spring test rest template : Could not extract response: no suitable HttpMessageConverter found for response type - spring

Question

I Get this exception
org.springframework.web.client.RestClientException: Could not extract
response: no suitable HttpMessageConverter found for response type [AnalyticsResponse] and content type [application/json;charset=UTF-8]
in my junit test cases only(Rest endpoints work fine) if my DTO contains a map with a user defined class as a key
#Data
public class AnalyticsResponse {
private List<Committer> commitersList; //OK
private Map<Committer , Long> comittersCommitsMap; // Problem
private Map<Date, List<CommitItem>> commitItemsTimeLineMap; //OK
}
If comittersCommitsMap field is removed, every thing goes fine
my test case code snippet:
ResponseEntity<AnalyticsResponse> analyticsResponse = testRestTemplate.getForEntity(ANALYSIS_CONTROLLER_BASE_URL+"analytics?repo-full-name=" + searchResponse.getBody().get(0).getFull_name() ,
AnalyticsResponse.class);
---update : Committer class
#Data
#AllArgsConstructor
#NoArgsConstructor
public class Committer {
private String name;
private String email;
}

Answer 1

By default, the ObjectMapper cannot determine serialization and deserialization for a Map in which a key is not a String, you have to provide your custom implementation.
Implement KeyDeserializer and JsonSerializer for Committer and Date(as key for Map)
Configure ObjectMapper - register module with KeyDeserializer and KeySerializer(JsonSerializer)
#SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
// KeyDeserializer for Committer (simple without 'null' check)
#RequiredArgsConstructor
public static class CommitterKeyDeserializer extends KeyDeserializer {
private final ObjectMapper mapper;
#Override
public Object deserializeKey(final String key,
final DeserializationContext ctxt)
throws IOException, JsonProcessingException {
return mapper.readValue(key, Committer.class);
}
}
// KeyDeserializer for Date (simple without 'null' check)
#RequiredArgsConstructor
public static class DateKeyDeserializer extends KeyDeserializer {
private final ObjectMapper mapper;
#Override
public Object deserializeKey(final String key,
final DeserializationContext ctxt)
throws IOException, JsonProcessingException {
return mapper.readValue(key, Date.class);
}
}
// JsonSerializer for Committer (simple without 'null' check)
#RequiredArgsConstructor
public static class CommitterJsonSerializer extends JsonSerializer<Committer> {
private final ObjectMapper mapper;
#Override
public void serialize(Committer committer,
JsonGenerator jgen,
SerializerProvider provider)
throws IOException, JsonProcessingException {
jgen.writeFieldName(mapper.writeValueAsString(committer));
}
}
// JsonSerializer for Date (simple without 'null' check)
public static class DateJsonSerializer extends JsonSerializer<Date> {
#Override
public void serialize(Date date,
JsonGenerator jgen,
SerializerProvider provider)
throws IOException, JsonProcessingException {
jgen.writeFieldName(String.valueOf(date.getTime()));
}
}
// ObjectMapper configuration
#Bean
public ObjectMapper objectMapper() {
ObjectMapper mapper = new ObjectMapper();
// register module with custom serializers and deserializers
mapper.registerModule(new SimpleModule()
.addKeyDeserializer(
Committer.class,
new CommitterKeyDeserializer(mapper))
.addKeyDeserializer(
Date.class,
new DateKeyDeserializer(mapper))
.addKeySerializer(
Committer.class,
new CommitterJsonSerializer(mapper))
.addKeySerializer(
Date.class,
new DateJsonSerializer()));
return mapper;
}
// RestTemplate configuration
#Bean
public RestTemplate restTemplate(List<HttpMessageConverter<?>> converters) {
RestTemplate restTemplate = new RestTemplate();
// add spring's predefined converters
restTemplate.setMessageConverters(converters);
return restTemplate;
}
}
Note that in this simple implementation the key Committer in comittersCommitsMap represented as a String in JSON response (RestTemplate with this implementation works as well):
{
"commitersList": [
{
"name": "name",
"email": "email"
}
],
"comittersCommitsMap": {
"{\"name\":\"name\",\"email\":\"email\"}": 1
},
"commitItemsTimeLineMap": {
"1570929503854": [
{
"data": "data"
}
]
}
}