Jackson Parsing for json object inside json

问题

I have sample json data like below

{"data":{"detection":[{"category":"building","coordinates":{"xmin":"0.31","ymin":"0.42","ymax":"0.82","xmax":"0.89"},"accuracy":"0.66"}]}}

Trying to parse data field in jackson parser and created ObjectCategories class(setter getter) for its values.

@JsonProperty("categories")
private List<ObjectCategory> categories;

@SuppressWarnings("unchecked")
@JsonProperty(DATA)
private void unpackNested(Map<String,Object> data) {
    this.categories = (ArrayList<ObjectCategory>) data.get("detection");
}

If we execute the above code, getting this exception - getCategories().get(0).getAccuracy() to java.util.LinkedHashMap cannot be cast to ObjectCategory

getCategories().get(0) returns Map value. How to parse with my ObjectCategory class.

回答1:

You can convert the value if you originally deserialized it to map.

this.categories = objectMapper
     .convertValue(data.get("detection"), 
                   new TypeReference<List<ObjectCategory>>() {});

来源：https://stackoverflow.com/questions/50503471/jackson-parsing-for-json-object-inside-json