L4. Spring MVC
Introduction to Spring MVC
Dr A Boronat
Sprint 2: developing and testing a web application
• Goal: mini project (16 November, 9am) – duration 4 weeks • agile development and testing of a basic online shop
• product catalogue
• order management
• individual assessment: 30% of overall mark
2/19
Sprint 2: schedule
• Schedule: calendar on Blackboard for sessions • Todo list:
• sprint 2 folder on Blackboard (a copy available in GitHub) • week a: foundations of a web application
• Spring MVC
• Spring Boot
• week b: development of more complex web pages with different views
• Java Server Pages
• Expression Language
• Java Standard Tag Library
• week c: test-driven development (agile testing) • JUnit and Hamcrest
• week d: behaviour-driven development with Cucumber
• Cucumber
• Spring Testing Framework
3/19
Web application
• Web application: client-server software application in which
• the client (or user interface) runs in a web browser
• the application server listens at some URL (base URL) and a port
• when developing a web application this will be http localhost 8080
by default
• web applications may contain
• static content: HTML, images
• dynamically generated content: HTML produced by JSPs after querying a
database
4/19
5/19
6/19
7/19
Web development frameworks (Java)
• According to a recent survey
• Spring framework: facilitates the development of enterprise applications
• can manage Java objects (beans) using dependency injection
• offers a lot of functionality off-the-shelf (web development support)
• Spring MVC: web component of Spring, implementing MVC
• Spring Boot: convention-over-configuration rapid application development
• configures Spring wherever possible automatically (opinionated approach)
• ideal for beginners (no XML configuration)
8/19
Spring Boot web application
Project structure
9/19
Spring Boot web application
SpringBootApplication class
@SpringBootApplication
public class LabMvcApplication {
public static void main(String[] args) { SpringApplication.run(LabMvcApplication.class, args);
} }
10/19
Spring Boot web application
Configuration
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
@Override
public void addResourceHandlers(ResourceHandlerRegistry
registry) { registry.addResourceHandler(“/resources/**”)
.addResourceLocations(“/resources/”); }
@Bean
public InternalResourceViewResolver viewResolver() {
InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
viewResolver.setViewClass(JstlView.class); viewResolver.setPrefix(“/WEB-INF/views/”); viewResolver.setSuffix(“.jsp”); viewResolver.setOrder(2);
return viewResolver; }
}
11/19
Controller
Responsibility: HTTP request handling
• links a HTTP request to a method with an annotation @RequestMapping • method parameters: get user input
• method body: population of the model
• business logic (access to database, computations, etc.) • determines view
• interprets exceptions arisen from business logic
• return value: view name
12/19
Handling HTTP requests (GET)
• attached to a class: defines relative url http://localhost:8080/index/ @RequestMapping(“/hello”)
public String hello(Model model) { .. }
• attached to a class: defines relative url http://localhost:8080/index/hello/
@RequestMapping(“/index”) public class IndexController {
@RequestMapping(“/hello”)
public String hello(Model model) { .. } }
13/19
Handling HTTP requests (GET): parameters
• using path variables with @PathVariable: http://localhost:8080/hello/World
@RequestMapping(“/hello/{value}”)
public String hello(@PathVariable String value, Model model)
{…}
• request parameters: http://localhost:8080/hello?value=World
@RequestMapping(“/hello”) public String greetingParam(
@RequestParam(value=”value”, required=false, defaultValue=”World”) String value,
Model model) { … }
14/19
Handling HTTP requests (GET): type conversion
• getting primitive datatypes: http://localhost:8090/hello?value=1
@RequestMapping(“/hello”)
public String primitive(@RequestParam Integer value, Model
model) { … }
• getting dates: http://localhost:8090/hello/2016-07-10
@RequestMapping(“/hello/{value}”) public String date(@PathVariable
@DateTimeFormat(iso=ISO.DATE) Date value, Model model) { … }
• getting collections: http://localhost:8090/hello?values=1&values=2
@RequestMapping(“/hello”)
public String collection(@RequestParam Collection
values , Model model) { … }
15/19
Handling HTTP requests (GET)
• Model parameter: allows us to access the model
@RequestMapping(“/hello”)
public String hello(Model model) {
model.addAttribute(“name”, “World”);
return “hello”; }
• @ModelAttribute
• fetches the object associated with the attribute user from the model
@RequestMapping(“/hello”)
public String hello(@ModelAttribute User user) {
return “hello”; }
• if the entry is not present in the model, the object is instantiated and added to the model
• the argument’s fields are populated from all request parameters that have matching names
16/19
Executing the web application
• with Gradle:
• from Mac/Linux: ./gradlew bootRun • from Windows: gradlew.bat bootRun
• with STS: use Boot Dashboard
• enables debugging from STS
17/19
To use resources from Pluralsight
• Slides and examples used in tutorial available under tab Exercises • Follow the guide on GitHub to avoid XML configuration
• Gradle: no need to deal with Maven POMs directly (XML) • Spring Boot: automated configuration
18/19
What’s next?
• Resources from Pluralsight
• Exercise 1: setting up for first Spring Boot application • Exercises from Pluralsight
• Exercise 2
• Mini project
• Lab session on Monday
19/19