Difference between revisions of "EclipseLink/UserGuide/DBWS/Overview"

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{{EclipseLink_UserGuide
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For the current version, see:
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'''[http://www.eclipse.org/eclipselink/documentation/2.4/dbws/toc.htm Developing Persistence Architectures Using EclipseLink Database Web Services, Release 2.4]'''
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|eclipselinktype=DBWS
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}}
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== EclipseLink DBWS Overview ==
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For EclispeLink DBWS Overview, see http://www.eclipse.org/eclipselink/documentation/2.4/dbws/overview.htm
 
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<onlyinclude>
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EclipseLink DBWS provides Java EE-compliant, client-neutral access to relational database artifacts via a Web service. EclipseLink DBWS extends EclipseLink's core capabilities while leveraging its existing ORM and OXM components.
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EclipseLink DBWS includes two parts
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*[[EclipseLink/UserGuide/DBWS/Overview/Design time|A design-time component]] (<tt>DBWSBuilder</tt>)
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*[[EclipseLink/UserGuide/DBWS/Overview/Runtime|A runtime provider component]] that takes a service descriptor (along with related deployment artifacts) and realizes it as a JAX-WS 2.0 Web service. The runtime provider uses EclipseLink to bridge between the database and the XML SOAP Messages used by Web service clients.
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An EclipseLink DBWS service may include any number of the following <b>operations</b>:
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# <b>insert</b> - inserts into the database persistent entities described by an XML document.
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# <b>update</b> - updates database persistent entities described by an XML document.
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# <b>delete</b> - removes from the database persistent entities described by an XML document.
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# <b>query</b> - retrieves from the database persistent entities described by an XML document. <br>Selection criteria for Query operations can be specified by:
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#* custom <tt>SQL SELECT</tt> statement
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#* Stored Procedure invocation
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#* EclipseLink Named Query (that can use the complete range of EclipseLink ORM Expression Framework APIs)
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The XML documents used by an <b>operation</b> conform to an XML Schema Definition (<tt>.xsd</tt> file).
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===XML-to-Relational Mapping (XRM)===
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EclipseLink's ORM and OXM features provides the basis for a powerful ''bridge'' between a database's relational structure(s) and XML's hierarchical structure. <br/>
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[[Image:XRRunTime.png]]
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===Configuration===
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A typical EclipseLink DBWS service is packaged in an archive (<tt>.jar</tt> or <tt>.war</tt> file) with a service descriptor file
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<tt><b>eclipselink-dbws.xml</b></tt> in the META-INF directory (or WEB-INF/classes/META-INF when packaged in a <tt>.war</tt> file).
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To bridge the relational database and XML worlds, an EclipseLink sessions.xml file <tt><b>eclipselink-dbws-sessions.xml</b></tt> points
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to two Eclipse projects - one for the ORM side, the other for the OXM side. The service also requires an XML Schema Definition file
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<tt><b>eclipselink-dbws-schema.xsd</b></tt> which in conjunction with the OXM project, specifies how information from the database
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is to be 'shaped' into XML documents.
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<source lang="text" enclose="div"></source>
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root of archive
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{not all files displayed ...}
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  \---META-INF
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    |  eclipselink-dbws.xml
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    |  eclipselink-dbws-sessions.xml -- name can be overriden by <sessions-file> entry in eclipselink-dbws.xml
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    |  eclipselink-dbws-or.xml
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    |  eclipselink-dbws-ox.xml
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    |  eclipselink-dbws-schema.xsd -- when deployed in a .war file, located in a different directory
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The EclipseLink DBWS service descriptor file (<tt><b>eclipselink-dbws.xml</b></tt>) is easy to read with minimum required information and simple defaults for omitted fields, allowing for both auto-generation by a utility or manual editing. The [[EclipseLink/UserGuide/DBWS/Overview/EclipseLink_DBWS_Service_Descriptor_File_(ELUG)| service descriptor file is described in full in the User Guide]].
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=====Example DBWS Service descriptor file=====
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<source lang="xml" enclose="div">
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<dbws xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
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  <name>example</name>
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  <sessions-file>example-dbws-sessions.xml</sessions-file>
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  <query>
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    <name>countEmployees
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    <result>
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      <type>xsd:int</type>
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    </result>
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    <sql><!--[CDATA[select count(*) from EMP]]--></sql>
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  </name>
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</query>
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</source>
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===XML Schema Definition===
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The EclipseLink DBWS service schema file (<tt><b>eclipselink-dbws-schema.xsd</b></tt>) can be created by hand,
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or auto-generated by the <tt>DBWSBuilder</tt> utility which derives XML element-tag names from Database metadata
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(column names, types, nullable, etc).
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====Example Simple XML Format (SXF) document====
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The <tt>DBWSBuilder</tt> utility will not generate an XML Schema Definition when the information returned by a <b>query operation</b> has no pre-determined structure, such as a resultSet from a custom SQL query, the results from a Stored Procedure or the row-count from an <b>update operation</b>. In these cases, the EclipseLink DBWS runtime provider uses information only available at the time of query execution to build the XML document:
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<source lang="xml" enclose="div">
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{Element tag names are direct copies of table's column names}
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<simple-xml-format>
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  <simple-xml>
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    <empno>7788</empno>
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    <ename>SCOTT</ename>
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    <job>ANALYST</job>
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    <mgr>7566</mgr>
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    <hiredate>1987-04-19T00:00:00.000-0400</hiredate>
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    <sal>3000</sal>
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    <deptno>20</deptno>
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  </simple-xml>
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  <simple-xml>
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    <empno>7369</empno>
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    <ename>SMITH</ename>
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    <job>CLERK</job>
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    <mgr>7902</mgr>
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    <hiredate>1980-12-17T00:00:00.000-0400</hiredate>
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    <sal>800</sal>
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    <deptno>20</deptno>
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  </simple-xml>
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</simple-xml-format>
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</source>
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These XML documents are 'dumb' as they cannot be validated against any pre-determined schema - or more accurately, only the followingfckLRvery &lt;b&gt;permissive&lt;/b&gt; 'sequence-of-any' schema can validate such documents:fckLRfckLR====Simple XML Format Schema====fckLR<source lang="xml" enclose="div"></source>
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<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
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  <xsd:complextype name="simple-xml-format">
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    <xsd:sequence>
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      <xsd:any minoccurs="0"></xsd:any>
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    </xsd:sequence>
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  </xsd:complextype>
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</xsd:schema>
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fckLRThe element tags &lt;tt&gt;&lt;b&gt;simple-xml-format&lt;/b&gt;&lt;/tt&gt; and &lt;tt&gt;&lt;b&gt;simple-xml&lt;/b&gt;&lt;/tt&gt; can be customized by setting the appropriate propertiesfckLRon an &lt;tt&gt;&lt;b&gt;operation&lt;/b&gt;&lt;/tt&gt;.fckLR</dbws></sessions-file></onlyinclude>
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[[Category:DBWS]]
 
[[Category:DBWS]]

Latest revision as of 08:39, 1 November 2012

For the current version, see: Developing Persistence Architectures Using EclipseLink Database Web Services, Release 2.4

For EclispeLink DBWS Overview, see http://www.eclipse.org/eclipselink/documentation/2.4/dbws/overview.htm