JSP Programming Technology 5-Shopping Cart implementation-session object, 5-session

JSP Programming Technology 5-Shopping Cart implementation-session object, 5-session

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The following is an example of my own shopping cart, which uses the JSP built-in session object to implement a session between the client and the server. I also said in the previous case, after connecting the client to the server and logging out, the session object will always exist.

First, create a client page. What I do is very simple. I hope you can understand this process first. What's important is this idea. I also add comments to the relevant position in the code.

The next step is to display the shopping cart page. When the client clicks "show Shopping Cart", the server returns the information of the current Shopping Cart. The session object exists throughout the process.

Well, a complete shopping cart will be implemented.

To sum up, first we need to establish a link between the client and the server (here I have already connected, see the previous article on the connection method) to generate a session object, as long as the client and the server are continuously connected, the session always exists. Otherwise, in many cases, the server can identify who is still connected or who is offline through the session object. Then the server obtains the information submitted by the client and executes the corresponding JSP program (that is, to identify what books the client has bought). Finally, when the client clicks "show Shopping Cart, the server returns to the shopping cart page to display the books currently purchased by the client.

I hope you can understand this process. This process is very helpful for WEB development in the future. Many of our things are built on session objects. If you have any questions, please comment or leave a message.

How to Use the jsp session object to write a shopping cart?

... This is simple and cannot be used simply to use session. setAttribute () to directly insert objects of items to be stored.
On a special page, use session. getAttribute () to read the stored items and display the shopping cart .........
Then, you can set a maximum of Session Timeout Cookies .....
 
Jsp implements Shopping Cart. Can I ask if the database operation is good or the session is good?

How much burden do you have to put on the database when using data inventory? In addition, for shopping carts, this kind of thing that requires real-time operations, the database is prone to concurrent errors or crashes when there is a large access volume.

It is undeniable that the use of sessions is indeed very efficient, and sessions are for various connections, so it is easy to manage, but the use of sessions is not perfect, because sessions are valid, the length varies depending on the server settings. If the Session times out during the shopping process, everything in the shopping cart will be lost.

I don't know if you have read Dangdang's shopping cart. When you go offline and go online again, things in the shopping cart still exist, which is very convenient for users.

Therefore, if your server is strong enough, you can use a static variable to save the shopping cart of all users. For example, you can use a static Map to use IP as the Key, differentiate the shopping cart of different users, so that the user can save the content in the shopping cart when going offline.

This method has been implemented, but it does not use a large number of concurrent access tests to test its stability, but it must be feasible.