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This article mainly introduces "what is the life cycle of Servlet in Java". In daily operation, I believe that many people have doubts about the life cycle of Servlet in Java. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the question of "what is the life cycle of Servlet in Java?" Next, please follow the editor to study!

The whole process of Servlet from creation to destruction:

Call the init () method after Servlet initialization

Servlet calls the service () method to process the client's request

Call the destroy () method before Servlet is destroyed

Finally, Servlet is GC by JVM's garbage collector

Init ()

It's only called once. It is called the first time the Servlet is created, and not again each time the user requests it. Therefore, it is used for one-time initialization.

The Servlet is created when the user first invokes the URL corresponding to the Servlet, but you can also specify that the Servlet is loaded the first time the server starts.

When a user invokes a Servlet, an instance of Servlet is created, and each user request generates a new thread that is handed over to the doGet or doPost method when appropriate. The init () method simply creates or loads data that will be used throughout the life cycle of the Servlet.

Public void init () throws ServletException {/ / initialization code.} service ()

The main way to perform practical tasks. The Servlet container (that is, the Web server) calls the service () method to process the request from the client (browser) and writes the formatted response back to the client.

Each time the server receives a Servlet request, the server generates a new thread and invokes the service. The service () method checks the HTTP request type (GET, POST, PUT, DELETE, etc.) and calls the doGet, doPost, doPut,doDelete, and so on methods when appropriate.

Public void service (ServletRequest request, ServletResponse response) throws ServletException, IOException {}

The service () method is called by the container, and the service method calls methods such as doGet, doPost, doPut, doDelete, and so on, when appropriate. So, you don't have to do anything with the service () method, you just need to override doGet () or doPost () depending on the type of request from the client.

The doGet () and doPost () methods are the most commonly used methods in every service request. Here are the characteristics of these two methods.

DoGet ()

The GET request comes from a normal request from a URL, or from an HTML form that does not specify a METHOD, which is handled by the doGet () method.

Public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/ / Servlet Code} doPost ()

The POST request comes from an HTML form that specifically specifies METHOD as POST, which is handled by the doPost () method.

Public void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/ / Servlet Code} destroy () method

The destroy () method is called only once, at the end of the Servlet life cycle. The destroy () method allows your Servlet to close database connections, stop background threads, write Cookie lists or click counters to disk, and perform other similar cleanup activities.

After calling the destroy () method, the servlet object is marked for garbage collection.

The definition of the destroy method is as follows:

Public void destroy () {/ / terminate the code.} architecture

The first HTTP request to arrive at the server is delegated to the Servlet container

The Servlet container loads Servlet before calling the service () method

The Servlet container then processes multiple requests generated by multiple threads, each of which executes a single Servlet instance's service () method

Spring is designed to enumerate:

Tomat is designed as an ordinary constant with no scope and can be broken through at will.

The difference is that enumerations are scoped.

At this point, the study on "what is the life cycle of Servlet in Java" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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