, deserialization while the version is being upgraded.
There are two ways to build:
One is the default 1L, for example: private static final long serialversionuid = 1L;
One is to generate a 64-bit hash field based on the class name, interface name, member method, and property, for example:
Private static final long serialversionuid = XXXXL;

When you implement the serializable interface in a class, if there is no definition serialversionuid,eclipse will provide this hint function to tell you to define.

develop good programming habits, the Java uid is best explicitly declared.

As long as any class implemented serializable this interface, if not joined Serialversionuid,eclipse will give you warning hint, This serialversionuid to make the category serializable backwards compatible.

If your class serialized on the hard drive, but then you change the category field (increase or decrease or rename), when you deserialize, it will appear exception, which will cause incompatibilities.

But when Serialversionuid is the same, it deserialize the different field with the default value of type, which avoids incompatibility issues.

"Java Basics" "Java serialization and deserialization and serialization ID"