scholl concepts

, when only to know the white Chocolate Williams, is the time to know Mutombo, but also which UFO let me always can not feel amazing, in fact, the beginning, I do not know.Some languages, which occupy a pivotal position here, are often mentioned, as if rightfully, and at this time we have to do, is to understand the things that are rightfully, even if only a noun change, may be less a little bit tacit understanding, understand it, at least you know what it is.Halfway decent program Road, since t

web Framework is a well-designed framework and a good alternative to web frameworks. Transaction Management: Spring provides a continuous transaction management interface that can be extended up to the local transaction down to the global transaction (JTA). Exception Handling: Spring provides a convenient API for translating specific technology-related exceptions (such as those thrown by jdbc,hibernate or JDO) into a consistent unchecked exception. The core idea of spring: (1) IOC

-bound//io Intensive9.IPCIpc:inter preocess communication: interprocess communicationProcess is not aware of the existence of other processesOn the same host:Signal//common means of communicationShm:shared MemorySemerphor:On different hosts:Rpc:remote procecure Call//Remote procedure invocationSocket: socket-based communicationA process listens in one place and can accept messages sent by othersOne end just sends data to the socket, the kernel automatically transmits the data to the other end, a

. This is the threat to the zombie process and should be avoided. (2) The orphan process is a process without a parent process. If a parent process terminates, the kernel will schedule the init process to be known as the adoptive father of its orphan process, the PID of the Init process is 1, the system is created by the kernel at boot, it does not terminate, it is the ancestor of all processes, and the kernel arranges the init process to reclaim them. So the orphan process does not have any ha

-level makefile file of the kernel, the m= option, let the makefile return to the module source code directory before constructing the modules target Insertion of the kernelInsmod Hello.koKernel parametersHow to use the Module_param function:Module_param (name, type, perm)Name: Names of kernel parameters, defined by themselves;Type: Types of kernel parameters, common types Byte, short, int, long, ULONG, BOOL, charp (character pointer);Perm: The kernel parameter has permission S_irugo (Read

faster understanding of the Linux partition and file system structure. in Linux only the directory does not have a folder , only/root and mounted disk , no c,d,e disk, this concept must be divided clearly.Summary: these are just the basis of the Linux Foundation, the premise of these basic understanding, so as to step-by-step, I also from the novice to step up the walk, wherein the pain believe that many beginners will encounter, so play these foundations, in the follow-up command learning will

, message processing."Messaging" and "message processing" are weak-related tasks, and "message processing" can be divided into "message decoding","Business Processing", these two tasks are relatively much more relevant.So "messaging" and "message processing" can be divided into process design, "message decoding", "Business processing" can be divided into threading design.Of course, this classification is not static, but also can be adjusted according to the actual situation.4): Threads that may

analysis, finally find out the general relationship.(3) Recursion: Starting from the known initial conditions, each successive introduction of the required intermediate and final results. Nature is also a kind of induction, recursive relationship is usually the result of induction.(4) Recursion: in solving some complex problems, in order to reduce the complexity of the problem of the program, usually the problem is divided into layers, and finally boils down to some of the simplest problems. It

Standards version, for standard application development, is also Java basic version.j2me--Full name Java 2 Micro Edition, is a miniature version of Java, for mobile phones, PDA and other embedded development, for mobile phone development, there is a dedicated J2ME Wireless Toolkit free package provided.All in all, J2ee,j2se,j2me is Java that provides different services for different categories of use, that is, providing different types of class libraries. Java EE (Java 2 Enterprise Edition) for

, this is not necessarily a disadvantage, if your project requires the source codes must be encrypted, then you should not use Python in the beginning to implement. Threads do not take advantage of multi-CPU problems, which is one of the most common drawbacks of Python, the Gil, the Global Interpreter lock (interpreter lock), is a tool that the computer programming language interpreter uses to synchronize threads so that only one thread executes at any moment, The python thread is the native

placed at the tail end of the TLS execution queue. Instead, it is placed in a separate sleep queue. In order for the threads on the sleep queue to run again, they need to be marked with a different interrupt, called a clock break. When a thread enters the sleep queue, it sets a clock interrupt to schedule when to wake the thread. When a clock break occurs, if this time matches the time that a thread on the sleep queue resumes running, the thread goes back to the executable queue and schedules t

" name.length //3var string = "ABCDE";　　var result =string.slice (3,4); // D　var result1 =string.split (); // ["ABCDE"] var result2 =string.split ("); //[" A "," B "," C "," D "," E "]Split splits are broken down by what symbols in the string, and if separated by an empty string (""), each character in the string is "," to be split.　var result3 =string.replace ("C", "F"); //"Abfde" (can be used for replacement)　　　var result4 =string.replace ("C", ""); //"Abde" (can be used to delete)　var result

error.Stack: The stack contains all the steps (frames) of a message at execution time. The data structure of the stack is "last in, first out", so when a frame is added to a stack, it is always put on top, and the event loop is processed from top to bottom to the frame in the stack.Queue:The queue contains a list of information to be executed, each of which is associated with a function. When the stack is empty, a message in the queue is fetched and processed. The process is to invoke the funct

determines what the component is going to look like.Componentdidmount1. Triggers after UI rendering is complete2. Execute only once3. This method usually triggers an AJAX request.When updatingThere are three scenarios that trigger update.Props has changed, setstate execution, forceupdate execution.ForceUpdateThe first two do not say, the third forceupdate trigger scene is relatively rare, if the Render method uses data other than props and state, this method is required.Here is an example.Shoul

():Join () causes a child thread to join a main thread and let the main thread wait for the child thread to end before it can continue.8.interrupt (): Interrupts a threadUsage of 2.synchronized KeywordsFirst : When a thread accesses the "synchronized method" or "Synchronized code block" of "an object", the other thread has the " synchronized method" or " Access to the synchronized code block will be blocked.Second: When a thread accesses the "synchronized method" or "Synchronized code block" of

-numeric value, the background call to the number () transformation function first converts it to a numeric value in the operation.Relational operators If the two operands are numeric, a numeric comparison is performed; If the two operands are all strings, the character encoding values corresponding to the two strings are compared; If an operand is a numeric value, the background will use the number () function to convert it to a numeric value and then compare it. If an oper

testsupportbinder, which retains an unmodified channel so that the test can interact directly and reliably with the channel. You can use the Extensible API to write your own binder.Spring Cloud Stream is configured with spring boot, and the binder abstraction allows the spring cloud stream application to have the flexibility to connect to the middleware. For example, a deployer can dynamically select the destination of a channel connection at run time (for example, Kafka topic or RABBITMQ Inter

attack DDoS Flow rate up to dozens of G Distributed (broiler, agent) Very difficult to defend Dos Attack defense Firewall Switch/router Flow Cleaning High Anti-IP Avoid heavy logic business Quick Fail Quick return Anti-avalanche mechanism Lossy services Cdn Replay attackThe request was intercepted or bugged, then exploited by the attacker and re-sentHarm Users have been spending multiple times User logon State stol

forms, iterative deadlocks and mutual invocation of deadlocks. A generic deadlock is caused by a mutex, and a partial deadlock problem can be avoided by using a reentrant lock.1.11 Thread Safety /Thread SafetyThread Safety is a multi-threaded access, with a locking mechanism, when a thread accesses one of the class's data, protection, other threads can not access until the thread is finished reading, other threads are available. There is no data inconsistency or data contamination. thread Insec

environment. The Web container is more of a deal with HTTP-based requests. And the EJB container is not. It is more about dealing with databases and other services. But they are all interacting with the outside world to reduce the burden on the application. For example, the servlet does not care about the details of HTTP, directly referencing the environment variable session,request,response, EJB does not care about the database connection speed, various transaction control, directly by the con