有没有一种方法可以使f:viewparam处理值列表?

问题描述

假设我已经在自定义类Car和String之间建立了一个转换器.

Let's say I already have a converter between a custom class Car and String.

有没有办法优雅地做到这一点

Is there a way to elegantly make this

<f:viewParam name="mycars" value="#{mybean.cars}" converter="carConverter" />

当mybean.cars是Set<Car>或List<Car>而不是单个Car时，

可以工作，而不必在汽车列表和字符串列表之间编写自定义转换器?换句话说，JSF是否有一些功能使我不必解析"[Audi,BMW,VW]"到["Audi","BMW","VW"]然后将它们一个接一个地转换(反之亦然)?

work when mybean.cars is a Set<Car> or List<Car> instead of just a single Car, without having to write a custom converter between lists of cars and lists of strings? In other words, is there some feature of JSF that gets me out of having to parse "[Audi,BMW,VW]" to ["Audi","BMW","VW"] and then convert those one by one (and vice versa)?

如果有类似的东西我会喜欢的

I'd love it if there was something like

<f:viewParam name="mycars" value="#{mybean.cars}" converter="carConverter" list="true" />

谢谢！

PS:我看过这篇关于转换器和selectManyMenu的帖子，在另一种情况下，实际上使用它，一切正常-selectManyMenu可以一一转换.但是现在我需要用viewParam来将列表作为URL传递.

PS: I've seen this post about converters and selectManyMenu, and in another context where I in fact use that, all works fine - selectManyMenu handles converting one by one. But right now I need viewParam to pass my list as an URL.

推荐答案

否，<f:viewParam> 不支持，也不处理具有多个值的单个参数.如果Mojarra甚至在其decode()方法:

No, the <f:viewParam> does not support nor handle a single parameter with multiple values. This is in case of Mojarra even confirmed in a comment hidden in its decode() method:

213    public void decode(FacesContext context) {
214        if (context == null) {
215            throw new NullPointerException();
216        }
217
218        // QUESTION can we move forward and support an array? no different than UISelectMany; perhaps need to know
219        // if the value expression is single or multi-valued
220        // ANSWER: I'd rather not right now.
221        String paramValue = context.getExternalContext().getRequestParameterMap().get(getName());
222
223        // submitted value will stay as previous value (null on initial request) if a parameter is absent
224        if (paramValue != null) {
225            setSubmittedValue(paramValue);
226        }
227
228        rawValue = (String) getSubmittedValue();
229        setValid(true);
230
231    }

对于具有多个值的单个参数，最好的选择是使用@ManagedProperty(在请求范围内的bean中！)

Your best bet on single parameter with multiple values is to use @ManagedProperty (in a request scoped bean!)

@ManagedProperty("#{paramValues.car}")
private String[] cars;

或手动从@PostConstruct内部的ExternalContext收集它.

or perhaps manually gather it from ExternalContext inside @PostConstruct.

您可能要发布新的<f:viewParams>标签的功能/增强请求.

You may want to post a feature/enhancement request for a new <f:viewParams> tag.

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