Tài liệu Transaction & Security ppt

Transaction & SecurityChuyên đề Lập trình Java & J2EE Chương 16 Biên soạn: Th.S Nguyễn văn Lành... Motivation for Transactions Atomic Operations  Recovery after Network or Machine Fail

Transaction & Security

Chuyên đề Lập trình Java & J2EE

Chương 16

Biên soạn: Th.S Nguyễn văn Lành

Motivation for Transactions

 Atomic Operations

 Recovery after Network or Machine Failure

 Multiple Users Sharing Data

 avoid those problems by properly using

The ACID Properties

 Atomicity guarantees that many operations are

bundled together and appear as one contiguous unit

of work

 Consistency guarantees that a transaction leaves

the system’s state to be consistent after a

transaction completes

 Isolation protects concurrently executing

transactions from seeing each other’s incomplete

results

 Durability guarantees that updates to managed

resources, such as database records, survive failures

Transactional Models

 Flat transaction is a series of

operations that are performed

atomically as a single unit of work

 Nested transaction allows to embed atomic units of work within other units

of work.

Required

Requires New

Mandatory

Never

Bean Managed Transaction

Java Transaction API (JTA)

 JTA can be used in client & bean code

to programmatically control

transactional boundaries.

 The interface you use to

programmatically control transactions is

UserTransaction interface

Code sample

Transactional Isolation

 Concurrency Control

 locking on the database to prevent the two components

from reading data

 Four transaction isolation levels:

Distributed Transactions

 Distributed flat transactions allow multiple

transaction participants, written by different vendors , to collaborate under one

transactional context.

 Two-Phase Commit Protocol

 Phase One begins by sending a before commit

message to all resources involved in the transaction

 Phase Two occurs only if Phase One completed

2PC protocol

EJB Security

 Authentication verifies that the client

is who he claims to be.

 Authorization checks to see if an

already authenticated client is allowed

to perform a task.

 Basic authentication

 The Web client supplies a username and password

to the Web server

 Form-based authentication.

 uses a customizable form, login screen

 Digest authentication

 Web client supplies a special message digest to

the Web server

 Certificate authentication

 The client can establish an identity with X.509