Grails命令对象数据绑定 [英] Grails command object data binding

问题描述

Grails已将请求参数绑定到域对象，并将其关联。这主要取决于检测以 .id 结尾的请求参数，并自动从数据库加载。

Grails has very good support for binding request parameters to a domain object and it's associations. This largely relies on detecting request parameters that end with .id and automatically loading those from the database.

但是，不清楚如何填充命令对象的关联。以下示例：

However, it's not clear how to populate the associations of a command object. Take the following example:

class ProductCommand {

    String name
    Collection<AttributeTypeCommand> attributeTypes 
    ProductTypeCommand productType
}

此对象具有单端关联 ProductTypeCommand 和与 AttributeTypeCommand 的多端关联。所有属性类型和产品类型的列表都可以从该接口的实现获得。

This object has a single-ended association with ProductTypeCommand and a many-ended association with AttributeTypeCommand. The list of all attribute types and product types are available from an implementation of this interface

interface ProductAdminService {
    Collection<AttributeTypeCommand> listAttributeTypes();
    Collection<ProductTypeCommand> getProductTypes();
}

我使用这个界面在GSP中填充产品和属性类型选择列表。我也依赖 - 将此接口注入到命令对象中，并使用它来模拟 attributeTypes 和 productType 属性命令对象

I use this interface to populate the product and attribute type selection lists in a GSP. I also dependency-inject this interface into the command object, and use it to "simulate" attributeTypes and productType properties on the command object

class ProductCommand {

    ProductAdminService productAdminService

    String name   

    List<Integer> attributeTypeIds = []
    Integer productTypeId

    void setProductType(ProductTypeCommand productType) {
        this.productTypeId = productType.id
    }

    ProductTypeCommand getProductType() {
        productAdminService.productTypes.find {it.id == productTypeId}        
    }

    Collection<AttributeTypeCommand> getAttributeTypes() {

        attributeTypeIds.collect {id ->
            productAdminService.getAttributeType(id)
        }
    }

    void setAttributeTypes(Collection<AttributeTypeCommand> attributeTypes) {
        this.attributeTypeIds = attributeTypes.collect {it.id}
    }
}

实际发生的是， code> attributeTypeIds 和 productTypeId 属性绑定到相关的请求参数，getters / setterssimulate productType 和 attributeTypes 属性。有一个更简单的方法来填充命令对象的关联？

What actually happens is that the attributeTypeIds and productTypeId properties are bound to the relevant request parameters and the getters/setters "simulate" productType and attributeTypes properties. Is there a simpler way to populate the associations of a command object?

推荐答案

您是否真的需要为attributeTypes和productType属性设置子命令？任何你不使用PropertyEditorSupport绑定的原因？例如：

Do you actually need to have sub-commands for attributeTypes and productType properties? Any reason you're not using PropertyEditorSupport binding? E.g.:

public class ProductTypeEditor extends PropertyEditorSupport
{
    ProductAdminService productAdminService // inject somewhow
    void setAsText(String s)
    {
        if (s) value = productAdminService.productTypes.find { it.id == s.toLong() }
    }

    public String getAsText()
    {
        value?.id        
    }
}

（和attributeType对象类似），并在编辑器注册商中注册：

(and something similar for attributeType object), and register these in a editor registrar:

import java.beans.PropertyEditorSupport
public class CustomEditorRegistrar implements PropertyEditorRegistrar {
    public void registerCustomEditors(PropertyEditorRegistry reg) {
        reg.registerCustomEditor(ProductType, new ProductTypeEditor())
        reg.registerCustomEditor(AttributeType, new AttributeTypeEditor())
    }
}

资源oovy：

beans =
{
    customEditorRegistrar(CustomEditorRegistrar)
}

然后在您刚刚拥有的Cmd中：

then in your Cmd you just have:

class ProductCommand {
    String name
    List<AttributeType> attributeTypes = []
    ProductType productType
}

如果您 需要实际的子命令关联，那么我已经做了类似于@Andre Steingress的建议，结合PropertyEditorSupport绑定：

If you do need actual sub-command associations then I've done something similar to what @Andre Steingress has suggested, in combination with PropertyEditorSupport binding:

// parent cmd
import org.apache.commons.collections.ListUtils
import org.apache.commons.collections.FactoryUtils
public class DefineItemConstraintsCmd implements Serializable
{
    List allItemConstraints = ListUtils.lazyList([], FactoryUtils.instantiateFactory(ItemConstraintsCmd))
    //...
}    
// sub cmd
@Validateable
class ItemConstraintsCmd implements Serializable
{
    Item item // this has an ItemEditor for binding
    //...
}

希望我没有误解你想要实现的目标：）

Hopefully I've not misunderstood what you're trying to achieve :)

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