What is servlet

#servlet is a platform- and protocol-independent server-side Java technology that can be used to generate dynamic Web pages. Compared with traditional CGI (Computer Graphics Interface) and many other similar CGI technologies, Servlet has the characteristics of better portability, more powerful functions, less investment, higher efficiency, and better security.

Servlet is a Java program that uses the Java Servlet application programming interface (API) and related classes and methods. Basically, Servlet can realize the functions that Java language can realize (except for graphical interface). Servlet is mainly used to process Http requests from the client and return a response. Generally speaking, Servlet refers to HttpServlet, which is used to process Http requests. The requests it can handle include doGet(), doPost(), service() and other methods. When developing Servlets, you can directly inherit javax.servlet.http.HttpServlet.

Servlet has a wide range of applications. Many of the popular framework technologies we use now have their most basic codes inseparable from the support of Servelt.

Servlet technology features

Efficient, convenient, cross-platform, powerful, flexible and scalable, shared data, safe.

1. Efficient

Only one Java virtual machine is running on the server. Its advantage is that when multiple requests from the client are accessed, the Servlet allocates a thread for each request. rather than process.

2. Convenience

Servlet provides a large number of utility routines, such as processing HTML form data that is difficult to complete, reading and setting HTTP headers, processing cookies and tracking sessions, etc.

3. Cross-platform

Servlet is written in Java classes and can run on different operating system platforms and application server platforms.

4. Powerful functions

In Servlet, many tasks that are difficult to complete with practical traditional CGI programs can be easily completed using Servlet technology. For example, Servlets can interact directly with Web servers, but ordinary CGI programs cannot. Servlets can also share data between various programs, making functions such as database connection pools easy to implement.

5. Flexibility and scalability

Web applications developed using Servlets have flexible applications and can be expanded at will due to the inheritance of Java classes, constructors and other characteristics.

6. Shared data

The database connection pool can be easily implemented by sharing data between Servlets. It can easily manage user requests, simplify the operation of Session and obtain the previous page information, but the communication between CGI is poor. Since each call to a CGI program starts a new process, communication between calls usually takes place through files and is therefore quite slow. Communication between different CGI programs on the same server is also quite troublesome.

7. Security

Some CGI versions have obvious security weaknesses. Even applying the latest standards, the system does not have a basic security framework. Java defines a complete security mechanism, including SSL\CA certification, security policy and other specifications.

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