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Spring Web
-Dobrin Horia
-Lefter Maria Izabela
-Manolache Antonia
-Maxim Robert-Gabriel
28th October 2024

Overview of the Spring
Framework and Its Ecosystem
The Spring Framework
? Definition: Spring is an open-source application
framework written in Java and initially created by Rod
Johnson in 2003. It provides comprehensive
infrastructure support for Java applications, primarily
for enterprise-level development.
? Purpose: It simplifies the development process by
providing an array of tools for managing the
complexity of enterprise applications. It offers
configurations for managing the components and
services, helping developers focus more on business
logic rather than boilerplate code.

Core Aspects of Spring
? Inversion of Control (IoC):
? Explanation: IoC is a design principle where the
control of object creation and dependency
management is passed to a container (the
Spring Framework) instead of being hard-coded.
Spring uses IoC to create and manage objects,
freeing developers from directly handling
dependencies.
? Dependency Injection (DI): A specific type of
IoC where dependencies are injected into an
object at runtime, enhancing modularity and
testability. For example, instead of creating a
new instance of a class, it can be injected into
another class that needs it.

? Aspect-Oriented Programming (AOP):
? Explanation: AOP is a programming
approach that allows the separation of cross-
cutting concerns (such as logging, transaction
management, and security) from business
logic, keeping code clean and focused.
? Example: Instead of writing logging code in
every method, AOP allows you to define
logging logic separately and apply it as an
aspect across different parts of the
application.

? Spring Boot:
? Purpose: Spring Boot is an extension of Spring,
designed to simplify application setup, especially for
web applications. It provides embedded servers, like
Tomcat, and preconfigured settings, reducing the
need for complex configurations.
? Why It Matters: Spring Boot lets developers create
production-ready applications quickly. For example,
you can start a web server with minimal
configuration, streamlining the development
process.
? Spring Modules and Extensions:
? Additional Modules: Spring Security (for
authentication and authorization), Spring Data (for
data access), Spring Batch (for batch processing),
and Spring Web (for web application development).

Importance of
Spring Web within
the Framework
Spring Web Module
? Overview: Spring Web is a core component of
the Spring Framework that provides the
essential tools for building robust web
applications. It��s built around the Model-View-
Controller (MVC) pattern, which separates the
application into three interconnected
components.
? MVC Architecture:
? Model: Represents the data or business
logic of the application.
? View: The user interface (UI), displaying
data and receiving user input.
? Controller: Manages interactions
between the Model and the View,
processing user input and updating the
View.

? Spring Boot Integration with Spring Web:
? Spring Boot simplifies setting up Spring
Web applications by offering preconfigured
templates, embedded servers, and auto-
configuration. This integration enables
faster, more efficient development cycles.
? Spring Web��s Role in RESTful Applications:
? REST Support: Spring Web supports REST
(Representational State Transfer), a popular
architectural style for APIs that allows web
services to communicate over HTTP. This
makes Spring Web ideal for developing
REST APIs, which are widely used in modern
web applications and microservices.

Key Benefits of Using Spring for Web
Development
Advantages of Spring for Web Development:
? Modularity: Spring's modular design allows developers to include only the modules they need, keeping applications lightweight and efficient.
? Dependency Injection:
? Why it��s Important: DI makes code easier to manage and test by allowing classes to receive dependencies from an external source rather than
creating them internally.
? Example: Suppose you have a service class that depends on a data access class. With DI, Spring automatically injects this dependency, decoupling the
classes and enabling flexible testing.
? Ease of Testing:
? Testing Support: Spring includes robust testing support, including JUnit and MockMvc, a tool for testing web controllers.
? Example: MockMvc allows testing of Spring MVC controllers without launching a web server, making unit and integration testing easier.
? Community and Documentation:
? Overview: Spring has an active and supportive community, vast online resources, and comprehensive documentation. This support network makes
troubleshooting and knowledge sharing accessible, which is essential for project scalability and new developers.
? Versatility:
? Applications: Spring��s flexibility allows it to support a wide variety of applications, from traditional monolithic apps to modern microservices.
? Example: A company using Spring can start with a monolithic architecture and gradually transition to microservices, reusing much of the same code
base due to Spring��s modularity.

Applications and Industries Where
Spring Web is Commonly Used
Industry-Specific Applications of Spring Web:
? E-commerce:
? Example: Companies like Amazon and eBay use Spring for managing large transaction volumes, handling thousands of concurrent users, and
implementing search and payment gateways.
? Finance and Banking:
? Example: Banks use Spring for handling sensitive data, managing transactions, and implementing secure APIs for mobile and web applications.
? Spring Security: An extension often used in these industries for secure authentication and authorization.
? Healthcare:
? Example: Many healthcare providers use Spring for patient management systems, appointment scheduling, and data protection compliant with
standards like HIPAA.
? Telecommunications:
? Example: Companies rely on Spring to build applications that can handle massive user data, handle customer management, and facilitate
seamless communication channels.

Core Components of Spring Web
1. DispatcherServlet
? Overview: The DispatcherServlet is the central component of the Spring Web MVC framework. It acts as the front controller, receiving incoming HTTP
requests and delegating them to the appropriate handler (controller).
? How It Works:
? Request Routing: When a request comes in, DispatcherServlet examines the URL pattern and determines which controller method should handle it.
? Handler Mapping: The DispatcherServlet consults handler mappings to match incoming requests to their corresponding handlers (controllers).
? View Resolution: After the controller processes the request, the DispatcherServlet selects an appropriate view (e.g., JSP, Thymeleaf) to render the
response.
? Example Flow:
? A user sends a request to /product/details.
? DispatcherServlet intercepts the request and uses handler mapping to direct it to a ProductController.
? After processing, it determines the view (e.g., a JSP page or a Thymeleaf template) to send back to the user.
? Benefits: It centralizes request processing, reduces complexity, and improves modularity within the application by clearly separating request routing
and handling.

2. Controllers
? Role of Controllers: Controllers are responsible for handling HTTP requests, processing data, and returning appropriate responses. They contain the
business logic and define how requests should be handled.
? @Controller Annotation:
? Purpose: Marks a class as a Spring MVC controller.
? Functionality: Each method within a @Controller class typically represents an endpoint (URL pattern) and processes HTTP requests (e.g., GET,
POST).
? Request Mapping: @RequestMapping is used to map URLs to specific methods within the controller, ensuring each request is routed to the correct
logic.
? Advantages: Organizes the application logic, making it modular and maintainable, as each controller is focused on a specific area (e.g., products,
users).

3. Views
? Overview: Views are responsible for presenting data to the user. In
Spring Web MVC, views are typically HTML pages created with a
templating engine (e.g., JSP or Thymeleaf).
? Types of View Templates:
? JSP (JavaServer Pages): A popular, Java-based template
engine often used with Spring MVC. JSP files mix HTML with
Java code to dynamically generate content.
? Thymeleaf: A modern templating engine specifically
designed for Spring applications. It offers a more natural
way to generate dynamic HTML content and is more flexible
and powerful than JSP.
? View Resolver: Spring��s view resolver component is responsible
for mapping logical view names (like ��productDetails��) to actual
view templates (like productDetails.html).
? Benefits: View templates separate presentation logic from
application logic, allowing frontend developers to work
independently on UI design without altering the backend code.

4. REST Controllers
? Overview: Unlike standard controllers that return views, REST controllers are designed to return data, typically in JSON or XML format, making them ideal
for RESTful web services and APIs.
? @RestController Annotation:
? Purpose: Marks a class as a RESTful controller, meaning each method returns data directly to the client, usually in JSON format.
? Key Difference from @Controller: Instead of returning a view, a @RestController method returns data (e.g., JSON or XML), which is usually consumed by
frontend applications or other systems.
? RESTful Endpoints:
? GET: Used to retrieve data. Example: GET /api/products returns a list of products.
? POST: Used to create new resources. Example: POST /api/products adds a new product.
? PUT: Used to update existing resources. Example: PUT /api/products/1 updates product with ID 1.
? DELETE: Used to delete resources. Example: DELETE /api/products/1 deletes product with ID 1.
? JSON Support: By default, Spring uses the Jackson library to automatically convert Java objects to JSON format, making it easier to build RESTful APIs.
? Advantages: REST controllers are essential for creating APIs that can interact with frontend applications, mobile apps, and other services, making Spring
Web highly versatile and suitable for modern architectures.

Key Features and Annotations
1. Annotations in Spring Web
? Annotations simplify the configuration and management of components in Spring Web by reducing XML configuration
and allowing configuration directly in code. Some key annotations in Spring Web are:
? @RequestMapping
? @GetMapping, @PostMapping, @PutMapping, @DeleteMapping
? @PathVariable
? @RequestParam
? @CrossOrigin
? @PatchMapping
? @RequestBody
? @ResponseBody
? @Service
? @Repository

? @RequestMapping:
? Purpose: Maps HTTP requests to
specific controller methods, letting
you define what URL patterns are
handled by which methods.
? Usage: It can be applied at both
class and method levels. When
applied at the class level, it specifies
the base path; when applied at the
method level, it further defines
specific actions.
? Advantages: @RequestMapping
provides flexibility for defining URL
structures and routing, making it
easier to build organized endpoints
in the application.

? @GetMapping, @PostMapping, @PutMapping, @DeleteMapping:
? Purpose: These annotations are specific shortcuts for @RequestMapping with HTTP
methods (GET, POST, PUT, DELETE), making it clear what type of request the method
handles.
? Benefits: Enhances code readability by specifying HTTP methods directly, helping
developers quickly identify the purpose of each method.

? @PathVariable:
? Purpose: Extracts values from the URI, allowing dynamic URL segments (e.g.,
/products/{
? Advantages: Simplifies the retrieval of dynamic data from URLs, improving the
flexibility and user-friendliness of APIs.id}).

? @RequestParam:
? Purpose: Binds query parameters from the URL to method parameters, commonly
used for optional values in the query string.
? Benefits: Facilitates passing additional optional data, such as search filters, through
URLs, making endpoints more versatile.

? @CrossOrigin
? Purpose: Enables Cross-Origin Resource Sharing (CORS) on specific endpoints, allow
? Usage: Often used in REST APIs to permit front-end applications on different domains
to access resources.ing requests from different origins.

? @PatchMapping
? Purpose: Maps HTTP PATCH requests to specific handler methods, used for partially
updating resources.
? Usage: Allows updating only certain fields of a resource without replacing the entire
resource.

? @RequestBody
? Purpose: Binds the body of an HTTP request to a Java object, commonly used in POST
and PUT requests for REST APIs.
? Usage: Essential for handling JSON or XML input in REST APIs.

? @ResponseBody
? Purpose: Indicates that the return value of a method should be written directly to the
HTTP res
? Usage: Commonly used in REST controllers for returning JSON data directly.ponse
body, rather than being interpreted as a view name.

? @Service
? Purpose: Marks a class as a service layer component in Spring��s architecture. It��s a
specialization of the @Component annotation, used specifically for business logic or
service classes.
? Usage: Indicates that this class contains business logic and acts as a middle layer
between controllers and repositories.
? Benefits: By marking a class with @Service, it becomes easy for Spring to identify it as
a service layer component, supporting better organization and easier application
testing. It also enables automatic detection of the class for dependency injection.

? @Repository
? Purpose: Marks a class as a Data Access Object (DAO) or repository layer component.
This annotation is also a specialization of @Component but is specifically used for
database access layers.
? Usage: Typically used in classes that interact directly with the database, such as those
using JPA or JDBC.
? Benefits: When a class is annotated with @Repository, Spring manages exceptions
more effectively by translating database-related exceptions into Spring's data access
exceptions. This makes error handling and debugging easier.

2. Configuration Options
? Spring offers flexible configuration options to cater to different application needs and
developer preferences.
? XML-based Configuration:
? Description: The original method for configuring Spring applications, where beans,
dependencies, and other settings are declared in XML files.
? Advantages: Allows separation of configuration from code and offers a centralized
place to view configurations.
? Drawbacks: Can become verbose and harder to maintain in large applications.

? Java-based Configuration:
? Description: Uses Java classes annotated with @Configuration to configure beans and
dependencies programmatically.
? Advantages: Offers type safety, readability, and is easier to refactor within IDEs. Also, changes in
code affect configuration directly, reducing redundancy.
? Spring Boot Auto-configuration:
? Purpose: Spring Boot automatically configures an application based on its dependencies. For
instance, if spring-boot-starter-web is included, it configures an embedded server (like Tomcat) and
default MVC setup.
? Advantages: Saves setup time, especially for simple or standardized applications, by reducing the
need for explicit configurations.

3. Dependency Injection (DI)
? Explanation: DI is a core feature of the Spring Framework that allows Spring to manage dependencies among
components by ��injecting�� them, promoting loose coupling and enhancing testability.
? How It Works:
? Dependencies are defined as beans in Spring, and Spring��s IoC container handles the injection of these beans
into classes that need them.
? @Autowired Annotation: This is a key annotation for DI in Spring. It allows Spring to automatically resolve and
inject a dependency bean into the specified field or constructor.
? Benefits of DI:
? Promotes modular and reusable code by decoupling components.
? Facilitates testing, as mock dependencies can easily replace real dependencies.
? Simplifies the management of complex dependencies across the application.

4. Middleware and Filters
? Middleware Concept:
? Middleware in web applications intercepts requests and responses, adding functionality like
logging, security, and performance monitoring. Spring Web supports middleware through filters
and interceptors.
? Filters:
? Purpose: A filter in Spring processes requests before they reach a servlet. It can modify requests
or responses and is often used for cross-cutting concerns like authentication or logging.
? Benefits: Filters are suitable for adding logic that applies globally to all requests, such as security
or logging.

? Interceptors:
? Purpose: Similar to filters, interceptors provide hooks for pre-processing and post-
processing requests at a higher level, just before and after the controller is called.
? Usage: Commonly used for handling authentication, measuring execution time, or
modifying request headers.
? Advantages: Provides a convenient way to add behavior before and after request
processing, specifically targeted to controller-level actions.

Demo
- https://docs.google.com/document/d/1uri5MOa-
LHdQXl1kMZdxYVcy8vE8zPs92KRgoDJQpzM/edit?usp=sharing

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Spring Web Presentation 123143242341234234

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