将具有多个对象的json文件读取到地图Java中

Question

Note: Before posting this here, I spent a chunk of time trying to look for a solution about this here, but couldn't find any.

I have this JSON file that contains multiple json objects that I want to read into a map, each object is of the format {"key1":"value1", "key2":"value2"} , I tried

Map<String, String> map = MAPPER.readValue(fixture("fixtures/file_name.json"), new TypeReference<Map<String, String>>() {});

as that worked for reading a file into a map of map of list ( Map<String, Map<String, List<String>>> ). Is there something that should be different?

My .json file looks like

[
   {"key1":"value1_1", "key2":"value2_1"},
   {"key1":"value1_2", "key2":"value2_2"},
   ...
]

I have also another json file that I want to read into a map, that looks like

[
   "key1": {
       "key1_1": [
           {"key1_1_1":"value1", "key1_1_2":"value2"},
           ...
       ],
       ...
    },
    "key2":<int>,
    "key3":{
        "key3_1":[],
        ...
    },
    ...
    "key_n":<string>,
    ...
]

Can you help me map those files correctly, without writing too many lines of code?

Answer 1

As you are handling different cases of nested objects varying from Strings to JsonArrays it would be good to implement your map as Map<String, Object> .

Follow the below implementation,

ObjectMapper mapper = new ObjectMapper();
MapType type = mapper.getTypeFactory().constructMapType(
    Map.class, String.class, Object.class);
Map<String, Object> data = mapper.readValue(jsonString, type);

Here I am reading the JSON as a string. You can change your implementation to accommodate file reading as well.

Answer 2

I would suggest you to use the Jackson library.

Here is a mkyong tutorial

Just change the code to

Map map = mapper.readValue(new File("c:\\whatever.json"), Map.class);