idempotent

AngularDart custom filter call() method required to be idempotent?

由 丶灬走出姿态 提交于 2019-11-29 23:33:12
问题 The main running example of the Angular Dart tutorial is a Recipe Book app . The exercise at the end of the Chapter 5 on filters and services suggests trying to " create a [custom] filter that will multiply all the amounts [of each ingredient listed] in the recipes " thus allowing a " user to double, triple, or quadruple the recipe ." E.g. an ingredient of "1/2 cup of flour" would become "1 cup of flour" when doubled. I have written such a custom filter: it takes a list of Ingredient s

How can I prevent database being written to again when the browser does a reload/back?

由 霸气de小男生 提交于 2019-11-29 22:15:00
问题 I'm putting together a small web app that writes to a database (Perl CGI & MySQL). The CGI script takes some info from a form and writes it to a database. I notice, however, that if I hit 'Reload' or 'Back' on the web browser, it'll write the data to the database again. I don't want this. What is the best way to protect against the data being re-written in this case? 回答1: Do not use GET requests to make modifications! Be RESTful; use POST (or PUT) instead the browser should warn the user not

Defining Idempotence

由 我只是一个虾纸丫 提交于 2019-11-29 17:54:21
问题 So "idempotence" can be defined as: An action, that if performed N times has the same effect as performing the action only once. Got it, easy enough. My question is about the subtlety of this definition -is an action considered idempotent by itself, or must you also consider the data being passed into the action? Let me clarify with an example: Suppose I have a PUT method that updates some resource, we'll call it f(x) Obviously, f(3) is idempotent, as long as I supply 3 as the input. And

How to get the installed yum packages with Ansible?

由 岁酱吖の 提交于 2019-11-29 08:24:42
I am trying to get all the installed yum package on an RHEL machine. I can easily get it through using shell commands which is not idempotent and would like to use the yum command instead. Shell command works fine: - name: yum list packages shell: yum list installed > build_server_info.config But when I try to use the yum command it just executes but do not give any results: - name: yum_command action: yum list=${pkg} list=available I can easily get it through using shell commands which is not idempotent You can't really talk about idempotence, when you are querying the current state of a

What does idempotent method mean and what are the side effects in case of calling close method of java.lang.AutoCloseable?

由 谁说我不能喝 提交于 2019-11-28 06:22:01
Java docs of close() method of java.lang.AutoCloseable says Note that unlike the close() method of Closeable , this close() method is not required to be idempotent . In other words, calling this close method more than once may have some visible side effect, unlike Closeable#close() which is required to have no effect if called more than once. However, implementers of this interface are strongly encouraged to make their close methods idempotent. What do they mean by idempotent method and what are the side effects of calling this close() method twice? And since interface Closeable extends

What are best practices for activation/registration/password-reset links in emails with nonce

由 。_饼干妹妹 提交于 2019-11-28 02:45:32
Applications send out emails to verify user accounts or reset a password. I believe the following is the way it should be and I am asking for references and implementations. If an application has to send out a link in an email to verify the user's address, according to my view, the link and the application's processing of the link should have the following characteristics: The link contains a nonce in the request URI ( http://host/path?nonce ). On following the link (GET), the user is presented a form, optionally with the nonce. User confirms the input (POST). The server receives the request

Should IDisposable.Dispose() implementations be idempotent?

由 ≯℡__Kan透↙ 提交于 2019-11-28 02:29:23
问题 The Microsoft.NET framework provides the IDisposable interface which requires an implementation of void Dispose() method. Its purpose is to enable manual, or scope-based releasing of expensive resources an IDisposable implementation may have allocated. Examples include database collections, streams and handles. My question is, should the implementation of the Dispose() method be idempotent - when called more than once on the same instance, the instance to be 'disposed of' only once, and

Hibernate Idempotent Update

由 随声附和 提交于 2019-11-28 02:16:38
问题 I tried searching this over the net but in vain. Is there a way to use hibernate to perform an idempotent update. One use case is to use HTTP PUT to update a specific field in the database via a REST API. So for example, if I have a database with columns : Id, Name, Phone, UpdateDate and I update the Phone field (of a specific Id ) with the same value multiple times only my first action must update the Phone (and also change my UpdateDate ). Subsequent updates must have no effect on the

How to get the installed yum packages with Ansible?

由 拟墨画扇 提交于 2019-11-28 01:46:01
问题 I am trying to get all the installed yum package on an RHEL machine. I can easily get it through using shell commands which is not idempotent and would like to use the yum command instead. Shell command works fine: - name: yum list packages shell: yum list installed > build_server_info.config But when I try to use the yum command it just executes but do not give any results: - name: yum_command action: yum list=${pkg} list=available 回答1: I can easily get it through using shell commands which

What does idempotent method mean and what are the side effects in case of calling close method of java.lang.AutoCloseable?

由 生来就可爱ヽ(ⅴ＜●) 提交于 2019-11-27 01:03:59
问题 Java docs of close() method of java.lang.AutoCloseable says Note that unlike the close() method of Closeable, this close() method is not required to be idempotent . In other words, calling this close method more than once may have some visible side effect, unlike Closeable#close() which is required to have no effect if called more than once. However, implementers of this interface are strongly encouraged to make their close methods idempotent. What do they mean by idempotent method and what
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