Mark Needham

Thoughts on Software Development

SharpCouch: Use anonymous type to create JSON objects

without comments

I’ve been playing around with CouchDB a bit today and in particular making use of SharpCouch, a library which acts as a wrapper around CouchDB calls. It is included in the CouchBrowse library which is recommended as a good starting point for interacting with CouchDB from C# code.

I decided to work out how the API worked with by writing an integration test to save a document to the database.

The API is reasonably easy to understand and I ended up with the following test:

[Test]
public void ShouldAllowMeToSaveADocument()
{
    var server = "http://localhost:5984";
    var databaseName = "sharpcouch";
    var sharpCouchDb = new SharpCouch.DB();
 
    sharpCouchDb.CreateDocument(server, databaseName, "{ key : \"value\"}");
}

In theory that should save the JSON object { key = “value” } to the database but it actually throws a 500 internal error in SharpCouch.cs:

275
HttpWebResponse resp = req.GetResponse() as HttpWebResponse;

Debugging into that line the Status property is set to ‘Protocol Error’ and a bit of Googling led me to think that I probably had a malformed client request.

I tried the same test but this time created the document to save by creating an anonymous type and then converted it to a JSON object using the LitJSON library:

[Test]
public void ShouldAllowMeToSaveADocumentWithAnonymousType()
{
    var server = "http://localhost:5984";
    var databaseName = "sharpcouch";
    var sharpCouchDb = new SharpCouch.DB();
 
    var savedDocument = new { key = "value"};
    sharpCouchDb.CreateDocument(server, databaseName, JsonMapper.ToJson(savedDocument));
}

That works much better and does actually save the document to the database which I was able to verify by adding a new method to SharpCouch.cs which creates a document and then returns the ‘documentID’, allowing me to reload it afterwards.

[Test]
public void ShouldAllowMeToSaveAndRetrieveADocument()
{
    var server = "http://localhost:5984";
    var databaseName = "sharpcouch";
    var sharpCouchDb = new SharpCouch.DB();
 
    var savedDocument = new {key = "value"};
    var documentId = sharpCouchDb.CreateDocumentAndReturnId(server, databaseName, JsonMapper.ToJson(savedDocument));
 
    var retrievedDocument = sharpCouchDb.GetDocument(server, databaseName, documentId);
 
    Assert.AreEqual(savedDocument.key, JsonMapper.ToObject(retrievedDocument)["key"].ToString());
}
public string CreateDocumentAndReturnId(string server, string db, string content)
{
    var response = DoRequest(server + "/" + db, "POST", content, "application/json");
    return JsonMapper.ToObject(response)["id"].ToString();
}

I’m not sure how well anonymous types work for more complicated JSON objects but for the simple cases it seems to do the job.

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Written by Mark Needham

May 31st, 2009 at 8:59 pm

Posted in .NET,CouchDB

Tagged with ,