如何将 Double 参数与 Play 2.0 路由绑定

2022-01-08 00:00:00 parameters routes double java playframework-2.0

我正在学习自己的 Play 2.0(使用 Java API)并希望有一个 double/float 参数(用于位置坐标)，例如 http://myfooapp.com/events/find?latitude=25.123456&longitude=60.251253.

I'm learning myself Play 2.0 (Java API used) and would like to have a double/float parameter (for location coordinates), something like http://myfooapp.com/events/find?latitude=25.123456&longitude=60.251253.

我可以通过获取参数作为字符串并在控制器等处解析它们来做到这一点，但是我可以在这里使用自动绑定吗?

I can do this by getting the parameters as String and parsing them at controller etc but can I use automatic binding here?

现在，我首先尝试简单地设置一个双精度值:

Now, I first tried simply having one double value:

GET     /events/foo                 controllers.Application.foo(doublevalue: Double)

与

public static Result foo(Double doublevalue) {
    return ok(index.render("Foo:" + doublevalue));
}

我得到的是没有为 Double 类型找到 QueryString 绑定器.尝试为此类型实现隐式 QueryStringBindable."

我是否错过了已经提供的内容或我是否必须制作一个解析 Double 的自定义 QueryStringBindable?

Have I missed something already provided or do I have to make a custom QueryStringBindable that parses Double?

我在 http://julien.richard-foy.fr/blog/2012/04/09/how-to-implement-a-custom-pathbindable-with-play-2/

我在包活页夹中实现了 DoubleBinder:

I implemented DoubleBinder at package binders:

import java.util.Map;
import play.libs.F.Option;
import play.mvc.QueryStringBindable;

public class DoubleBinder implements QueryStringBindable<Double>{

    @Override
    public Option<Double> bind(String key, Map<String, String[]> data) {
        String[] value = data.get(key);
        if(value == null || value.length == 0) {
            return Option.None();
        } else {
            return Option.Some(Double.parseDouble(value[0]));
        }
    }

    @Override
    public String javascriptUnbind() {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public String unbind(String key) {
        // TODO Auto-generated method stub
        return null;
    }
}

并尝试将其添加到 project/Build.scala 的 main 中:

And tried to add it to project/Build.scala's main:

routesImport += "binders._"

但结果相同:找不到类型 Double.... 的 QueryString 绑定器"

but same result : "No QueryString binder found for type Double...."

  • 我还将路由签名更改为 java.lang.Double，但这也无济于事
  • 我还更改了 DoubleBinder 以使用 Double & 实现 play.api.mvc.QueryStringBindable(而不是 play.mvc.QueryStringBindable).java.lang.Double 在路由签名处，但仍然没有帮助

推荐答案

目前(在 Play 2.0 中)，Java binders 仅适用于自递归类型.也就是说，类型如下所示:

Currently (in Play 2.0), Java binders only work with self-recursive types. That is, types looking like the following:

class Foo extends QueryStringBindable<Foo> {
  …
}

所以，如果你想为 java.lang.Double 定义一个 binder，它是 Java 的现有类型，你需要将它包装在一个自递归类型中.例如:

So, if you want to define a binder for java.lang.Double, which is an existing type of Java, you need to wrap it in a self-recursive type. For example:

package util;

public class DoubleW implements QueryStringBindable<DoubleW> {

    public Double value = null;

    @Override
    public Option<DoubleW> bind(String key, Map<String, String[]> data) {
        String[] vs = data.get(key);
        if (vs != null && vs.length > 0) {
            String v = vs[0];
            value = Double.parseDouble(v);
            return F.Some(this);
        }
        return F.None();
    }

    @Override
    public String unbind(String key) {
        return key + "=" + value;
    }

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

}

然后你可以在你的应用程序中使用它:

Then you can use it as follows in your application:

GET    /foo     controllers.Application.action(d: util.DoubleW)


public static Result action(DoubleW d) {
      …
}

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