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JPA JPQL advantages and disadvantage

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wrong side with this JPQL query content belongs to ibm developer site highly thanks to them for basic and detailed explanation- https://www.ibm.com/developerworks/library/j-typesafejpa/ The Java developer community has welcomed JPA since its introduction in 2006. The next major update of the specification — version 2.0 (JSR 317) — will be finalized later in 2009 (see  Resources ). One of the key features introduced in JPA 2.0 is the Criteria API, which brings a unique capability to the Java language: a way to develop queries that a Java compiler can verify for correctness at compile time. The Criteria API also includes mechanisms for building queries dynamically at run time. This article introduces the Criteria API and the closely associated  metamodel  concept. You will learn how to use the Criteria API to develop queries that a Java compiler can check for correctness to reduce run-time errors, in contrast to string-based Java Persistence Query Language (JPQ...
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Enum , Strategy pattern, Open/close principle -  Strategy design pattern - is based upon open closed design principle, the 'O' of famous SOLID design principles.  Strategy pattern allows to encapsulate possible changes in a process and encapsulate that in a Strategy class. By doing that your process (mainly a method) depends upon a strategy, higher level of abstraction than implementation. This makes your process open for extension by providing new Strategy implementation, but closed for modification, because the introduction of a new strategy doesn't require a change in a tested method. That's how it confirms open closed design principle.Strategy pattern is one of the famous pattern, which takes advantage of polymorphism, to remove switch cases and strive for open close design principle. Formally it encapsulate related algorithm, known as strategy and make them interchangeable. open/closed principle - In object-oriented programming, the open/closed principle s...
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Java8 Collectors mapping and joining function usages

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