Grails绑定收集枚举 [英] Grails bind collection enum

问题描述

  public enum RelationshipStatus {
 
 Single_Never_Married ，
分居，
离婚，
丧偶; 
} 
  

我已经定义了这个命令对象：

  class MyCommand {
列表< RelationshipStatus>关系状态
} 
  

我在我的一个控制器操作中使用

  def myAction = {MyCommand myCommand  - > 
} 
  

当我通过参数提交此操作的请求

  user.relationshipStatuses = Separated& user.relationshipStatuses =离婚
  

我希望 myCommand.relationshipStatuses 将包含 RelationshipStatus.Separated 和 RelationshipStatus.Divorced ，但实际上它是空的。

我的理解是Grails自动执行请求参数 - >枚举转换枚举的名字。只是这样，它没有，我尝试定义一个属性编辑器进行这种转换：

  class RelationshipStatusEnumEditor extends PropertyEditorSupport {
 
 public String getAsText（）{
 value.name（）
} 
 
 public void setAsText（String text）{
 RelationshipStatus.valueOf文本）
} 
} 
  

我用Grails / Spring注册了这个编辑器，再次尝试，但结果是一样的。是否可以将请求参数绑定到枚举的集合？

解决方案

使用介绍的数据绑定Grails 2.3，我想出了将请求参数转换为枚举的集合的以下解决方案。例如，给定这些枚举

 枚举性别{
 MALE，FEMALE 
} 
 
 enum季节{
春季，夏季，秋季，冬季
} 
  

和这个命令对象

  class MyCommand {
 Collection< Gender>性别
集合<季节>季节
} 
  

，假设我们要转换像 MALE，FEMALE和春天，夏天，冬天到相应的枚举集合。首先，提供执行转换的 FormattedValueConverter 的实现

 类EnumCollectionConverter实现FormattedValueConverter {
 
 / ** 
 *要使其他枚举可绑定，只需将它们添加到此列表中
 * / 
 private static final List< Class&Enum> > convertableEnums = [性别，季节] 
 
 @Override 
对象转换（值，字符串格式）{
 
类&枚举> targetEnumClass = convertableEnums.find {it.simpleName == format} 
 
 if（targetEnumClass）{
列表< String> enumConstantNames = value.toString（）。tokenize（'，'）
 return enumConstantNames.collect {targetEnumClass.valueOf（it）} 
} 
值
} 
 
 @Override 
类<？> getTargetType（）{
 
 //此类转换为集合< T扩展枚举< T>>但是该方法的返回值
 //不能比Collection更具体，因为类型为erasure 
集合
} 
} 
  

然后在 resources.groovy中注册 EnumCollectionConverter 作为Spring bean - 您为该bean选择的名称无关紧要。然后使用上面的类将逗号分隔的字符串转换为num集合，用

 类MyCommand { 
 @BindingFormat（'Gender'）
集合<性别>性别
 
 @BindingFormat（'Season'）
集合< Season>季节
} 
  

传递给 @BindingFormat 应该是将被存储在绑定集合中的枚举类型的简单名称。

In my grails app, I have this enum:

public enum RelationshipStatus{

  Single_Never_Married, 
  Separated,
  Divorced, 
  Widowed;  
}

I've defined this command object:

class MyCommand {
  List<RelationshipStatus> relationshipStatuses
}

which I use in one of my controller actions

def myAction = {MyCommand myCommand ->
}

when I submit a request to this action with parameters

user.relationshipStatuses=Separated&user.relationshipStatuses=Divorced

I expect that myCommand.relationshipStatuses will contain RelationshipStatus.Separated and RelationshipStatus.Divorced, but in fact it is null.

My understanding is that Grails automatically performs request param -> enum conversion based on the enum's name. Just it case it doesn't, I tried defining a property editor that does this conversion:

class RelationshipStatusEnumEditor extends PropertyEditorSupport {    

    public String getAsText() {
        value.name()
    }

    public void setAsText(String text) {
        RelationshipStatus.valueOf(text)
    }
}

I registered this editor with Grails/Spring and tried again, but the result was the same. Is it possible to bind request parameters to a Collection of Enum?

解决方案

Using the databinder introduced in Grails 2.3, I came up with the following solution for converting request params to collection of enums. For example, given these enums

enum Gender {
    MALE, FEMALE
}

enum Season {
    SPRING, SUMMER, AUTUMN, WINTER
}

and this command object

class MyCommand {
    Collection<Gender> genders
    Collection<Season> seasons
}

and assume we want to convert strings like "MALE,FEMALE" and "SPRING,SUMMER,WINTER" to the corresponding enum collections. Firstly, provide an implementation of FormattedValueConverter that does the conversion

class EnumCollectionConverter implements FormattedValueConverter {

   /**
    * To make other enums bindable, just add them to this list
    */
    private static final List<Class<Enum>> convertableEnums = [Gender, Season]

    @Override
    Object convert(value, String format) {

        Class<Enum> targetEnumClass = convertableEnums.find { it.simpleName == format }

        if (targetEnumClass) {
            List<String> enumConstantNames = value.toString().tokenize(',')
            return enumConstantNames.collect { targetEnumClass.valueOf(it) }
        }
        value
    }

    @Override
    Class<?> getTargetType() {

        // this class converts to a Collection<T extends Enum<T>> but the return value 
        // of this method can't be any more specific than Collection due to type erasure
        Collection
    }
}

Then register EnumCollectionConverter as a Spring bean in resources.groovy - it doesn't matter what name you choose for the bean. Then to use the class above to convert a comma-separated string to an num collection, annotate the relevant properties with

class MyCommand {
    @BindingFormat('Gender')
    Collection<Gender> genders

    @BindingFormat('Season')
    Collection<Season> seasons
}

The value passed to the @BindingFormat should be the simple name of the enum type that will be stored in the bound collection.

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