jsongroovyjsonbuilder

How to construct json using JsonBuilder with key having the name of a variable and value having its value?


How to construct json using JsonBuilder with key and value having same name?

import groovy.json.JsonBuilder

def userId = 12 // some user id obtained from else where.

def json = new JsonBuilder()
def root = json {
    userId userId
}
print json.toString()

Which produces the error

groovy.lang.MissingMethodException: No signature of method: java.lang.Integer.call() is applicable for argument types: (java.lang.Integer) values: [12] Possible solutions: wait(), any(), abs(), wait(long), wait(long, int), and(java.lang.Number)

Quoting the key does has no effect. Any idea how to make this work.

Edit:

I want the JSON to be like { userId: 12 }. Also, why does writing the key as string not work?

long userId = 12   
def json = new JsonBuilder()
def root = json {
    "userId" userId
}

The example provided is just a snippet. The situation is that I have a lot of controller actions, which has various variables already. Now I am adding a part where I am trying to create a JSON string with various values the variables hold. So it's not very practical to change existing variable names and if I could construct the JSON string with the same name, it would be more consistent. Writing accessor methods for all the variables I wanted is also not an elegant method. What I did at present is to use different naming scheme like user_id for userId but again, it's not consistent with rest of the conventions I follow. So I am looking for an elegant approach and the reason why JsonBuilder behaves in this manner.

In case of JavaScript,

var a = 1
JSON.stringify({a: a})    // gives "{"a":1}"

which is the expected result.


Solution

  • as

    import groovy.json.JsonBuilder
    
    def getUserId(){
        def userId = 12 // some user id obtained from else where.
    }
    
    def json = new JsonBuilder()
    def root = json{
        userId userId
    }
    print json.toString()
    

    then

    import groovy.json.JsonBuilder
    
    def userId = 12 // some user id obtained from else where.
    
    def json = new JsonBuilder()
    def root = json{
        "$userId" userId
    }
    print json.toString()
    

    as

    import groovy.json.JsonBuilder
    
    userId = 12
    
    def json = new JsonBuilder()
    def root = json{
        userId userId
    }
    print json.toString()
    

    UPDATE

    Local variables can also be used as map keys (which is String by default) while building JSON.

    import groovy.json.JsonBuilder
    
    def userId = 12 
    def age = 20 //For example
    def email = "abc@xyz.com"
    
    def json = new JsonBuilder()
    def root = json userId: userId, age: age, email: email
    
    print json.toString() //{"userId":12,"age":20,"email":"abc@xyz.com"}