Parse multiple JSON entries using org.springframework.boot.json.JsonParser - spring-boot

Question

I'd like to parse a JSON Array using the native JsonParser available in Spring Boot:
String url="https://restservice.com";
RestTemplate restTemplate = new RestTemplate();
String resp = restTemplate.getForObject(url, String.class);
JsonParser springParser = JsonParserFactory.getJsonParser();
Map<String, Object> map = springParser.parseMap(resp);
That works if there's just one item in the Array. If multiple items are returned, an exception is thrown:
Caused by: org.springframework.boot.json.JsonParseException: Cannot parse JSON
at org.springframework.boot.json.AbstractJsonParser.tryParse(AbstractJsonParser.java:60) ~[spring-boot-2.1.0.RELEASE.jar!/:2.1.0.RELEASE]
at org.springframework.boot.json.JacksonJsonParser.parseMap(JacksonJsonParser.java:55) ~[spring-boot-2.1.0.RELEASE.jar!/:2.1.0.RELEASE]
at com.example.samplewebapp.DemoApplication.lambda$demo$2(DemoApplication.java:50) [classes!/:0.0.1-SNAPSHOT]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:813) [spring-boot-2.1.0.RELEASE.jar!/:2.1.0.RELEASE]
... 13 common frames omitted
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.LinkedHashMap` out of START_ARRAY token
What is the correct API to return a List of Map JSON objects?

Answer 1

Showing the JSON you are trying to parse would be helpful for getting a good answer to your problem.
Anyway, if you are trying to get a list you should use the parseList() method instead. This required doing a cast from objects to maps, but worked fine for me otherwise. Here's a quick example:
String json = "[{\"key\":\"value1\"}, {\"key\":\"value2\"}]";
JsonParser springParser = JsonParserFactory.getJsonParser();
List<Object> list = springParser.parseList(json);
for(Object o : list) {
if(o instanceof Map) {
Map<String,Object> map = (Map<String,Object>) o;
//do processing here
}
}
However, I would suggest calling the desired parser (Jackson, gson, etc.) directly if you need more control over the process. Jackson provides a handy ObjectMapper class to help with this sort of thing and avoid messy type conversions.