Jira REST API: create issue linked to another one - api

Question

I'd like to link an issue to an existing one at creation using the REST API. The idea is not to CREATE then UPDATE, but just CREATE.
Here is my JSON:
{
"issueUpdates": [
{
"fields": {
"project": {
"key": "CMDB"
},
"issuetype": {
"id": "10500"
},
"summary": "VMP-MYSQL-01",
"issuelinks": [
{
"type": {
"name": "Relates",
"inward": "relates to",
"outward": "relates to"
},
"inwardIssue": {
"key": "CMDB-825"
},
"outwardIssue": "CMDB-825"
}
],
"customfield_10600": "VMP-MYSQL-01"
}
}
]
}
The error I get is:
{
"issues": [],
"errors": [
{
"status": 400,
"elementErrors": {
"errorMessages": [],
"errors": {
"issuelinks": "Field does not support update 'issuelinks'"
}
},
"failedElementNumber": 0
}
]
}
Does the API support the creation of Linked Issue at creation? Using the GUI works.
Jira is running v6.2.

Answer 1

Since this question is a bit older, I've been experiencing same issue as you. After some searching I found that instead of fields you can use update in the json you send to server.
Alternatively, you can use issueLink method to add links after creating the issue.
Complete code to create an issue with a link to a different issue:
{
"fields": {
"summary": "Sample Issue",
"project": {
"id": 14505
},
"issuetype": {
"id": 11002
}
},
"update": {
"issuelinks": [
{
"add": {
"type": {
"name": "Relates"
},
"inwardIssue": {
"key": "PRJ-1"
}
}
}
]
}
}

Answer 2

This will solve your problem. This will create an issue with one jira issue linked to it.
key is a project key,
Blocks or related to whichever you want.
put below json into http://jsonlint.com/. It will do proper formatting.
{
"fields": {
"summary": "Test Adapter",
"project": {
"key": "WFM"
},
"description": "Testing of Jira from Adapter",
"issuetype": {
"name": "Bug"
},
"update": {
"issuelinks": [{
"add": {
"type": {
"name": "Blocks",
"inward": "is blocked by",
"outward": "blocks"
},
"outwardIssue": {
"key": "WFM-28",
"fields": {
"summary": "Test Adapter"
}
}
}
}]
}
}
}