Spring REST training

• HTTP
• Important concepts
• Create custom Exceptions
• Swagger (now Open Api)
• Persitence
• Working with APIs
• Testing
• Generate Code with Swagger2
• HATEOAS

HTTP

Messages

• Request
  • URL
    • Address of the resource
    • Optional parameters
  • Method: POST, PUT, DELETE, GET, …
  • Headers
    • Accept (content type)
    • Authentication
  • Body (for PUT and POST operations)
• Response
  • Status Code
  • Headers: content type, date, …
  • Body (for most request)

    Verbs

Status

https://www.restapitutorial.com/httpstatuscodes.html

Important concepts

https://start.spring.io/ → create spring boot project from scratch.

• REST Clients
  • HTTPie
  • Postman
• @RestController
• @GetMapping

Create custom Exceptions

Swagger (now Open Api)

• Add dependencies to pom.xml

<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger2</artifactId>
  <version>2.4.0</version>
</dependency>
<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger-ui</artifactId>
  <version>2.4.0</version>
</dependency>

• Add config class

package com.adiaz;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.service.Contact;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.swagger2.annotations.EnableSwagger2;
@Configuration
@EnableSwagger2
public class SwaggerConfig {
    private static final Contact CONTACT = new Contact ("a_name", "http://www.contact_url.org", "contact@email.com");
    private static final ApiInfo MY_API_INFO = new ApiInfo("My awesonme API Documentation",
                "This is an  getting started proof of concept API", "1.0.1",
                "https://en.wikipedia.org/wiki/MIT_License",
                CONTACT, "MIT", "https://opensource.org/licenses/MIT");
    @Bean
    public Docket api() {
        return new Docket(DocumentationType.SWAGGER_2).apiInfo(MY_API_INFO);
    }
}

• Ask for urls
  http://localhost:8080/swagger-ui.html
  http://localhost:8080/v2/api-docs

Persitence

1. Add dependencies JPA and H2
   • JPA: persistence standard for Java.
   • H2: database in memory for development purpose.

<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>

1. Add annotations:
   • @Entity
   • @Id
   • @GenerateValue

1. H2 console:
   http://localhost:8080/h2-console
   Default database name: jdbcmem:testdb

Working with APIs

• Swagger
• RAML
• API BluePrint
• OpenAPI 2 (Swagger2)

• Swagger Tools

  • Swagger Editor
  • Swagger UI
  • Swagger Codegen

• YAML: http://www.yamllint.com/

https://editor.swagger.io

Testing

http://dredd.org

1. Generate yaml with swagger Editor (https://editor.swagger.io/)
2. Save locally
3. Start server
4. Call dredd to test

   dreed api-description-hellobean.yml http://localhost:8080

swagger: "2.0"
info:
  version: "1.0"
  title: "Example API"
basePath: /
schemes:
  - http
paths:
  /helloBean:
    get:
      produces:
        - application/json;charset=utf-8
      responses:
        '200':
          description: 'OK'
          schema:
            type: object
            properties:
              message:
                type: string
            required:
              - message

• CodeFirst
• Contract or API or design FIRST

Generate Code with Swagger2

• From Swagger Editor generate server, select spring
• Extract zip
• Import project as: “Existing maven project”

HATEOAS

Add links with resources to response.
Example:

{
    "id": 2,
    "name": "antonio",
    "birthDate": "2019-02-27T14:20:22.994+0000",
    "_links": {
        "all-users": {
            "href": "http://localhost:8080/users"
        }
    }
}

1. Add library to pom.xml.

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-hateoas</artifactId>
</dependency>

1. Add code to Controller

@GetMapping("/users/{id}")
public Resource<User> usersRetrieve(@PathVariable int id) throws UserNotFoundException {
  User user = serviceUser.findUser(id);
  if (user==null) {
    throw new UserNotFoundException("No existe listillo");
  }
  Resource<User> resource = new Resource<>(user);
  ControllerLinkBuilder linkTo = linkTo(methodOn(this.getClass()).usersRetrieve());
  resource.add(linkTo.withRel("all-users"));
  return resource;
}