How can you restrict access to resources and services with the Proxy pattern?

Proxy pattern is extensively used in many frameworks like Spring. This is a great way to implement cross cutting concerns like transaction, security, tracing etc. E.g. one can create Proxy for bean/ service classes and add common code like metrics, caching etc. within it. A developer using that proxied beans/ services will take the advantage of common features without the need to implement them.

The Proxy pattern is one of the 23 software design patterns described in the 1994 book "Design Patterns: Elements of Reusable Object-Oriented Software" by the "Gang of Four" aka GoF. The Proxy class implements the Subject interface and has a reference to the RealSubject class. Proxy class can act as a substitute for Subject objects and forward requests to the RealSubject object. The Decorator pattern is another very similar structural design pattern. A Proxy restricts access to its delegate functionality while Decorator enhances what its delegate does. Unlike Delegate, Proxy knows the concrete type of its delegate. The Decorator forwards requests to its delegate, while the Proxy responds instead and may not even instantiate it.

The Proxy pattern creates a proxy object that acts as an intermediary between the client and the real object, providing additional functionality and controlling access. Its aim is to provide greater flexibility and extensibility, and it is commonly used in remote, virtual, caching, and protection proxies.

A structural design pattern called the Proxy pattern acts as a stand-in or placeholder for another object, allowing access control over that item. Put otherwise, the proxy serves as a middleman between a client and the real object, giving the proxy the ability to control access to the real object or add more functionality. When an object is expensive to generate or you wish to add functionality before or after accessing the object, this pattern might be helpful in controlling access to the object.

The Proxy pattern controls access to resources or services by introducing a proxy class between the client and the real object. This proxy enforces access restrictions or adds functionality. Here's a brief summary: Define an interface for the resource or service. Create the real object implementing the interface. Develop a proxy class that also adheres to the interface. Apply access control logic in the proxy, making decisions based on user credentials, roles, or other criteria. Use the proxy in place of direct calls to the real object in your application. It's useful for access control, resource management, and added functionality.

The Proxy pattern is a structural design pattern that acts as a gatekeeper for controlling access to resources. It allows you to create a proxy object with the same interface as the original subject but with added logic or functionality to manage access. In a practical scenario, you can use the Proxy pattern to implement access control for downloadable resources on a website, distinguishing between free and premium users.

The Proxy pattern enhances control, security, and resource management, while also offering performance improvements, simplification, and dynamic behavior, making it a versatile pattern for a variety of software design and architectural scenarios.

The proxy can perform various tasks such as lazy loading, access control, logging, or caching, without the client being aware of it.

The Proxy pattern helps create a security layer that can be easily adapted to changes in the backend service. It allows you to separate security concerns from the actual service provided by the real objec

Pros: Security: It helps keep your stuff safe from the wrong things. Speed: It makes things work faster by remembering what it did before. Logging: It writes down what it's doing, like a diary, which helps figure out problems. Saves Memory and Time: It's like a helper that saves your computer's memory and makes it work faster. Cons: Adds complexity: Sometimes, it makes things more complicated. Slows things down: In some cases, it might not make things faster but slower. More work: It's like having an extra helper, but sometimes you might not need one. Costs: It might be expensive to use, especially in really big systems.

Create an intermediary object that act as an interface to actual/ targeted object. This intermediary will provides a surrogate for the real component and protects it from the underlying complexity.

Proxy pattern is not only limited within the same module. It can also be applied as a reverse proxy such as mod_proxy in Apache HTTPD, Envoy proxy, Zuul proxy. Common cross cutting concerns are: Authentication - Login Authorization - Entitlement including functional entitlement and data entitlement Input validation - Check for cross cutting patterns such as Cross Site Scripting, SQL Injection, etc. Resource Caching - Cache static resources such as images, JavaScript files, etc

One real-life example of the Proxy Pattern can be the use of a credit card. Consider the situation where you want to make a purchase using a credit card. You don't directly interact with the actual account or money. Instead, you use the proxy, which is the credit card, to complete the transaction. The credit card acts as a proxy to your bank account. Here's how it maps to the Proxy Pattern: Real Subject: The actual bank account Proxy: The credit card, which represents and stands in place of the bank account. Client: You In this scenario, the proxy (credit card) handles tasks such as verifying your identity, checking your available credit, and processing the transaction, without exposing the complexity of accessing your actual bank account

An example of a proxy pattern is the WCF client proxy which communicates with the remote service. This is a type of a remote proxy pattern . It hides the serialisation details from the client , takes the input and sends a SOAP request in case of a SOAP based service. Another example is a cache proxy pattern where a client proxy caches frequently requested information. If the data requested has been recently cached and the parameters match the data is served locally and round trip to server is not required Smart proxies can be used for Authorization checks, logging and auditing prior to access.

The Proxy pattern is widely used in popular Java frameworks. The class java.lang.reflect.Proxy and CGLIB proxy are essential parts of any framework including Spring Framework, Hibernate ORM and Mockito. The proxy concept is not limited to object-oriented programming. Eg, Popular web-server Nginx can also serve as a proxy to other web-servers, while limiting access with authentication, by IP addresses, by geographical location, by request rate. Enabling Nginx caching allows the proxy server to cache certain website dynamic content to improve performance.

Load balancing is a crucial aspect of modern software systems that handle high volumes of traffic. It ensures that the workload is distributed evenly across multiple servers, preventing any single server from becoming overwhelmed. In Java, one popular technique for implementing load balancing is through the use of the Proxy Pattern. The Proxy Pattern is a design pattern that allows for the creation of a surrogate or placeholder object. This object acts as an intermediary between the client and the actual object, providing additional functionality such as caching, logging, or load balancing.

Cache Proxy - stores the results of expensive operations and returns cached results when the same operation is requested again. This can greatly improve the performance of database queries or web service calls. Lazy Loading Proxy - a lazy loading proxy can be used to load related objects from the database only when they are actually needed. This can reduce the amount of data fetched from the database and improve performance. Smart Reference Proxy - smart reference proxies are used in distributed systems to keep track of references to objects that exist remotely. They can optimize network traffic by managing object references intelligently.

Proxy is a good candidate whenever the source or consumer should not be directly connected with the service provider, because the provider can change in future. It can be either the provider itself, or its interface points or other functionality concerned. If the consumer is built by directly binding it with the producer, any future change in the latter, will impact the former. In such cases having a proxy between the two will help minimize or nullify the impact on the consumer when the producer undergoes changes. From my experience: intranet apps won't connect to 3rd party services directly but via a proxy, to help centralized logging, data validation, authn, ability to change the vendor/vendor interface without updating internal apps.

How to connect without proxy when Connection is made through proxy or v others Just a simple concern data connection ??

The proxy pattern is applied in projects when constructing the structure of your application. The main service object will implement your primary business logic, while adding one or more proxies to perform cross cutting or non-business logic helps simplify your application design. Adding a security proxy and then a logging and then a caching proxy adds additional functionality without getting in the way of straightforward business logic design and without modification to your existing objects. During initialization of your application, chaining the proxy objects is typically done and then passing the first proxy in the chain in place of the original object. Using frameworks that use inversion of control is a common implementation.

Implement a logging proxy to keep track of method invocations and their parameters. This can be useful for creating an audit trail, debugging, and performance monitoring.

There are many use cases of proxy usage like other contributors said. Some more examples of proxy pattern implementation like API gateway to rate-limit and authenticate API calls. A proxy can even implement interfaces from multiple subjects to act as a facade to provide an aggregated view of underlying abstractions. The essence of proxy pattern is to wrap the real subject with the same interface to control the pre and post condition of the logic.

In terms of implementation, the proxy object should have the same interface as the real object so that the client can use it without knowing that it is a proxy. The proxy object should also be able to create the real object only when it is needed. To restrict access to resources and services with the Proxy pattern, we can create a proxy object that performs additional checks before allowing the client to access the real object. For example, we can create a proxy object that checks the user’s role or permissions before allowing them to access certain resources or services. We can also create a proxy object that caches frequently accessed resources to improve performance.