Form JSON structure and add values of all child record of a parent object

Question

I have to populate the values in a JSON structure. The values are obtained from the fields of a parent object and also the child object. I may have more than 1 child records of a parent object. how can I populate that in the below code. How can I traverse through all the child and update it in the JSON strcuture

 String JSONString=JSON.serialize(
        new Map<String, Object> { 
            'ElementA' => new Object[] {
                new Map<String, Object> {
                'ParentField1' => field1__C,
                'ParentField2' => field2__C,            
                'child' => new Object[] {
                    new Map<String, Object> {
                    'childName' => how do i get each child Name to repeat here,
                    'childfield1' => how do i get each child's field 1 to repeat here
                    }
                },
                'ParentField3' => field3__C,
                'ParentField4' => 'field4__C
                }
}
            );

Exact JSON:

{
    "Parent": [{
        "SerialNumber": "33455724",
        "EventDay": "1",
        "EventMonth": "12",
        "EventYear": "2016",
        "Child": [{
            "Child": " ",
            "Level1": " ",
            "Level2": " ",
            "Description": " ",
            "RecordType": " "
        }],
        "AccountName": "Account 001",
        "AccountNumber": "123333",
        "Address": "NY",
        "Contact": [{
            "FirstName": " ",
            "LastName": " ",
            "Phone": " ",
            "Address": " ",
            "Email": " "
        }],
        "Lot": " ",
        "Num": " "
    }]
}

JSON2APex Class:

public class Child {
    public String Child;
    public String Level1;
    public String Level2;
    public String Description;
    public String RecordType;
}

public class Parent {
    public String SerialNumber;
    public String EventDay;
    public String EventMonth;
    public String EventYear;
    public List<child> Child;
    public String AccountName;
    public String AccountNumber;
    public String Address;
    public List<Contact> Contact;
    public String Lot;
    public String Num;
}

public class Contact {
    public String FirstName;
    public String LastName;
    public String Phone;
    public String Address;
    public String Email;
}

public class JSON2Apex {
    public List<parent> parent;
}

What I intend to do:

Parent__C pr = [select id,......... where id=parent.id];

Parent p = new Parent();
p.SerialNumber = pr.serial__c;
..
..
List<Child__C> c = [select childname,Level1,Level2,Description from child__c where child.parent__c = pr.id];
List<Child> ch = new List<Child>();
For(Child__c chld : c){
ch.Level1 = chld.Level1;
..
ch.RecordType = chld.RecordType;
}
p.Child = ch;

// similarly I will get the list of contact and do
p.Contact = contactList 

List<parent> plist = new List<parent>();
plist.add(p);


JSON2Apex j = new JSON2Apex();
j.parent = plist

String JsonString = JSON.serialize(j);

Does the above code looks correct?

Answer 1

A simple class to illustrate this would be:

public class myExampleObject{

    public String field1;
    public String field2;
    public myChildObject[] children;

    public class myChildObject{

         public string childField1;
         public string childField2;

    }

}

Then you could simply populate as follows (may require debugging, writing ad lib here):

myExampleObject parentObject = New myExampleObject();
parentObject.field1 = 'abc';
parentObject.myChildObject theChild = New parentObject.myChildObject();
theChild.childField1 = 'ghi';

parentObject.children = New parentObject.myChildObject[]{theChild};

Then serialize:

String serialized = JSON.serialize(parentObject);

If you know the object names it could be as simple as:

public class myWrapper{

    public Account theParentAccount;
    public Contact[] accountContacts;


}

You can always take an example of your desired final JSON output as throw it into json2apex to get the class as well. A lot depends on how the JSON needs to be as a final result as to how you structure the class

Answer 2

You would add each as a separate Map<String, Object>:

'children' => new List<Object>
{
    new Map<String, Object>
    {
        'Name' => 'Child 1',
        'SomeField__c' => 'Some Value'
    },
    new Map<String, Object>
    {
        'Name' => 'Child 2',
        'SomeField__c' => 'Some Other Value'
    }
}