Office web apps are now getting more and more popular with the SharePoint 2013 environment. In the native SharePoint environment when you click on a document it will open in Office online (OWA) based on configuration.

But if you a writing a SharePoint Hosted app or a Provider Hosted app; you might wonder how to open it in Office web apps and what is the URL you are going to use.

You can use JSOM and SharePoint REST services to achieve this.

First, you need to send a REST request by mentioning the file name.

url: AppWebUrlUrl + "/_api/web/GetFileByServerRelativeUrl('server relative file name')",
method: "GET",
contentType: "application/json;odata=verbose",
headers: { "Accept": "application/json; odata=verbose" }
You should carefully give the server the relative file name for this operation. Regardless of app type (Provider hosted or a SharePoint Hosted ) file name it coming with app web URL.

Ex:

Absolute File URL

https://oapp-bfb82901075d6b.sharepoint.com/sites/dev/myapp/lists/lcrdocs/file1.doc

Relative File URL

/sites/dev/myapp/lists/lcrdocs/file1.doc

Depending on the App type either you need to use the RequestExecutor or normal rest approach.

Using RequestExecutor in Provider Hosted Apps


var executor = new SP.RequestExecutor("app web url"); // you need to pass app web url
 
executor.executeAsync({
url: "app web url" + "/_api/web/GetFileByServerRelativeUrl('relative doc url')",
method: "GET",
contentType: "application/json;odata=verbose",
headers: { "Accept": "application/json; odata=verbose" },
success: function (data) {
    var arry = JSON.parse(data.body).d;
    if (arry.LinkingUrl) {
        // can open with office web apps
        var owaurl = "app web url" + "/_layouts/15/WopiFrame.aspx?sourcedoc={" + arry.UniqueId + "}&file=" + encodeURIComponent(arry.Title) + "&action=default";                   
    } else {
        // can not open with office web apps (ex:txt)
    }
},
error: function (data, errorCode, errorMessage) {
// error
}
});
If the LinkingUrl available indicates it can be open via Office web apps. LinkingUrl sometimes returns direct web app URL. Thus you don’t need to create the URL by amending items but sometimes it returns the absolute document URL. This approach suits both occasions.

Ajax Request in SharePoint Hosted Apps


$.Ajax({ // Jquery needed
url: "app web url" + "/_api/web/GetFileByServerRelativeUrl('relative doc url')",
method: "GET",
contentType: "application/json;odata=verbose",
headers: { "Accept": "application/json; odata=verbose" },
success: function (data) {
    var arry = JSON.parse(data.body).d;
    if (arry.LinkingUrl) {
        // can open with office web apps
        var owaurl = "app web url" + "/_layouts/15/WopiFrame.aspx?sourcedoc={" + arry.UniqueId + "}&file=" + encodeURIComponent(arry.Title) + "&action=default";                   
    } else {
        // can not open with office web apps (ex:txt)
    }
},
error: function (data, errorCode, errorMessage) {
// error
}
});