Professional Concept Summary 1

1.JDBC:

Java Database Connectivity (JDBC) is used to implement database operations in Java programs, which provides a way to execute SQL statements, access various databases, and provide a unified operating interface for a variety of different databases, java.sql package

All classes that contain the JDBC operations database

The role of 2.class.forname:

In the Java language, any class is reproduced in the JVM to run. The function of the Class.forName () method is to load the class into the JVM, which returns a class or interface with the given string name.

Associated class object, and the JVM loads the class, and the JVM executes a static block of code for that class.

3.Hibernate:

Is the encapsulation of the JDBC, in the form of a configuration file to write the database connection parameters to the XML file, as to access to the database or through JDBC to complete.

4. How can I generate dynamic pages?

@1. Using the Public Gateway Interface (CGI), CGI is a Perl script program that can be used to generate dynamic pages, and the other way is to use servlet technology

@2.servlet is a server-side program written in the Java language that runs in the servlet container of a Web server, whose primary function is to provide a request/Response Web service pattern that dynamically generates web content that is

The functionality that HTML does not have.

5.Servlet Advantages:

@1. Better portability-deploy to many different types of Web servers without the need to modify the code

@2. High execution efficiency. Because CGI creates a process for each request, and the servlet creates a thread for each request to execute, and the creation of the line turndown creates a process with little overhead,---

@3. Powerful. A servlet can interact with a Web server, but CGI cannot interact directly with the Web server.

@4. Easy to use. Provides a number of useful interfaces for reading or setting HTTP header messages, processing cookies and tracking session state, etc.

@5. Strong scalability. Because the servlet is written in the Java language, it has all the advantages of the Java language. The Java language is a robust, object-oriented programming language that is easily extensible, so---

6.JSP: (Java Server Pages) is a dynamic technology standard pioneered by Sun, many companies, and in essence, HTML files embedded in Java code (JSP pages are best to write less Java code)

The introduction of JSP to some extent solves the shortcomings of the servlet, the realization of the concept is that each servlet only responsible for its corresponding business logic processing, so that the JSP responsible for the user's HTML display, so that the implementation of the business logic and view implementation of the separation, thereby greatly improving the scalability of the system.

What are the similarities and differences between 7.Servlet and JSP?

JSP can be seen as a special servlet, it is just an extension of the servlet, as long as the JSP can do the work, using the servlet can be done, such as generating dynamic pages. Since the JSP page will eventually be converted to a servlet to execute, the compiled servlet is processed when the request is handled.

Different points:

@1. Different programming methods: JSP is developed to solve the relatively difficult programming techniques in servlets, so JSP is much easier to write the program than the servlet, the servlet strictly follows the Java language Programming standard, while JSP follows the programming standard of the scripting language.

@2.servlet must be executed after compilation, and JSP does not need to be compiled separately, JSP container will do this automatically, and the servlet will need to compile after each code modification to execute.

@3. Operating speed is different: Because JSP container the JSP program to compile into a servlet, it takes some time, so the JSP run slower than the servlet, but if the JSP file is not changed to reuse, It will run as fast as the servlet in the first call.

8.Ajax (asynchronrous JavaScript and XML, asynchronous JavaScript and XML) is a combination of Java technology, XML, and JavaScript programming techniques, Its main purpose is to improve the user experience by interacting with small amounts of data with the server without refreshing the page to improve the interactivity of the page and reduce the response time.

9.J2EE------

Is the Java Platform Enterprise Edition abbreviation, is used to develop and deploy enterprise-class application of a framework, it provides a unified, open standard multi-layer platform, the platform is mainly composed of components, services and communication three modules.

The client component consists primarily of applets and application clients, and the server artifacts consist primarily of web artifacts (Servlets, JSPs) and EJBs (Enterprise Java beans).

The service is implemented by the Java EE platform provider and is divided into service APIs (used at development time) and runtime services.

Communication is the communication that is provided by the container to support the collaboration artifacts.

In essence, the Java EE is an industry standard that simplifies application development and deployment by providing a single, portable, multi-user, enterprise-level platform that is designed to be used on a server-side. It is just a standard and not a mature product, so as long as the development of the application conforms to the Java EE Standard, it can be deployed on the Java EE server that follows the Java EE Development standard.

This standard allows developers to focus on the business logic and architecture design of a variety of application systems without much consideration of the cumbersome programming of the underlying system, and the efficiency of the development and deployment of the systems is greatly improved.

Common terms in the Java EE are: Web servers, web containers, EJB containers, applet containers, application client containers, JNDI, JMS, JTA, JAF, RMI, and so on.

Web server: Refers to a computer program residing on the internet, which is a service program whose main task is to receive requests from clients and then return the results of the request to the client. (Passive program-sends a response only when a request from the client is received)

The two most popular web servers are: IIS (Internet information Services) and Apache Http Server (Apache)

Web container: Also called a Web application server, it is a service program that provides a running environment for programs running in it, such as Servlets, JSPs, and so on. Because of the presence of the Web container, the servlet only needs to focus on the processing of the business logic without paying attention to the interaction with the client, because these interactions have been handed over to the Web container for assistance.

Common Web containers: Tomcat, JBoss, WebLogic, and WebSphere

EJB container: is a server-side container, is the technical standard of the business layer of the Java EE application, as long as the components that satisfy the Java EE specification can be run in the EJB container, this component will be managed efficiently by the EJB container. At the same time, the EJB container can provide a safe and superior service environment for the components running in it, such as transaction management, mail service, etc.

Applet container: Is a client container that contains components applet,-is a lightweight client embedded in the browser, which is generally used only when the Web page does not adequately represent the data or application interface. is a means of replacing web pages, developers can only use the Java EE Development applet, for security reasons, applets cannot use the various service and API of the Java EE

Application Client Container: is a clients component that contains a component application client. In contrast to applets, the application client is a lighter-level agent that can use the various service and API of the Java EE

JNDI: All called Java Naming and directory Interface (Java naming and directory interface). It provides a directory system and associates the service name with the object, allowing the developer to access the object using the name during development

The Jms:--java messaging service, an API for message intermediate components in a Java platform, primarily enables asynchronous communication between applications, including creating, sending, receiving, and reading messages.

Jta:--java transaction Service, which provides a variety of distributed transaction services, provides important support for the implementation of distributed transaction processing in Java EE.

The Jaf--java activation Framework, a dedicated data processing framework, provides a way to unify the processing of different data formats.

rmi--Remote Method Invocation, which is used primarily for remote invocation of a service, allows you to invoke a program running on another computer like a local function, without concern for the system or language used by the remote computer.

10.XML

Extensible Markup Language is a set of languages that define semantic tagging rules that can be used to describe business data, mathematical data, and so on.

Four major advantages: 1. Practicality--is stored in the form of text rather than binary data, so it is easy to modify and debug it. In addition, it is not only used for applications where data volumes are small (structs-config.xml hibernate.cfg.xml and Web. xml), but also for storing large amounts of data (the database stored in the archive)

2. Fast access--using hierarchies

3. Scalability---Not only can be used to store and display data, but also through the relevant attributes to mark the data properties and types, so that the application can choose different data according to the actual situation.

4. Good cross-platform---XML has a uniform standard syntax, so the XML files that are not partially supported by the system have the same grammatical structure, which makes them have a good cross-platform nature.

11. Parsing methods FOR XML:

A:dom parsing: Creating a tree structure in memory based on a given XML file can take up more memory and dramatically reduce efficiency when working with large files. And Dom has to load the entire document into memory before parsing the file, so it's suitable for random access to XML and frequently modifying XML content.

B:sax parsing: Treat each request to the data as an event by traversing the file to get the data the user needs. Usage scenarios-typically sequential access to XML, XML files too large to fit in memory

12. Database Connection Pool

is responsible for allocating, managing, and freeing the database connection, which allows the application to reuse an existing database connection instead of re-establishing a new database connection to avoid missing the database connection because the database connection was not freed.

13.Struts Frame:

The struts name derives from the support metal frame used in the building and the old aircraft, which is a reusable framework of MVC2 patterns made up of custom tags, information resources, Servlets, and JSPs.

14.Hibernate:

is an open source Object Relational mapping framework that can be run not only in the Java EE container, but also outside of the Java EE container. He has a very lightweight object encapsulation of JDBC, and any place where JDBC can be used can be replaced with hibernate.

15.HTML:

Hypertext Markup Language-----is a markup Language for Web page creation and other information design that can be seen in Web browsers. --maintained by the World Wide Web (WWW)

16. Browser Kernel:

The core part is the translation of "Rendering engine" into an interpreter, but we are accustomed to calling the browser kernel---responsible for interpreting the page syntax and rendering the display page. The rendering engine determines how the browser displays the contents of the page and the formatting information of the page

17. The reflection mechanism of the class:

In the running state, for any class, you can know all the properties and methods of this class, for any one object, can call one of his methods, class reflection required classes are: Filed, Constructor, Method, class, Object proxy mode is often used. Everything in spring is reflection, and struts and hibernate are developed through the reflection of the class.

18.JVM:

Java virtual machines, a specification for computing devices, can be implemented in different ways (soft/hard), including a set of bytecode instructions, a set of registers, a garbage-collected heap, and a method storage domain.

Determines the platform-agnostic nature of the Java language. Java run: Write-and-compile run (that is, the Java interpreter translates bytecode files into machine code, executes and displays the results).

Java source files (*.java)---> java (compiler)---> Bytecode files (*.class)---> java (interpreter)---> Run

is a virtual machine process that can execute Java bytecode, and Java source files are compiled into bytecode file bytecode that can be executed by a Java Virtual machine: is the instruction group of the Java Virtual machine

19.java:

. SDK: Generally refers to the software development package, can contain function library, compile program, etc.

. JDK: A JDK for Java developers that provides a Java development environment and a running environment-------------to do Java development installation JDK

. JRE: Java is a running environment for Java users, not developers-------------------------run Java programs such as table pet, install the JRE

20.HTTP Communication protocol:

Application-layer communication protocol that is architected over TCP/IP (the way communication between two computers)

HTTP is basically a request/response-based communication protocol

After the server responds to the client, it forgets everything, also known as a stateless communication protocol

Professional Concept Summary 1