从String对象中创建Groovy中的动态闭包 [英] Create dynamically closures in Groovy from a String object

问题描述

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

  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。上例中的字符串将是assoc.parent.code。我通过点分割字符串（通过执行 String.split（\\\。））但我不知道如何构建嵌套闭包：

  assoc {
父母{
 eq（code，val）
} 
} 
  

动态地基于上面拆分字符串的数组。

解决方案

那么 createAlias ？您可以尝试如下所示：

  def path =assoc.parent.code
 
 def split = path.split（/\./）
 
 MyEntity.createCriteria（）。list {
 //这会让你'createAlias（assoc.parent，alias1）'
 createAlias split.take（split.size（） -  1），alias1
 
 //这会让你'eq（alias1.code，userInput）'
 eqalias1 。$ {split [-1]}，userInput 
} 
  

这段代码不是通用，但你明白了。

---

更新

不是常规的，但是您可以使用闭包构建一个包含代码的字符串，并使用

  assoc ='assoc.parent.child.name'
 split = assoc.split（/\./）
 path = split [-2..0] //会让我们'child.parent .assoc'; 
 //我们将从内部构建它
 
 def firstClosure ={eq'$ {split [-1]}'，'john doe'}
 def lastClosure = firstClosure 
 
（实体在路径中）{
 def criteriaClosure ={$ {entity {$ {lastClosure}}
 lastClosure = criteriaClosure 
} 
 
 assert lastClosure =={assoc {parent {child {eq'name'，'john doe'}}}}
 def builtClosure = new GroovyShell（）。evaluate（return + lastClosure）
 assert buildClosure instanceof Closure 
  

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)
      }
   }
}

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)
      }
   }

dynamically based on the array of the splitted Strings above.

解决方案

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
}

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

---

Update

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

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