How to Build a JSON DSL in Spring Boot with Jayway JsonPath

Scenario

After setting up a RuoYi Spring Boot project (referencing the linked CSDN guide) and adding the required libraries—fastjson, hutool and com.jayway.jsonpath:json-path:2.8.0 —the article explains how to treat Jayway JsonPath as a DSL for reading JSON documents returned by third‑party APIs.

Sample JSON

{
  "store": {
    "book": [
      {"category": "reference", "author": "Nigel Rees", "title": "Sayings of the Century", "price": 8.95},
      {"category": "fiction", "author": "Evelyn Waugh", "title": "Sword of Honour", "price": 12.99},
      {"category": "fiction", "author": "Herman Melville", "title": "Moby Dick", "isbn": "0-553-21311-3", "price": 8.99},
      {"category": "fiction", "author": "J. R. R. Tolkien", "title": "The Lord of the Rings", "isbn": "0-395-19395-8", "price": 22.99}
    ],
    "bicycle": {"color": "red", "price": 19.95}
  },
  "expensive": 10
}

Quick start examples

Read all author fields:

List<String> authors = JsonPath.read(body, "$.store.book[*].author");

Read the title of the first book (two equivalent expressions):

String title = JsonPath.read(body, "$['store']['book'][0]['title']");
String title2 = JsonPath.read(body, "$.store.book[0].title");

Get the total number of books: Integer number = JsonPath.read(body, "$..book.length()"); Filter books with price greater than 10:

List<Map<String, Object>> expensiveBooks = JsonPath.read(body, "$.store.book[?(@.price > 10)]");

Dynamic extraction via configurable mapping

The article shows how to first obtain the book count, then iterate and use a JSON mapping that stores JsonPath expressions with placeholders. The mapping is parsed with fastjson:

int dataSize = JsonPath.read(body, "$..book.length()");
JSONObject mapping = JSON.parseObject("{\"title\":\"$.store.book[%d].title\",\"author\":\"$.store.book[%d].author\"}");
for (int i = 0; i < dataSize; i++) {
    String titleName = mapping.containsKey("title") ? JsonPath.read(body, String.format(mapping.getString("title"), i)).toString() : null;
    System.out.println(titleName);
    String author = mapping.containsKey("author") ? JsonPath.read(body, String.format(mapping.getString("author"), i)).toString() : null;
    System.out.println(author);
}

Complete unit‑test example

import cn.hutool.http.HttpRequest;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.jayway.jsonpath.JsonPath;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
import java.util.Map;

@RunWith(SpringRunner.class)
@SpringBootTest(classes = RuoYiApplication.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class JsonPathTest {
    @Test
    public void getData() {
        String body = "";
        try {
            // Simulate fetching API data
            body = HttpRequest.get("http://127.0.0.1:4523/m1/2858210-0-default/testJsonPath")
                             .timeout(20000)
                             .execute()
                             .body();
            // All authors
            List<String> authors = JsonPath.read(body, "$.store.book[*].author");
            System.out.println(authors);
            // First book title (two ways)
            String title = JsonPath.read(body, "$['store']['book'][0]['title']");
            String title2 = JsonPath.read(body, "$.store.book[0].title");
            System.out.println(title);
            System.out.println(title2);
            // Book count
            Integer number = JsonPath.read(body, "$..book.length()");
            System.out.println(number);
            // Books priced > 10
            List<Map<String, Object>> expensiveBooks = JsonPath.read(body, "$.store.book[?(@.price > 10)]");
            System.out.println(expensiveBooks);
            // Dynamic extraction based on mapping
            int dataSize = JsonPath.read(body, "$..book.length()");
            JSONObject mapping = JSON.parseObject("{\"title\":\"$.store.book[%d].title\",\"author\":\"$.store.book[%d].author\"}");
            for (int i = 0; i < dataSize; i++) {
                String titleName = mapping.containsKey("title") ? JsonPath.read(body, String.format(mapping.getString("title"), i)).toString() : null;
                System.out.println(titleName);
                String author = mapping.containsKey("author") ? JsonPath.read(body, String.format(mapping.getString("author"), i)).toString() : null;
                System.out.println(author);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Test result

The article concludes that JsonPath provides a concise, XPath‑like syntax for navigating JSON structures, and by storing expressions in configuration one can dynamically extract arbitrary fields without hard‑coding paths.