How to serialize a part of json-CodePudding

I have a json file with users, each users has email and password and corresponding POJO exist to deserialize them.

However, I want to add users at will, and create a method to find them by their description, let's say this is my json:

{
  "user1": {
    "email": "[email protected]",
    "password": "qwe123",
  },
  "user2": {
    "email": "[email protected]",
    "password": "abc123",
  },

...
  "userX": {
    "email": "[email protected]",
    "password": "omg123",
  }
}

This is my POJO:

public record User(String email, String password) {}

I dont want to create superPOJO and add each user as I create them.

I would like to create method that would read my json, and returned the User object based on String input.

For now I created users in array and get them using their index, but now situation requires giving users "nicknames" and getting them by their nickname.

Now I am keeping user like this:

[
  {
    "email": "[email protected]",
    "password": "xxx111",
  },
  {
    "email": "[email protected]",
    "password": "yyy222",
  }
]

This is my current method:

public User getPredefinedUser(int index) throws IOException {
    return Parser.deserializeJson(getUserFile(), User[].class)[index];
}

where Parser#deserializeJson() is:

public <T> T deserializeJson(String fileName, Class<T> clazz) throws IOException {
    return new ObjectMapper().readValue(Utils.reader(fileName), clazz);
}

And Utils.reader just brings file from the classpath.

I would like a method like this:

public User getPredefinedUser(String nickname) throws IOException {
    return Parser.deserializeJson(getUserFile(), User.class);
}

and when calling this method with parameter nickname of user2 I'd get User object with fields: email [email protected] and password abc123

CodePudding user response：

Given your input json is an object (map) of User-like objects:

{
  "user1": {
    "email": "[email protected]",
    "password": "qwe123",
  },
  "user2": {
    "email": "[email protected]",
    "password": "abc123",
  },

...
  "userX": {
    "email": "[email protected]",
    "password": "omg123",
  }
}

then you should be able to deserialize it into a (Hash)Map of Users:

public <T> T deserializeJson(String fileName, Class<T> clazz) throws IOException {
    return new ObjectMapper().readValue(Utils.reader(fileName), new TypeReference<HashMap<String, clazz>>(){});
}

and then use it like so:

public User getPredefinedUser(String nickname) throws IOException {
    return Parser.deserializeJson(getUserFile(), User.class).get(nickname);
}

(Although you probably want to parse once and store that somewhere, not parse every time).

Note, I'm doing this from memory, my java syntax may be a bit off, but I think this demonstrates the principle well...

CodePudding user response：

After putting some thought into my own problem I decided to do it like this:

I am using com.googlecode.json-simple - JSON.simple as well as com.fasterxml.jackson.core - Jackson Databind.

I used helper function from Parser class where PARSER is new JSONParser():

    public JSONObject toJsonObject(String fileName) throws IOException, ParseException {
        return ((JSONObject) PARSER.parse(Utils.reader(fileName)));
    }

Then parsed whole user file, while getting interesting user and converting all toString()

Parser.toJsonObject(USER_FILE).get(nickname).toString()

I wrapped it all together in method I wanted (that searches by nickname) and everything works fine, I get desired User object in the end:

    public User getSpecificUser(String nickname) throws IOException, ParseException {
        return Parser.parseJson(Parser.toJsonObject(USER_FILE).get(nickname).toString(), User.class);
    }

And now the test:

    @Test(groups = Group.TEST)
    public void jsonTest() throws IOException, ParseException {
        User user = Utils.getSpecificUser("user2");
        log.warn(user.email());
        log.warn(user.password());
    }

output is:

2022-11-23 T 00:56:55.391 0100 [28][WARN] tests.smoke.SmokeTest->jsonTest [email protected]
2022-11-23 T 00:56:55.391 0100 [28][WARN] tests.smoke.SmokeTest->jsonTest abc123