Java Message Service or JMS is a Java API that is part of J2EE. JMS is an abstraction of a messaging system and can be used to make a Java application use of all messaging middleware that has a JMS API. JMS is for messaging what JDBC is for databases.
JMS is an important part of the J2EE that JMS is more or less the core of J2EE's ability to serve as EAI technology. By being able to connect to messaging technology (very popular with mainframes and similar technology), it becomes possible to use J2EE applications to relocate and insert older classes of applications with ease in the modern ICT landscape of a company.
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