How to create simple rest apis with springboot

As a part of this article you will be building 2 simple Using . This article will give an idea on how to quickly get started with springboot. REST apis Springboot So let’s get started 😄 Pre-requisite Ensure you have Maven Installed in your system before starting with this article. You can Install Maven from https://maven.apache.org/ Also ensure Maven is set in the PATH so that comands work. mvn you can verify if maven is installed and can be accessed using the command mvn -v Also ensure is set. JAVA_HOME Project Setup The first step is to setup your project. Setting up a Springboot project is pretty easy. Go to . https://start.spring.io/ In the Site enter the Artifact name as and under dependencies add . You can enter any Other Artifact name as well. simple-rest-apis Web Also in the top Ensure you are creating a Project with using Springboot version This is to ensure that the results in this article are reproducible. Once you are done with this article, You can experiment by choosing the other options 😄 Maven Java 2.0.6 Once you enter the information, the screen should look like this Click on Generate Project, this will download a zip file onto your computer. Extract this zip file. The extracted folder is your springboot project. You can import the project into your preferred IDE. I used eclipse to try this out. Project Structure Explained pom.xml This file has all the maven dependencies. The main dependency to note is the following org.springframework.boot spring-boot-starter-web dependency ensures that the project can be used for web applications spring-boot-starter-web Also one other important thing to notice in pom.xml is the following org.springframework.boot spring-boot-starter-parent 2.0.6.RELEASE is made as the parent of this project. This ensures that any internal dependencies needed by springboot are automatically taken care off, and the developer need not worry about it. spring-boot-starter-parent SimpleRestApisApplication.Java This file is named after the project name, followed by an . Application This file is present inside folder and inside package. src/main/java com.example.simplerestapis This file has the following piece of code package com.example.simplerestapis;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class SimpleRestApisApplication { public static void main(String[] args) { SpringApplication.run(SimpleRestApisApplication.class, args); }} The main highlight here is the annotation . This internally is a combination of the following 3 annotations @SpringBootApplication : Needed for Manual Spring configurations. Adding this annotation ensures that configuration can be done in a java class itself instead of using a separate xml file. @Configuration : Spring needs a lot of configuration to be done. This annotation ensures that a lot of the configuration is done automatically. @EnableAutoConfiguration : This tells Spring, where all to scan for components. @ComponentScan The Line bootstraps the application. SpringApplication.run(SimpleRestApisApplication.class, args); Application.properties This file is present inside . The file can be used to list out the various properties to use while running the application. For example it can be used to mention on which port the application should run. src/main/resources Code The code for the API’s which are built here can be found here Create your first API Our First API will be a simple API demonstrating GET request. Create a package called . Inside this package create a file called as com.example.simplerestapis.models SampleResponse.java Copy the following code into SampleResponse.java package com.example.simplerestapis.models;public class SampleResponse { private String message; private long id; public String getMessage() { return message; } public void setMessage(String message) { this.message = message; } public long getId() { return id; } public void setId(long id) { this.id = id; }} is just a model class. It indicates the fields which are present in the response of your api. SampleResponse.java Create a package called . Inside this package create a file called as com.example.simplerestapis.controller WebController.java Copy the following code into WebController.java package com.example.simplerestapis.controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.RestController;import com.example.simplerestapis.models.SampleResponse;@RestControllerpublic class WebController { @RequestMapping("/sample") public SampleResponse Sample(@RequestParam(value = "name", defaultValue = "Robot") String name) { SampleResponse response = new SampleResponse(); response.setId(1); response.setMessage("Your name is "+name); return response; }} In the Above Code the Annotation indicates that this class will have Rest End points. This Annotation basically tells that this class is a controller and the value returned from a function in this class will either be converted to JSON or XML. Default in JSON. @RestController maps the endpoint to Function @RequestMapping /sample Sample indicates that the endpoint will have one Query parameter called . The default value of is “Robot” @RequestParam /sample name name The code inside the function is pretty straight forward. The response is being set based on value. name Go to command prompt. Go into your project folder and run the following command to start the application mvn spring-boot:run By Default the application runs on port 8080 in localhost. In order to test api end points you can use . Download postman from the link given. Postman Go to postman and type the following url and hit send. localhost:8080/sample?name=aditya This will give the following response back { "message": "Your name is aditya", "id": 1} Now Try the following url and hit send localhost:8080/sample This will give the following response back { "message": "Your name is Robot", "id": 1} Congrats 😄 You have created your first API using springboot. You have learnt how to create a simple with a query parameter GET rest api Create your second API The Second API will demonstrate how to create an API which supports POST Request Inside package, create a java class called com.example.simplerestapis.models PostRequest.java Copy the following code into PostRequest.java package com.example.simplerestapis.models;public class PostRequest { int id; String name; public int getId() { return id; } public String getName() { return name; } public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; }} A POST Request generally has a POST body which is sent as an input. indicates all the fields which are present in the input POST body PostRequest.java Inside package, create a java class called com.example.simplerestapis.models PostResponse.java Copy the following code into PostResponse.java package com.example.simplerestapis.models;public class PostResponse { int id; String message; String extra; public String getExtra() { return extra; } public int getId() { return id; } public String getMessage() { return message; } public void setExtra(String extra) { this.extra = extra; } public void setId(int id) { this.id = id; } public void setMessage(String message) { this.message = message; }} indicates the fields which are present in the output of the POST Request. PostResponse.java In add the following imports WebController.java import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMethod;import com.example.simplerestapis.models.PostRequest;import com.example.simplerestapis.models.PostResponse; Also add the following function in WebController.java @RequestMapping(value = "/test", method = RequestMethod.POST)public PostResponse Test(@RequestBody PostRequest inputPayload) { PostResponse response = new PostResponse(); response.setId(inputPayload.getId()*100); response.setMessage("Hello " + inputPayload.getName()); response.setExtra("Some text"); return response;} This code creates a new endpoint called as and maps it to function /test Test Also the code indicates that api end point can accept POST Requests method = RequestMethod.POST /test indicates that the post request will have an input post body of type . The input post body is stored in Object. @RequestBody PostRequest inputPayload PostRequest inputPayload The code is pretty straightforward wherein the response is set, based on the input that is coming. The from input payload is multiplied by 100 and set to the output payload id The parameter is appended with and set to the output payload name Hello parameter is hardcoded to a string value of extra Some text The final code code in looks as follows WebController.java import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.RestController;import com.example.simplerestapis.models.PostRequest;import com.example.simplerestapis.models.PostResponse;import com.example.simplerestapis.models.SampleResponse;@RestControllerpublic class WebController { @RequestMapping("/sample") public SampleResponse Sample(@RequestParam(value = "name", defaultValue = "Robot") String name) { SampleResponse response = new SampleResponse(); response.setId(1); response.setMessage("Your name is "+name); return response; } @RequestMapping(value = "/test", method = RequestMethod.POST) public PostResponse Test(@RequestBody PostRequest inputPayload) { PostResponse response = new PostResponse(); response.setId(inputPayload.getId()*100); response.setMessage("Hello " + inputPayload.getName()); response.setExtra("Some text"); return response; }} Go to command prompt. Go into your project folder and run the following command to start the application mvn spring-boot:run Open Postman and set the values as shown in the image below Basically the request type is set to POST The enpoint URL is entered as localhost:8080/test To enter the post body, Go to , Select and select Body raw JSON (application/json) The input POST body given is the following { "id": 1, "name": "aditya"} On clicking , The following output would be shown Send { "id": 100, "message": "Hello aditya", "extra": "Some text"} You can experiment with this by sending different input post bodies. Congrats 😄 You now know how to create simple GET and POST request based REST APIS using Springboot 😄 You can checkout to Learn more about Spring and Springboot https://spring.io/ About the author I love technology and follow the advancements in the field. I also like helping others with my technology knowledge. Feel free to connect with me on my LinkedIn account https://www.linkedin.com/in/aditya1811/ You can also follow me on twitter https://twitter.com/adityasridhar18 My Website: https://adityasridhar.com/ Other Posts by Me An introduction to Git How to use Git efficiently How did that weird bug come in the code Originally published at adityasridhar.com .