36-Spring Web with Spring Boot

Question 1

Types of Spring MVC applications

Answer 1

1. Web Servlet

2. Web Reactive

Question 2

What is the starter for Spring MVC?

Answer 2

spring-boot-starter-web

Question 3

What jar files that spring-boot-starter-web includes?

Answer 3

spring-web.jar
spring-webmvc.jar
spring-boot-starter.jar
jackson*.jar
tomcat-embed.jar

Question 4

Does the web starter depend on the validation starter?

Answer 4

No

Question 5

List out Spring MVC components created at startup time

Answer 5

1. DispatcherServlet
2. HandlerAdapter
3. MessageConverter
4. ContentTypeManager
5. HandlerMapper
6. ViewResolver, LocalResolver, ExceptionResolver

Question 6

What is the processing lifecycle of a REST request?

Answer 6

client -> DispatcherServlet -> Controller -> MessageConverter -> DispatcherServlet -> client

Question 7

What are message-converters in Spring MVC?

Answer 7

If found on the classpath, Spring will use:

1. Jackson for JSON/XML *
2. JAXB for XML*
3. GSON for JSON*
4. Byte[], String, BufferredImage
5. Form-based data
6. Protobuf*
7. Feed data such as ATOM/RSS*
8. JAXP Source

Note:

1. • Requires 3rd party libs on the classpath
2. Protobuf is not setup automatically

Question 8

When need to use @ResponseBody?

Answer 8

In the controller class with @Controller, the method needs to mark with @ResponseBody to convert the return object to JSON before sending it to the client.
We don't need this in @RestController controller class

Question 9

How can Spring lookup for @PathVariable, @RequestParam parameters without a name? e.g. @PathVariable long accountId

Answer 9

1. To do this the compiled class needs extra metadata – the names of the method parameters by using flag -parameters
2. Spring will lookup using parameter names:
   a. @PathVariable(“accountId”) long accountId -> @PathVariable long accountId
   b. @RequestParam(“overdrawn”) boolean overdrawn -> @RequestParam boolean overdrawn

Question 10

How to set a request parameter optional?

Answer 10

@RequestParam(required=false) Integer location

Question 11

How to enable message converters?

Answer 11

1. Auto-configure if it’s Spring Boot app
2. If not, need to
   @Configuration @EnableWebMvc class Config {}

Question 12

How to customize message-converters?

Answer 12

1. Override WebMvcConfigurer.configureMessageConverters, annotate with @Configuration
2. Mark this class with @Configuration

Question 13

How to replace embedded tomcat with jetty?

Answer 13

In pom.xml,

1. exclude sprint-boot-starter-tomcat from spring-boot-starter-web
2. add dependency spring-boo-starter-jetty

Question 14

How to configure to run the app from both the command line and web container?

Answer 14

1. Extends SpringBootServletInitializer
2. Implement SpringBootServletInitializer.configure(SpringApplicationBuilder)
   add: builder.sources(Application.class)
3. Add normal main class (to run from the command line)

Question 15

What does mvn package produce?

Answer 15

1. app-0.0.1.jar: fat & executable jar

2. app-0.0.1.jar.original: traditional jar

Question 16

What is the starter for spring mvc and web?

Answer 16

spring-boot-starter-web

Question 17

What plugin builds fat & executable jar?

Answer 17

spring-boot-maven-plugin

Question 18

What is the purpose of @EnableWebMvc?

Answer 18

Without Spring Boot, we need to use @EnableWebMvc to:

1. Auto-configure controllers, views
2. Auto-configure rest support, message converters
3. Stateless converters

Question 19

What if you add @EnableWebMvc to a Spring Boot app?

Answer 19

All extra configs from Spring Boot will disappear

Question 20

List out template engines supported by Spring MVC

Answer 20

1. Mustache
2. Thymeleaf
3. GSP
4. Freemarker
5. Velocity
   and more

Question 21

What is the front controller in MVC-based applications?

Answer 21

DispatcherServlet