Do you expect to save #1) the input JSON object or
#2) a dump of the converted result?
For both:

set stream=##class( %Stream.GlobalCharacter).%New()

#1)  with myjson as your JSON input

do stream.Write(myjson)
do stream.%Save()  

#2) dump the generated Object  obj  using my package Full-OBJ-Dump described here

do ##class(Z.obj).dumpToStream(.stream,obj,1)
do stream.%Save()  

Take a closer look to Caché I/O Device Guide
especially Chapter 5: TCP Client/Server Communication

As you operate on 2014.*  just write it down as any other string.

after 2017.1 you may (but are not forced to) use %DynamicObjects and %%DynamicArrays.
but the result looks the same 

Status= 1 justteslls you tht the HTTP connection was processed OK.
Next you need to take a look into your response object.

set res=Httprequest.HttpResponse
in terminal then ZW res to see in the Status is 200 OK
otherwise what you see I  res.Data might be just an error page.
Which is also OK for HTTP but not for your content.

• property ReasonPhrase as %String;

This is the human readable reason that goes with the StatusCode.

• property StatusCode as %Integer;

The HTTP status code. This is useful to determine if the request was successful. Look in the rfc for HTTP to see which codes are supported and what they mean. A human readable form of this code is stored as the ReasonPhrase

• property StatusLine as %String;

The HTTP status line. This is the first line of the response and signals if the request was successful or if there was a problem.

I found %DynamicObjects first in Caché 2017.1 Class Ref
https://cedocs.intersystems.com/ens20171/csp/documatic/%25CSP.Documatic.cls?&LIBRARY=%25SYS&CLASSNAME=%25Library.DynamicObject

In 2014 this was somehow buried in %ZAN.Auxilary.???

You might take a look to this article Global archiver - Moving a part of a global.
And the related package in OEX global-archiver

Now with the class definition available, I understand(?) what you are looking for.
I see 2 possible solutions: embedded SQL or an Index on Title
#1

btw: SQLCODE=0 means success. 
and you get the RowId by 

SET RowId=##class(REST.TITLE).TitleToRowId(obj.Title)  ;obj=JSON
SET task.Title = ##class(RESTAPI.TITLE).%OpenId(RowId)
SET book.Title = ##class(RESTAPI.TITLE).%OpenId(RowId) ; recent example

#2
 creating an Index on Title in REST.TITLE.
 but you have all trouble on duplicates, max. string length on that index
 So I'd position it as elegant but rather risky on maintenance
 

the story is clear.  Your class definition is not.
once more pls show class definitions for RESTAPI.TITLE   and    ??.BOOK   
(every class has also a package, default is User) 
you may need Studio od VSCode  to see it.

and {"ID":17, "Title":"LEARNING CAHE REST API"} is a
Dynamic JSON object unrelated to any class definition

• so your obj is a DynamicObject and looks something like { "ID":17, "Title": 44 }
• class All.Allbooks has this Property Title As User.Book. 
• To set it you need an oref !!

therefore to create the required oref :

SET task.Title = ##class(User.Book).%OpenId(obj.Title)

I guess you look for this:

ClassMethod GetABookById(id As %Integer) As %Status
{ 
 SET MyBooks = ##class(All.Allbooks).%OpenId(id)
 SET obj={} 
 set obj.ID=MyBooks.%Id()
 set obj.Title=MyBooks.Title
 WRITE obj.%ToJSON()
 Quit 1
}

ATTENTION:
MyBooks.Title is just a reference to User.Book

namespace %SYS ?
all required privileges ?

Checked Class Docu for 2017.1  >>>  query Detail exists !

https://cedocs.intersystems.com/ens20171/csp/documatic/%25CSP.Documatic.cls

this worked for me

select CAST(0+AVG(PackingTimeSpent) as TIME) average ....

the 0+ forces Integer, then CAST understands you
and pls. don't ask why. I just tried 
the output from AVG() is definitely NOT Integer

this are not properties but an ERROR Status Object.
the boxes are non-printable binary values from $LB() or similar.

You are right.
But it works in a test within a Try-Catch bloxk
   

     try {
         ;;; run your code
         }
     catch e {  
        if $ze["<RESJOB>" while $TLEVEL { tcommit }
        }

Do you still expect some echo?
Or is the question meanwhile just out of date?

To force it to string you have to append some non numeric character ! 
but this one is then part of the subscript as $c(0) or whatever you append
in addition, you break the numeric sort and change to string sorting.

USER>set s1=111,s2=444,q="."
USER>set a(s2)=1,a(s1)=2,a(s1_q)=3,a(s2_q)=4
 
USER>zw a
a(44)=1
a(111)=2
a("111.")=3
a("44.")=4

Do you still expect some echo?
Or is the question meanwhile just out of date?

Do you still expect some echo?
Or is the question meanwhile just out of date?

 
USER>set s1=111,s2=444
USER>set a(s2_$c(0),s1_$c(0))=77
USER>set a($c(0)_s1,$c(0)_s2)=99
USER>zwrite
a("111","444")=99
a("444","111")=77
s1=111
s2=444
USER>

"save it from the class " ?  whatever that may mean .... ?

An object might not fit well a Global with a reasonable number of nodes.
But by SQL you get it line by line. check this:   Show Global by SQL SELECT