Spring Boot Introduction

Transcript

1. {} Coding Saint . http://codingsaint.com | http://codingsaint.in
2. Spring Boot - Introduction
3. 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.
4. 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
5. 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
6. Bootstrapping the first Spring Boot Project
7. Spring Initializr Spring Initializr • https://start.spring.io
8. First Hello World !!! Handling a URL Url : http://localhost:8080/greetings http://localhost:8080/greetings Hello ,World
9. First Hello World !!! Handling a URL Url : http://localhost:8080/greetings http://localhost:8080/greetings @RestController public class UserController { @RequestMapping(path="greetings", method=RequestMethod.GET) protected String greetings() { return "Hello, World"; } } Hello ,World
10. @SpringBootApplication 1. @SpringBootConfiguration 2. @EnableAutoConfiguration 3. @ComponentScan
11. @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.
12. RequestMapping in Detail @RequestMapping(path="greetings", method=RequestMethod.GET) @RequestMapping("greetings") @GetMapping("greetings")
13. Configuring Database http://localhost:8080/users List of users query to database
14. 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
15. 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.
16. 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.
17. 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
18. 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
19. HTTP GET Model public class User { private Long id; private String firstName; private String lastName; private String email; //getters and setters } Controller @RequestMapping(path={"/user/{id}"}, method=RequestMethod.GET) public ResponseEntity<User> get(@PathVariable ("id") String id){ //logic } http://localhost:8080/user/1 { "id": 1, "firstName": "Ray", "lastName": "McFallen", "email": "Ray@codingsaint.com" } Response Body in JSON Response as User (JSON) with id
20. 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.
21. 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", "lastName": "McFallen", "email": "Ray@codingsaint.com" } Request Body in JSON
22. 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.
23. HTTP DELETE Controller @RequestMapping(path={"/user/{id}"}, method=RequestMethod.DELETE) public ResponseEntity<Void> delete(@PathVariable ("id") String id){ //logic } http://localhost:8080/user/1
24. User Information API - Introduction { "id": 1, "firstName": "Ray", "lastName": "McFallen", "email": "Ray@codingsaint.com" } public class User { private Long id; private String firstName; private String lastName; private String email; //getters and setters }
25. HTTP Status Codes Status Code Range Description 1XX Informational 2XX Success 3XX Redirect 4XX Client error 5XX Server Error
26. 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
27. 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
28. Exception Handling and Status Codes
29. Custom Exception and Status Code
30. @ExceptionHandler and @ControllerAdvice - Custom Exception Handling
31. Content Negotiation - XML /JSON or your own Content Type at ease
32. Message Converters MappingJackson2HttpMessageConverter – To convert JSON if Jackson2 is on classpath MappingJacksonHttpMessageConverter – To convert JSON if Jackson is on classpath Jaxb2RootElementHttpMessageConverter – To convert Java objects to/from XML if JAX2B is on classpath FormHttpMessageConverter: read and write the "application/x-www-form-urlencoded" media type as MultiValueMap<String, String> ByteArrayHttpMessageConverter : Converts ByteArray StringHttpMessageConverter : Converts String ResourceHttpMessageConverter : org.springframework.core.io.Resource for any type of octet stream SourceHttpMessageConverter: converts javax.xml.transform.Source AtomFeedHttpMessageConverter – To convert Atom feeds if Rome is on classpath RssChannelHttpMessageConverter – To convert RSS feeds if Rome is on classpath
33. Custom Message Converters
34. HATEOAS & Richardson maturity Model LEVEL 1 • Not at all RESTful. • No URL sanity • No method sanity 0
35. HATEOAS & Richardson Maturity Model LEVEL 0 • Not at all RESTful. • No URL sanity • No method sanity • http://server:port/postCust omer • http://localhost:8080/delete Order LEVEL 1 • URL sanity. • Single HTTP methods for single resource • http://localhost:8080/order • http://localhost:8080/order/1 LEVEL 2 • URL sanity. • Multiple HTTP methods for single resource POST • http://localhost:8080/order GET : to retrieve DELETE : to purge • http://localhost:8080/order/1 LEVEL 3 • URL sanity. • Multiple HTTP methods for single resource • More information about possible next actions or other useful resources
36. HATEOAS & Richardson maturity Model 1 Add pom dependency spring-boot-starter-hateoas 2 Bean extends ResourceSupport org.springfram ew ork.hateoas.ResourceSupport 3 Change M ethod return type w ith Resource<T> and add Links org.springfram ew ork.hateoas.ResourceSupport
37. Configurations and Properties 1. Devtools global settings properties on your home directory (~/.spring-boot-devtools.properties when devtools is active). 2. @TestPropertySource annotations on your tests. 3. properties attribute on your tests. Available on @SpringBootTest and the test annotations for testing a particular slice of your application. 4. Command line arguments. 5. Properties from SPRING_APPLICATION_JSON (inline JSON embedded in an environment variable or system property). 6. ServletConfig init parameters. 7. ServletContext init parameters. 8. JNDI attributes from java:comp/env. 9. Java System properties (System.getProperties()). 10. OS environment variables. 11. A RandomValuePropertySource that has properties only in random.*. 12. Profile-specific application properties outside of your packaged jar (application-{profile}.properties and YAML variants). 13. Profile-specific application properties packaged inside your jar (application-{profile}.properties and YAML variants). 14. Application properties outside of your packaged jar (application.properties and YAML variants). 15. Application properties packaged inside your jar (application.properties and YAML variants). 16. @PropertySource annotations on your @Configuration classes. 17. Default properties (specified by setting SpringApplication.setDefaultProperties).
38. Reading Properties @Value and Environment
39. Placeholder in properties app.name=User Application app.version=1.0.0 app.description = ${app.name} - ${app.version} is an application to store user details.
40. Configuring Random Values
41. Configuring Random Values app.random=${random.value} app.random.integer=${random.int} app.random.long=${random.long} app.random.uuid=${random.uuid} app.random.less.than.hundred=${random.int(100)} app.random.within.range=${random.int[1000,9999]}
42. Type-safe Configuration properties 1. @Value can difficult to use when there are lot of values to be read. 2. It could be even tough if the values are hierarchical in nature. 3. Type Safe configuration using @ConfigurationProperties are amazing way to handle it.
43. Profiles in Spring 1. Spring profiles helps in segregating part of the application configuration and make it available to certain environment. dev-db prod db User service
44. 404 This status code was not found in previous slide. It means resource not found. URL is wrong
45. This lecture is a part of Udemy course. You can find the discount coupon for full course in description
46. MVC : Lets add UI
47. Adding UI We will cover JSP support. This is not basically a REST api , but we will learn rendering HTML and a web app.