OData 에 대해서 알아보자.

<span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">얼마 전에 어떤 회사에 인터뷰를 하러 간 적이 있었다.</span></span><br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">당시 그 회사는 자체 솔루션을 개발할 기술인력을 찾고 있었고 내부적으로 OData를 사용한다고 했다. 좀 창피한 이야기일 수도 있지만 나름 기술적인 부분에서는 많은 정보를 가지고 있다고 했던 것이 무색하게 OData란 단어를 그 회사 사장님에게서 처음 들었다.</span></span><br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">작고, 단순한 사이트들만을 계속해서 작업을 하다 보니 어느덧 큰 줄기들을 잃어버린 것을 느끼기 시작했다. 명색이 개발이 좋고, 기술적인 기반을 만들려고 하는 인간이 단어조차도 모른다는 것은 있을 수 없는 것이라서 다시 새로운 단어들과 개념들을 알아보는 시간을 가지려고 한다.</span></span><br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;"><br /></span></span> <h3> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">OData (Open Data Protocol) 란?</span></span></h3> <div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span></div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">간단히 정리하면 웹 상에서 손쉽게 데이터를 조회하거나 수정할 수 있도록 주고 받는 웹(프로토콜)을 말한다.</span></span><br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">서비스 제공자 입장에서는 웹으로 데이터를 제공하는 방식으로 각 포탈 사이트들이 제공하는 OPEN API 포맷을 독자적인 형식이 아니라 오픈된 공통규약으로 제공 가능하며, 개발자는 이 정보를 다양한 언어의 클라이언트 라이브러리로 어플리케이션에서 소비할 수 있도록 사용하면 된다.</span></span><br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">공식 사이트는 </span></span><a href="http://www.odata.org/"><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">www.odata.org</span></span></a><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"> 이며 많은 언어들을 지원하고 있다.</span></span><br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">좀더 상세하게 정의를 해 보면 OData는 Atom Publishing Protocol  (RFC4287) 의 확장 형식이고 REST (REpresentational State Transfer) Protocol 이다. 따라서 웹 브라우저에서 OData 서비스로 노출된 데이터를 볼 수 있다. 그리고 AtomPub 의 확장이라고 했듯이 데이터의 조회만으로 한정되는 것이 아니라 CRUD 작업이 모두 가능하다.</span></span><br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;"><br /></span></span> <h3> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">Example</span></span></h3> <div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span></div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">웹 브라우저에서 </span></span><a href="http://services.odata.org/website/odata.svc"><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">http://services.odata.org/website/odata.svc</span></span></a><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"> 를 열어 보도록 하자.</span></span><br /> <span style="font-family: 나눔고딕;"></span> <br /> <br /> <div id="codeSnippetWrapper" style="background-color: #f4f4f4; border-bottom: silver 1px solid; border-left: silver 1px solid; border-right: silver 1px solid; border-top: silver 1px solid; cursor: text; direction: ltr; font-family: 'Courier New', courier, monospace; font-size: 8pt; line-height: 12pt; margin: 20px 0px 10px; max-height: 200px; overflow: auto; padding-bottom: 4px; padding-left: 4px; padding-right: 4px; padding-top: 4px; text-align: left; width: 97.5%;"> <pre id="codeSnippet" style="background-color: #f4f4f4; border-bottom-style: none; border-left-style: none; border-right-style: none; border-top-style: none; color: black; direction: ltr; font-family: 'Courier New', courier, monospace; font-size: 8pt; line-height: 12pt; margin: 0em; overflow: visible; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; width: 100%;"><span style="font-family: Segoe UI;">This XML file does not appear to have any style information associated with it. The document tree is shown below. <span style="color: blue;"><</span><span style="color: maroon;">service</span> <span style="color: red;">xmlns:atom</span><span style="color: blue;">="http://www.w3.org/2005/Atom"</span> <span style="color: red;">xmlns:app</span><span style="color: blue;">="http://www.w3.org/2007/app"</span> <span style="color: red;">xmlns</span><span style="color: blue;">="http://www.w3.org/2007/app"</span> <span style="color: red;">xml:base</span><span style="color: blue;">="http://services.odata.org/Website/odata.svc/"</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">workspace</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span>Default<span style="color: blue;"></</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">collection</span> <span style="color: red;">href</span><span style="color: blue;">="ODataConsumers"</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span>ODataConsumers<span style="color: blue;"></</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">collection</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">collection</span> <span style="color: red;">href</span><span style="color: blue;">="ODataProducerApplications"</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span>ODataProducerApplications<span style="color: blue;"></</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">collection</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">collection</span> <span style="color: red;">href</span><span style="color: blue;">="ODataProducerLiveServices"</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span>ODataProducerLiveServices<span style="color: blue;"></</span><span style="color: maroon;">atom:title</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">collection</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">workspace</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">service</span><span style="color: blue;">></span></span></pre> <br /></div> <br /> <span style="font-family: 'Segoe UI';">위와 같은 결과를 볼 수 있을 것이다. 이 결과는 OData에서 workspace라고 부르는 Entity Sets (Feeds) 리스트를 보여주는 것이다.</span><br /> <br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">위의 리스트들 중에서 ODataConsumers라는 데이터 컬렉션을 확인해 보기 위해서 </span></span><a href="http://services.odata.org/website/odata.svc/ODataConsumers"><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">http://services.odata.org/website/odata.svc/ODataConsumers</span></span></a><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"> 로 URL을 변경해 보도록 한다. (ODataConsumers라는 정보는 REST로 전달되는 정보이므로 대/소문자를 구분해야 한다)</span></span><br /> <div id="codeSnippetWrapper" style="background-color: #f4f4f4; border-bottom: silver 1px solid; border-left: silver 1px solid; border-right: silver 1px solid; border-top: silver 1px solid; cursor: text; direction: ltr; font-family: 'Courier New', courier, monospace; font-size: 8pt; line-height: 12pt; margin: 20px 0px 10px; max-height: 200px; overflow: auto; padding-bottom: 4px; padding-left: 4px; padding-right: 4px; padding-top: 4px; text-align: left; width: 97.5%;"> <pre id="codeSnippet" style="background-color: #f4f4f4; border-bottom-style: none; border-left-style: none; border-right-style: none; border-top-style: none; color: black; direction: ltr; font-family: 'Courier New', courier, monospace; font-size: 8pt; line-height: 12pt; margin: 0em; overflow: visible; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-align: left; width: 100%;"><span style="font-family: Segoe UI;"><span style="color: blue;"><?</span><span style="color: maroon;">xml</span> <span style="color: red;">version</span><span style="color: blue;">="1.0"</span> <span style="color: red;">encoding</span><span style="color: blue;">="utf-8"</span> <span style="color: red;">standalone</span><span style="color: blue;">="yes"</span>?<span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">feed</span> <span style="color: red;">xml:base</span><span style="color: blue;">="http://services.odata.org/Website/odata.svc/"</span> <span style="color: red;">xmlns:d</span><span style="color: blue;">="http://schemas.microsoft.com/ado/2007/08/dataservices"</span> <span style="color: red;">xmlns:m</span><span style="color: blue;">="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"</span> <span style="color: red;">xmlns</span><span style="color: blue;">="http://www.w3.org/2005/Atom"</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">title</span> <span style="color: red;">type</span><span style="color: blue;">="text"</span><span style="color: blue;">></span>ODataConsumers<span style="color: blue;"></</span><span style="color: maroon;">title</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">id</span><span style="color: blue;">></span>http://services.odata.org/website/odata.svc/ODataConsumers<span style="color: blue;"></</span><span style="color: maroon;">id</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">updated</span><span style="color: blue;">></span>2013-08-10T06:20:56Z<span style="color: blue;"></</span><span style="color: maroon;">updated</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">link</span> <span style="color: red;">rel</span><span style="color: blue;">="self"</span> <span style="color: red;">title</span><span style="color: blue;">="ODataConsumers"</span> <span style="color: red;">href</span><span style="color: blue;">="ODataConsumers"</span> <span style="color: blue;">/></span> <span style="color: blue;"><</span><span style="color: maroon;">entry</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">id</span><span style="color: blue;">></span>http://services.odata.org/Website/odata.svc/ODataConsumers(1)<span style="color: blue;"></</span><span style="color: maroon;">id</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">title</span> <span style="color: red;">type</span><span style="color: blue;">="text"</span><span style="color: blue;">></span>Browsers<span style="color: blue;"></</span><span style="color: maroon;">title</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">summary</span> <span style="color: red;">type</span><span style="color: blue;">="text"</span><span style="color: blue;">></span>Most modern browsers allow you to browse Atom based feeds. Simply point your browser at one of the OData Producers.<span style="color: blue;"></</span><span style="color: maroon;">summary</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">updated</span><span style="color: blue;">></span>2013-08-10T06:20:56Z<span style="color: blue;"></</span><span style="color: maroon;">updated</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">author</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">name</span> <span style="color: blue;">/></span> <span style="color: blue;"></</span><span style="color: maroon;">author</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">link</span> <span style="color: red;">rel</span><span style="color: blue;">="edit"</span> <span style="color: red;">title</span><span style="color: blue;">="ODataConsumer"</span> <span style="color: red;">href</span><span style="color: blue;">="ODataConsumers(1)"</span> <span style="color: blue;">/></span> <span style="color: blue;"><</span><span style="color: maroon;">category</span> <span style="color: red;">term</span><span style="color: blue;">="ODataServices.ODataConsumer"</span> <span style="color: red;">scheme</span><span style="color: blue;">="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme"</span> <span style="color: blue;">/></span> <span style="color: blue;"><</span><span style="color: maroon;">content</span> <span style="color: red;">type</span><span style="color: blue;">="application/xml"</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">m:properties</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:Id</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.Int32"</span><span style="color: blue;">></span>1<span style="color: blue;"></</span><span style="color: maroon;">d:Id</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:Name</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.String"</span><span style="color: blue;">></span>Browsers<span style="color: blue;"></</span><span style="color: maroon;">d:Name</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:Description</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.String"</span><span style="color: blue;">></span>Most modern browsers allow you to browse Atom based feeds. Simply point your browser at one of the OData Producers.<span style="color: blue;"></</span><span style="color: maroon;">d:Description</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:ApplicationUrl</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.String"</span><span style="color: blue;">></</span><span style="color: maroon;">d:ApplicationUrl</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">m:properties</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">content</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">entry</span><span style="color: blue;">></span> ... <span style="color: blue;"><</span><span style="color: maroon;">entry</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">id</span><span style="color: blue;">></span>http://services.odata.org/Website/odata.svc/ODataConsumers(14)<span style="color: blue;"></</span><span style="color: maroon;">id</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">title</span> <span style="color: red;">type</span><span style="color: blue;">="text"</span><span style="color: blue;">></span>(Unofficial) SSIS import script<span style="color: blue;"></</span><span style="color: maroon;">title</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">summary</span> <span style="color: red;">type</span><span style="color: blue;">="text"</span><span style="color: blue;">></span>A SQL Server Integration Services script for importing OData into SQL Server.<span style="color: blue;"></</span><span style="color: maroon;">summary</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">updated</span><span style="color: blue;">></span>2013-08-10T06:20:56Z<span style="color: blue;"></</span><span style="color: maroon;">updated</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">author</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">name</span> <span style="color: blue;">/></span> <span style="color: blue;"></</span><span style="color: maroon;">author</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">link</span> <span style="color: red;">rel</span><span style="color: blue;">="edit"</span> <span style="color: red;">title</span><span style="color: blue;">="ODataConsumer"</span> <span style="color: red;">href</span><span style="color: blue;">="ODataConsumers(14)"</span> <span style="color: blue;">/></span> <span style="color: blue;"><</span><span style="color: maroon;">category</span> <span style="color: red;">term</span><span style="color: blue;">="ODataServices.ODataConsumer"</span> <span style="color: red;">scheme</span><span style="color: blue;">="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme"</span> <span style="color: blue;">/></span> <span style="color: blue;"><</span><span style="color: maroon;">content</span> <span style="color: red;">type</span><span style="color: blue;">="application/xml"</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">m:properties</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:Id</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.Int32"</span><span style="color: blue;">></span>14<span style="color: blue;"></</span><span style="color: maroon;">d:Id</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:Name</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.String"</span><span style="color: blue;">></span>(Unofficial) SSIS import script<span style="color: blue;"></</span><span style="color: maroon;">d:Name</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:Description</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.String"</span><span style="color: blue;">></span>A SQL Server Integration Services script for importing OData into SQL Server.<span style="color: blue;"></</span><span style="color: maroon;">d:Description</span><span style="color: blue;">></span> <span style="color: blue;"><</span><span style="color: maroon;">d:ApplicationUrl</span> <span style="color: red;">m:type</span><span style="color: blue;">="Edm.String"</span><span style="color: blue;">></span>http://www.cozyroc.com/script/odata-source<span style="color: blue;"></</span><span style="color: maroon;">d:ApplicationUrl</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">m:properties</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">content</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">entry</span><span style="color: blue;">></span> <span style="color: blue;"></</span><span style="color: maroon;">feed</span><span style="color: blue;">></span></span></pre> <br /></div> <br /> <span style="font-family: 'Segoe UI';">위의 결과와 같이 ODataConsumers 의 구성 Entity 들을 확인할 수 있다.</span><br /> <br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">내용을 잠시 확인해 보면 entry 는 ID 로 유일하게 식별할 수 있는 URL 값을 가지고 있고, 그 외에 몇 가지 속성들을 가지고 있는 것을 볼 수 있다. 가장 중요한 부분은 “content” 로 표준 엔터티 데이터 모델 (EDM – Entity Data Model) 을 가지고 있다.</span></span><br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span> <h3> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">Queries</span></span></h3> <div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span></div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">OData에서는 URL을 통해서 모든 데이터 처리를 수행하게 된다.</span></span><br /> <br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">예를 들어 Consumer 들 중에서 최 상위 3명 만을 추출하고 싶은 경우는 다음과 같이 URL을 정의하면 된다.</span></span><br /> <br /> <span style="font-family: 나눔고딕;"></span><span style="font-family: 나눔고딕;"><a href="http://services.odata.org/website/odata.svc/ODataConsumers?$top=3"><span style="font-family: Segoe UI;">http://services.odata.org/website/odata.svc/ODataConsumers?$top=3</span></a></span><br /> <br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">$top 연산자는 상위 몇 개를 골라는 내는 것이고 그 밖에는 아래와 같이 대표적인 연산자들이 존재한다.</span></span><br /> <br /> <table bgcolor="silver" border="1" bordercolor="black" bordercolordark="white" bordercolorlight="white" style="width: 100%px;"><tbody> <tr><td width="166"><br /> <div align="center"> <strong><span style="color: black; font-family: Segoe UI;">Query String</span></strong></div> </td><td width="273"><br /> <div align="center"> <span style="color: black; font-family: Segoe UI;"><strong>Description</strong></span></div> </td><td width="334"><br /> <div align="center"> <strong><span style="color: black; font-family: Segoe UI;">Sample</span></strong></div> </td></tr> <tr><td width="166"><span style="color: black; font-family: Segoe UI;">$skip=<n></span></td><td width="273"><span style="color: black; font-family: Segoe UI;">처음 n개를 생략하고 나머지를 반환한다.</span></td><td width="334"><a href="http://services.odata.org/website/odata.svc/ODataConsumers?$skip=5"><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">http://services.odata.org/website/odata.svc/ODataConsumers?$skip=5</span></span></a></td></tr> <tr><td width="166"><span style="color: black; font-family: Segoe UI;">$orderBy=<property-name></span></td><td width="273"><span style="color: black; font-family: Segoe UI;">지정한 속성을 기준으로 정렬하여 반환한다.</span></td><td width="334"><a href="http://services.odata.org/website/odata.svc/ODataConsumers?$orderby=Name"><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">http://services.odata.org/website/odata.svc/ODataConsumers?$orderby=Name</span></span></a></td></tr> <tr><td width="166"><span style="color: black; font-family: Segoe UI;">$filter=<filter expression></span></td><td width="273"><span style="color: black; font-family: Segoe UI;">필터 표현에 따라서 필터링된 결과를 반환한다. (<, >, == 등에 대한 특수문자 처리 필요)</span></td><td width="334"><a href="http://services.odata.org/website/odata.svc/ODataConsumers?$filter=Id%20gt%203"><span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">http://services.odata.org/website/odata.svc/ODataConsumers?$filter=Id%20gt%203</span></span></a></td></tr> </tbody></table> <br /> <br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">물론 더 많은 연산자들이 존재한다. </span><a href="http://www.odata.org/developers/protocols/uri-conventions#QueryStringOptions"><span style="font-family: Segoe UI;">http://www.odata.org/developers/protocols/uri-conventions#QueryStringOptions</span></a><span style="font-family: Segoe UI;"> 를 찾아보면 된다.</span></span><br /> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span> <h3> <span style="font-family: Segoe UI;">Updates</span></h3> <div> <span style="font-family: Segoe UI;"><br /></span></div> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">OData 는 조회만을 위한 것이 아니라 CRUD 도 가능하다고 언급을 했었고, REST Protocol 이라고 했었다. 따라서 Http Verbs 에 따라서 데이터에 대한 CRUD 작업을 수행할 수 있다.</span></span><br /> <br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">Http Verbs 는 “GET” – Reading, “PUT” – Creating, “POST” – Update, “DELETE” – Delete 으로 처리가 된다.</span></span><br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;"><br /></span></span> <h3> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">JSON</span></span></h3> <div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span></div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">기본적으로 OData는 Atom XML 포맷을 반환한다. 그러나 JSON 형식의 출력도 제공하고 있다. JSON 포맷의 출력을 받기 위해서는 HTTP Header를 조정해 주어야 한다. 자세한 설명은  </span><a href="http://www.odata.org/developers/protocols/operations#RepresentationFormatAndContentTypeNegotiation"><span style="font-family: Segoe UI;">http://www.odata.org/developers/protocols/operations#RepresentationFormatAndContentTypeNegotiation</span></a><span style="font-family: Segoe UI;"> 부분을 참고하면 된다.</span></span><span style="font-family: 'Segoe UI';">  </span><br /> <span style="font-family: 'Segoe UI';"><br /></span> <h3> <span style="font-family: Segoe UI;">언제 사용하는 것이 좋을까?</span></h3> <div> <span style="font-family: Segoe UI;"><br /></span></div> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">일반적으로 제공되는 기능 (Web Service, WCF 등) 대신에 OData를 사용하는 것에는 이유와 타당성이 있어야 한다.</span></span><br /> <br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">우선 OData는 표준이라는 점이고, 외부 업체나 증가될 가능성이 있는 기타 다양한 클라이언트들을 대상으로 처리하는 경우에 적합하고, 닷넷의 입장에서 보면 이미 .NET Framework에 연계되어 있기 때문에 클라이언트에서 LINQ 등을 사용할 수 있고, EXCEL 2010 의 Pivot 테이블처리에서 인식이 가능하다.</span></span><br /> <br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">또한 일반적인 Web Service 환경에서 Get<EntityName> By <Creteria> 와 같은 형식을 대체할 수 있는 것으로 의미가 있을 듯 하다. 예를 들어 Web Service 에서 처리할 데이터들에 따라서 “GetAllEmployees”, “GetEmployeeByID”, “GetEmployeeByDepartment” 등을 별개로 만들어서 노출하는 것들을 URL 처리로 통합할 수 있는 것도 의미가 있는 것이고, 이후에 또 다른 조건들이 생겨서 추가작업과 배포, 유지관리의 문제가 생기는 것을 방지할 수도 있다.</span></span><br /> <br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">가장 큰 이점은 하나의 OData 를 구성해 놓으면 클라이언트가 다양하게 조건들을 변형(URL) 해서 사용할 수 있다는 것이다.</span></span><br /> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;"><br /></span></span> <h3> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;">Conclution</span></span></h3> <div> <span style="font-family: 나눔고딕;"><span style="font-family: Segoe UI;"><br /></span></span></div> <span style="font-family: Segoe UI;"><span style="font-family: 나눔고딕;">이번에는 개념적인 부분과 간략한 설명을 위주로 정리하였다. 다음에는 실제 서버 상에서 OData를 구성하는 것과 이를 다양하게 사용하는 클라이언트 샘플을 기준으로 다시 한번 정리해 보도록 할 것이다.</span></span>