Thirteen J2EE specifications

I think everyone is familiar with J2EE. It seems that javaee is more popular nowadays. No matter how the name changes, the core and thinking are not changed. To learn about J2EE, we must first understand its specifications. Let's take a look at its 13 specifications.

 

1. JDBC (Java database connectivity)

 

Java APIs used to execute SQL statements can provide unified access to multiple relational databases. They are composed of a group of classes and interfaces written in Java.

My personal understanding: similar to Microsoft's ODBC, it should be said that it is a combination of ODBC and ADO. It can be understood as an object-oriented ODBC. There is no doubt that the object-oriented interface for JavaProgramIt is easier to understand. ODBC puts simple functions together with advanced functions, which is relatively difficult to learn, while JDBC tries its best to ensure the simplicity of simple functions, while at the same time using advanced functions as needed. JDBC has been optimized for Java's style and advantages, making it easier to use.

 

2. JNDI (Java name and Directory Interface)

APIS for accessing naming and directory services in Java applications. The naming service associates the name with the object so that we can access the object with the name.

Personal Understanding: JNDI is used to access the Directory infrastructure used in advanced network application development. This directory is actually a special database that provides quick access to stored data, unlike traditional directory service access methods, different api interfaces must be provided to access different directory services (such as LDAP, NIS, ads, and so on ), it unifies the access interfaces for different types of directories. Both jdni and JDBC are built on the abstraction layer.

3. EJB (Enterprise JavaBean)

EJB is Sun's server component model. The design goal and core application are to deploy distributed applications. EJB is the core of JavaCodeSession Bean, Entity Bean, and messagedriven bean ).

My understanding: EJB is the core of J2EE and is widely used by programmers. EJB provides a framework for developing and implementing distributed business logic, which greatly simplifies the development complexity and is easy to expand enterprise applications. For the three types of beanArticleAnd I will not talk about it here.

 

4. RMI (Remote Method invoke)

RMI refers to remote method call. It is a mechanism that allows objects on a Java Virtual Machine to call methods on objects in another Java virtual machine. Any object that can be called using this method must implement this remote interface.

Personal Understanding: RMI is a very important underlying technology and the basis of distributed systems. The EJB just mentioned is based on RMI. Compared with heavyweight components such as Web Service, RMI is simpler and more suitable for small applications.

 

5. Java IDL/CORBA

Java Interface Definition Language/Public Object Request proxy Architecture

Personal Understanding: with the support of Java IDL, developers can integrate Java and CORBA. They can create Java objects and expand them in corba orb, or they can also create Java classes and serve as the customers of the CORBA objects expanded with other orb. The latter method provides another way through which Java can be used to integrate your new applications with old systems.

 

6. jsp (Java Server Pages)

JSP is a traditional webpage HTML file (*. htm ,*. insert the Java program segment (scriptlet) and JSP tag in HTML to form a JSP file (*. JSP ). Web applications developed using JSP are cross-platform.

My personal understanding: JSP is similar to ASP. asp is added to HTML.. Net code, while JSP is added with Java code on the basis of HTML. They are dynamic web pages. The biggest advantage of JSP is that it can run on a Windows platform not only, it can also run on Linux or other operating systems.

 

7. servlet

Servlet is a server-side Java application that has the characteristics of being independent from the platform and protocol and can generate dynamic web pages. It serves as the intermediate layer between customer requests (Web browsers or other HTTP client programs) and server responses (databases or applications on the HTTP server. Servlet is a Java application on the server inside the Web server. Unlike the traditional Java application started from the command line, servlet is loaded by the Web server, the Web server must contain a Java virtual machine that supports servlet.

My personal understanding: most of the functions provided by servlets are the same as those provided by JSP, which uses a somewhat different method. Most of JSP code is HTML code, with only a small amount of Java code, while servlets is the opposite. It is completely written in Java and can generate HTML code. JSP does not add any functions that cannot be implemented by Servlet in essence. However, it is more convenient to compile static HTML in JSP, and you do not need to use the println statement to output each line of HTML code. More importantly, with the separation of content and appearance, different types of tasks in page creation can be easily separated: for example, HTML design is performed by page designers, at the same time, we also set aside space for servlet programmers to insert dynamic content. Servlet is similar to Microsoft's general processing program.

 

8, XML (Extensible Markup Language)

It is used to mark electronic files so that they have a structured markup language. It can be used to mark data and define data types. It is a source language that allows users to define their own markup language. XML is a subset of the standard General Markup Language (SGML) and is suitable for web transmission. XML provides a unified way to describe and exchange structured data independent of applications or vendors.

Personally, XML is a language used to define other Markup languages. It can be used for data sharing between businesses. XML Development and Java are independent of each other. However, Java and Java share the same objective of cross-platform. By combining Java with XML, we can get a completely platform-independent solution.

 

9. JMS (Java Message Service)

The Java Message Service (JMS) application interface is an API for message-oriented middleware (MOM) on the Java platform. It is used between two applications, or send messages in a distributed system for asynchronous communication. Java Message Service is an API unrelated to a specific platform. Most mom providers provide support for JMS.

My understanding: JMS is an application interface (API) used to communicate with message-oriented middleware ). It supports both point-to-point domains and publish/subscribe domains, and supports the following types: Approved message transmission and transactional message transmission, supports consistent messages and persistent subscribers. JMS also provides another way to integrate your application with the old background system.

 

10, JTA (Java transaction Architecture)

Java transaction API. Allow applications to execute Distributed Transaction Processing-access and update data on two or more network computer resources. The JTA support of the JDBC driver greatly enhances data access capabilities.

Personal Understanding: JTA defines a standard API through which the application can access the transaction monitor. JTA transactions are more powerful than JDBC transactions. A jta transaction can have multiple participants, while a JDBC transaction is limited to a single database connection.

 

11. JTs (Java Transaction Service API)

JTs is a basic implementation of the corba ots transaction monitor. JTs specifies a Transaction Manager implementation (Transaction Manager), which supports Java transaction API (JTA) specifications at a high level, in addition, Java ing of omg ots specifications is implemented at a low level. A JTs Transaction Manager provides transaction services for the application server, resource manager, standalone application, and Communication Resource Manager.

 

 

12. javamail

 

Javamail is an API used to access the mail server. The javamail API provides an abstract class to model a mail system. Supports SMTP and IMAP servers.

 

13. JAF (JavaBean activation Framework)

 

JAF is a dedicated Data Processing framework used to encapsulate data and provide interfaces for applications to access and operate data. The main function of JAF is to let Java applications know how to view, edit, and print a data source.
All versions of mail API require JavaBeans activation framework to support the input and corresponding processing of any data block. There seems to be few features, but currently many browsers and mail tools can find this basic mime-type support. The activation. jar file is the JAF framework jar package.

Finally, I had to say that it was time-consuming, laborious, and costly to write such abstract things! At present, the understanding of J2EE is still superficial, and we need to continue to deepen our study and practice in the future. I hope you can give more advice.