DWP 8.1

What is web programming?

Web programming is the practice of creating applications that run on the internet, accessed by users through web browsers. It includes both static web pages and dynamic web applications.

What is TCP/IP?

TCP/IP (Transmission Control Protocol/Internet Protocol) is the fundamental communication protocol suite of the internet. TCP breaks data into packets, sends them, and reassembles them; IP handles addressing and routing.

What is DNS?

DNS (Domain Name System) is the "phone book" of the internet. It translates human-readable domain names (like google.com) into numerical IP addresses that computers use to locate each other.

What is HTTP/HTTPS?

HTTP (Hypertext Transfer Protocol) is the set of rules for formatting and transmitting messages on the web. HTTPS is the secure version where the messages are encrypted.

What are HTML, CSS, and JavaScript?

HTML (HyperText Markup Language) defines the structure of a web page; CSS (Cascading Style Sheets) controls the styling (colors, layout); JavaScript adds interactivity and dynamic behavior.

What is client‑server architecture?

It is a model where the client (e.g., a web browser) sends requests to a server, and the server processes the requests and returns responses. The two roles are separate and can evolve independently.

What is an API?

An API (Application Programming Interface) is a contract or set of rules that allows one software program to interact with another. It defines what requests can be made and what responses to expect.

What is a REST API?

A REST API is an API that follows the REST (Representational State Transfer) architectural style. It uses standard HTTP methods, URIs, and is stateless, making it simple, scalable, and reliable.

What are the six constraints of a RESTful system?

1. Uniform Interface – consistent conventions. 2. Stateless – no client context stored on server. 3. Cacheable – responses can be cached. 4. Client‑Server – separation of concerns. 5. Layered System – intermediaries can be used. 6. Code on Demand (optional) – server can send executable code.

What does "stateless" mean in REST?

Stateless means that the server does not remember anything about the client from one request to the next. Every request must contain all the information the server needs to process it.

What are the five main HTTP methods and their CRUD equivalents?

GET = Read (retrieve a resource); POST = Create (create a new resource); PUT = Update (replace entire resource); PATCH = Update (partial modification); DELETE = Delete (remove a resource).

What should be the format of REST endpoint URLs?

Endpoints should use nouns (resources) rather than verbs (actions). For example, use /todos instead of /getAllTodos.

Should REST resource names be singular or plural?

Use plural nouns for resource names to keep it simple and consistent, e.g., /todos, /users, /items.

What is the rule about GET and state changes?

GET should never change the state of a resource. It must be used only for retrieval. Any state change should use POST, PUT, PATCH, or DELETE.

How do you specify data formats in a REST API?

Use HTTP headers: Content-Type defines the format of the request body (e.g., application/json); Accept defines the desired format of the response.

How do you represent relationships between resources in REST?

Use sub-resources (nested URLs). For example, GET /todos/923/items retrieves all items belonging to todo #923.

What is API versioning and how is it done?

API versioning is a way to manage changes without breaking existing clients. It is often done by including the version in the URL, e.g., /api/v1/. Use whole numbers, not decimals.

How do you allow sorting in a REST API?

Use query parameters. For example, GET /items?cost for ascending by cost, and GET /items?-cost,+color for descending by cost then ascending by color.

What is paging in a REST API?

Paging is a technique to return large result sets in smaller, manageable chunks. It is often implemented with limit and offset parameters, e.g., GET /items?limit=20&offset=10.

What are HTTP status code categories?

1xx: Informational; 2xx: Success; 3xx: Redirection; 4xx: Client Error; 5xx: Server Error.

What does status code 200 OK mean?

The request succeeded and the response contains the requested data.

What does status code 201 Created mean?

The request succeeded and a new resource was created.

What does status code 400 Bad Request mean?

The server could not understand the request due to invalid syntax (client error).

What does status code 401 Unauthorized mean?

The client must authenticate itself to get the requested response.

What does status code 403 Forbidden mean?

The client does not have access rights to the content.

What does status code 404 Not Found mean?

The server cannot find the requested resource.

What does status code 500 Internal Server Error mean?

The server encountered a situation it doesn't know how to handle (server error).

What is Spring Boot?

Spring Boot is a Java framework for building server-side web applications. It simplifies development with auto-configuration, embedded servers (like Tomcat), and pre-built components.

What is JHipster?

JHipster is a code generator that creates a complete, modern, production-ready web application template. It uses Spring Boot for the backend and a frontend framework like Angular, React, or Vue.

What are the main benefits of using JHipster?

JHipster saves time (hundreds of hours), follows industry standards, includes REST server, CRUD UI, login and admin UI, and serves as an excellent template for learning best practices.

What backend technologies does a JHipster‑generated app include?

Java/Spring Boot, Hibernate/JPA (for ORM), Liquibase (for database schema management), Swagger (for API documentation), and JWT (for authentication).

What is JDL?

JDL (JHipster Domain Language) is a simple, human-readable language used to describe the data model (entities, fields, relationships) of a JHipster application. JHipster then generates all the corresponding code.

What is an entity in JDL?

An entity represents a main concept or business object (e.g., Customer, Product). In the database it becomes a table; in Java it becomes a class; in the frontend it becomes a management UI.

What are fields in JDL?

Fields define the attributes of an entity. Each field has a name and a type (e.g., String, Integer). They become columns in the database table.

What field modifiers are available in JDL?

required (cannot be null/empty), unique (value must be unique), minlength(n) / maxlength(n) (string length constraints), and min(x) / max(y) (numeric bounds).

How do you define a relationship between entities in JDL?

Use the relationship keyword followed by the relationship type (e.g., OneToOne, OneToMany, ManyToOne, ManyToMany) and the entity links. Example: relationship OneToOne { Car{theEngine(engineNumber)} to Engine }.

Can you modify the built-in User entity in JHipster?

No, the built-in User entity is fixed. To add custom fields to a user, create a new entity (e.g., UserExtra) and link it to User with a one-to-one relationship using the builtInEntity keyword.

What is pagination in JDL and what options exist?

Pagination controls how large lists are fetched. Options: pagination (buttons), infinite-scroll (loads on scroll), no (all records at once).

What is a service layer and how do you enable it in JDL?

A service layer contains business logic separate from the REST controller. In JDL, use service all with serviceClass to generate a service for all entities.

What are DTOs and how are they used in JDL?

DTOs (Data Transfer Objects) are custom objects that shape data for the frontend. They improve security and control. In JDL, dto all with mapstruct generates DTOs and uses MapStruct to automatically map between DTOs and entities.

What does the JDL option dto all with mapstruct do?

It creates Data Transfer Objects for all entities and configures MapStruct, a Java library, to automatically convert between the DTO and the database entity.

What is the time constant in an RC circuit?

The time constant τ (tau) is the time required to charge a capacitor to about 63.2% of its final voltage, given by τ = R * C.

Define electric charge.

Electric charge is a fundamental property of matter that causes it to experience a force in an electromagnetic field, measured in coulombs (C).

What is the formula for energy stored in a capacitor?

E = (1/2) * C * V^2, where E is energy (joules), C is capacitance (farads), V is voltage (volts).