When dealing with large nested JSON objects, converting them to a flattened key-value pair form is a very useful technique. This makes for easier processing and analysis, especially when JSON data needs to be imported into a database. In this post, we'll introduce the library "json-flattener", a Java library for flattening JSON data.
What is "json-flattener"?
"json-flattener" is an open source Java library that provides a way to convert nested JSON objects into a flattened key-value map. The library can be conveniently used in Java. It also supports converting flattened key-value map back to JSON object form.
How to use "json-flattener"?
maven configuration
First, you need to add the "json-flattener" library to your Maven project's dependencies. You can add the following line to your project's pom.xml file:
com.github.wnameless
json-flattener
0.16.4
flatter example
Here's an example of converting a nested JSON object to a flattened key-value map:
import com.github.wnameless.json.flattener.JsonFlattener;
import java.util.Map;
public class FlattenerExample {
public static void main(String[] args) {
String json = "{\"person\":{\"first\":\"John\",\"last\":\"Doe\"},\"age\":30}";
Map<String, Object> flattenedJson = JsonFlattener.flattenAsMap(json);
System.out.println(flattenedJson);
}
}
The output is as follows:
{
"person.first": "John",
"person. last": "Doe",
"age": 30
}
You can see that the original JSON object has been successfully converted into a flattened key-value map.
unflatter example
Here's an example of converting a flattened key-value map to a raw JSON object:
import com.github.wnameless.json.flattener.JsonFlattener;
import com.github.wnameless.json.unflattener.JsonUnflattener;
public class UnflattenerExample {
public static void main(String[] args) {
String flattenedJson = "{\"person.first\":\"John\",\"person.last\":\"Doe\",\"age\":30}";
String unflattenedJson = JsonUnflattener.unflatten(flattenedJson);
System.out.println(unflattenedJson);
}
}
The output is as follows:
{
"person": {
"first": "John",
"last": "Doe"
},
"age": 30
}
You can see that the flattened key-value map has been successfully converted back to the original JSON object.
Summarize
In this article, we introduced the library "json-flattener", a Java library for flattening JSON data. We showed how to use the library to convert nested JSON objects into flattened key-value maps, and also showed how to convert flattened key-value maps back to raw JSON objects. Also for other nested POJO objects, you can first convert the POJO into a JSON string and then flatten it. The advantage of the "json-flattener" library is that it handles nested JSON data conveniently and is very easy to use.
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