如何以更好的方式为以下示例创建JSON

Question

I have below data with in hashmap

{age={Middle-aged={yes=0.417, no=0.125}, youth={yes=0.25, no=0.5}, senior={yes=0.333, no=0.375}}}

How can I convert this hashmap to below json

{"age":{"data":[{"key":"yes","values":[{"name":"Middle-aged","value":0.417},{"name":"youth","value":0.25},{"name":"senior","value":0.33}]},{"key":"no","values":[{"name":"Middle-aged","value":0.125},{"name":"youth","value":0.5},{"name":"senior","value":93}]}]}}

To do so should I need to group my data like this

yes- grp all yes values(middle-aged, senior,youth)

No-grp all no values for(middle-aged,senior,youth)

and then create a POJO class ? Or I can directly load into POJO class.

Please suggest a better way.

Answer 1

You can model your structure using a POJO to convert to a flat structure:

public class MyData{
    private String groupName;
    private String yesNoGroup;
    private double value;
    public MyData(String n, String g, double v){
        groupName=n;
        yesNoGroup=g;
        value=v;
    }
    // getter and setters
}

Then convert them into JSON string using GSON or Jackson

Apart from the conversion, I would suggest you convert data into a flatter structure. Yours now look like a normalised database schema, but this made too many layers in the JSON. If you could denormalise it and give better names than "value", "key" and etc, the JSON would be more readable and easier for conversion.

{
    "age":{
        "data":[
            {
                "key":"yes",
                "values":[
                    {
                        "name":"Middle-aged",
                        "value":0.417
                    },
                    {
                        "name":"youth",
                        "value":0.25
                    },
                    {
                        "name":"senior",
                        "value":0.33
                    }
                ]
            },
            {
                "key":"no",
                "values":[
                    {
                        "name":"Middle-aged",
                        "value":0.125
                    },
                    {
                        "name":"youth",
                        "value":0.5
                    },
                    {
                        "name":"senior",
                        "value":93
                    }
                ]
            }
        ]
    }
}

Such sample data can be created from the constructor of "MyData" like

List<MyData> list=new List<MyData>();
list.add(new MyData("Middle-aged","yes",0.417));
list.add(new MyData("youth","yes",0.25));
list.add(new MyData("senior","yes",0.33));
list.add(new MyData("Middle-aged","no",0.125));
list.add(new MyData("youth","no",0.5));
list.add(new MyData("senior","no",93));

Gson g=new Gson();
String output=g.toJson(list);

In this way, you can have a flatter structure of the same data representation, which is good for everyone handling this data.

Answer 2

Below structure will be useful to get the required json structure.

class Age {
    private List<Data> data;
    //getter setter
}

class Data {
    private String key;
    private List<Values> values;
    //getter setter
}

class Values {
    private String name;
    private String value;
    //getter setter
}

Now iterate through your HashMap and fill the values in object of class Age. And then you can use GSON or Jackson to convert Age object into json string.