Spring is not 100% a replacement for Java EE — but it replaces almost all of Java EE’s painful parts and only relies on a few foundational Java EE/Jakarta EE APIs underneath.

Let’s break it down clearly.

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Is Spring a full replacement for J2EE?

• Practically YES (for most developers).
• Technically NO (because Spring still uses a few underlying Java EE/Jakarta EE specs).

Spring was created specifically to replace the heavyweight parts of J2EE such as:

• EJB (Enterprise JavaBeans)
• J2EE container-managed transactions
• J2EE security
• J2EE messaging complexity
• XML-heavy configuration
• Vendor-specific application servers

Spring became the mainstream choice because it solves all those problems.

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What parts of J2EE does Spring replace?

J2EE Component	Spring Replacement
EJB	Spring Beans, @Service, @Transactional
JSP/JSF/Servlet MVC complexity	Spring MVC (@RestController)
JTA (complex transactions)	Simplified Spring Tx + declarative transactions
JMS API complexity	Spring JMS abstractions
Security	Spring Security
JAX-RS	Spring Web (REST controllers)
Application Server (JBoss, WebLogic)	Embedded Tomcat/Jetty with Spring Boot

Spring basically eliminated the need for:

• EAR files

• WAR deployment to app servers

• EJB containers

• JNDI hell

• XML descriptors

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What parts of J2EE/Jakarta EE does Spring still depend on?

This is important:

✔ Spring still uses Servlet API

Even Spring MVC runs inside the Java EE Servlet model:

• javax.servlet.* (Java EE era)

• jakarta.servlet.* (Jakarta EE era)

Servlet API provides:

• Request/response handling

• Filters

• Dispatchers

• Underlying HTTP model

Spring Boot bundles embedded Tomcat/Jetty which implement this API.

✔ Spring integrates with JPA API

Spring Data JPA uses:

• jakarta.persistence.*
  JPA is still a Java EE/Jakarta spec, implemented by Hibernate, EclipseLink, etc.

✔ Spring integrates with JTA (optional)

If distributed transactions are needed.

✔ Spring can use JMS API

Spring JMS wraps JMS (Java Message Service).

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Important distinction

Spring does NOT require a Java EE Application Server.

Everything can run with:

• Embedded Tomcat
• Jetty
• Undertow
• Netty (for WebFlux)

This is why Spring revolutionized Java development.

Spring depends on parts of Java EE specs (like Servlet & JPA API), but it does not depend on Java EE runtime containers like:

• JBoss
• WebSphere
• WebLogic
• GlassFish

Instead, Spring Boot bundles only the needed pieces inside your JAR.

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Analogy (very intuitive)

• Java = The language
• J2EE = A big enterprise machine with many heavy parts
• Spring = A modern toolkit that replaces 90% of that machine with lightweight tools
• Spring Boot = Spring + Auto-config + Built-in engine + Ready to drive

Spring uses only a few base components of the old machine (Servlet, JPA specs), but otherwise runs independently.

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Final Answer 

Spring is effectively a full replacement for J2EE application development.

It no longer depends on Java EE containers, but it still uses a few core Java EE (now Jakarta EE) APIs—such as Servlets, JPA, JMS—as building blocks.

So:
Spring replaces the J2EE programming model, not the underlying J2EE/Jakarta EE specifications.

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