JsonPath Syntax

Below table summarises the syntax that we should follow while extracting the data from json document.

JSONPath	Description
$	Represents root element
@	Represent current object
. or []	Child Operator. Used to access child document.
..	Recursive descent
*	All objects
[]	Array Operator
[,]	Union operator in XPath results in a combination of node sets. JSONPath allows alternate names or array indices as a set.
[start:end:step]	Array Slice Operator
?()	Applies a filter or expression
()	Script Expression, using the underlying script engine.

I am going to explain each JsonPath syntax in my upcoming posts.

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JsonPath: Parse the document before querying

In my previous post, I explained how to extract the information from a json document using 'JsonPath.read()' method. If you want to extract the data once this is OK. In case you need to extract other parts of the data as well this is not the way to go since the document will be parsed every time you call JsonPath.read(...). To avoid the problem you can parse the json first.

Example

Object jsonDocument = Configuration.defaultConfiguration().jsonProvider().parse(json);

String firstOrganization = JsonPath.read(jsonDocument, "$.org[0].name");

String secondOrganization = JsonPath.read(jsonDocument, "$.org[1].name");

String firstName = JsonPath.read(jsonDocument, "$.empName.firstName");

String lastName = JsonPath.read(jsonDocument, "$.empName.lastName");

double salary = JsonPath.read(jsonDocument, "$.salary");

Input

{
 "org": [{
  "name": "Honeywell",
  "yrsOfExperience": 2.2
 }, {
  "name": "IBM",
  "yrsOfExperience": 1.8
 }],

 "empName": {
  "firstName": "Krishna",
  "lastName": "Rama"
 },

 "salary": 80000.0
}

App.java

package com.sample.app;

import com.jayway.jsonpath.Configuration;
import com.jayway.jsonpath.JsonPath;

public class App {

 public static void main(String[] args) {

  String json = "{\n" + 
    " \"org\": [{\n" + 
    "  \"name\": \"Honeywell\",\n" + 
    "  \"yrsOfExperience\": 2.2\n" + 
    " }, {\n" + 
    "  \"name\": \"IBM\",\n" + 
    "  \"yrsOfExperience\": 1.8\n" + 
    " }],\n" + 
    "\n" + 
    " \"empName\": {\n" + 
    "  \"firstName\": \"Krishna\",\n" + 
    "  \"lastName\": \"Rama\"\n" + 
    " },\n" + 
    "\n" + 
    " \"salary\": 80000.0\n" + 
    "}";

  Object jsonDocument = Configuration.defaultConfiguration().jsonProvider().parse(json);
  
  String firstOrganization = JsonPath.read(jsonDocument, "$.org[0].name");
  String secondOrganization = JsonPath.read(jsonDocument, "$.org[1].name");
  String firstName = JsonPath.read(jsonDocument, "$.empName.firstName");
  String lastName = JsonPath.read(jsonDocument, "$.empName.lastName");
  double salary = JsonPath.read(jsonDocument, "$.salary");

  System.out.println("firstOrganization : " + firstOrganization);
  System.out.println("secondOrganization : " + secondOrganization);
  System.out.println("firstName : " + firstName);
  System.out.println("lastName : " + lastName);
  System.out.println("salary : " + salary);


 }

}

Output

firstOrganization : Honeywell

secondOrganization : IBM

firstName : Krishna

lastName : Rama

salary : 80000.0

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JsonPath: Hello World Application

Let's extract organization names, employee firstName, lastName and salary from below json document.

{
 "org": [{
  "name": "Honeywell",
  "yrsOfExperience": 2.2
 }, {
  "name": "IBM",
  "yrsOfExperience": 1.8
 }],

 "empName": {
  "firstName": "Krishna",
  "lastName": "Rama"
 },

 "salary": 80000.0
}

"$.empName.firstName": Extract firstName from the document.

"$.empName.lastName": Extract lastNam from the document.

"$.org[0].name": Extract first organisation name

"$.org[1].name": Extract second organisation name

"$" represents root element.

Example

String firstOrganization = JsonPath.read(json, "$.org[0].name");

String secondOrganization = JsonPath.read(json, "$.org[1].name");

String firstName = JsonPath.read(json, "$.empName.firstName");

String lastName = JsonPath.read(json, "$.empName.lastName");

double salary = JsonPath.read(json, "$.salary");

App.java

package com.sample.app;

import com.jayway.jsonpath.JsonPath;

public class App {

 public static void main(String[] args) {

  String json = "{\n" + 
    " \"org\": [{\n" + 
    "  \"name\": \"Honeywell\",\n" + 
    "  \"yrsOfExperience\": 2.2\n" + 
    " }, {\n" + 
    "  \"name\": \"IBM\",\n" + 
    "  \"yrsOfExperience\": 1.8\n" + 
    " }],\n" + 
    "\n" + 
    " \"empName\": {\n" + 
    "  \"firstName\": \"Krishna\",\n" + 
    "  \"lastName\": \"Rama\"\n" + 
    " },\n" + 
    "\n" + 
    " \"salary\": 80000.0\n" + 
    "}";

  String firstOrganization = JsonPath.read(json, "$.org[0].name");
  String secondOrganization = JsonPath.read(json, "$.org[1].name");
  String firstName = JsonPath.read(json, "$.empName.firstName");
  String lastName = JsonPath.read(json, "$.empName.lastName");
  double salary = JsonPath.read(json, "$.salary");

  System.out.println("firstOrganization : " + firstOrganization);
  System.out.println("secondOrganization : " + secondOrganization);
  System.out.println("firstName : " + firstName);
  System.out.println("lastName : " + lastName);
  System.out.println("salary : " + salary);


 }

}

Output

firstOrganization : Honeywell
secondOrganization : IBM
firstName : Krishna
lastName : Rama
salary : 80000.0

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Introduction to jsonPath

jsonPath is used to analyse, transform and selectively extract data out of json documents.

I am going to use below maven dependency.

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.4.0</version>
</dependency>

Reference

https://goessner.net/articles/JsonPath/

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