Using Salesforce Partner API from community portal

Question

I've created a custom button on the opportunity layout which calls out to an external java app. It passes the session id and the partner API URL. The external app then creates a SOAP binding (leveraging the partner wsdl downloaded from Setup). The first thing I do with the binding is call SoapBindingStub.getUserInfo().

My org has the Communities feature enabled to allow partner users to log in through community portals. When I click the custom button coming from a community portal, the above fails and I see "Caused by: (411)Length Required" in the stack. It works just fine if I click the button coming from salesforce (rather than a community portal).

Any ideas what's causing the RemoteException? I'm using the same user for both scenarios. Here's the full stack trace:

Caused by: (411)Length Required at 
org.apache.axis.transport.http.CommonsHTTPSender.invoke(CommonsHTTPSender.java:218) at 
org.apache.axis.strategies.InvocationStrategy.visit(InvocationStrategy.java:32) at 
org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:118) at 
org.apache.axis.SimpleChain.invoke(SimpleChain.java:83) at 
org.apache.axis.client.AxisClient.invoke(AxisClient.java:165) at 
org.apache.axis.client.Call.invokeEngine(Call.java:2784) at 
org.apache.axis.client.Call.invoke(Call.java:2767) at 
org.apache.axis.client.Call.invoke(Call.java:2443) at 
org.apache.axis.client.Call.invoke(Call.java:2366) at 
org.apache.axis.client.Call.invoke(Call.java:1812) at 
com.sforce.soap.partner.SoapBindingStub.getUserInfo(SoapBindingStub.java:3994)

I'm wondering if the URL is the cause. Is there some setting/permission in communities that needs to be set in order to do this? Here are the URLS observed:

https://myCommunityDomainName.force.com/myCommunityName/services/Soap/u/28.0/00Di0000000eG2r -does not work

https://na15.salesforce.com/services/Soap/u/28.0/00Di0000000eG2r -works

Answer 1

Found an answer for this.

I used SOAP UI to try making these calls, and I got a more helpful error message: "API access is disabled for Communities". From there I was able to find a blog post with some details.

Apparently, when coming from a Community portal, the API.Parner_Server_URL should not be used to make API calls back to Salesforce (what?!). Salesforce support says to use the endpoint that would result from a standard salesforce user clicking the link (na15.salesforce.com/... as seen above, for example). They claim it is working as designed, which makes me wonder what the heck API.Parner_Server_URL is any good for when coming though a community portal.

Here's the blog post for reference: http://boards.developerforce.com/t5/APIs-and-Integration/API-Access-Disabled-for-Communities/td-p/644035

EDIT: See Dana's answer below; according to the author, support for this has been added as of Summer '15.

Answer 2

I can confirm that as of Summer 15, the RESTful Identity URL returns a usable partner url:

https://custom-dev-ed.my.salesforce.com/services/Soap/u/{version}/orgidorgidorgidorgid

Additionally, the API Enabled option must be selected on the community user's profile. From there I was able to access the API on behalf of a community user.

{
   "id":"https://login.salesforce.com/id/orgidorgidorgidorgid/useriduseriduserid",
   "asserted_user":true,
   "user_id":"useriduseriduserid",
   "organization_id":"orgidorgidorgidorgid",
   "username":"[email protected]",
   "nick_name":"custom",
   "display_name":"custom",
   "email":"[email protected]",
   "email_verified":true,
   "first_name":"custom",
   "last_name":"custom",
   "timezone":"America/Los_Angeles",
   "photos":{
      "picture":"https://custom-dev-ed.my.salesforce.com/img/userprofile/default_profile_200.png",
      "thumbnail":"https://custom-dev-ed.my.salesforce.com/img/userprofile/default_profile_45.png"
   },
   "addr_street":"123 Some Street",
   "addr_city":"Anytown",
   "addr_state":"PA",
   "addr_country":"USA",
   "addr_zip":"80000",
   "mobile_phone":null,
   "mobile_phone_verified":false,
   "status":{
      "created_date":null,
      "body":null
   },
   "urls":{
      "enterprise":"https://custom-dev-ed.my.salesforce.com/services/Soap/c/{version}/orgidorgidorgidorgid",
      "metadata":"https://custom-dev-ed.my.salesforce.com/services/Soap/m/{version}/orgidorgidorgidorgid",
      "partner":"https://custom-dev-ed.my.salesforce.com/services/Soap/u/{version}/orgidorgidorgidorgid",
      "rest":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/",
      "sobjects":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/sobjects/",
      "search":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/search/",
      "query":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/query/",
      "recent":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/recent/",
      "profile":"https://custom-dev-ed.my.salesforce.com/useriduseriduserid",
      "feeds":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/chatter/feeds",
      "groups":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/chatter/groups",
      "users":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/chatter/users",
      "feed_items":"https://custom-dev-ed.my.salesforce.com/services/data/v{version}/chatter/feed-items",
      "custom_domain":"https://custom-dev-ed.my.salesforce.com"
   },
   "active":true,
   "user_type":"POWER_PARTNER",
   "language":"en_US",
   "locale":"en_US",
   "utcOffset":-28800000,
   "last_modified_date":"2015-07-22T10:34:51-06:00",
   "is_app_installed":true
}