JPA or JDBC how are they different

Question

I am learning Java EE and I downloaded the eclipse with glassfish for the same  I saw some examples and also read the Oracle docs to know all about Java EE 5  Connecting to a database was very simple  I opened a dynamic web project  created a session EJB    I used EntityManager and with the get methods could access the stored data table   For my next project I had create a simple class and then access some DB table  The very first problem I encountered was that the PersistenceUnit attribute would only be recognized by EJB Servlet etc and not a simple java class  So then I could not use the EntityManager way or can I     I was asked to go via the  JDBC  way  The very first problem I encountered was to get the connection to the DB  It seems all this must be hardcoded  I had a persistence xml with which I could easily configure the data base connection  Even setting up a driver for the DB was easy  Also there no get set methods in the JDBC for accessing table entities   How do I understand JPA and persistence in relation to JDBC  What was JPA thought for  Why is there set get methods  Can someone throw some light on the essence of these two and what are the pros cons without  jargons    Please also suggest some links  A simple google search for JPA and JDBC differences led me to some sites full of  terminology  I couldn t follow

User · Answer

Main difference between JPA and JDBC is level of abstraction.

JDBC is a low level standard for interaction with databases. JPA is higher level standard for the same purpose. JPA allows you to use an object model in your application which can make your life much easier. JDBC allows you to do more things with the Database directly, but it requires more attention. Some tasks can not be solved efficiently using JPA, but may be solved more efficiently with JDBC.

User · Answer

JDBC is the predecessor of JPA    JDBC is a bridge between the Java world and the databases world  In JDBC you need to expose all dirty details needed for CRUD operations  such as table names  column names  while in JPA  which is using JDBC underneath   you also specify those details of database metadata  but with the use of Java annotations    So JPA creates update queries for you and manages the entities that you looked up or created updated  it does more as well    If you want to do JPA without a Java EE container  then Spring and its libraries may be used with the very same Java annotations

User · Answer

JDBC is a much lower-level  and older  specification than JPA  In it s bare essentials  JDBC is an API for interacting with a database using pure SQL - sending queries and retrieving results  It has no notion of objects or hierarchies  When using JDBC  it s up to you to translate a result set  essentially a row column matrix of values from one or more database tables  returned by your SQL query  into Java objects   Now  to understand and use JDBC it s essential that you have some understanding and working knowledge of SQL  With that also comes a required insight into what a relational database is  how you work with it and concepts such as tables  columns  keys and relationships  Unless you have at least a basic understanding of databases  SQL and data modelling you will not be able to make much use of JDBC since it s really only a thin abstraction on top of these things

User · Answer

In layman s terms    JDBC is a standard for Database Access JPA is a standard for ORM   JDBC is a standard for connecting to a DB directly and running SQL against it - e g SELECT   FROM USERS  etc   Data sets can be returned which you can handle in your app  and you can do all the usual things like INSERT  DELETE  run stored procedures  etc   It is one of the underlying technologies behind most Java database access  including JPA providers    One of the issues with traditional JDBC apps is that you can often have some crappy code where lots of mapping between data sets and objects occur  logic is mixed in with SQL  etc   JPA is a standard for Object Relational Mapping  This is a technology which allows you to map between objects in code and database tables   This can  hide  the SQL from the developer so that all they deal with are Java classes  and the provider allows you to save them and load them magically   Mostly  XML mapping files or annotations on getters and setters can be used to tell the JPA provider which fields on your object map to which fields in the DB   The most famous JPA provider is Hibernate  so it s a good place to start for concrete examples   Other examples include OpenJPA  toplink  etc   Under the hood  Hibernate and most other providers for JPA write SQL and use JDBC to read and write from and to the DB

[java] JPA or JDBC, how are they different?

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