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.

Written by Mark Needham

May 31st, 2009 at 8:59 pm

Posted in .NET,CouchDB

Tagged with ,

«
»