Learn Jakarta EE: From Zero to Enterprise Application Master
Goal: Deeply understand the Jakarta EE platform and its core specifications—Jakarta Servlets, Contexts and Dependency Injection (CDI), and Jakarta Persistence API (JPA). This learning path will guide you from the foundational principles of enterprise Java to building robust, scalable, and maintainable applications, enabling you to master the “why,” “what,” and “how” of modern enterprise Java development without relying on external frameworks like Spring.
Why Jakarta EE Matters
In the world of enterprise software, Jakarta EE (formerly Java EE) is the bedrock. While many developers flock to Spring, Jakarta EE provides the standard specifications that define how Java enterprise applications should work. It’s the “blueprint” of the industry.
Understanding Jakarta EE means you aren’t just learning a tool; you’re learning the fundamental architecture of the JVM’s enterprise ecosystem.
- Standardization: Your code is portable across runtimes (GlassFish, Payara, WildFly, Open Liberty).
- Stability: Specifications move at a deliberate pace, ensuring long-term maintainability for systems that must last decades.
- Modernity: Jakarta EE 10+ has fully embraced cloud-native patterns, microservices (via the Core Profile), and modern Java features like Records and Sealed Classes.
- The Foundation: Most popular frameworks (including Spring) are built on top of these standards (like Servlets and JPA).
The Architecture: The Container Model
The most important concept in Jakarta EE is the Container. You don’t “run” a Jakarta EE app; you deploy it into a container that provides services (Security, Transactions, Injection) so you can focus solely on business logic.
+-------------------------------------------------------------+
| Jakarta EE Runtime |
| (WildFly / GlassFish / Open Liberty / Payara / Tomee) |
| |
| +-----------------------+ +-------------------------+ |
| | Web Container | | CDI Container | |
| | (Servlets, JAX-RS) | | (Dependency Injection) | |
| +-----------------------+ +-------------------------+ |
| | | |
| +--------------+---------------+ |
| | |
| +------------------------------+ |
| | Persistence Provider | |
| | (JPA / Hibernate) | |
| +------------------------------+ |
+-------------------------------------------------------------+
Core Concept Analysis
1. Jakarta Servlets: The Gateway
Servlets handle the “plumbing” of the web. They manage the lifecycle of an HTTP request: from the socket connection to the final byte sent back to the browser.
Request --> [Filter] --> [Servlet Service Method] --> [Response]
| |
+------------------+--> [Session Management]
2. Jakarta CDI: The Glue
CDI (Contexts and Dependency Injection) is the “Type-Safe Glue” of your application. It manages which object talks to which, and how long those objects live (Scopes).
3. Jakarta JPA: The Bridge
JPA (Jakarta Persistence) maps the “Object” world of Java to the “Relational” world of SQL. It handles the “Object-Relational Impedance Mismatch.”
Concept Summary Table
| Concept Cluster | What You Need to Internalize |
|---|---|
| The Container | Code doesn’t live in isolation. It relies on the runtime to manage lifecycle and services. |
| Servlet Lifecycle | init(), service(), destroy(). Understanding the single-instance, multi-threaded nature of Servlets. |
| CDI Scopes | @RequestScoped vs @SessionScoped vs @ApplicationScoped. Where state lives and for how long. |
| Entity State | Transient, Managed, Detached, Removed. The “Magic” of the Persistence Context. |
| JTA Transactions | Atomicity across the enterprise. How @Transactional actually works under the hood. |
Deep Dive Reading by Concept
Foundation & Web
| Concept | Book & Chapter |
|---|---|
| Servlet Fundamentals | “Beginning Jakarta EE” by Juneau — Ch. 3: “Java Servlets” |
| Request/Response Lifecycle | “The Jakarta EE Tutorial” — Part II: “Web Tier” |
Dependency Injection
| Concept | Book & Chapter |
|---|---|
| CDI Basics | “Beginning Jakarta EE” by Juneau — Ch. 7: “Contexts and Dependency Injection” |
| Advanced CDI (Events/Interceptors) | “CDI in Action” by Antoine Sabot-Durand — Ch. 4 & 5 |
Persistence
| Concept | Book & Chapter |
|---|---|
| Entity Mapping | “Pro JPA 2” by Merrick — Ch. 4: “Mapping” |
| Querying (JPQL/Criteria) | “Java Persistence with Hibernate” by Bauer/King — Ch. 14: “Object-Relational Querying” |
Project List
Project 1: The Request-Response Log Analyzer (Zero-Library Web)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin, Scala
- Coolness Level: Level 2: Practical but Forgettable
- Business Potential: 1. The “Resume Gold”
- Difficulty: Level 1: Beginner
- Knowledge Area: Web / HTTP Internals
- Software or Tool: Jakarta Servlet 6.0
- Main Book: “Beginning Jakarta EE” by Juneau
What you’ll build: A specialized web gateway that intercepts all incoming requests, parses headers, inspects query parameters, and generates a visual dashboard of “Traffic Health” using only standard Servlets and Filters.
Why it teaches Jakarta EE: This forces you to handle raw HttpServletRequest and HttpServletResponse objects. You’ll learn the Servlet Filter chain—the foundation of all security and logging frameworks in the Java world.
Project 2: The Modular Enterprise Registry (CDI Architecture)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 3: Genuinely Clever
- Business Potential: 1. The “Resume Gold”
- Difficulty: Level 2: Intermediate
- Knowledge Area: Software Architecture / Dependency Injection
- Software or Tool: Jakarta CDI 4.0 (Weld)
- Main Book: “CDI in Action” by Antoine Sabot-Durand
What you’ll build: A modular system for a company that manages different types of “Resources” (Employees, Vehicles, Computers). The system must allow adding new resource types via “Plugins” (CDI Beans) without modifying the main registry logic.
Why it teaches Jakarta EE: CDI is the heart of Jakarta EE. This project moves you beyond simple “@Inject” and into the “Contextual” part of CDI. You’ll learn how the container finds beans, how to use Qualifiers to choose implementations at runtime, and how Scopes manage object lifecycles.
Project 3: The Transactional Ledger (JPA Persistence)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 3: Genuinely Clever
- Business Potential: 3. The “Service & Support” Model
- Difficulty: Level 3: Advanced
- Knowledge Area: Databases / Persistence / Transactions
- Software or Tool: Jakarta Persistence 3.1 (Hibernate/EclipseLink)
- Main Book: “Pro JPA 2” by Merrick
What you’ll build: A double-entry bookkeeping system where “Transactions” move “Value” between “Accounts”. It must handle complex relations, ensure ACID compliance, and use JPQL for financial reporting.
Why it teaches Jakarta EE: Persistence is where most enterprise apps fail. You’ll learn the “EntityManager” lifecycle, how to map complex relationships without creating “N+1” query problems, and how JTA (Jakarta Transactions) ensures your data isn’t corrupted if a server crashes mid-transfer.
Project 4: The Enterprise Audit Log (CDI Interceptors)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 3: Genuinely Clever
- Business Potential: 3. The “Service & Support” Model
- Difficulty: Level 2: Intermediate
- Knowledge Area: Aspect-Oriented Programming (AOP) / CDI
- Software or Tool: Jakarta CDI 4.0
- Main Book: “CDI in Action” by Antoine Sabot-Durand
What you’ll build: A cross-cutting security engine using a custom @Audit annotation. When placed on any method, it automatically logs the call, parameters, and outcome without writing logging code inside the business method.
Project 5: Multi-tenant SaaS Inventory (Advanced JPA)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 4: Hardcore Tech Flex
- Business Potential: 5. The “Industry Disruptor”
- Difficulty: Level 4: Expert
- Knowledge Area: Databases / Multi-tenancy / Dynamic Querying
- Software or Tool: Jakarta Persistence 3.1
- Main Book: “High-Performance Java Persistence” by Vlad Mihalcea
What you’ll build: A SaaS Inventory system sharing one database between multiple tenants. You’ll implement isolation and a search engine using the JPA Criteria API.
Project 6: Event-Driven Notification Engine (CDI Events)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 3: Genuinely Clever
- Business Potential: 2. The “Micro-SaaS”
- Difficulty: Level 2: Intermediate
- Knowledge Area: Reactive Programming / Decoupling
- Software or Tool: Jakarta CDI 4.0
- Main Book: “CDI in Action” by Antoine Sabot-Durand
What you’ll build: A decoupled system where an “Order Placed” event triggers emails, analytics, and dashboard updates via CDI @Observes without the core service knowing about the listeners.
Project 7: Clean RESTful API (JAX-RS + Bean Validation)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 3: Genuinely Clever
- Business Potential: 2. The “Micro-SaaS”
- Difficulty: Level 2: Intermediate
- Knowledge Area: Web APIs / Validation / Error Handling
- Software or Tool: Jakarta REST (JAX-RS) 3.1 / Jakarta Bean Validation 3.0
- Main Book: “Beginning Jakarta EE” by Juneau
What you’ll build: A robust Support Ticket API using JAX-RS. Focus on automatic validation of input DTOs and standardized JSON error mapping using ExceptionMapper.
Project 8: Secure Banking Portal (Jakarta Security)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 4: Hardcore Tech Flex
- Business Potential: 3. The “Service & Support” Model
- Difficulty: Level 3: Advanced
- Knowledge Area: Security / Authentication
- Software or Tool: Jakarta Security 3.0
- Main Book: “Beginning Jakarta EE” by Juneau
What you’ll build: A bank portal where security is handled entirely by the container. You’ll use @DatabaseIdentityStoreDefinition to link users to your database and @RolesAllowed to protect methods.
Project 9: Distributed Transaction Workflow (JTA)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 4: Hardcore Tech Flex
- Business Potential: 4. The “Open Core” Infrastructure
- Difficulty: Level 4: Expert
- Knowledge Area: Distributed Transactions / Reliability
- Software or Tool: Jakarta Transactions (JTA) 2.0
- Main Book: “Java Transaction Design Strategies” by Mark Little
What you’ll build: A complex workflow system where a single business action must update two different databases (e.g., Inventory and Fulfillment) atomically using the Two-Phase Commit (2PC) protocol managed by JTA.
Project 10: Real-time Async Order Processor (Jakarta Messaging)
- File: JAKARTA_EE_ENTERPRISE_MASTERY.md
- Main Programming Language: Java
- Alternative Programming Languages: Kotlin
- Coolness Level: Level 4: Hardcore Tech Flex
- Business Potential: 4. The “Open Core” Infrastructure
- Difficulty: Level 3: Advanced
- Knowledge Area: Messaging / Asynchronous Processing
- Software or Tool: Jakarta Messaging (JMS) 3.1
- Main Book: “Beginning Jakarta EE” by Juneau
What you’ll build: A high-throughput order processor that uses JMS Queues and Message-Driven Beans (MDBs) to process orders asynchronously, ensuring no data is lost even during high traffic spikes.
Project Comparison Table
| Project | Difficulty | Time | Depth of Understanding | Fun Factor |
|---|---|---|---|---|
| 1. Log Analyzer | Level 1 | Weekend | HTTP Lifecycle | 3/5 |
| 2. CDI Registry | Level 2 | 1 Week | Decoupling | 4/5 |
| 3. Ledger | Level 3 | 2 Weeks | ACID / ORM | 3/5 |
| 4. Audit Interceptor | Level 2 | 4 Days | AOP / Containers | 5/5 |
| 5. Multi-tenant SaaS | Level 4 | 3 Weeks | Architecture | 4/5 |
| 6. Event Engine | Level 2 | 1 Week | Reactive Design | 4/5 |
| 7. Support API | Level 2 | 1 Week | API Standards | 3/5 |
| 8. Secure Bank | Level 3 | 1 Week | Security | 3/5 |
| 9. JTA Workflow | Level 4 | 2 Weeks | Reliability | 2/5 |
| 10. JMS Processor | Level 3 | 2 Weeks | Async Messaging | 5/5 |
Recommendation
If you are a Spring developer: Start with Project 4 (Interceptors) and Project 6 (Events). This will reveal the “magic” behind Spring’s @Transactional and @EventListener by showing you the standard Jakarta EE way of doing it.
If you are a Beginner: Start with Project 1 (Servlets). Understanding the request lifecycle is the foundation for everything else.
Final Overall Project: The Enterprise ERP Backbone
What you’ll build: A comprehensive ERP (Enterprise Resource Planning) system that integrates all previous projects. It will have a REST API (Project 7), multi-tenancy for different companies (Project 5), a secure banking/payment module (Project 8), a messaging-based shipping processor (Project 10), and a full audit trail (Project 4).
Success Criteria:
- All components are loosely coupled via CDI Events.
- Security is handled via the container (no custom login filters).
- The system survives a database crash mid-transaction without losing data (JTA).
- Deployable to a standard Jakarta EE server without any external dependencies besides the JDBC driver.
Summary
This learning path covers Jakarta EE through 10 hands-on projects. Here’s the complete list:
| # | Project Name | Main Language | Difficulty | Time Estimate |
|---|---|---|---|---|
| 1 | Log Analyzer | Java | Beginner | Weekend |
| 2 | CDI Registry | Java | Intermediate | 1 Week |
| 3 | Ledger | Java | Advanced | 2 Weeks |
| 4 | Audit Interceptor | Java | Intermediate | 5 Days |
| 5 | Multi-tenant SaaS | Java | Expert | 3 Weeks |
| 6 | Event Engine | Java | Intermediate | 1 Week |
| 7 | Support API | Java | Intermediate | 1 Week |
| 8 | Secure Bank | Java | Advanced | 1 Week |
| 9 | JTA Workflow | Java | Expert | 2 Weeks |
| 10 | JMS Processor | Java | Advanced | 2 Weeks |
Expected Outcomes
After completing these projects, you will:
- Understand the JVM’s Enterprise Container model.
- Master the three pillars: Servlets (Web), CDI (Injection), and JPA (Data).
- Be able to build robust, distributed systems using only standards.
- Understand the “Magic” behind modern Java frameworks.
- Be fully prepared for Senior Java Backend Engineer interviews.
You’ll have built 10 working projects that demonstrate deep understanding of Jakarta EE from first principles.