播放框架 - 绑定路由中的枚举 [英] play framework - bind enum in routes

问题描述

我正在玩java 2.2中构建一个应用程序。

我有一个java枚举作为我在路由中使用的函数中的参数。

这是我的枚举类。我搜索到，发现我需要实现QueryStringBindable在路由中使用它。

  public enum Something implements QueryStringBindable< Something> {
 a，
 b，
 c; 
 
 @Override 
 public F.Option< ClientStatus> bind（String key，Map< String，String []¶m）{
 String [] arr = params.get（key）; 
 if（arr == null || arr.length == 0）{
 return F.Option.None（）; 
} else {
 Something status = Something.valueOf（arr [0]）; 
 return F.Option.Some（status）; 
} 
} 
 
 @Override 
 public String unbind（String key）{
 return null; 
} 
 
 @Override 
 public String javascriptUnbind（）{
 return null; 
} 
} 
  

然而我尝试在我的路线：

  GET / someurl controllers.Application.function（status：util.enums.Something）
  pre> 
 
 
但是它返回错误的请求，并显示以下错误消息：
 
 
 'GET / someurl'[util.enums.Something] 
 
 
我在Google上找不到任何答案。我有没有想过的东西或播放不支持绑定枚举？
解决方案
我有同样的问题，我终于发现它不可解决。
 
 
 
通过阅读 PathBindable 和 QueryStringBindable 我发现play framework 要求 Bindable提供一个无参数的公共构造函数。根据定义，Java中的枚举是不可能的。
 
 
 
所以我必须包装我的枚举来解决这个问题。在你的例子中，我们会有一些类似的东西：
  public enum Something {
a，
b，$ b $公元前; 
 
 public static class Bound implements QueryStringBindable< Bound> {
 private Something value; 
 
 @Override 
 public F.Option< ClientStatus> bind（String key，Map< String，String []¶m）{
 String [] arr = params.get（key）; 
 if（arr！= null&& arr.lenght> 0）{
 this.value = Something.valueOf（arr [0]）; 
 return F.Option.Some（this）; 
} else {
 return F.Option.None（）; 
} 
} 
 
 @Override 
 public String unbind（String key）{
 return this.value.name（）; 
} 
 
 @Override 
 public String javascriptUnbind（）{
 return this.value.name（）; 
} 
 
 public Something value（）{
 return this.value; 
} 
} 
} 
  
然后你必须使用
 
 
 
编辑：使用它在一个模板稍微更棘手一点。而你必须知道一点scala。 
跟随@ Aleksei的评论
 < a href =@ routes.MyController.showStuff（myEnumVar）> ; LINK< / A> 
  
应该成为
 code>< a href =@ {
 routes.MyController.showStuff（new MyEnumVarWrapper（myEnumVar））。url 
}> link< / a> 
  
 
I am building an app in java on play 2.2. 

I have a java enum as a parameter in a function that I use in routes.

This is my enum class. I searched around and found out I need to implements QueryStringBindable to use it in routes.
public enum Something implements QueryStringBindable<Something> {
    a,
    b,
    c;

    @Override
    public F.Option<ClientStatus> bind(String key, Map<String, String[]> params) {
        String[] arr = params.get(key);
        if (arr == null || arr.length == 0) {
            return F.Option.None();
        } else {
            Something status = Something.valueOf(arr[0]);
            return F.Option.Some(status);
        }
    }

    @Override
    public String unbind(String key) {
        return null;
    }

    @Override
    public String javascriptUnbind() {
        return null;
    }
}
Yet I tried in my routes: 
GET    /someurl     controllers.Application.function(status: util.enums.Something)
But it returns bad request with error message as:

  
For request 'GET /someurl' [util.enums.Something]
I googled and didn't find any answer working in my case. Did I miss something or play doesn't support binding enums?
解决方案
I had the same problem and I finally found out that it is not solvable as is.

By reading the documentation for PathBindable and QueryStringBindable I found that play framework requires the Bindable to provide a No Argument public constructor. Which by definition is no possible with enum in Java.

So I had to wrap my enum to solve this. In your example we would have something like:
public enum Something {
    a,
    b,
    c;

    public static class Bound implements QueryStringBindable<Bound>{
       private Something value;

        @Override
        public F.Option<ClientStatus> bind(String key, Map<String, String[]> params) {
            String[] arr = params.get(key);
            if (arr != null && arr.lenght > 0) {
                this.value = Something.valueOf(arr[0]);
                return F.Option.Some(this);
            } else {
                return F.Option.None();
            }
        }

        @Override
        public String unbind(String key) {
            return this.value.name();
        }

        @Override
       public String javascriptUnbind() {
            return this.value.name();
       }

       public Something value(){
           return this.value;
       }
    }
}
and then you have to use the type some.package.Something.Bound as a type in your routes file.

EDIT: using that in a template is slightly more tricky. And you have to know a bit of scala.
To follow @Aleksei's comment
<a href="@routes.MyController.showStuff(myEnumVar)">link</a>
should become
<a href="@{
   routes.MyController.showStuff(new MyEnumVarWrapper(myEnumVar)).url
}">link</a>


                        
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