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Spring Boot JsonNode

In computer science, marshalling is the process of transforming the representation of an object to a data format suitable for storage or transmission. In this technical post we will describe how we can marshall and unmarshall using Jackson, JsonNode and Spring Boot. If you want to know more about how to create Spring Webflux please go to my previous post getting started with Spring Webflux here. First let’s create a new Spring Boot Webflux project:

spring init --dependencies=webflux,lombok --build=gradle --language=java spring-boot-json-node

This is the build.gradle file generated:

plugins {
  id 'org.springframework.boot' version '2.1.3.RELEASE'
  id 'java'
}

apply plugin: 'io.spring.dependency-management'

group = 'com.jos.dem.springboot.json.node'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

configurations {
  compileOnly {
    extendsFrom annotationProcessor
  }
}

repositories {
  mavenCentral()
}

dependencies {
  implementation 'org.springframework.boot:spring-boot-starter-webflux'
  compileOnly 'org.projectlombok:lombok'
  annotationProcessor 'org.projectlombok:lombok'
  testImplementation 'org.springframework.boot:spring-boot-starter-test'
  testImplementation 'io.projectreactor:reactor-test'
}

Now let’s add Junit5 dependencies and support:

plugins {
  id 'org.springframework.boot' version '2.1.3.RELEASE'
  id 'java'
}

apply plugin: 'io.spring.dependency-management'

def junitJupiterVersion = '5.4.0'

group = 'com.jos.dem.springboot.json.node'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

configurations {
  compileOnly {
    extendsFrom annotationProcessor
  }
}

repositories {
  mavenCentral()
}

dependencies {
  implementation 'org.springframework.boot:spring-boot-starter-webflux'
  compileOnly('org.projectlombok:lombok')
  annotationProcessor('org.projectlombok:lombok')
  testImplementation('org.springframework.boot:spring-boot-starter-test'){
    exclude group: 'junit', module: 'junit'
  }
  testImplementation "org.junit.jupiter:junit-jupiter-api:$junitJupiterVersion"
  testRuntime "org.junit.jupiter:junit-jupiter-engine:$junitJupiterVersion"
  testImplementation 'io.projectreactor:reactor-test'
  testCompile 'org.junit.platform:junit-platform-commons:1.4.0'
  testCompile 'org.junit.platform:junit-platform-launcher:1.4.0'
}

test {
  useJUnitPlatform()
}

From Json to JsonNode

Let’s validate Json to JsonNode transformation, in order to parse a Json string we only need an ObjectMapper

ObjectMapper mapper = new ObjectMapper();
String json = "{\"id\":1196,\"nickname\":\"josdem\",\"email\":\"joseluis.delacruz@gmail.com\"}";
JsonNode node = mapper.readTree(json);

Please, consider this test case to validate our transformation to JsonNode.

@Test
@DisplayName("Validate Json to JsonNode transformation")
void shouldGetJsonNodeFromJson() throws Exception {
  log.info("Running: Validate json to json node transformation at {}", new Date());

  assertAll("node",
    () -> assertEquals(1196, node.get("id").intValue(), "Should get id"),
    () -> assertEquals("josdem", node.get("nickname").textValue(), "Should get nickname"),
    () -> assertEquals("joseluis.delacruz@gmail.com", node.get("email").textValue(), "should get email")
  );

}

JsonNode to Bean

Next, let’s validate a JsonNode to POJO transformation

package com.jos.dem.springboot.json.node.model;

import lombok.Setter;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.AllArgsConstructor;

@Setter
@Getter
@NoArgsConstructor
@AllArgsConstructor
public class Person {
  private Integer id;
  private String nickname;
  private String email;
}

Here is our test case

@Test
@DisplayName("Validate JsonNode to Person transformation")
void shouldGetPersonFromJsonNode() throws Exception {
  log.info("Running: Validate json to json node transformation at {}", new Date());

  Person person = mapper.treeToValue(node, Person.class);

  assertAll("person",
    () -> assertEquals(1196, person.getId(), "Should get id"),
    () -> assertEquals("josdem", person.getNickname(), "Should get nickname"),
    () -> assertEquals("joseluis.delacruz@gmail.com", person.getEmail(), "should get email")
  );

}

Bean to JsonNode

Now, let’s validate a POJO to JsonNode transformation

@Test
@DisplayName("Validate Person to JsonNode transformation")
void shouldGetJsonNodeFromPerson() throws Exception {
  log.info("Running: Validate person to json node transformation at {}", new Date());
  Person person = new Person(1196, "josdem","joseluis.delacruz@gmail.com");
  JsonNode node = mapper.valueToTree(person);

  assertAll("person",
    () -> assertEquals(1196, node.get("id").intValue(), "Should get id"),
    () -> assertEquals("josdem", node.get("nickname").textValue(), "Should get nickname"),
    () -> assertEquals("joseluis.delacruz@gmail.com", node.get("email").textValue(), "should get email")
  );

}

Parameters to JsonNode

Finally let’s create a JsonNode with just arguments

@Test
@DisplayName("Validate Arguments to Json Node transformation")
void shouldGetJsonNodeFromArguments() throws Exception {
  log.info("Running: Validate arguments to json node transformation at {}", new Date());
  Integer id = 1196;
  String nickname = "josdem";
  String email = "joseluis.delacruz@gmail.com";

  JsonNode node = mapper.createObjectNode();
  ((ObjectNode) node).put("id", 1196);
  ((ObjectNode) node).put("nickname", "josdem");
  ((ObjectNode) node).put("email", "joseluis.delacruz@gmail.com");

  assertAll("person",
    () -> assertEquals(1196, node.get("id").intValue(), "Should get id"),
    () -> assertEquals("josdem", node.get("nickname").textValue(), "Should get nickname"),
    () -> assertEquals("joseluis.delacruz@gmail.com", node.get("email").textValue(), "should get email")
  );

}

Here is our complete test case

package com.jos.dem.springboot.json.node;

import static org.junit.jupiter.api.Assertions.assertAll;
import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.Date;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;

import com.jos.dem.springboot.json.node.model.Person;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class JsonNodeTest {

  private JsonNode node;
  private ObjectMapper mapper = new ObjectMapper();
  private Logger log = LoggerFactory.getLogger(this.getClass());

  @BeforeEach
  void init() throws Exception {
    log.info("Getting Json Node from Json");
    String json = "{\"id\":1196,\"nickname\":\"josdem\",\"email\":\"joseluis.delacruz@gmail.com\"}";
    node = mapper.readTree(json);
  }


  @Test
  @DisplayName("Validate Json to JsonNode transformation")
  void shouldGetJsonNodeFromJson() throws Exception {
    log.info("Running: Validate json to json node transformation at {}", new Date());

    assertAll("node",
      () -> assertEquals(1196, node.get("id").intValue(), "Should get id"),
      () -> assertEquals("josdem", node.get("nickname").textValue(), "Should get nickname"),
      () -> assertEquals("joseluis.delacruz@gmail.com", node.get("email").textValue(), "should get email")
    );

  }

  @Test
  @DisplayName("Validate JsonNode to Person transformation")
  void shouldGetPersonFromJsonNode() throws Exception {
    log.info("Running: Validate json to json node transformation at {}", new Date());

    Person person = mapper.treeToValue(node, Person.class);

    assertAll("person",
      () -> assertEquals(1196, person.getId(), "Should get id"),
      () -> assertEquals("josdem", person.getNickname(), "Should get nickname"),
      () -> assertEquals("joseluis.delacruz@gmail.com", person.getEmail(), "should get email")
    );

  }

  @Test
  @DisplayName("Validate Person to JsonNode transformation")
  void shouldGetJsonNodeFromPerson() throws Exception {
    log.info("Running: Validate person to json node transformation at {}", new Date());
    Person person = new Person(1196, "josdem","joseluis.delacruz@gmail.com");
    JsonNode node = mapper.valueToTree(person);

    assertAll("person",
      () -> assertEquals(1196, node.get("id").intValue(), "Should get id"),
      () -> assertEquals("josdem", node.get("nickname").textValue(), "Should get nickname"),
      () -> assertEquals("joseluis.delacruz@gmail.com", node.get("email").textValue(), "should get email")
    );

  }

  @Test
  @DisplayName("Validate Arguments to Json Node transformation")
  void shouldGetJsonNodeFromArguments() throws Exception {
    log.info("Running: Validate arguments to json node transformation at {}", new Date());
    Integer id = 1196;
    String nickname = "josdem";
    String email = "joseluis.delacruz@gmail.com";

    JsonNode node = mapper.createObjectNode();
    ((ObjectNode) node).put("id", 1196);
    ((ObjectNode) node).put("nickname", "josdem");
    ((ObjectNode) node).put("email", "joseluis.delacruz@gmail.com");

    assertAll("person",
      () -> assertEquals(1196, node.get("id").intValue(), "Should get id"),
      () -> assertEquals("josdem", node.get("nickname").textValue(), "Should get nickname"),
      () -> assertEquals("joseluis.delacruz@gmail.com", node.get("email").textValue(), "should get email")
    );

  }

  @AfterEach
  void finish() throws Exception {
    log.info("Test execution finished");
  }

}

Dealing with complex Json structures

Let’s consider this Json structure

{
  "batchId": "fbe07c89-ffa7-4c86-9832-5f75cf765737",
  "eventType": "EmployeeClockIn",
  "publishedAt": "2019-03-09T07:36:43-05:00",
  "messages" : [{
  	"messageId" : "4aeaa175-e46d-42eb-83d3-cd02865d4863",
  	"eventAt": "2019-03-09T07:36:43-05:00",
  	"data": {
  		"firstname": "Jose",
  		"lastname": "Morales",
  		"nickname": "josdem",
  		"employeeNumber": 1196,
  		"email": "joseluis.delacruz@gmail.com",
  		"clockInDateTime": "2019-03-09T07:36:43-05:00"
  	}
  }]
}

This could be our bean representation: Event

package com.jos.dem.springboot.json.node.model;

import java.time.OffsetDateTime;

import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class Event {
  private String batchId;
  private String eventType;
  private OffsetDateTime publishedAt;
  private Message[] messages;
}

Message

package com.jos.dem.springboot.json.node.model;

import java.time.OffsetDateTime;

import lombok.Getter;
import lombok.Setter;

import com.fasterxml.jackson.databind.JsonNode;

@Getter
@Setter
public class Message {
  private String messageId;
  private OffsetDateTime eventAt;
  private JsonNode data;
}

So to unmarshall this complex Json structure the best strategy is to create a service to delegate that responsibility

package com.jos.dem.springboot.json.node.service;

import java.io.File;
import java.io.IOException;

import com.jos.dem.springboot.json.node.model.Event;

public interface UnmarshallerService {

  Event read(File jsonFile) throws IOException;

}

Here is our service implementation

package com.jos.dem.springboot.json.node.service.impl;

import java.io.File;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.IOException;

import javax.annotation.PostConstruct;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

import org.springframework.stereotype.Service;

import com.jos.dem.springboot.json.node.model.Event;
import com.jos.dem.springboot.json.node.service.UnmarshallerService;

@Service
public class UnmarshallerServiceImpl implements UnmarshallerService {

  private ObjectMapper mapper = new ObjectMapper();

  @PostConstruct
  public void setup() {
    mapper.registerModule(new JavaTimeModule());
  }

  public Event read(File jsonFile) throws IOException {
    InputStream inputStream = new FileInputStream(jsonFile);
    JsonNode jsonNode = mapper.readTree(inputStream);
    return mapper.treeToValue(jsonNode, Event.class);
  }

}

And here is our complete test case to unmarshall it

package com.jos.dem.springboot.json.node;

import static org.junit.jupiter.api.Assertions.assertAll;
import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.Date;
import java.time.OffsetDateTime;

import com.fasterxml.jackson.databind.JsonNode;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.extension.ExtendWith;

import java.io.File;
import java.io.InputStream;
import java.io.FileInputStream;

import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit.jupiter.SpringExtension;
import org.springframework.beans.factory.annotation.Autowired;

import com.jos.dem.springboot.json.node.model.Event;
import com.jos.dem.springboot.json.node.model.Message;
import com.jos.dem.springboot.json.node.service.UnmarshallerService;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@ExtendWith(SpringExtension.class)
@SpringBootTest
public class UnmarshallerServiceTest {

  private Logger log = LoggerFactory.getLogger(this.getClass());

  @Autowired
  private UnmarshallerService service;

  private Event event;
  private Message message;
  private Message[] messages;

  @BeforeEach
  void init() throws Exception {
    log.info("Getting Event from ClockIn json file");
    File jsonFile = new File("src/main/resources/ClockIn.json");
    event = service.read(jsonFile);
    Message[] messages = event.getMessages();
    message = messages[0];
  }

  @Test
  @DisplayName("Validate Event values from ClockIn Json file")
  void shouldGetEventFromClockInFile() throws Exception {
    log.info("Running: Validate Event values from ClockIn Json file at {}", new Date());

    assertAll("event",
      () -> assertEquals("fbe07c89-ffa7-4c86-9832-5f75cf765737", event.getBatchId(), "Should get batch id"),
      () -> assertEquals("EmployeeClockIn", event.getEventType(), "Should get event type"),
      () -> assertEquals(OffsetDateTime.parse("2019-03-09T12:36:43Z"), event.getPublishedAt(), "Should get published at time")
    );

  }

  @Test
  @DisplayName("Validate Message values from Event")
  void shouldGetMessageFromEvent() throws Exception {
    log.info("Running: Validate Message values from event at {}", new Date());

    assertAll("message",
      () -> assertEquals("4aeaa175-e46d-42eb-83d3-cd02865d4863", message.getMessageId(), "Should get message id"),
      () -> assertEquals(OffsetDateTime.parse("2019-03-09T12:36:43Z"), event.getPublishedAt(), "Should get published at time")
    );

  }

  @Test
  @DisplayName("Validate Data values from message")
  void shouldGetDataFromMessage() throws Exception {
    log.info("Running: Validate Data values from message at {}", new Date());

    JsonNode data = message.getData();
    assertAll("data",
      () -> assertEquals("Jose", data.get("firstname").textValue(), "Should get Firstname"),
      () -> assertEquals("Morales", data.get("lastname").textValue(), "Should get Lastname"),
      () -> assertEquals("josdem", data.get("nickname").textValue(), "Should get Nickname"),
      () -> assertEquals(1196, data.get("employeeNumber").intValue(), "Should get Employee Number"),
      () -> assertEquals("joseluis.delacruz@gmail.com", data.get("email").textValue(), "Should get Email"),
      () -> assertEquals("2019-03-09T07:36:43-05:00", data.get("clockInDateTime").textValue(), "Should get clockIn time")
    );

  }

  @AfterEach
  void finish() throws Exception {
    log.info("Test execution finished");
  }

}

To run the project with Gradle:

gradle test

To run the project with Maven:

mvn test

To browse the project go here, to download the project:

git clone git@github.com:josdem/spring-boot-json-node.git

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