为什么是“立即"?添加到 EditableValueHolders 的属性? [英] Why was "immediate" attribute added to the EditableValueHolders?
问题描述
最初 immediate 标志仅用于 ActionSource 接口.但后来它也被添加到 EditableValueHolder 接口中.设计决策的原因是什么?
Initially immediate flag was only intended for ActionSource interface. But later on it was added to the EditableValueHolder interface also. What was the reason for design decision ?
推荐答案
用于对同一表单中的多个 EditableValueHolder 组件进行优先级验证.
It's to be used to prioritize validation on several EditableValueHolder components in the same form.
想象一个表单，它包含带有 immediate="true" 的输入组件和没有这个属性的输入组件.立即输入将在应用请求值阶段(比平时早一个阶段)进行验证.非即时输入将在验证阶段(这是通常的阶段)进行验证.如果至少一个即时输入的验证失败，则非即时输入根本不会被转换/验证，因此不会生成任何转换/验证错误消息.这在具有复杂验证规则的表单中特别有用，当(立即)组件 X 的验证无论如何失败时，验证组件 Y 没有意义.
Imagine a form containing input components with immediate="true" as well as input components without this attribute. The immediate inputs will be validated during apply request values phase (which is one phase earlier than usual). The non-immediate inputs will be validated during validations phase (which is the usual phase). If validation fails for at least one of the immediate inputs, then the non-immediate inputs won't be converted/validated at all and thus won't generate any conversion/validation error messages. This is particularly useful in forms with complex validation rules where it doesn't make sense to validate component Y when validation for (immediate) component X has failed anyway.
当在相同形式的命令按钮上与 immediate="true" 结合使用时，这将导致所有非立即输入被完全跳过.一个很好的现实世界示例是具有 2 个字段用户名"的登录表单.和密码"使用 required="true" 和 2 个按钮:登录"和忘记密码".您可以将 immediate="true" 放在用户名"上字段和忘记密码"按钮跳过密码字段上的 required="true" 检查.
When used in combination with immediate="true" on a command button in the same form, this will cause all non-immediate inputs being completely skipped. A good real world example is a login form with 2 fields "username" and "password" with required="true" and 2 buttons: "login" and "password forgotten". You could put immediate="true" on the "username" field and the "password forgotten" button to skip the required="true" check on the password field.
在黑暗的 JSF 1.x 时代，immediate="true" 也经常 (ab) 与 valueChangeListener 和 结合用作黑客>FacesContext#renderResponse()，在级联下拉列表中经常出现.长话短说，这是一篇关于此的旧博客文章.就此而言，它使开发人员能够在
In the dark JSF 1.x ages, the immediate="true" was also often (ab)used as a hack in combination with valueChangeListener and FacesContext#renderResponse(), more than often in cascading dropdown lists. Long story short, here's an old blog article on that. To the point, it enables developers to execute a backing bean method on change of a <h:selectOneMenu> without that all other inputs in the same form are been validated. But these days, with the ajax awesomeness, this hack is unnecessary. You can find a concretre example of this case at the bottom of our <h:selectOneMenu> wiki page.
如今，immediate="true" 仍然经常 (ab) 使用，以便拥有一个完全绕过所有其他输入的特定按钮，例如;"中的注销按钮.神形"反模式(其中 一切 都被放在一个巨大的 immediate="true" 以正确方式输入其中一个时，这样的按钮就会中断.您最好将这样的注销按钮放在自己的表单中，或者将其更改为仅处理自己(PrimeFaces 中的 process=@this").而且你最好把这样的取消按钮改成只是通过 <h:button value=Cancel" 来同步刷新页面./>.如果表单绑定到请求/视图范围的 bean 并且浏览器缓存是 在动态页面上禁用.
These days, the immediate="true" is still often (ab)used in order to have a specific button which completely bypasses all other inputs, such as a logout button in a "God-form" antipattern (whereby everything is been thrown together in a huge <h:form>), or a cancel button which incorrectly submits the form. Such a button would break when you start to actually need the immediate="true" the right way on one of the inputs. You'd better put such a logout button in its own form, or to change it to process only itself (process="@this" in PrimeFaces). And you'd better change such a cancel button to just refresh the page synchronously by <h:button value="Cancel" />. This works fine if the form is tied to a request/view scoped bean and browser caching is disabled on dynamic pages.
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