Searching JSON data for strings and returning a subset as JSON

ambuli
April 25, 2024
202 views
1 vote
2 Answers

I am working on a Java Spring Boot application. I have a JSON in the following format. I need to search for a string and return the results in the same JSON format containing only the matching entries.

The original JSON is:

{
    "version": "1.0.2",
    "students": ["John Smith", "John Green", "Martin King"],
    "teachers": ["John Lord", "Martin Evans", "Steve John", "Gordon Lee", "Leo Martin"],
    "authors" : ["Martin Fowler", "Erich Gamma"]
}

For example, if I search for the string "mart", it should return the JSON below:

{
    "version": "1.0.2",
    "students": ["Martin King"],
    "teachers": ["Martin Evans", "Leo Martin"],
    "authors" : ["Martin Fowler"]
}

How can I do this efficiently? Thank you.

Answers

We can use java HashMaps for this. here is an example of how you can do this in spring.

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

@RestController
public class SearchController {

    private final String jsonData = "{n" +
            "    "version": "1.0.2",n" +
            "    "students": ["John Smith", "John Green", "Martin King"],n" +
            "    "teachers": ["John Lord", "Martin Evans", "Steve John", "Gordon Lee", "Leo Martin"],n" +
            "    "authors" : ["Martin Fowler", "Erich Gamma"]n" +
            "}";

    private final ObjectMapper objectMapper = new ObjectMapper();

    @GetMapping("/search")
    public Map<String, Object> search(@RequestParam String keyword) {
        try {
            Map<String, Object> data = objectMapper.readValue(jsonData, HashMap.class);
            Map<String, Object> filteredData = new HashMap<>();
            filteredData.put("version", data.get("version"));
            filteredData.put("students", filterList((List<String>) data.get("students"), keyword));
            filteredData.put("teachers", filterList((List<String>) data.get("teachers"), keyword));
            filteredData.put("authors", filterList((List<String>) data.get("authors"), keyword));

            return filteredData;
        } catch (Exception e) {
            e.printStackTrace();
            return new HashMap<>();
        }
    }

    private List<String> filterList(List<String> list, String keyword) {
        return list.stream()
                .filter(item -> item.toLowerCase().contains(keyword.toLowerCase()))
                .collect(Collectors.toList());
    }
}

and after sending a request to the endpoint with the keyword mart this is the output

{
    "version": "1.0.2",
    "students": ["Martin King"],
    "teachers": ["Martin Evans", "Leo Martin"],
    "authors": ["Martin Fowler"]
}

You can create a record/POJO called Result that syncs up with the JSON data, and filter on the fields.

Here is an immutable/functional approach:

import java.util.*;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class FilterJSON {
    public record Result(String version, List<String> students, List<String> teachers, List<String> authors) {}

    private static final ObjectMapper objectMapper = new ObjectMapper();

    public static void main(String[] args) throws JsonProcessingException {
        String data = """
                {
                    "version": "1.0.2",
                    "students": ["John Smith", "John Green", "Martin King"],
                    "teachers": ["John Lord", "Martin Evans", "Steve John", "Gordon Lee", "Leo Martin"],
                    "authors" : ["Martin Fowler", "Erich Gamma"]
                }
                """;

        Result result = objectMapper.readValue(data, Result.class);
        Result filtered = filter(result, "mart");
        System.out.println(objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(filtered));
    }

    public static Result filter(Result result, String term) {
        String criteria = term.toLowerCase();
        List<String> students = filterList(result.students(), criteria);
        List<String> teachers = filterList(result.teachers(), criteria);
        List<String> authors = filterList(result.authors(), criteria);
        return new Result(result.version(), students, teachers, authors);
    }

    private static List<String> filterList(List<String> list, String term) {
        return list.stream()
                .filter(name -> Optional.ofNullable(name)
                        .map(String::toLowerCase)
                        .orElse("")
                        .contains(term))
                .toList();
    }
}

Result

{
  "version" : "1.0.2",
  "students" : [ "Martin King" ],
  "teachers" : [ "Martin Evans", "Leo Martin" ],
  "authors" : [ "Martin Fowler" ]
}

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