spring - 当尝试从非 Artefact Groovy 文件中的静态方法访问服务时，在静态作用域中发现了明显的变量 'serviceName'

Question

在 Grails 3 应用程序中，我使用 Spring Beans 将两个服务注入(inject)到位于 src/main/groovy/demo/Menu.groovy 的非工件 Groovy 文件中。然后，我尝试从 Controller 调用创建菜单静态方法，但是当从静态方法调用注入(inject)服务的方法时出现错误

菜单类如下所示

package demo

import org.springframework.beans.factory.annotation.Autowired
import demo.CategoryService
import demo.ItemService

class Menu {

    @Autowired
    CategoryService categoryService

    @Autowired
    ItemService itemService

    List<Category> categoryList
    List<Item> itemList

    public static final Menu create(final String categoryName) {
        List<Category> categoryList = categoryService.listByEnabled(true)

        new Menu (
            categoryList: categoryList,
            itemList: itemService.listByCategoryName(categoryName ?: categoryList[0].name)
        )
    }
}

CategoryService 和 ItemService 均为 GORM Data Services并在resource.groovy文件中使用Spring bean注入(inject)

beans = {    
    menu(demo.Menu)
}

当我调用 create Menu 静态方法时从 Controller 操作

class MenuController {

    def menu(final String categoryName) {
        respond Menu.create(categoryName)
    }
}

我收到以下错误:

/home/desktop/pos/src/main/groovy/demo/Menu.groovy: 17: Apparent variable 'categoryService' was found in a static scope but doesn't refer to a local variable, static field or class. Possible causes:
You attempted to reference a variable in the binding or an instance variable from a static context.
You misspelled a classname or statically imported field. Please check the spelling.
You attempted to use a method 'categoryService' but left out brackets in a place not allowed by the grammar.
 @ line 17, column 39.
           List<Category> categoryList = categoryService.listByEnabled(true)

itemService 也是如此

/home/desktop/pos/src/main/groovy/demo/Menu.groovy: 21: Apparent variable 'itemService' was found in a static scope but doesn't refer to a local variable, static field or class. Possible causes:
You attempted to reference a variable in the binding or an instance variable from a static context.
You misspelled a classname or statically imported field. Please check the spelling.
You attempted to use a method 'itemService' but left out brackets in a place not allowed by the grammar.
 @ line 21, column 23.
               itemList: itemService.listByCategoryName(categoryName ?: categoryList[0].name)

感谢您的宝贵时间

Answer 1

发生错误的原因是您将 categoryService 定义为实例字段(无 static 修饰符)，您无法从 static< 访问该字段 方法。

由于您已经创建了 Menu bean，因此只需尝试注入(inject)它，而不是使 create 方法静态:

class MenuController {

    def menu // Grails should inject it by bean name here

    def menu(final String categoryName) {
        respond menu.create(categoryName)
    }
}

然后从声明中删除 static:

public final Menu create(final String categoryName) {

这确实引出了一个问题，为什么不让 Menu 成为一个完善的 Grails 服务呢？例如。将其移至 grails-app/services 并让 Grails 管理创建和注入(inject)其他服务？