Generation of UUID--java

A UUID is a number generated on a machine that guarantees that all machines in the same time and space are unique. Typically the platform provides the API to generate the UUID. The UUID is based on the standards established by the Open Software Foundation (OSF), using Ethernet card addresses, nanosecond-seconds, chip ID codes, and many possible numbers. A combination of the following: the current date and time (the first part of the UUID is related to the time, if you generate a UUID after a few seconds, the first part is different, the rest is the same), the clock sequence, the globally unique IEEE Machine identification number (if there is a network card, from the network card, No network cards are available in other ways, the only drawback to the UUID is that the resulting string will be longer. The most common use of UUID for this standard is the GUID of Microsoft (Globals Unique Identifiers).

The way to generate the UUID in Java is as follows:

Calling the JAVA.util.UUID class

That is: uuid uuid = Uuid.randomuuid ();

String str = uuid.tostring ();

The results obtained are "a933bd2c-de9f-4e3a-8782-b4e11dc42641";

The "-" may be removed by intercepting the string:

namely: Str.substring (0,8) +str.substring (9,13) +str.substring (14,18) +str.substring (19,23) +str.substring (24);

Available from: a933bd2cde9f4e3a8782b4e11dc42641

The UUID is composed of the following parts:

(1) The current date and time, the first part of the UUID is related to the time, if you generate a UUID after a few seconds to generate a UUID, then the first part is different, the rest is the same.

(2) Clock sequence

(3) Globally unique IEEE machine identification number, if there is a network card, from the network card MAC address obtained, no network card is obtained in other ways.

The only drawback to the UUID is that the resulting string will be longer. The most common use of UUID for this standard is the GUID of Microsoft (Globals Unique Identifiers). In ColdFusion, the UUID can be easily generated using the Createuuid () function in the form of: Xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxxxxxx (8-4-4-16), where each x is 0-9 or a-f A hexadecimal number within the range. The standard UUID format is: xxxxxxxx-xxxx-xxxx-xxxxxx-xxxxxxxxxx (8-4-4-4-12), which can be converted from cflib download CreateGUID () UDF.

The benefits of using UUID are reflected in distributed software systems (e.g. DCE/RPC, Com+,corba), which ensures that the identities generated by each node are not duplicated, and that the benefits of the UUID will be more pronounced with the development of integrated technologies such as Web services. Depending on the specific mechanism used, the UUID must not only be guaranteed to be different from each other, or at least be very different from any other generic unique identifiers that were generated before the 3400 AD.

The universal unique identifier can also be used to point to most possible objects. Microsoft and some other software companies tend to use the globally unique identifier (GUID), which is a type of universal unique identifier that can be used to point to the Building object module object and other software components. The first universal unique identifier is a component created in the Snare computer system (NCS) and subsequently become a distributed computing environment (DCE) of the Open Software Foundation (OSF).

Generation of UUID--java