Week 5 - HTTP and Javalin - Intro to HTTP and Javalin, Dependency Management with Maven

Question 1

What is HTTP?

Answer 1

HTTP stands for HyperText Transfer Protocol is used to send hypermedia over the internet

Question 2

HTTP works by

Answer 2

making a connection to a server, sending a request, and receiving a response

Question 3

A request contains

Answer 3

contains the method used, the endpoint, and optional headers and a body

Question 4

A response contains

Answer 4

the status code, status message, and optional headers and a body

Question 5

A body contains

Answer 5

a resource, which is just some data

Question 6

HTTP Methods:

Answer 6

HTTP defines a set of request methods to indicate the desired action to be performed for a given resource. Although they can also be nouns, these request methods are sometimes referred to as HTTP verbs.

Question 7

GET requests

Answer 7

GET method is used to retrieve data from a server at the specified resource. For example, say you have an API with a /users endpoint. Making a GET request to that endpoint should return a list of all available users.

Question 8

POST requests

Answer 8

are used to send data to the API server to create or update a resource. The data sent to the server is stored in the request body of the HTTP request.

Question 9

PUT requests

Answer 9

are used to send data to the API to update or create a resource.

Question 10

Difference between PUT and POST requests

Answer 10

The difference is that PUT requests are idempotent. That is, calling the same PUT request multiple times will always produce the same result. In contrast, calling a POST request repeatedly may have side effects when creating the same resource multiple times.

Question 11

PATCH request

Answer 11

you only apply partial modifications to the resource.

Question 12

DELETE method (request)

Answer 12

delete the resource at the specified URL

Question 13

HEAD method

Answer 13

is almost identical to GET, except without the response body

In other words, if GET /users returns a list of users, then HEAD /users will make the same request but won’t get back the list of users.

HEAD requests are useful for checking what a GET request will return before actually making a GET request – like before downloading a large file or response body. Learn more about HEAD requests on MDN.

Question 14

OPTIONS request

Answer 14

should return data describing what other methods and operations the server supports at the given URL.

Question 15

Informational responses

Answer 15

(100–199)

Question 16

Successful responses

Answer 16

(200–299)

Question 17

Redirection messages

Answer 17

(300–399)

Question 18

Client error responses

Answer 18

(400–499)

Question 19

Server error responses

Answer 19

(500–599)

Question 20

What is javalin?

Answer 20

Javalin is a lightweight web framework for building modern, scalable, and high-performance web applications in Java and Kotlin. It is designed to be simple, intuitive, and easy to use, with a minimalistic API that is focused on getting things done quickly.

Question 21

Syntax: GET javalin instance

Answer 21

Javalin app = Javalin.create().start(7000);
app.get(“/”, ctx -> ctx.result(“Hello World”));
}

Question 22

What are the three main javalin handlers?

Answer 22

before-handlers, endpoint-handlers, and after-handlers.

Question 23

Before handlers

Answer 23

Before-handlers are matched before every request (including static files).

app.before(ctx -> {
// runs before all requests
});
app.before(“/path/*”, ctx -> {
//

Question 24

Endpoint handlers

Answer 24

Endpoint handlers are the main handler type, and defines your API. You can add a GET handler to server data to a client, or a POST handler to receive some data.

Endpoint-handlers are matched in the order they are defined.

app.get(“/output”, ctx -> {
// some code
ctx.json(object);
});

app.post(“/input”, ctx -> {
// some code
ctx.status(201);
});

Question 25

After handlers

Answer 25

After-handlers run after every request (even if an exception occurred). You might know after-handlers as filters, interceptors, or middleware from other libraries.

app.after(ctx -> {
// run after all requests
});
app.after(“/path/”, ctx -> {
// runs after request to /path/
});

Question 26

The before-, endpoint- and after-handlers require three parts:

Answer 26

A verb, one of: before, get, post, put, patch, delete, after (… head, options, trace, connect)
A path, ex: /, /hello-world, /hello/{name}
A handler implementation, ex ctx -> { … }, MyClass implements Handler, etc

Question 27

The Handler interface has a void return type. You use a method like _____________ to set the response which will be returned to the us

Answer 27

ctx.result(result), ctx.json(obj), or ctx.future(future)

Question 28

Describe Maven

Answer 28

Maven is a dependency manager and build automation tool for Java programs. Maven project configuration and dependencies are handled via the Project Object Model, defined in the pom.xml file. This file contains information about the project used to build the project, including project dependencies and plugins.

Question 29

What is a package?

Answer 29

A package is a collection of classes, interfaces, and enums in a hierarchial manner.

Question 30

Why packages?

Answer 30

Packages enable you to keep your classes separate from the classes in the Java API.
Packages allow you to reuse classes in other applications.
Packages allow you to distribute your classes to others.