understanding netflow

Understanding about Cache Usage and understanding about Cache Usage First of all, the advantage of caching is that the cache stores data in the memory and extracts the data from the memory when needed (compared with the data obtained from the hard disk, the cache speed is much faster) prompt speed Cache category: Page cache data source cache (permanent and time-limited) Dependency items cache database depe

Basic understanding 2: CSS3 button animation, understanding css3 button Animation A Css3 button works very well. after reading it carefully, we found that: after,: before is followed by transition, transform, and other effects. Focus on the following points for easy implementation: 1. position is required for the pseudo class, and positioning is required for the relative button. 2. Set the z-index attribute

2. in-depth understanding of floating and positioning, and in-depth understanding of floating PositioningFloating and positioning 1. There are several notes on absolute positioning: 1) absolute positioning is used to offset an "existing" ancestor element "of its" nearest. If no ancestor element has been located, the browser window is used as the benchmark for offset; 2) If the parent element is not posit

A deep understanding of the synchronous and asynchronous mechanisms in JavaScript programming and a deep understanding of javascript One of the advantages of JavaScript is how it handles asynchronous code. Asynchronous code will be put into an event queue and will not block the thread until all other code is executed. However, it may be difficult for beginners to write asynchronous code. In this article, I

A deep understanding of Spring transaction principles and a deep understanding of springI. Basic principles of transactions The essence of Spring transactions is the database's support for transactions. Without the database's support for transactions, spring cannot provide transaction functions. To use transactions to operate databases only using JDBC, follow these steps: With the Spring transaction managem

A deep understanding of javascript variable declaration and a deep understanding of javascript Compared with C/C ++, The for loop in ECMAScript cannot create a local context. Copy codeThe Code is as follows:For (var k in {a: 1, B: 2 }){Alert (k );} Alert (k); // although the loop has ended, the variable k is still in the current scopeVariables can only be declared by using the var keyword at any time.The ab

Understanding the prototype and prototype chain in javascript, understanding the prototype of javascript Prototype As we all know, JavaScript does not contain the traditional class inheritance model, but uses the prototype model. Code implementation is like this. function Student(name){ this.name = name;} var Kimy = new Student("Kimy"); Student.prototype.say = function(){ console.log(this.name + "say");}Ki

In-depth understanding of the scope and context of Javascript, and deep understanding of javascript Overview The implementation of scopes and context in Javascript is unique to the Javascript language. To some extent, Javascript is very flexible. Functions in Javascript can use various contexts, and the scopes can be encapsulated and saved. Thanks to these features, Javascript also provides many useful desi

Deep understanding of building and introducing Maven environments, and deep understanding of building maven Maven is a Java tool for project management. In JavaEE, we can use Maven to conveniently manage projects in team collaboration. Now we are learning the JavaEE framework and can use Maven to manage the library, it is effective and convenient for other personnel in the team. The project has been complet

Deep understanding of Java Virtual Machine-learning notes and deep understanding of Java Virtual Machine JVM Memory Model and partition JVM memory is divided: 1.Method Area: A thread-shared area that stores data such as class information, constants, static variables, and Code Compiled by the real-time compiler loaded by virtual machines. 2.Heap:The thread-shared area, the storage object instance, and the me

A deep understanding of the Python crawler proxy pool service and a deep understanding of python Crawlers The company built a stable proxy pool service for Distributed Deep Web crawlers to provide effective proxy services for thousands of crawlers, ensuring that all crawlers receive valid proxy IP addresses for their websites, so as to ensure the fast and stable operation of crawlers, of course, the work do

Understanding classes and instances in Python and understanding Python instances The most important concepts of object-oriented are Class and Instance. You must remember that classes are abstract templates, such as Student classes, instances are specific "objects" created based on classes. Each object has the same method, but its data may be different. Taking the Student class as an example, in Python, the

Deep understanding of Java Virtual Machine-Chapter 2: deep understanding of Java Virtual Machine Chapter 2 Java memory zone and memory overflow exceptions Running data area 1. The Program Counter (Program Counter Register) is a small memory space, which can be seen as the row number indicator of the bytecode executed by the current thread. 2. the Java Virtual Machine Stack (Stack) thread is private. A Stack

Deep understanding of Python3 built-in functions and deep understanding of python3 This article mainly introduces Python3 built-in functions and shares them with you as follows: Built-in functions The following code uses Python3.6.1 as an example: # Coding = UTF-8 # builtin_function.py built-in Function import osdef fun (): all ([True, False]) # all elements of the iterator (empty or) are true, returns tru

Deep understanding of Java Virtual Machine-Chapter 1, deep understanding of Java Virtual Machine Chapter 2 Virtual Machine bytecode execution engine 8.2 runtime stack frame structure Stack Frame is a data structure used to support virtual machines for method calling and method execution. Each stack frame includes a local variable table, an operand stack, a dynamic connection, a method return address, and s

Deep understanding of Java: basic concepts of Annotation and in-depth understanding of annotation What is Annotation ): Annotation (Annotation) is a way and method for Java to associate any information with any metadata (metadata) in elements of a metaprogram. Annotion (annotation) is an interface. The program can obtain the Annotion object of the specified program element through reflection, and then obtai

A deep understanding of the class loading mechanism of Java virtual machines and a deep understanding of virtual machines1. class loading time For the first phase of class loading-loading, the virtual machine has no mandatory constraints,For the initialization phase, Virtual machine mandatory provisionYes and onlyIn the following 5 cases, initialization must begin. Of course, the loading, verification, and

Correct understanding of I = I ++, and correct understanding of I I = I ++ has been frequently encountered in the recent written examination. This problem is still relatively simple, but it doesn't matter if I + = I ++ doesn't matter, I saw a big problem. Common sense 1. result + = expression is equivalent to result = result + expression in all languages. 2. int I = B ++; how is this done? First, the system

[Python] -- first understanding python, first understanding pythonPython InstallationWindows: 1. Download the installation package https://www.python.org/downloads/2?install the default installation path: C: \ python273. Configure the environment variable [Right-click the computer] -- "[attribute] --" [advanced system settings] -- "[advanced] --" [environment variable] -- "[in the second content find a line

In-depth understanding of ini configuration in php (2), in-depth understanding of ini Continue with the previous article.1. Change the configuration during running As mentioned in the previous article, the ini_set function can dynamically modify some php configurations during php Execution. Note that not all configurations can be modified dynamically. For information on the modifiable ini configuration, see