问题描述
我想知道如何创建组件范围的" bean，或者说是复合组件内部的局部变量"，它们对于复合组件的实例是私有的，并且在该实例中一直存在生活.
I was wondering how I could create "component-scoped" beans, or so-to-say, "local variables inside a composite component" that are private to the instance of the composite component, and live as long as that instance lives.
下面是更多详细信息，并通过示例进行说明:
Below are more details, explained with an example:
假设有一个计算器"组件-允许用户键入数学表达式并评估其值的组件. (可选)它还会绘制关联的函数.
Suppose there is a "calculator" component - something that allows users to type in a mathematical expression, and evaluates its value. Optionally, it also plots the associated function.
我可以制造具有以下特征的复合组件
I can make a composite component that has:
- 用于接受数学表达式的文本框
- 两个按钮分别为评估"和绘图"
- 另一个绘制函数的嵌套组件
这显然是一个独立的功能；这样一来，想要使用它的人就可以说< math:expressionEvaluator/>
It is evidently a self-contained piece of function; so that somebody who wants to use it may just say <math:expressionEvaluator />
但是显然，该实现需要一个Java对象-一些用于评估表达式的对象，一些用于计算绘图点的对象，等等-我想它可以是一个bean-仅针对 this 此组件的实例，而不是在该组件的所有实例之间共享的视图范围或请求范围的bean.
But obviously, the implementation would need a java object - something that evaluates the expression, something that computes the plot points, etc. - and I imagine it can be a bean - scoped just for this instance of this component, not a view-scoped or request-scoped bean that is shared across all instances of the component.
如何创建这样的bean?复合组件甚至可以做到吗?
How do I create such a bean? Is that even possible with composite components?
推荐答案
没有按组件实例"范围.但是您仍然可以达到预期的效果.
There is no "per-component instance" scope. But you can still achieve your desired effect.
使用ViewScoped bean进行评估和绘图-这些函数是无状态的"，因此由您的输入提供.
Use a ViewScoped bean to do the evaluating and plotting - these functions are "stateless" and so are fed by your input.
您的输入将由用户提供的bean支持-用相同的方式，文本框或日历小部件需要将输入框绑定到用户提供的bean.这将保存您的无状态"范围的Bean所作用的数据.
Your input would be backed by a user supplied bean - in the same way a text box or calendar widget needs an input box bound to a user supplied bean. This holds the data that your "stateless" viewscoped bean acts on.
如果您真的想保留组件中包含的所有内容，我想您可以使用ViewScoped bean支持输入，该bean包含以输入id为键的映射.不确定是否可以.
If you really wanted to keep everything contained in the component, I guess you could back the input with a ViewScoped bean that contains a map keyed by the input id. Not sure if that would work though.
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