Re: Thoughts and questions about data mapping and DDD in general
"Rupesh Kumar Tiwari [email protected] [domaindrivendesign]" <[email protected]> Thu, 27 Apr 2017 17:30:20 -0400
| Newsgroups | gmane.comp.programming.domain-driven-design |
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| Message-ID | <CACWF3vVbvErnz-07FMwom9CsP9hwPsGhrz3QpHfa-Yd99NKmLQ@mail.gmail.com> |
--94eb2c19105e262ad0054e2cabac Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" Hi Pedro, I loved the way you explained every steps. I also practice DDD an= d in my project we did all of the above steps exactly you said. However we= do 2 things different. *1) How we save domain objects* In order to save d= omain models we do not convert it in some other dto. We just save the Domai= n Model as it is. We use Entity Framework and it supports Code First that i= s what we use. Our Repository implementation in the Infrastructure directly= saves Entity ( Aggregate Root ) in Database. Therefore, we do not need map= per here. *2) How we map domain object to UI dtos* In our application laye= r itself we have class called as Assembler and that class basically convert= s Model To DTO and DTO to Model. For example if I have Order Aggregate Root= Then I have Order Folder in Application Service Layer. Order Folder has Or= derAppService.cs and OrderAssembler.cs. OrderAppService takes dependency of= OrderAssembler and calls MapToDto method by giving domain entity. Basicall= y we have our mapper in Application layer itself. Hope this helps! = Thanks, Rupesh kumar Tiwari On Thu, Apr 27, 2017 at 12:44 PM, pedro= [email protected] [domaindrivendesign] <[email protected]= > wrote: > > > Hey guys, > > > How do you manage data mapping in DDD? > > = To me, to follow DDD principles, we'd need to do the following: > > > - = clients have their own DTO, to represent the data in their level > - cli= ents do NOT work with domain objects such entities, aggregates > ... dom= ain model, in general; > - clients call, via controllers/application ser= vices, the domain > services from the domain > - domain services talk= to repositories, and both work with the domain > model > - repositor= y definition belongs to the domain layer, but > implementation belongs t= o infrastructure; > - repository implementation need mappers to convert = from domain model > to DTO and vice-versa; > > Some consequences of the = DDD are that, in the domain model, I'd never put > JPA annotations (and any= other infrastructure-related stuff). DTOs, in the > infrastructure layer, = would be the classes that are actually mapped with > such a thing. > > But = then we need data mapping between client and domain and also domain > and i= nfrastructure. > Where do you usually put it? Would it be kind of separate = modules such as: > > - a module (separate library) that maps client DTO'= s to domain > objects, and the model depends on it; > - a module (sep= arate library) that maps domain objects to > infrastructure (example: DB= ) model and vice-versa, and the infrastructure > depends on it (reposito= ry implementation receives domain objects as > parameters, convert them = or build whatever query it needs, persist/fetch > data and, eventually, = converts data back to domain objects to return to the > caller); > > Tha= t's the only way I can think of, preserving the DDD principles. > Doing so,= we kinda preserve domain talking about domain, infra talking > about data,= no 'infra-related' configuration on domain objects, and also no > clients = speaking in the domain terms. > > What do you think? How do you play with d= ata mapping? > By the way, do you agree with my words? > > Cheers, > Pedro = > > > --94eb2c19105e262ad0054e2cabac Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <head> <style type=3D"text/css"> <!-- /* start of attachment style */ .ygrp-photo-title{ clear: both; font-size: smaller; height: 15px; overflow: hidden; text-align: center; width: 75px; } div.ygrp-photo{ background-position: center; background-repeat: no-repeat; background-color: white; border: 1px solid black; height: 62px; width: 62px; } div.photo-title=20 a, div.photo-title a:active, div.photo-title a:hover, div.photo-title a:visited { text-decoration: none;=20 } div.attach-table div.attach-row { clear: both; } div.attach-table div.attach-row div { float: left; /* margin: 2px;*/ } p { clear: both; padding: 15px 0 3px 0; overflow: hidden; } div.ygrp-file { width: 30px; valign: middle; } div.attach-table div.attach-row div div a { text-decoration: none; } div.attach-table div.attach-row div div span { font-weight: normal; } div.ygrp-file-title { font-weight: bold; } /* end of attachment style */ --> </style> </head> <html> <head> <style type=3D"text/css"> <!-- #ygrp-mkp { border: 1px solid #d8d8d8; font-family: Arial; margin: 10px 0; padding: 0 10px; } #ygrp-mkp hr { border: 1px solid #d8d8d8; } #ygrp-mkp #hd { color: #628c2a; font-size: 85%; font-weight: 700; line-height: 122%; margin: 10px 0; } #ygrp-mkp #ads { margin-bottom: 10px; } #ygrp-mkp .ad { padding: 0 0; } #ygrp-mkp .ad p { margin: 0; } #ygrp-mkp .ad a { color: #0000ff; text-decoration: none; } --> </style> </head> <body> <!-- |**|begin egp html banner|**| --> <br><br> <!-- |**|end egp html banner|**| --> <div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-family:verdana,= sans-serif;font-size:small;color:#000000">Hi Pedro,</div><div class=3D"gmai= l_default" style=3D"font-family:verdana,sans-serif;font-size:small;color:#0= 00000">I loved the way you explained every steps.=C2=A0</div><div class=3D"= gmail_default" style=3D"font-family:verdana,sans-serif;font-size:small;colo= r:#000000">I also practice DDD and in my project we did all of the above st= eps exactly you said.</div><div class=3D"gmail_default" style=3D"font-famil= y:verdana,sans-serif;font-size:small;color:#000000"><br></div><div class=3D= "gmail_default" style=3D"font-family:verdana,sans-serif;font-size:small;col= or:#000000">However we do 2 things different.=C2=A0</div><div class=3D"gmai= l_default" style=3D"font-family:verdana,sans-serif;font-size:small;color:#0= 00000"><br></div><div class=3D"gmail_default" style=3D"font-family:verdana,= sans-serif;font-size:small;color:#000000"><b>1) How we save domain objects<= /b></div><div class=3D"gmail_default" style=3D"font-family:verdana,sans-ser= if;font-size:small;color:#000000">In order to save domain models we do not = convert it in some other dto.=C2=A0</div><div class=3D"gmail_default" style= =3D"font-family:verdana,sans-serif;font-size:small;color:#000000">We just s= ave the Domain Model as it is. We use Entity Framework and it supports Code= First that is what we use. Our Repository implementation in the Infrastruc= ture directly saves Entity ( Aggregate Root ) in Database.</div><div class= =3D"gmail_default" style=3D"font-family:verdana,sans-serif;font-size:small;= color:#000000">Therefore, we do not need mapper here.</div><div class=3D"gm= ail_default" style=3D"font-family:verdana,sans-serif;font-size:small;color:= #000000"><br></div><div class=3D"gmail_default" style=3D"font-family:verdan= a,sans-serif;font-size:small;color:#000000"><b>2) How we map domain object = to UI dtos</b></div><div class=3D"gmail_default" style=3D"font-family:verda= na,sans-serif;font-size:small;color:#000000">In our application layer itsel= f we have class called as Assembler and that class basically converts Model= To DTO and DTO to Model.=C2=A0</div><div class=3D"gmail_default" style=3D"= font-family:verdana,sans-serif;font-size:small;color:#000000">For example i= f I have Order Aggregate Root Then I have Order Folder in Application Servi= ce Layer. Order Folder has OrderAppService.cs and OrderAssembler.cs.=C2=A0<= /div><div class=3D"gmail_default" style=3D"font-family:verdana,sans-serif;f= ont-size:small;color:#000000">OrderAppService takes dependency of OrderAsse= mbler and calls MapToDto method by giving domain entity. Basically we have = our mapper in Application layer itself.=C2=A0</div><div class=3D"gmail_defa= ult" style=3D"font-family:verdana,sans-serif;font-size:small;color:#000000"= ><br></div><div class=3D"gmail_default" style=3D"font-family:verdana,sans-s= erif;font-size:small;color:#000000">Hope this helps!</div><div class=3D"gma= il_default" style=3D"font-family:verdana,sans-serif;font-size:small;color:#= 000000"><br></div><div class=3D"gmail_default" style=3D"font-family:verdana= ,sans-serif;font-size:small;color:#000000"><br></div><div class=3D"gmail_de= fault" style=3D"font-family:verdana,sans-serif;font-size:small;color:#00000= 0"><br></div><div class=3D"gmail_default" style=3D"font-family:verdana,sans= -serif;font-size:small;color:#000000"><br></div><div class=3D"gmail_default= " style=3D"font-family:verdana,sans-serif;font-size:small;color:#000000"><b= r></div><div class=3D"gmail_default" style=3D"font-family:verdana,sans-seri= f;font-size:small;color:#000000"><br></div><div class=3D"gmail_default" sty= le=3D"font-family:verdana,sans-serif;font-size:small;color:#000000"><br></d= iv><div class=3D"gmail_default" style=3D"font-family:verdana,sans-serif;fon= t-size:small;color:#000000"><br></div><div class=3D"gmail_default" style=3D= "font-family:verdana,sans-serif;font-size:small;color:#000000"><br></div><d= iv class=3D"gmail_default" style=3D"font-family:verdana,sans-serif;font-siz= e:small;color:#000000"><br></div></div><div class=3D"gmail_extra"><br clear= =3D"all"><div><div class=3D"gmail_signature" data-smartmail=3D"gmail_signat= ure"><div dir=3D"ltr"><div><div dir=3D"ltr"><div><font size=3D"2"><br><span= style=3D"background-color:rgb(255,255,255)"><br><font face=3D"verdana, san= s-serif" color=3D"#000000">Thanks,</font></span></font></div><div><span sty= le=3D"background-color:rgb(255,255,255)"><font size=3D"2" face=3D"verdana, = sans-serif" color=3D"#000000">Rupesh kumar Tiwari</font></span></div><div s= tyle=3D"color:rgb(102,51,0);font-family:verdana,sans-serif"><font size=3D"2= "><b>=C2=A0</b></font></div></div></div></div></div></div> <br><div class=3D"gmail_quote">On Thu, Apr 27, 2017 at 12:44 PM, <a href=3D= "mailto:[email protected]">[email protected]</a> [domaindrivend= esign] <span dir=3D"ltr"><<a href=3D"mailto:domaindrivendesign@yahoogrou= ps.com" target=3D"_blank">[email protected]</a>></span>= wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;bor= der-left:1px #ccc solid;padding-left:1ex"> <u></u> =20 <div style=3D"background-color:#fff"> <span style=3D"display:none">=C2=A0</span> <div id=3D"m_-5464398084282839754ygrp-mlmsg"> <div id=3D"m_-5464398084282839754ygrp-msg"> <div id=3D"m_-5464398084282839754ygrp-text"> =20=20=20=20=20=20 =20=20=20=20=20=20 <p></p><p><span>Hey guys,=C2=A0</span></p><p><span><br></span></p><p>= <span>How do you manage data mapping in DDD?</span></p><p>To me, to follow = DDD principles, we'd need to do the following:</p><p></p><ul><li>client= s have their own DTO, to represent the data in their level</li><li>clients = do NOT work with domain objects such entities, aggregates ... domain model,= in general;</li><li>clients call, via controllers/application services, th= e domain services from the domain</li><li>domain services talk to repositor= ies, and both work with the domain model</li><li>repository definition belo= ngs to the domain layer, but implementation belongs to infrastructure;</li>= <li>repository implementation need mappers to convert from domain model to = DTO and vice-versa;</li></ul><div>Some consequences of the DDD are that, in= the domain model, I'd never put JPA annotations (and any other infrast= ructure-related stuff). DTOs, in the infrastructure layer, would be the cla= sses that are actually mapped with such a thing.=C2=A0</div><div><br></div>= <div>But then we need data mapping between client and domain and also domai= n and infrastructure.=C2=A0</div><div>Where do you usually put it? Would it= be kind of separate modules such as:</div><div><ul><li>a module (separate = library) that maps client DTO's to domain objects, and the model depend= s on it;</li><li>a module (separate library) that maps domain objects to in= frastructure (example: DB) model and vice-versa, and the infrastructure dep= ends on it (repository implementation receives domain objects as parameters= , convert them or build whatever query it needs, persist/fetch data and, ev= entually, converts data back to domain objects to return to the caller);</l= i></ul><div>That's the only way I can think of, preserving the DDD prin= ciples.=C2=A0</div><div>Doing so, we kinda preserve domain talking about do= main, infra talking about data, no 'infra-related' configuration on= domain objects, and also no clients speaking in the domain terms.=C2=A0</d= iv><div><br></div><div>What do you think? How do you play with data mapping= ?=C2=A0</div><div>By the way, do you agree with my words?</div><div><br></d= iv><div>Cheers,=C2=A0</div><div>Pedro</div></div><p></p> <p></p></div> =20=20=20=20=20 =20=20=20=20 <div style=3D"color:#fff;height:0"></div> </div> =20=20 </blockquote></div><br></div> <!-- |**|begin egp html banner|**| --> <br> <br> <!-- |**|end egp html banner|**| --> <div width=3D"1" style=3D"color: white; clear: both;"/>__._,_.___</div> =20=20=20=20=20=20 =20=20 =20=20=20=20 <div id=3D"fromDMARC" style=3D"clear:both; margin-top: 10px;"> <hr style=3D"height:2px ; border-width:0; color:#E3E3E3; backgroun= d-color:#E3E3E3;"> Posted by: Rupesh Kumar Tiwari <[email protected]> <h= r style=3D"height:2px ; border-width:0; color:#E3E3E3; background-color:#E3= E3E3;"> </div> <!-- Start Recommendations --> <!-- End Recommendations --> <!-- |**|begin egp html banner|**| --> <img src=3D"http://geo.yahoo.com/serv?s=3D97476590/grpId=3D8116923/grpspI= d=3D1705007181/msgId=3D24819/stime=3D1494000664" width=3D"1" height=3D"1"> = <br> <!-- |**|end egp html banner|**| --> =20=20 <!-- |**|begin egp html banner|**| --> <br> =20=20=20 =20=20=20=20=20 =20 <!-- |**|begin egp html banner|**| --> <div id=3D"ygrp-vital" style=3D"background-color: #f2f2f2; font-fam= ily: Verdana; font-size: 10px; margin-bottom: 10px; padding: 10px;"> <span id=3D"vithd" style=3D"font-weight: bold; color: #333; text-tr= ansform: uppercase; "><a href=3D"https://groups.yahoo.com/neo/groups/domain= drivendesign/info;_ylc=3DX3oDMTJlb3ZxMzAwBF9TAzk3MzU5NzE0BGdycElkAzgxMTY5Mj= MEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwN2dGwEc2xrA3ZnaHAEc3RpbWUDMTQ5NDAwMDY2NA--"= style=3D"text-decoration: none;">Visit Your Group</a></span> <ul style=3D"list-style-type: none; margin: 0; padding: 0; display: in= line;"> <li style=3D"border-right: 1px solid #000; font-weight: 700; di= splay: inline; padding: 0 5px; margin-left: 0;"> <span class=3D"cat"><a href=3D"https://groups.yahoo.com/neo/groups/do= maindrivendesign/members/all;_ylc=3DX3oDMTJmZ2ZwbWthBF9TAzk3MzU5NzE0BGdycEl= kAzgxMTY5MjMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwN2dGwEc2xrA3ZtYnJzBHN0aW1lAzE0OT= QwMDA2NjQ-" style=3D"text-decoration: none;">New Members</a></span> <span class=3D"ct" style=3D"color: #ff7900;">3</span> </li> </ul> </div> <div id=3D"ft" style=3D"font-family: Arial; font-size: 11px; margin-top: 5p= x; padding: 0 2px 0 0; clear: both;"> <a href=3D"https://groups.yahoo.com/neo;_ylc=3DX3oDMTJkZWZhbHVjBF9TAzk3ND= c2NTkwBGdycElkAzgxMTY5MjMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwNmdHIEc2xrA2dmcARzd= GltZQMxNDk0MDAwNjY0" style=3D"float: left;"><img src=3D"http://l.yimg.com/r= u/static/images/yg/img/email/new_logo/logo-groups-137x15.png" height=3D"15"= width=3D"137" alt=3D"Yahoo! 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