Passing an object to a controller with Ajax - which contains an Enum - ajax

Question

I'm trying to pass an object Consumer to my Controller. A Consumer has a one-to-many relationship with Policy. This is what I tried:
function changeConsumer(){
var newConsumer = {
"id" : /*[[${consumer.id}]]*/,
"name" : document.getElementById('0').value,
"endpoint" : document.getElementById('1').value,
"policies" : /*[[${policies}]]*/
}
$.ajax({
type: "PUT",
url: "/rest/consumer/update",
data: JSON.stringify(newConsumer),
contentType: "application/json; charset=utf-8",
success : function(response) {
...
});
}
If I pass the Consumer like this, with an empty array of Policies - it works:
function changeConsumer(){
var newConsumer = {
"id" : /*[[${consumer.id}]]*/,
"name" : document.getElementById('0').value,
"endpoint" : document.getElementById('1').value,
"policies" : []
}
$.ajax({
type: "PUT",
url: "/rest/consumer/update",
data: JSON.stringify(newConsumer),
contentType: "application/json; charset=utf-8",
success : function(response) {
...
});
}
This is the stacktrace I'm receiving, which leads me to think there a problem with the Enum "Effect" in the Policy object:
2017-11-18 16:28:22.255 WARN 7884 --- [nio-8080-exec-6] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of com.policyMgmt.policy.Effect out of START_OBJECT token
at [Source: java.io.PushbackInputStream#56bd85f4; line: 1, column: 93] (through reference chain: com.policyMgmt.consumer.Consumer["policies"]->java.util.ArrayList[0]->com.policyMgmt.policy.Policy["effect"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of com.policyMgmt.policy.Effect out of START_OBJECT token
at [Source: java.io.PushbackInputStream#56bd85f4; line: 1, column: 93] (through reference chain: com.policyMgmt.consumer.Consumer["policies"]->java.util.ArrayList[0]->com.policyMgmt.policy.Policy["effect"])
2017-11-18 16:28:22.255 WARN 7884 --- [nio-8080-exec-6] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved exception caused by Handler execution: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of com.policyMgmt.policy.Effect out of START_OBJECT token
at [Source: java.io.PushbackInputStream#56bd85f4; line: 1, column: 93] (through reference chain: com.policyMgmt.consumer.Consumer["policies"]->java.util.ArrayList[0]->com.policyMgmt.policy.Policy["effect"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of com.policyMgmt.policy.Effekt out of START_OBJECT token
at [Source: java.io.PushbackInputStream#56bd85f4; line: 1, column: 93] (through reference chain: com.policyMgmt.consumer.Consumer["policies"]->java.util.ArrayList[0]->com.policyMgmt.policy.Policy["effect"])
The Policy object which looks like this:
#Entity
public class Policy {
#Id
#GeneratedValue
#Column(name = "id")
private Integer id;
#Column(name = "name")
private String name;
#Column (name = "consumer_id")
private Integer consumer;
#Enumerated(EnumType.STRING)
#Column(name="effect")
private Effect effect;
public Policy() {}
....
}
Maybe it helps, this is what a Consumer looks like:
#Entity
public class Consumer {
#Id
#GeneratedValue
#Column(name = "id")
private Integer id;
#Column(name = "name")
private String name;
#Column(name = "endpoint")
private String endpoint;
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
#JoinColumn(name ="consumer_id")
private List<Policy> policies;
public Consumer() {
}
}
Rest API
#Controller
#RequestMapping(value = "/rest/consumer")
public class ConsumerController {
...
#PutMapping(value = "/update")
#ResponseBody
public List<Consumer> updateConsumer(#RequestBody Consumer consumer) {}
...
}
Does anyone have experience passing enums within Ajax to a Controller?

Answer 1

I can't say for certain why #RequestBody is having difficulty deserializing JSON like { "$type": "Effekt", "$name": "deny" } into an instance of the Effekt enum, but I think you should try writing a custom JsonDeserializer for your enum.
Here's another Stackoverflow question that is similar, but not identical to the issue you're facing. Take a look at the second answer -- the one that includes a code example of a JsonDeserializer.
With a bit of trail-and-error, you can probably come up with something that successfully processes JSON like you're already getting into instances of Effekt.
The other option would be to change the JSON representation of Effekt in that gets sent to the server. Perhaps if it looked like this...
"effekt": "deny"
it would work directly with #RequestBody. You could try hard-coding it in the JavaScript to test.
If you want to go this route, you will probably need to implement a custom JsonSerializer -- the reverse of the earlier option.