J2EE (1)-13 specifications

What problems can be solved?

 

In many enterprise applications, such as database connection, mail service, and transaction processing, these modules are common enterprise requirement modules. If each development process is completed by developers, this will cause issues such as long development cycle and code reliability. So many large companies developed their ownGeneral module Service. These service software series are also called middleware.

Based on the above requirements, many companies have developedSelf-built MiddlewareBut their communication with users is different,As a result, users cannot assemble different middleware from different companies to serve themselves.This leads to bottlenecks. For general purposes, standards must be put forward. Otherwise, standards cannot be achieved.

 

Easy to understand:Each company abstracts the general part, and the 13 standard is to make the general part of each company can be assembled to serve the company.

 

 

1. JDBC (Java database connectivity): Java Database Connection

 

It provides Java developers with an industry standard API that establishes a database-independent connection between Java applications and relational databases without writing any programs. To create a connection with ODBC, you also need to use ADO for database operations.

 

2. JNDI (Java name and Directory Interface): Java Naming and Directory Interface

 

The jndi api is used to execute the name and Directory Service. It associates the identifier with the resource for searching:

Web application environment variables, ejbs environment variables, datasources database connection pool, JMS target and connection Factory

Allows applications from other regions to leave their own indexes on them to meet the needs of Fast Searching and locating.

 

3. EJB (Enterprise JavaBean): Java Enterprise Bean

 

The design goal and core application are to deploy distributed applications.

EJB is the core code of Java, including Session Bean, Entity Bean, and messagedriven bean)

Session Bean: Used to implement business logic. It describes a short session with the client. After the client completes the execution, the Session Bean and its data will disappear;

Entity Bean: describes a row of persistent and stable data stored in a database table. If the service ends or the service ends, the underlying service stores Entity Bean data.

Message-driven Bean: integrates the Session Bean and Java Information Service (JMS) Information listener functions, which allows a commercial component to asynchronously accept JMS messages.

 

4. RMI (Remote Method invoke): Remote method call

 

An application programming interface used to implement remote process calls. It allows programs running on the client to call objects on the remote server. The remote method call feature enables Java programmers to distribute operations in the network environment. RMI is a more underlying protocol used by EJB.

 

5. Java IDL/CORBA (Common Object Request proxy architecture is a standard for software construction ):

 

Java IDL is an extension of the CORBA function in Java 2 development platform. Java IDL is introduced in Java 2, so that omg idl can be used to define basic functions of service objects, and the IDL is mapped to the Java language according to the requirements of the CORBA specification, and develop standard distributed applications with interoperability and connectivity.

 

6. jsp

 

The JSP page consists of HTML code and Java code embedded in it. the server processes the Java code after the page is requested by the client, and then returns the generated HTML page to the client browser. asp is embedded in the HTML code. net code. the biggest advantage of JSP is that it can run on both Windows and Linux or other operating systems.

 

7. Java Servlet

 

Servlet is a small Java program that extends the functions of web servers. as a server application, it is executed when requested, which is similar to cgi Perl script. most of the functions provided by Servlet are similar to those provided by JSP, but the implementation methods are different. JSP usually embeds a small amount of Java code in most HTML code, while servlets are all written in Java and generate HTML.

 

8. xml: Extensible Markup Language

 

It is a language that can be used to define other Markup languages. It is used to share data in different business processes. The development of XML and Java are independent of each other. The same goal is platform independence.

 

9. JMS (javamessageserver): Java Message Service

 

Provides a common method to create, send, receive, and read messages from the enterprise message communication system.

By combining Java technology with enterprise messaging, jms api provides a new and powerful tool to solve enterprise computing problems. By defining a set of message concepts and programming strategies, the jms api improves the programmer's production efficiency;

 

10. JTA (Java transactionapi): Java transaction API

 

JTA is used to communicate with the transaction service and provides standard Java APIs for starting, connecting, committing, and revoking transactions.

 

11. JTs (Java Transaction Service): Java Message Service

 

JTs is the basic implementation of the transaction monitoring function of CORBA ots. JTs specifies the implementation method of transaction management. the transaction Manager supports Java transaction API specifications at the high-level level, and implements omg ots specification and Java impressions at a lower level. the JTs Transaction Manager provides transaction services for application servers, resource managers, independent applications, and student resource managers.

Differences between JTA and JTs:

JTA is a high-level transmission API that allows applications and J2EE servers to manage transactions. JTs indicates the specific implementation of the Transaction Manager.

 

12. javamail

 

Provides mail storage and transmission functions. He is the core of the mail function in programming. Not only supports SMTP servers, but also supports IMAP servers.

 

13. JAF (JavaBeans activation framework): Data Processing Framework

 

Is a dedicated Data Processing framework used to encapsulate data and provide interfaces for applications to access and operate data. The main function is to let Java applications know how to view, edit, and print a data source.

 

13 embodiment of specifications in the J2EE system

 

Typical J2EE layer-4 structure:

Client Machine: Customer layer component

J2EE server: web layer components

J2EE server: business logic layer component

EIS server: enterprise information system layer software

J2EE is a standard, not a ready-made product. Only by developing under unified standards can we improve work efficiency and competitiveness in applications.