Spring Boot RESTful Web Services Versioning Example

Welcome, in this tutorial, we will show a RESTful API by using the Accept Header versioning technique in a Spring Boot app.

1. Introduction

Before going further in this tutorial, we will look at the common terminology such as introduction to Spring Boot and Lombok.

1.1 Spring Boot

1.2 Lombok

1.2.1 Lombok features

Feature Details
val Local variables are declared as final
var Mutable local variables
@Slf4J Creates an SLF4J logger
@Cleanup Will call close() on the resource in the finally block
@Getter Creates getter methods for all properties
@Setter Creates setter for all non-final properties
@EqualsAndHashCode
  • Generates implementations of equals(Object other) and hashCode()
  • By default will use all non-static, non-transient properties
  • Can optionally exclude specific properties
@ToString
  • Generates String of class name, and each field separated by commas
  • Optional parameter to include field names
  • Optional parameter to include a call to the super toString method
@NoArgsConstructor
  • Generates no-args constructor
  • Will cause compiler error if there are final fields
  • Can optionally force, which will initialize final fields with 0/false/null var – mutable local variables
@RequiredArgsContructor
  • Generates a constructor for all fields that are final or marked @NonNull
  • The constructor will throw a NullPointerException if any @NonNull fields are null val – local variables are declared final
@AllArgsConstructor
  • Generates a constructor for all properties of the class
  • Any @NotNull properties will have null checks
@Data
  • Generates typical boilerplate code for POJOs
  • Combines – @Getter, @Setter, @ToString, @EqualsAndHashCode, @RequiredArgsConstructor
  • No constructor is generated if constructors have been explicitly declared
@Builder
  • Implements the Builder pattern for object creation
@Value
  • The immutable variant of @Data
  • All fields are made private and final by default

Let us go ahead with the tutorial implementation but before going any further I’m assuming that you’re aware of the Spring boot basics.

2. Spring Boot RESTful Web Services Versioning Example

2.1 Tools Used for Spring boot application and Project Structure

We are using Eclipse Kepler SR2, JDK 8, and Maven. In case you’re confused about where you should create the corresponding files or folder, let us review the project structure of the spring boot application.

Fig. 1: Project structure

Let us start building the application!

3. Creating a Spring Boot application

Below are the steps involved in developing the application.

3.1 Maven Dependency

Here, we specify the dependency for the Spring boot (Web and JPA, Spring doc Open API (for swagger interface)), H2 database, Java Faker (to generate the dummy data), and Lombok. The updated file will have the following code.

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.2</version>
        <relativePath/> <!-- lookup parent fromV1 repository -->
    </parent>
    <groupId>com.versioning</groupId>
    <artifactId>VersioningRestfulServices</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>VersioningRestfulServices</name>
    <description>Versioning restful services in spring boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.github.javafaker</groupId>
            <artifactId>javafaker</artifactId>
            <version>1.0.2</version>
        </dependency>
        <dependency>
            <groupId>org.springdoc</groupId>
            <artifactId>springdoc-openapi-ui</artifactId>
            <version>1.5.3</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

3.2 Application yml file

Create a new YML file at the location: VersioningRestfulServices/src/main/resources/ and add the following code where we will define –

You’re free to change the application or the database details as per your wish.

application.yml

server:
  error:
    include-stacktrace: never
  port: 9800
spring:
  application:
    name: versioning-restful-services
  datasource:
    driverClassName: org.h2.Driver
    password: ''
    url: 'jdbc:h2:mem:testdb'
    username: sa
  h2:
    console:
      enabled: true
      path: /h2-console
  jpa:
    database-platform: org.hibernate.dialect.H2Dialect
    hibernate:
      ddl-auto: create-drop
    properties:
      hibernate:
        show_sql: true
springdoc:
  swagger-ui:
    path: /swagger-ui-custom.html

3.3 Java Classes

Let us write the important java class(es) involved in this application. For brevity, we will skip the following classes –

3.3.1 Implementation/Main class

Add the following code to the main class to bootstrap the application from the main method. Always remember, the entry point of the spring boot application is the class containing @SpringBootApplication annotation and the static main method.

VersioningRestfulServicesApplication.java

package com.versioning;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
//lombok annotation
@Slf4j
//spring annotation
@SpringBootApplication
public class VersioningRestfulServicesApplication {
	public static void main(String[] args) {
		SpringApplication.run(VersioningRestfulServicesApplication.class, args);
		log.info("Versioning restful services in a spring boot application");
	}
}

3.3.2 Implementation of the Response class

Add the following code to the response class which will be responsible to map the database layer response. The class methods will map the response data based on the media-type header param received by the controller methods. Such mappers are helpful where the non required attributes for a particular type are to be set null. This class –

EmployeeResponse.java

package com.versioning.dto;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.versioning.entity.Employee;
import io.swagger.v3.oas.annotations.media.Schema;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.lang.Nullable;
import java.util.UUID;
//lombok annotations
@Data
@NoArgsConstructor
@AllArgsConstructor
//Jackson annotations
//Ensures that the null properties are not included in the response
//(i.e. only properties with non-null values are to be included)
@JsonInclude(JsonInclude.Include.NON_NULL)
public class EmployeeResponse {
    //while sending out the response to the users we are mapping the reference id stored in the db as a primary key
    //as an ideal practice we never share the primary key of the records
    UUID id;
    String fullName;
    String emailAddress;
    String gender;
    //makes it clear that this value can be null
    @Nullable
    //Swagger annotation is used to define a schema.
    @Schema(nullable = true, description = "Phone number can be null")
    String phoneNumber;
    //makes it clear that this value can be null
    @Nullable
    //Swagger annotation is used to define a schema.
    @Schema(nullable = true, description = "Work department can be null")
    String workDepartment;
    //this method will send the employee details where phone number and work department
    //is marked as null (meaning these two attributes are not required by the integrating parties)
    @Deprecated
    public static EmployeeResponse fromV1(final Employee employee) {
        return new EmployeeResponse(
                employee.getReferenceId(),
                employee.getFullName(),
                employee.getEmailAddress(),
                employee.getGender(),
                null,
                null);
    }
    //this method is newer version of 'fromV1(...)' method where in all the required details are
    //passed
    public static EmployeeResponse fromV2(final Employee employee) {
        return new EmployeeResponse(
                employee.getReferenceId(),
                employee.getFullName(),
                employee.getEmailAddress(),
                employee.getGender(),
                employee.getPhoneNumber(),
                employee.getWorkDepartment());
    }
}

3.3.3 Controller class

Add the following code to the controller class to specify the different endpoints. The controller methods are annotated with the HTTP GET mapping annotation wherein the annotation also excepts an Accept header in the incoming request whose value can either be application/vnd.jcg.app-1.0+json or application/vnd.jcg.app-2.0+json. Based on this media-type the response will be generated and you can verify it by hitting the application endpoints. For brevity we have –

EmployeeController.java

package com.versioning.controller;
import com.versioning.dto.EmployeeResponse;
import com.versioning.entity.Employee;
import com.versioning.exception.EntityNotFoundException;
import com.versioning.service.EmployeeService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.*;
import java.util.List;
import java.util.UUID;
import java.util.stream.Collectors;
//lombok annotation
@Slf4j
//spring annotations
@RestController
@RequestMapping("/api/employee")
public class EmployeeController {
    //media types versioning example
    private static final String EMPLOYEE_V_1_0 = "application/vnd.jcg.app-1.0+json";
    private static final String EMPLOYEE_V_2_0 = "application/vnd.jcg.app-2.0+json";
    @Autowired
    EmployeeService service;
    //URL :: http://localhost:9800/api/employee/get-all
    //Request header :: Accept=application/vnd.jcg.app-1.0+json
    @GetMapping(value = "/get-all", produces = EMPLOYEE_V_1_0)
    @ResponseStatus(HttpStatus.OK)
    public List<EmployeeResponse> getEmployees() {
        log.info("Getting all employee for v1 media type");
        final List<Employee> employees = service.getEmployees();
        return employees.stream().map(EmployeeResponse::fromV1).collect(Collectors.toList());
    }
    //URL :: http://localhost:9800/api/employee/get?id=e45f2c96-be5b-4779-803c-a611ff5f150f
    //Request header :: Accept=application/vnd.jcg.app-1.0+json
    @GetMapping(value = "/get", produces = EMPLOYEE_V_1_0)
    @ResponseStatus(HttpStatus.OK)
    public EmployeeResponse getEmployee(@RequestParam("id") final UUID id)
            throws EntityNotFoundException {
        log.info("Getting employee id = {} for v1 media type", id);
        final Employee e = service.getEmployeeById(id);
        return EmployeeResponse.fromV1(e);
    }
    //URL :: http://localhost:9800/api/employee/get-all
    //Request header :: Accept=application/vnd.jcg.app-2.0+json
    @GetMapping(value = "/get-all", produces = EMPLOYEE_V_2_0)
    @ResponseStatus(HttpStatus.OK)
    public List<EmployeeResponse> getEmployeesV2() {
        log.info("Getting all employee for v2 media type");
        final List<Employee> employees = service.getEmployees();
        return employees.stream().map(EmployeeResponse::fromV2).collect(Collectors.toList());
    }
    //URL :: http://localhost:9800/api/employee/get?id=e45f2c96-be5b-4779-803c-a611ff5f150f
    //Request header :: Accept=application/vnd.jcg.app-2.0+json
    @GetMapping(value = "/get", produces = EMPLOYEE_V_2_0)
    @ResponseStatus(HttpStatus.OK)
    public EmployeeResponse getEmployeeV2(@RequestParam("id") final UUID id)
            throws EntityNotFoundException {
        log.info("Getting employee id = {} for v2 media type", id);
        final Employee e = service.getEmployeeById(id);
        return EmployeeResponse.fromV2(e);
    }
}

4. Run the Application

To execute the application, right-click on the VersioningRestfulServicesApplication.java class, Run As -> Java Application.

Fig. 2: Run the Application

5. Project Demo

When the application is started, open the Postman tool to hit the application endpoints. You are free to choose any tool of your choice and for this tutorial, we will use the spring swagger interface (accessible at the following URL – http://localhost:9800/swagger-ui-custom.html).

Application endpoints

-- HTTP GET endpoints –
//Endpoint name – Get all employees
//media type – application/vnd.jcg.app-1.0+json
//URL :: http://localhost:9800/api/employee/get-all
//Request header :: Accept=application/vnd.jcg.app-1.0+json
//Endpoint name – Get employee by id
//URL :: http://localhost:9800/api/employee/get?id=e45f2c96-be5b-4779-803c-a611ff5f150f
//Request header :: Accept=application/vnd.jcg.app-1.0+json
//Endpoint name – Get all employees
//media type – application/vnd.jcg.app-2.0+json
//URL :: http://localhost:9800/api/employee/get-all
//Request header :: Accept=application/vnd.jcg.app-2.0+json
//Endpoint name – Get employee by id
//URL :: http://localhost:9800/api/employee/get?id=e45f2c96-be5b-4779-803c-a611ff5f150f
//Request header :: Accept=application/vnd.jcg.app-2.0+json

That is all for this tutorial and I hope the article served you whatever you were looking for. Happy Learning and do not forget to share!

6. Summary

In this section, you learned,

You can download the sample application as an Eclipse project in the Downloads section.

7. Download the Project

In this tutorial, we showed a RESTful API by using the Accept Header versioning technique in a spring boot app.

Download
You can download the full source code of this example here: Spring Boot RESTful Web Services Versioning Example
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