docs: improvements to the Context Object docs

Author: iluwatar

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)

context-object/src/main/java/com/iluwatar/context/object/ServiceContext.java

@@ -26,7 +26,6 @@
 
 import lombok.Getter;
 import lombok.Setter;
-import lombok.ToString;
 
 /**
  * Where context objects are defined.