在骡子中连接两个数组

Concatenating two arrays in mule

我正在尝试连接两个数组:

arr1: [{"a":"value"}] 
arr2: [{"b":"value"}]
expected result:[{{"a":"value"},{"b":"value"}}]
vars.arr1 ++ vars.arr2  gives an error when arr1 is null. 

    org.mule.runtime.core.api.expression.ExpressionRuntimeException: "You called the function '+' with these arguments: 
      1: Null (null)
      2: Object 

我应该如何处理以下情况:

  1. 当两个数组都为空时
  2. 当数组之一为空时。

如果您不介意在两个输入数组都为 null 时获取空数组,请尝试此操作:

%dw 2.0
output application/dw

var arr1 = null
var arr2 = null

---
(arr1 default []) ++ (arr2 default [])