🔸 TL;DR
A .war is basically a JAR-shaped archive for web apps. web.xml is optional (but has a strict location if present), you can build a WAR with jar, and EJBs can live inside a WAR. JCA resource adapters? Not inside a WAR.
🔸 QUIZ TIME (PICK 2 ✅)
Which statements are true about WAR (.war) files?
▪️ A) A WAR must include a web.xml file inside WEB-INF/.
▪️ B) You can create a WAR using the jar command/tool.
▪️ C) You can package JCA resource adapters inside a WAR.
▪️ D) You can package EJBs inside a WAR.
(Stop here and pick 2 😉)
🔸 ANSWER KEY ✅
✅ B) Yes — A WAR is essentially a ZIP/JAR-style archive, so the jar tool can package it. (war is just an extension + conventions.)
✅ D) Yes — EJBs can be included in a WAR, either:
▪️ as classes in WEB-INF/classes/
▪️ or as JARs in WEB-INF/lib/
❌ A) No — web.xml is not mandatory anymore (annotations + programmatic config exist).
But if you do include it, it must be located at:
▪️ WEB-INF/web.xml
❌ C) No — JCA resource adapters are packaged as RAR files and handled at the application server level, not bundled inside a WAR.
🔸 TAKEAWAYS 🧠
▪️ WAR = “web module archive” with standard folders like WEB-INF/
▪️ web.xml is optional, but location rules are strict if used
▪️ WAR packaging can be done with jar (same underlying format idea)
▪️ EJB-in-WAR is valid in Jakarta EE / Java EE deployments
▪️ JCA adapters ≠ WAR content (think RAR + server-managed)
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