diff --git a/context-object/README.md b/context-object/README.md index 15848371b..711c91ddc 100644 --- a/context-object/README.md +++ b/context-object/README.md @@ -1,74 +1,49 @@ --- -title: Context object -category: Creational +title: Context Object +category: Behavioral language: en tags: -- Data access + - Context + - Decoupling + - Encapsulation --- -## Name / classification - -Context Object - ## Also known as -Context, Encapsulate Context +* Context +* Context Encapsulation +* Context Holder ## Intent -Decouple data from protocol-specific classes and store the scoped data in an object independent -of the underlying protocol technology. +Encapsulate the context (state and behaviors) relevant to the user or the request being processed in order to decouple application components from the complexities of the environment. ## Explanation Real-world example -> This application has different layers labelled A, B and C with each extracting specific information -> from a similar context for further use in the software. Passing down each pieces of information -> individually would be inefficient, a method to efficiently store and pass information is needed. +> This application has different layers labelled A, B and C with each extracting specific information from a similar context for further use in the software. Passing down each pieces of information individually would be inefficient, a method to efficiently store and pass information is needed. In plain words -> Create an object and store the data there and pass this object to where it is needed. +> Create an object to store the context data and pass it where needed. [Core J2EE Patterns](http://corej2eepatterns.com/ContextObject.htm) says -> Use a Context Object to encapsulate state in a protocol-independent way to be shared throughout your application. +> Use a Context Object to encapsulate state in a protocol-independent way to be shared throughout your application. **Programmatic Example** -We define what data a service context object contains. +Define the data that the service context object contains. ```Java +@Getter +@Setter public class ServiceContext { - String ACCOUNT_SERVICE, SESSION_SERVICE, SEARCH_SERVICE; - - public void setACCOUNT_SERVICE(String ACCOUNT_SERVICE) { - this.ACCOUNT_SERVICE = ACCOUNT_SERVICE; - } - - public void setSESSION_SERVICE(String SESSION_SERVICE) { - this.SESSION_SERVICE = SESSION_SERVICE; - } - - public void setSEARCH_SERVICE(String SEARCH_SERVICE) { - this.SEARCH_SERVICE = SEARCH_SERVICE; - } - - public String getACCOUNT_SERVICE() { - return ACCOUNT_SERVICE; - } - - public String getSESSION_SERVICE() { - return SESSION_SERVICE; - } - - public String getSEARCH_SERVICE() { - return SEARCH_SERVICE; - } - - public String toString() { return ACCOUNT_SERVICE + " " + SESSION_SERVICE + " " + SEARCH_SERVICE;} + String accountService; + String sessionService; + String searchService; } ``` @@ -83,10 +58,10 @@ public class ServiceContextFactory { } ``` -Instantiate the context object in the first layer and the adjoining layer upcalls the context in the current layer, which -then further structures the object. +Instantiate the context object in the first layer. The adjoining layer calls the context in the current layer, which then further structures the object. ```Java +@Getter public class LayerA { private static ServiceContext context; @@ -95,15 +70,12 @@ public class LayerA { context = ServiceContextFactory.createContext(); } - public static ServiceContext getContext() { - return context; - } - public void addAccountInfo(String accountService) { context.setACCOUNT_SERVICE(accountService); } } +@Getter public class LayerB { private static ServiceContext context; @@ -112,15 +84,12 @@ public class LayerB { this.context = layerA.getContext(); } - public static ServiceContext getContext() { - return context; - } - public void addSessionInfo(String sessionService) { context.setSESSION_SERVICE(sessionService); } } +@Getter public class LayerC { public static ServiceContext context; @@ -129,54 +98,71 @@ public class LayerC { this.context = layerB.getContext(); } - public static ServiceContext getContext() { - return context; - } - public void addSearchInfo(String searchService) { context.setSEARCH_SERVICE(searchService); } } ``` + Here is the context object and layers in action. ```Java -var layerA = new LayerA(); -layerA.addAccountInfo(SERVICE); -LOGGER.info("Context = {}",layerA.getContext()); -var layerB = new LayerB(layerA); -layerB.addSessionInfo(SERVICE); -LOGGER.info("Context = {}",layerB.getContext()); -var layerC = new LayerC(layerB); -layerC.addSearchInfo(SERVICE); -LOGGER.info("Context = {}",layerC.getContext()); +var layerA=new LayerA(); + layerA.addAccountInfo(SERVICE); + LOGGER.info("Context = {}",layerA.getContext()); + var layerB=new LayerB(layerA); + layerB.addSessionInfo(SERVICE); + LOGGER.info("Context = {}",layerB.getContext()); + var layerC=new LayerC(layerB); + layerC.addSearchInfo(SERVICE); + LOGGER.info("Context = {}",layerC.getContext()); ``` Program output: ```Java -Context = SERVICE null null -Context = SERVICE SERVICE null -Context = SERVICE SERVICE SERVICE +Context=SERVICE null null + Context=SERVICE SERVICE null + Context=SERVICE SERVICE SERVICE ``` ## Class diagram ![alt text](./etc/context-object.png "Context object") -## Application +## Applicability -Use the Context Object pattern for: - -* Sharing information across different system layers. -* Decoupling software data from protocol-specific contexts. -* Exposing only the relevant API's within the context. +* When there is a need to abstract and encapsulate context information from different parts of an application to avoid cluttering the business logic with environment-specific code. +* In web applications, to encapsulate request-specific information and make it easily accessible throughout the application without passing it explicitly between functions or components. +* In distributed systems, to encapsulate contextual information about the task being performed, user preferences, or security credentials, facilitating their propagation across different components and services. ## Known uses + +* Web application frameworks often implement a Context Object to encapsulate HTTP request and response objects, session information, and other request-specific data. +* Enterprise applications use Context Objects to manage and propagate transactional information, security credentials, and user-specific settings across different layers and services. * [Spring: ApplicationContext](https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/context/ApplicationContext.html) * [Oracle: SecurityContext](https://docs.oracle.com/javaee/7/api/javax/ws/rs/core/SecurityContext.html) * [Oracle: ServletContext](https://docs.oracle.com/javaee/6/api/javax/servlet/ServletContext.html) +## Consequences + +Benefits: + +* Decoupling: Components and services are decoupled from the specificities of the execution environment, enhancing modularity and maintainability. +* Centralization: Contextual information is centralized in one place, making it easier to manage, access, and debug. +* Flexibility: The pattern allows for flexible and dynamic context management, which can adapt to changes in the environment or requirements. + +Trade-offs: + +* Overhead: Introducing a Context Object can add overhead in terms of performance, especially if not implemented efficiently. +* Complexity: If the Context Object is not well-designed, it can become a bloated and complex monolith, difficult to manage and understand. + +## Related Patterns + +* [Singleton](https://java-design-patterns.com/patterns/singleton/): The Context Object is often implemented as a Singleton to ensure a global point of access. +* [Strategy](https://java-design-patterns.com/patterns/strategy/): Context Objects can use Strategies to adapt their behavior based on the context they encapsulate. +* [Decorator](https://java-design-patterns.com/patterns/decorator/): Can be used to dynamically add responsibilities to the Context Object. + ## Credits * [Core J2EE Design Patterns](https://amzn.to/3IhcY9w) diff --git a/context-object/src/main/java/com/iluwatar/context/object/ServiceContext.java b/context-object/src/main/java/com/iluwatar/context/object/ServiceContext.java index dcd4e1450..2092ddf78 100644 --- a/context-object/src/main/java/com/iluwatar/context/object/ServiceContext.java +++ b/context-object/src/main/java/com/iluwatar/context/object/ServiceContext.java @@ -26,7 +26,6 @@ package com.iluwatar.context.object; import lombok.Getter; import lombok.Setter; -import lombok.ToString; /** * Where context objects are defined.