Traverson Library to consume a RESTful webservice throws error with JSONPath - web-services

Question

I'm currently trying to get the traverson library to fetch some information from an REST interface provided by SpringBoot.
My goal for now would be to get traverson to follow the path to
http ://localhost/users and fetch the information by using this code
traverson.from('http://localhost:8090')
.json()
.follow('$._links.user')
.getResource(function(err, resource){
if(err){
console.log(err);
return;
}
console.log(resource);
});
The json structure which is returned upon calling the endpoint looks like this:
{
"_links" : {
"ressource" : {
"href" : "http://localhost:8090/ressource{?page,size,sort}",
"templated" : true
},
"user" : {
"href" : "http://localhost:8090/user{?page,size,sort}",
"templated" : true
},
"alert" : {
"href" : "http://localhost:8090/alert{?page,size,sort}",
"templated" : true
}
}
Unfortunately this results in an error:
Uncaught TypeError: a.step.url.search is not a function
However if I just fetch the endpoint without the JSONPath Syntax it provides me the mentioned structure.
It will produce a more sensible error when I mess up the JSONPath Expression:
[Error: JSONPath expression $.links.user returned no match in document:
{"_links":{"ressource":{"href":"http://localhost:8090/ressource{?page,size,sort}
","templated":true},"user":{"href":"http://localhost:8090/user{?page,size,sort}"
,"templated":true},"alert":{"href":"http://localhost:8090/alert{?page,size,sort}
","templated":true}}]
Might be that I'm missing something super obvious which would be nice...
At least thanks for reading this far :)

Answer 1

To whom it might concern,
After some trial and error it turns you have to be very careful about the JSON Path expression you provide.
traverson.from('http://localhost:8090')
.json()
.follow('$._links.user.href')
.getResource(function(err, resource){
if(err){
console.log(err);
return;
}
console.log(resource);
});
This will work while this:
traverson.from('http://localhost:8090')
.json()
.follow('$._links.user')
.getResource(function(err, resource){
if(err){
console.log(err);
return;
}
console.log(resource);
});
will not.
The reason seems to be that $._links.user points to an object not an object attribute (see the endpoint structure above). This causes the evaluating function within the traverson library to cause a somewhat unintelligible error.
Let's hope that someone might make use of this information and doesn't spend hour brooding over this.
EDIT 1: After filling an issue with the library’s owner, this issue should now longer occur