Invalid JSON data. Found a value that is not a string

Problem:

When POST with a JSON parameter of

{
  "$class": "test.SampleAsset",
  "assetId": "ID-2",
  "owner": {},
  "value": "3000"
}

The error below appears

{ "error": { "statusCode": 500, "name": "Error", "message": "Invalid JSON data. Found a value that is not a string: [object Object] for relationship RelationshipDeclaration {name=owner, type=test.SampleParticipant, array=false, optional=false}", "stack": "Error: Invalid JSON data. Found a value that is not a string: [object Object] for relationship RelationshipDeclaration {name=owner, type=test.SampleParticipant, array=false, optional=false}\n at JSONPopulator.visitRelationshipDeclaration (/usr/local/lib/node_modules/composer-rest-server/node_modules/composer-common/lib/serializer/jsonpopulator.js:249:27)\n at JSONPopulator.visit (/usr/local/lib/node_modules/composer-rest-server/node_modules/composer-common/lib/serializer/jsonpopulator.js:58:25)\n at RelationshipDeclaration.accept (/usr/local/lib/node_modules/composer-rest-server/node_modules/composer-common/lib/introspect/decorated.js:54:24)\n at JSONPopulator.visitClassDeclaration (/usr/local/lib/node_modules/composer-rest-server/node_modules/composer-common/lib/serializer/jsonpopulator.js:83:60)\n at JSONPopulator.visit (/usr/local/lib/node_modules/composer-rest-server/node_modules/composer-common/lib/serializer/jsonpopulator.js:56:25)\n at AssetDeclaration.accept (/usr/local/lib/node_modules/composer-rest-server/node_modules/composer-common/lib/introspect/decorated.js:54:24)\n at Serializer.fromJSON (/usr/local/lib/node_modules/composer-rest-server/node_modules/composer-common/lib/serializer.js:189:26)\n at ensureConnected.then (/usr/local/lib/node_modules/composer-rest-server/node_modules/loopback-connector-composer/lib/businessnetworkconnector.js:634:43)\n at <anonymous>\n at process._tickCallback (internal/process/next_tick.js:188:7)" } }


Solution:

1. Assign owner value like,

{
  "$class": "test.SampleAsset",
  "assetId": "ID-2",
  "owner": "O-1",
  "value": "3000"
}