在 Groovy 中从 String 对象动态创建闭包 [英] Create dynamically closures in Groovy from a String object

问题描述

我想使用 Grails (GORM) 中的 Criteria API 创建一个查询.查询必须是这样的:

i would like to create a query with the Criteria API in Grails (GORM). The query will have to be something like this:

MyEntity.createCriteria().list{
   assoc{
      parent{
         eq("code", val)
      }
   }
}

我需要的是从 String 对象动态构建嵌套闭包.上面示例的字符串将是 "assoc.parent.code" .我按点分割字符串(通过执行 String.split("\.") )但我不知道如何构造嵌套闭包:

What i need is to build the nested closure dynamically from a String object. The String for the example above will be "assoc.parent.code" . I splitted the String by dot (by doing String.split("\.") ) but i don't know how to construct the nested closures:

   assoc{
      parent{
         eq("code", val)
      }
   }

动态地基于上面拆分的字符串数组.

dynamically based on the array of the splitted Strings above.

推荐答案

createAlias?.你可以试试这样的:

What about createAlias?. You could try something like this:

def path = "assoc.parent.code"

def split = path.split(/./)

MyEntity.createCriteria().list {
  // this will get you 'createAlias( assoc.parent, alias1 )'
  createAlias split.take( split.size() - 1 ), "alias1"

  // this will get you 'eq(alias1.code, userInput)'
  eq "alias1.${split[-1]}", userInput
}

这个片段不是通用的，但你懂的.

This snippet is not generic, but you get the idea.

更新

不是传统的，但您可以构建一个包含闭包代码的字符串，并使用 GroovyShell:

Not conventional, but you can build a string containing the code with the closures and evaluate it using GroovyShell:

assoc = 'assoc.parent.child.name'
split = assoc.split( /./ )
path  = split[-2..0] // will get us 'child.parent.assoc';
                     // we will build it from inside-out

def firstClosure = "{ eq '${split[-1]}', 'john doe' }"
def lastClosure = firstClosure

for (entity in path) {
  def criteriaClosure =  "{ ${entity} ${lastClosure} }"
  lastClosure = criteriaClosure
}

assert lastClosure == "{ assoc { parent { child { eq 'name', 'john doe' } } } }"
def builtClosure = new GroovyShell().evaluate("return " + lastClosure)
assert builtClosure instanceof Closure

这篇关于在 Groovy 中从 String 对象动态创建闭包的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！