Shulou(Shulou.com)06/02 Report--

This article mainly introduces "what is the java backend". In the daily operation, I believe many people have doubts about what the java backend is. 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 doubts about "what is the java backend?" Next, please follow the editor to study!

We all know that Java is a back-end language, the back-end refers to the server, the server code generally runs on the server, usually we run Java programs on the server is the Linux server.

These servers are usually placed in a place called the computer room in Internet companies, so the code of Java programmers like us usually runs on the servers in these computer rooms.

There is a concept in Java called a virtual machine, which you can think of as an Android simulator. For example, if you install an Android simulator on your computer, you can use it to run Android applications, such as APP, mobile games and so on.

So when you install something called JDK on your computer, you have JRE, the Java environment, on your computer, and with this environment, you can run Java applications.

After knowing how Java programs run on computers, let's talk about some of the basics of Java that we usually learn. What is the use of them?

In fact, usually these basic Java grammars are just some basic knowledge of writing code, which is equivalent to 26 letters in English, such as basic type variables, for loops, if else and so on. After mastering these basic knowledge, you can start writing some very simple code.

In addition, Java has some special concepts, such as object-oriented features, including classes, interfaces, and so on. Why does Java introduce these things, in fact, to enable users to better design, abstract and program.

For beginners, you don't need to understand particularly deeply, because these things can only be understood gradually after you actually write the code.

You will use a List to see if it is right, so the purpose of collection classes is to allow you to better store data in programming.

In fact, the concept of set class originated from data structures, because there are many special data storage structures in computers, such as file trees, linked lists and arrays, so computer theory abstracts these data storage models into some common structures, collectively called data structures.

So, what is the concurrent programming in Java? multithreading in Java is to make better use of the CPU core in the computer. Through concurrent programming, the efficiency of program concurrency can be improved.

But concurrent programming requires the support of the operating system and computer hardware, so if you want to fully understand multithreading, it is not just enough to understand the Thread or thread pool in Java, you also need to understand the operating system and how the computer is made up.

Similar to concurrent programming, Java also has the concept of network programming. Network programming in Java is more or less the same as other languages. In fact, it is also a set of API based on TCP/IP protocol. Through network programming, you can transfer the data you want to transfer to the other end of the network. With network programming and concurrent programming, Java programmers have a lot of power.

After talking about these points, let's talk about what we usually call the Java back-end technology. Take Alipay as an example. Once there were not many Alipay users. One server and one database can support all the business.

When there are more and more users of Alipay, one server can not meet the needs of a large number of users at the same time, so multiple servers begin to appear, and multiple servers form a cluster. Users can access these servers through load balancing, and each user may access different machines, which achieves the effect of diversion and reduces the pressure on the server.

Because the database needs to ensure the reliability of the data, in case a database is down and there is no backup, then the data cannot be accessed, which is not allowed in large systems, so, there is a master-slave deployment of the database.

But in fact, with the development of the business, the pressure on the database is increasing, and the active and standby deployment can not solve the problem of database access performance, so we need to divide the database into tables on the basis of the master and standby of the database. We will split a table with a large amount of data into multiple tables, and divert database requests to different data, such as 100 databases and 100 tables. It is equivalent to dividing a data table into 10000 data tables.

At this time, there is another problem. If a database has multiple slave databases, and master-slave switching is needed when the master database is down, the data between the master and slave databases may be inconsistent, and this is also one of the problems in distributed theory research. Because it is more complex, we will skip it here.

I just talked about distributed technology. In fact, load balancing and sub-database and sub-table are all an implementation of distributed technology. If you do not want to do sub-database and sub-table, is there any other way to reduce the pressure of database access? So the cache appears, the cache allows the server to first hit the request to the cache, because the cached data is generally in memory, so the access speed will be very fast, these requests do not need to go through the database.

With the development of business, the single point of pressure on caching will be greater, so distributed caches appear. Generally speaking, caching is difficult to guarantee the reliability of data, because their data may be lost. At the same time, caching can only store part of the data, which does not solve all problems.

Therefore, when the number of requests for some services is very large, caching alone can not solve the problem. At this time, we can also use message queues to help us solve the problem of concurrent requests with large traffic.

We can store part of the request messages through the message queue, and then extract the messages step by step according to the ability of our server to process the requests, and then process these messages gradually, so that the problem of high concurrency can be well solved. Of course, the premise is that message queues ensure the reliability of message storage, which is what most message queues guarantee.

At this point, the study of "what is the back end of 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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