Ali on three sides, it's really difficult to successfully get the offer rated P7

If you want to work in a big factory, you can say that thousands of troops are crossing a single wooden bridge . We must pass the tests , Brush problem It must be essential .

As a typical representative of Internet technology in China , Alibaba's technology has always been the focus of attention . Can work in Ali , Is the goal and dream of many developers , To help developers improve their interview skills 、 Interview of Internet companies with high efficiency , Xiao Bian took the latest one to Ali offer The interview experience of programmers is shared with you , I hope that helps .

one side

• Self introduction.
• Monitoring in the project ： What are the common monitoring indicators ？
• What are the technologies involved in microservices and what problems should be paid attention to ？
• Registry what do you know about ？
• consul Do you understand the reliability of ？
• consul Have you ever gone into the mechanism of ？ Have you compared it with other registries ？
• The project with Spring More , Do you understand Spring Principle ？AOP and IOC Principle
• Spring Boot In addition to automatic configuration , Compared with traditional Spring What are the other differences ？
• Spring Cloud What do you know ？
• Spring Bean Life cycle of
• HashMap and hashTable difference ？
• Object Of hashcode Method overridden ,equals Should we change the method ？
• Hashmap Thread unsafe scenario
• Online services CPU What should I do ？ What measures can we take to find the problem
• JDK Which thread pools are in ？ By the way, I've talked about thread pools all over the world
• Should try to avoid in where Used in clauses != or <> The operator , Otherwise, the engine will discard the index and scan the whole table
• SQL Order of indexes , Order of fields
• see SQL Is index used ？（ What are the tools ）
• TCP and UDP The difference between ？TCP How to be reliable in the process of data transmission ？
• Let's talk about the sort algorithm you know
• Find the median of an array ？

Two sides

Do you have any questions for me ？（ Regular questions ）

• Self introduction. 、 Work experience 、 Technology stack
• What technology did you learn in the project ？
• Granularity of microservice segmentation ？
• How to guarantee the high availability of microservices ？
• Load balancing and reverse agent , Isolation , Current limiting , Downgrade , Timeout and retry , Roll back , Stress testing and contingency plans
• Common load balancing , How to use , Can you say something ？

（ Technical questions ）

• http Redirect
• DNS Load balancing
• Reverse agent load balancing
• IP Load balancing (LVS-NAT)
• Direct routing (LVS-DR)
• IP Tunnel (LVS-TUN)
• What benefits can gateways bring to back-end services ？
• Spring Bean Life cycle of
• xml Configured in init、destroy How can methods call specific methods ？ The mechanism of reflection
• Object Methods in class
• Whether the object comparison is the same
• hashmap put How to judge whether the method is repeated when storing
• Object toString Methods are commonly used , Why rewrite this method
• Set and List difference ？
• ArrayList and LinkedList difference
• If access to the same data ,ArrayList and LinkedList Who takes up more space ？
• Set Is the order of storage orderly ？
• common Set What are the implementations of ？
• TreeSet What are the requirements for storing data ？
• HashSet The underlying implementation of ？
• TreeSet Have you seen the underlying source code ？
• HashSet Is it thread safe ？ Why not thread safe ？
• Java Which thread safe Map？
• HashTable Do you know ？
• How to ensure thread safety ？
• synchronized、lock
• volatile The atomicity of ？ Why? i++ This doesn't support atomicity ？ The reason why atomicity can't be guaranteed in terms of the design of Computer Principles happens before principle
• cas operation
• lock and synchronized The difference between ？
• Fair and non-fair locks
• Java Read-write lock
• What is the main problem of read-write lock design ？
• In addition to writing Java Code , And front-end code , Do you know what the front-end framework is ？
• MySQL Paging query statement
• MySQL Transaction characteristics and isolation levels

Two 、 Concurrency of transactions

• What scene does non repeatable reading appear in ？
• sql having Usage scenarios of
• One of the front browser addresses http How is the whole process from request to backend ？
• http Default port ,https Default port
• DNS Do you know what it is ？
• Use your ide What is it ？ You can say idea A few commonly used shortcut keys ？
• What do you use for code version management ？
• git rebase and merge What's the difference? ？

Does your company work overtime ？（ Digression ）

Give an example to answer ：

The project with Spring More , Do you understand Spring Principle ？AOP and IOC Principle

answer ：(1). IoC（Inversion of Control） The container controls the relationship between program objects , Not in traditional implementation , Directly controlled by program code . Control is transferred from the application code to the external container , The transfer of control is called reversal . about Spring for , Is the Spring To control the life cycle of an object and the relationship between objects ;IoC There's another name ——“ Dependency injection （Dependency Injection）”. Understand from the name , So called dependency injection , That is, the dependencies between components are determined by the container during the runtime , That is to say, the container dynamically injects some kind of dependency into the component .

(2). stay Spring In the way we work , All classes will be in spring Register... In container , tell spring This is something , What do you need , then spring When the system is running properly , Offer you what you want , At the same time, give you to other things that need you . Creation of all classes 、 Destroyed by spring To control , That is to say, it is no longer the object that references it that controls the object's life cycle , It is spring. For a specific object , It used to control other objects , Now it's all the objects that are spring control , So this is called inversion of control .

(3). In system operation , Dynamically provide some object with other objects it needs .

(4). The idea of dependency injection is realized through reflection mechanism , When instantiating a class , It calls the class through reflection set Methods will be saved in advance in HashMap Class attributes in the class are injected into the class . To make a long story short , In the traditional way of object creation , It's usually up to the caller to create an instance of the callee , And in the Spring The work of creating callees in is done by Spring To complete , Then inject the caller , It's called dependency injection or Inversion of control . There are two ways to inject ： Dependency injection and setup Injection ; IoC The advantages of ： Reduced coupling between components , Reduces the complexity of replacing business objects , Make it flexible to manage objects .

AOP（Aspect Oriented Programming）

(1). AOP Aspect oriented programming is based on IoC, It's right OOP A useful addition to ;

(2). AOP Use a method called “ Crosscut ” Technology , Dissect the inside of the sealed object , And put those influences on The common behavior of multiple classes is encapsulated into a reusable module , And call it “Aspect”, In other words . So-called “ aspect ”, In short , It's not about business , But it is called by the business module Logic or responsibility , Like logging , Ease of reducing system duplication , Reduce the coupling between modules , And is conducive to the future of operability and maintainability .

(3). AOP It represents a horizontal pass system , take “ object ” It's like a hollow cylinder , It encapsulates the properties and behaviors of objects ; Aspect oriented programming method , Is to cut this cylinder in the form of a section , Selectively provide business logic . and The open section , It's called “ aspect ” 了 . Then it restores these cut sections with its skillful hand of seizing the sky skill , Leave no trace , But it's done .

(4). Realization AOP Technology , There are two main categories ： One is to adopt dynamic agent technology , Using the method of intercepting messages , Decorate the message , To replace the execution of the original object behavior ; The other is static weaving , Introduce specific syntax to create “ aspect ”, This allows the compiler to weave information about “ aspect ” Code for .

(5). Spring Realization AOP：JDK Dynamic proxy sum CGLIB agent JDK A dynamic proxy ： Its proxy object must be the implementation of an interface , It accomplishes the proxy of the target object by creating an interface implementation class during runtime ; The two core classes are InvocationHandler and Proxy. CGLIB agent ： The implementation principle is similar to JDK A dynamic proxy , But the proxy object it generates during runtime is a subclass of the target class extension .CGLIB It's an efficient code generation package , The bottom is dependent on ASM（ Open source java Bytecode editing class library ） Operating bytecode , Performance ratio JDK strong ; Need to introduce package asm.jar and cglib.jar. Use AspectJ Injection section and @AspectJ In fact, the annotation driven aspect is realized by dynamic proxy .

(6). AOP Use scenarios ：

• Authentication Permission check
• Caching cache
• Context passing Content delivery
• Error handling Error handling
• Lazy loading Delay loading
• Debugging debugging
• logging, tracing, profiling and monitoring logging , track , Optimize , calibration
• Performance optimization performance optimization , Efficiency check
• Persistence Persistence
• Resource pooling Resource pool
• Synchronization Sync
• Transactions Business management

in addition Filter Implementation and struts2 The implementation of the interceptor is AOP The embodiment of thought .

Ali's interview scene and interview answers （ Document summary ）

Last

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