Shulou(Shulou.com)05/31 Report--

How does Spring's Controller ensure the security of concurrency? in view of this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

Controller is singleton by default, do not use non-static member variables, otherwise data logic confusion will occur. It is not thread-safe because of the singleton.

Let's have a simple verification:

Package com.xttblog.springbootdemo.controller

Import org.springframework.context.annotation.Scope

Import org.springframework.stereotype.Controller

Import org.springframework.web.bind.annotation.RequestMapping

/ * *

* @ author amateur grass, official account

, /

@ Controller

Public class ScopeTestController {

Private int num = 0

@ RequestMapping ("/ testScope")

Public void testScope () {

System.out.println (+ + num)

}

@ RequestMapping ("/ testScope2")

Public void testScope2 () {

System.out.println (+ + num)

}

}

We first visited http://localhost:8080/testScope and got an answer of 1.

Then we visit http://localhost:8080/testScope2 and the answer is 2.

Gets a different value, which is not thread-safe.

Next, let's add more examples of @ Scope ("prototype") to controller.

Package com.xttblog.springbootdemo.controller

Import org.springframework.context.annotation.Scope

Import org.springframework.stereotype.Controller

Import org.springframework.web.bind.annotation.RequestMapping

/ * *

* @ author amateur grass, official account

, /

@ Controller

@ Scope ("prototype")

Public class ScopeTestController {

Private int num = 0

@ RequestMapping ("/ testScope")

Public void testScope () {

System.out.println (+ + num)

}

@ RequestMapping ("/ testScope2")

Public void testScope2 () {

System.out.println (+ + num)

}

}

We still visit http://localhost:8080/testScope first, and the answer is 1.

Then we visit http://localhost:8080/testScope2 and the answer is still 1.

I believe it is not difficult to find out:

❝

Singletons are unsafe and can cause attributes to be reused.

❞solutions do not define member variables in Controller. In case you have to define a non-static member variable, set it to multiple-instance mode by annotating @ Scope ("prototype"). Supplementary instructions on using the ThreadLocal variable in Controller

There are five spring bean scopes:

Singleton: singleton mode. When spring creates an applicationContext container, spring will want to initialize all instances of the scope and add lazy-init to avoid preprocessing; prototype: prototype mode, each time the bean is obtained through getBean, a new instance will be generated, and spring will no longer manage it after creation

(the following is only used under the web project)

Request: everyone engaged in web should understand the domain of request, that is, a new instance is generated for each request. Unlike prototype, after creation, spring is still listening; session: every session, same as above; global session: global web domain, similar to application in servlet. This is the answer to the question about how Spring's Controller ensures concurrent security. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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