Spring project uses maven-shade-plugin while spring boot project uses spring-boot-maven-plugin for packaging the single executable jar with all the the dependencies

spring project jar file size is -



while spring boot project jar is -



Spring project opend jar looks like this -



It looks like shade plugin merged all the dependency jars along with application classes/objects together in a single jar

while spring boot project opened jar looks like this -



In spring boot jar, spring boot loader classes are inside org folder, BOOT-INF folder has application classess/objects plus all the dependencies in lib folder

Spring project MANIFEST.MF file looks like this -



while spring boot MANIFEST.MF is like this -



Note: Spring boot jar packaging looks much better than the spring project jar, dependencies are nicely separated. Also, notice the Main-Class and Start-Class in spring boot manifest file. This means when you run spring boot jar the JarLauncher class gets triggered which must be taking care of executing @SpringBootApplication class ( Start-Class) with the required class-path set.

Go and compare both the pom files.(https://github.com/mane-ashok/simple-spring-webapp-monolith/blob/main/pom.xml & https://github.com/mane-ashok/simple-springboot-webapp-monolith/blob/main/pom.xml)

spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.url=jdbc:h2:~/myFirstH2Database
spring.datasource.username=sa
spring.datasource.password=sa
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

spring.jpa.show-sql=true
spring.jpa.generate-ddl=true
spring.messages.basename=messages
spring.mvc.static-path-pattern=/resources/**
spring.web.resources.static-locations=classpath:/css/,classpath:/images/

Note: Spring application created 86 beans while spring boot created 256 beans, this might add to the memory foot print. You will see all the beans created in the console logs. You may exclude the unnecessary beans in the @SpringBootApplication(exclude={...})