Spring Boot and REST API

{} Coding Saint .
http://codingsaint.com | http://codingsaint.in

Overview
Spring Boot
● An easy , robust ,faster way to create
production ready spring application
● It is a very opinionated approach of
Spring boot library and third party
application with a motive of starting
an application without much
configuration.

Primary Goals of Spring Boot
● A faster way for developers to create
spring application
● Out of the box opinions to provide
defaults for spring and third party
configurations.
● Providing range of non functional
features like health checks, metrics,
embedded servers, security etc
● No code generation and no
requirement of XML configuration

Requirements and Prerequisites
As an application
Java Version 8
Maven 3.2 + or Gradle 4
Servlet Container as Tomcat 8.5 /Jetty 9.4
/Undertow 1.3
While proceeding further we do expect that
you have Java version 8, Maven 3.2 or Gradle
As a developer
Knowledge of Java
Good to have prior knowledge of Spring
Framework

Bootstrapping the first Spring Boot
Project

Spring Initializr Spring Initializr
● https://start.spring.io

First Hello World !!!
Handling a URL
Url :
http://localhost:8080/greetings
Hello ,World

First Hello World !!!
Handling a URL
Url :
@RestController
public class UserController {
@RequestMapping(path="greetings",
method=RequestMethod.GET)
protected String greetings() {
return "Hello, World";
}
}
Hello ,World

@SpringBootApplication
1. @SpringBootConfiguration
2. @EnableAutoConfiguration
3. @ComponentScan

@RestController
1. Denotes that the class contains request mappings.
2. Automatically serialize and deserialize java object response to Json /XML or any format
whatever is intended.

RequestMapping in Detail
@RequestMapping(path="greetings", method=RequestMethod.GET) @RequestMapping("greetings") @GetMapping("greetings")

Configuring Database
http://localhost:8080/users
List of users
query to database

Connecting to database
Creating dataSource
Just tell Spring boot app about which database to connect.
# H2
spring.h2.console.enabled=true
spring.h2.console.path=/h2
# Datasource
spring.datasource.url=jdbc:h2:file:~/user
spring.datasource.username=sa
spring.datasource.password=
spring.datasource.driver-class-name=org.h2.Driver
application.properties

HTTP POST
● HTTP POST request : Used to create a resource on server.
● Most of the time it’s like creating INSERT(s) at database.
● POST should be used for non-idempotent request, which changes the state of
server.

HTTP POST
Model
public class User {
private Long id;
private String
firstName;
private String
lastName;
private String email;
//getters and setters
}
Controller
@RequestMapping(path={"/user"}, method=RequestMethod.POST)
public ResponseEntity<Void> add(@RequestBody User
user){
//logic
}
http://localhost:8080/user
{
"firstName":"Ray",
"lastName":"McFallen",
"email":"Ray@codingsaint.com"
}
Request Body in JSON

HTTP GET
HTTP GET request : Used to get the information already present on
server/database.
GET request doesn’t change state of server but only fetch the data.
http://localhost:8080/user/1

HTTP GET
Model
public class User {
private Long id;
private String
firstName;
private String
lastName;
}
Controller
@RequestMapping(path={"/user/{id}"}, method=RequestMethod.GET)
public ResponseEntity<User> get(@PathVariable ("id")
String id){
//logic
}
{
"id": 1,
"firstName": "Ray",
"lastName": "McFallen",
"email": "Ray@codingsaint.com"
}
Response Body in JSON
Response as User (JSON) with id

HTTP PUT
HTTP PUT request : Used to update an existing resource on server.
PUT should be used for non-idempotent request, which changes the state of
server.

HTTP PUT
Controller
@RequestMapping(path={"/user"}, method=RequestMethod.PUT)
public ResponseEntity<Void> update(@RequestBody
User user){
//logic
}
http://localhost:8080/user
{
"id": 1,
"firstName": "Tim",
}
Request Body in JSON

HTTP DELETE
HTTP DELETE request : Used to remove/purge an existing resource on server.
DELETE should be used for non-idempotent request, which changes the state of
server.

HTTP DELETE
Controller
@RequestMapping(path={"/user/{id}"}, method=RequestMethod.DELETE)
public ResponseEntity<Void> delete(@PathVariable ("id") String id){
//logic
}

User Information API - Introduction
{
"id": 1,
"firstName": "Ray",
}
public class User {
private Long id;
private String firstName;
private String lastName;
}

HTTP Status Codes
Status Code Range Description
1XX Informational
2XX Success
3XX Redirect
4XX Client error
5XX Server Error

Famous HTTP Codes
200 OK
201 Created
204 No content
301 Moved permanently
400 Bad Request
401 Unauthorized
405 Method not allowed
403 Forbidden access
415 Unsupported Media Type
500 Internal server error

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