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<title>Java Data Objects</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Java Data Objects</span></span>

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<p><b>Java Data Objects</b> (<b>JDO</b>) is a specification of <a href="Java_platform" class="mw-redirect" title="Java platform">Java</a> <a href="Object_(computer_science)" title="Object (computer science)">object</a> <a href="Persistence_(computer_science)" title="Persistence (computer science)">persistence</a>. One of its features is a transparency of the persistence services to the <a href="Domain_model" title="Domain model">domain model</a>. JDO persistent objects are ordinary <a href="Java_(programming_language)" title="Java (programming language)">Java programming language</a> <a href="Class_(computer_science)" class="mw-redirect" title="Class (computer science)">classes</a> (<a href="Plain_old_Java_object" title="Plain old Java object">POJOs</a>); there is no requirement for them to implement certain <a href="Interface_(Java)" title="Interface (Java)">interfaces</a> or extend from special classes. JDO 1.0 was developed under the <a href="Java_Community_Process" title="Java Community Process">Java Community Process</a> as <a rel="nofollow" class="external text" href="http://www.jcp.org/en/jsr/detail?id=12">JSR 12</a>. JDO 2.0 was developed under <a rel="nofollow" class="external text" href="http://www.jcp.org/en/jsr/detail?id=243">JSR 243</a> and was released on May 10, 2006. JDO 2.1 was completed in Feb 2008, developed by the <a rel="nofollow" class="external text" href="https://db.apache.org/jdo/">Apache JDO</a> project. JDO 2.2 was released in October 2008. JDO 3.0 was released in April 2010.

</p><p>Object persistence is defined in the external <a href="XML" title="XML">XML</a> metafiles, which may have vendor-specific extensions. JDO vendors provide developers with <i>enhancers</i>, which modify compiled Java class files so they can be transparently persisted. (Note that byte-code enhancement is not mandated by the JDO specification, although it is the commonly used mechanism for implementing the JDO specification's requirements.) Currently, JDO vendors offer several options for persistence, e.g. to <a href="Relational_database" title="Relational database">RDBMS</a>, to <a href="Object_database" title="Object database">OODB</a>, or to <a href="Computer_file" title="Computer file">files</a>.

</p><p>JDO enhanced classes are portable across different vendors' implementation. Once enhanced, a Java class can be used with any vendor's JDO product.

</p><p>JDO is integrated with <a href="Java_Platform%2C_Enterprise_Edition" class="mw-redirect" title="Java Platform, Enterprise Edition">Java EE</a> in several ways. First of all, the vendor implementation may be provided as a <span class="clarify-content" style="padding-left:0.1em; padding-right:0.1em; color:var(--color-subtle, #54595d); border:1px solid var(--border-color-subtle, #c8ccd1);">JEE Connector</span>. Secondly, JDO may work in the context of JEE <a href="Java_transaction_service" title="Java transaction service">transaction services</a>.

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<p><a href="Enterprise_JavaBeans" class="mw-redirect" title="Enterprise JavaBeans">Enterprise JavaBeans</a> 3.0 (EJB3) specification also covered persistence, as had EJB v2 with <a href="Entity_Bean" title="Entity Bean">Entity Beans</a>. There have been standards conflicts between the two standards bodies in terms of pre-eminence. JDO has several commercial implementations.

</p><p>In the end, persistence has been "broken out" of "EJB3 Core", and a new standard formed, the <a href="Java_Persistence_API" class="mw-redirect" title="Java Persistence API">Java Persistence API</a> (JPA). JPA uses the <code>javax.persistence</code> package, and was first specified in a separate document within the EJB3 spec <a rel="nofollow" class="external text" href="http://www.jcp.org/en/jsr/detail?id=220">JSR 220</a>, but was later moved to its own spec <a rel="nofollow" class="external text" href="http://www.jcp.org/en/jsr/detail?id=317">JSR 317</a>. Significantly, <code>javax.persistence</code> will <b>not</b> require an EJB container, and thus will work within a Java SE environment as well, as JDO always has. JPA, however, is an <a href="Object-relational_mapping" class="mw-redirect" title="Object-relational mapping">object-relational mapping</a> (ORM) standard, while JDO is both an object-relational mapping standard and a transparent object persistence standard. JDO, from an API point of view, is agnostic to the technology of the underlying datastore, whereas JPA is targeted to RDBMS datastores (although there are several JPA providers that support access to non-relational datastores through the JPA API, such as DataNucleus and ObjectDB).

</p><p>Leading JDO commercial implementations and open source projects also offer a JPA API implementation as an alternative access to their underlying persistence engines, formerly exposed solely via JDO in the original products. There are many open source implementations of JDO.

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<div class="mw-heading mw-heading2"><h2 id="New_Features_in_JDO_Version_2_Not_Found_In_Version_1">New Features in JDO Version 2 Not Found In Version 1</h2></div>

<ul><li>Disconnected object graphs concept</li>

<li>Standardized ORM mapping descriptors (for ORM-based JDO implementations)</li>

<li>JDOQL Enhancements (Single String Form; more String, Map & Math methods support mandated)</li>

<li>Get e.g. a <code><a rel="nofollow" class="external text" href="https://docs.oracle.com/en/java/javase/24/docs/api/java.sql/java/sql/Connection.html">Connection</a></code> from <code>javax.jdo.PersistenceManager</code></li>

<li>More: Named Queries (pm.newNamedQuery), FetchPlan, Sequence, Delete by Query, multiple User Objects on PM</li></ul>

<div class="mw-heading mw-heading2"><h2 id="JDO_Reference_Implementations">JDO Reference Implementations</h2></div>

<ul><li>JDO 1.0 : FOStore</li>

<li>JDO 2.2 : <a href="DataNucleus" title="DataNucleus">DataNucleus</a> AccessPlatform 1.0.1</li>

<li>JDO 3.0 : <a href="DataNucleus" title="DataNucleus">DataNucleus</a> AccessPlatform 2.1.0</li>

<li>JDO 3.1 : <a href="DataNucleus" title="DataNucleus">DataNucleus</a> AccessPlatform 3.2.0</li>

<li>JDO 3.2 : <a href="DataNucleus" title="DataNucleus">DataNucleus</a> AccessPlatform 5.2.0</li></ul>

<ul><li><a href="Object-relational_mapping" class="mw-redirect" title="Object-relational mapping">Object-relational mapping</a></li>

<li><a href="Object_database" title="Object database">Object database</a></li>

<li><a href="Java_Persistence_API" class="mw-redirect" title="Java Persistence API">Java Persistence API</a> (JPA)</li>

<li><a href="DataNucleus" title="DataNucleus">DataNucleus</a></li>

<li><a href="ObjectDB" title="ObjectDB">ObjectDB</a></li>

<li>ActiveJPA</li></ul>

<div class="mw-heading mw-heading2"><h2 id="Bibliography">Bibliography</h2></div>

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</style><cite id="CITEREFJordanRussell2003" class="citation book cs1">Jordan, David; Russell, Craig (April 22, 2003). <a rel="nofollow" class="external text" href="http://oreilly.com/catalog/9780596002763"><i>Java Data Objects</i></a> (1st ed.). <a href="O'Reilly_Media" title="O'Reilly Media">O'Reilly Media</a>. p. 384. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-596-00276-9</bdi>.</cite></li>

<li><cite id="CITEREFTyagiVorburgerMcCammonBobzin2003" class="citation book cs1">Tyagi, Sameer; Vorburger, Michael; McCammon, Keiron; Bobzin, Heiko (September 21, 2003). <a rel="nofollow" class="external text" href="http://www.informit.com/store/product.aspx?isbn=0131407317"><i>Core Java Data Objects</i></a> (1st ed.). <a href="Prentice_Hall" title="Prentice Hall">Prentice Hall</a>. p. 576. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-13-140731-7</bdi>.</cite></li>

<li><cite id="CITEREFEzzio2003" class="citation book cs1">Ezzio, David (June 6, 2003). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20101223171047/http://apress.com/book/view/9781590590430"><i>Using and Understanding Java Data Objects</i></a> (1st ed.). <a href="Apress" class="mw-redirect" title="Apress">Apress</a>. p. 456. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>1-59059-043-0</bdi>. Archived from <a rel="nofollow" class="external text" href="http://www.apress.com/book/view/9781590590430">the original</a> on December 23, 2010<span class="reference-accessdate">. Retrieved <span class="nowrap">February 8,</span> 2010</span>.</cite></li></ul>

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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://www.jcp.org/en/jsr/detail?id=12">JDO 1.0 specification</a></li>

<li><a rel="nofollow" class="external text" href="http://www.jcp.org/en/jsr/detail?id=243">JDO 2.0 specification</a></li>

<li><a rel="nofollow" class="external text" href="https://db.apache.org/jdo/specifications.html">JDO 2.1 specification</a></li>

<li><a rel="nofollow" class="external text" href="https://db.apache.org/jdo/specifications.html">JDO 2.2 specification</a></li>

<li><a rel="nofollow" class="external text" href="https://db.apache.org/jdo/specifications.html">JDO 3.0 specification</a></li></ul>

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