Hi all,
This is the first post of a series that will engage with the development, from start to end, of a simple application on the SAP HANA platform, accompanied of course by the underlying theory. To offer a spherical presentation of the platform, I tried to use a variety of HANA capabilities, but of course some things will be missing. Further information can be found in the developer guide.
- Application
To begin with, let’s see what our application is about. The application that I will present here is called BlogProject and I think that what it will do is pretty obvious considering the name, but I am going to describe it anyway. So, in the app a user will be able to login/register, search for and view a post, write one or write a comment on a certain post. Simple as that. I may extend the application, adding a user profile, for a user to be able to see his/her own posts and comments, or some kind of statistics page, for example a geographical distribution of the posts.
- Prerequisites
1. You have access to an SAP HANA system. If you don’t have, then explore your options and choose the right one for
you: http://scn.sap.com/community/hana-in-memory/blog/2014/05/21/get-access-to-a-sap-hana-instance
2. Add your HANA system to your HANA studio
- Studio explanation
Let’s take a glimpse to the HANA studio. The studio includes different perspectives, each giving a different view.
Project Explorer: here we can see all our projects and files included in each.
Repositories: here we see all your local workspaces
Systems: in this view we can add and manage our HANA systems and database objects
- Repository Workspace
First, we have to create a workspace for our project. In the “Repositories” view right click -> New Repository Workspace. In the window choose your user (SYSTEM in this case). Then give a name to your workspace. In our case “workspace1” (don’t ask why…) and a location where to save it.
- Project
After the workspace creation we have to create our project. To do so we have to go to the “Project Explorer”, right click and then “New” -> “Project”. Then find and choose XS Project (SAP HANA -> Application Development).
After the project is created, it is a good practice to create the following folders, in order for our project to be organized: data, model, procedures, services and ui. We will see later what files we create in each folder.
Share and activate the project: To be able to activate our project we have to share it first, adding it to our workspace. To share it follow this procedure: right click on your project-> “Team” -> “Share Project” -> Choose “SAP HANA Repository” -> Choose (or add) your Workspace and click “Finish”.
We must always activate our project when we make any changes, for them to be committed and shared. To do so right click on your project or the file(s) you want to activate -> “Team” -> ”Activate”.
.xsapp .xsaccess files: These files are necessary for exposing any content via the XSEngine web server. Create the three files but without a name, just the extension. The .xsapp file does not contain any content. In the .xsaccess file paste the following:
{
"exposed":true
}
- Schema
For our application to be able to create and access database objects we have to create a schema, which will hold all the database objects we will create, such as tables, SQL views and stored procedures. By default we are granted a schema called “SYSTEM”, but it is a better practice to create a separate schema for our application, so that your database is more organized.
The procedure is very easy. We just have to create in the “data” folder of our project a new file with the extension .hdbschema. The definition of the schema is the following
schema_name="BlogProject";
Or we can open the SQL console from the “Systems” view and execute the following create statement:
CREATE SCHEMA BlogProject [OWNED BY SYSTEM]
- Authorization model
Authorization is about providing access to specific resources only to certain users. The basic entity of the authorization model is a privilege. Privileges can be granted to a role, which is a group of privileges, or a user. Additionally, a user can be granted certain roles. The best practice it to assign privileges to roles and roles to users. That way the authorization model will be more organized.
First, let’s create a privilege to our application. We have to create an .xsprivileges file without a name. In the .xsprivileges paste the following:
{
"privileges":[
{
"name":"Basic",
"description":"Basic usage privilege"
},
{
"name":"Admin",
"description":"Administration privilege"
} ]
Now that we have created the privileges to our application, we must grant them to a role so that we can have access. To create a role we just create a new file with the extension .hdbrole. Inside the file we type the following definition.
role MyBlogProject::model_access {
application privilege: MyBlogProject::Admin;
}
Now our role has Admin rights upon our application. Then to assign the role to our user “SYSTEM” we have to go to the “Systems” view -> “Security” -> “Users” -> SYSTEM -> “Granted Roles” and then add the role MyBlogProject::model_access we created.
Next for our user and application to be able to access and write on the schema we created, we have to go to again to the security tab -> “roles” -> MyBlogProject::model_access -> object privileges and add our schema “BlogProject. Now that we added this privilege to our role, all the users who have the certain role will also have the same privileges to the schema.
As you may have noticed I granted our role certain privileges twice, the first time via the .hdbrole file in the repository and the second via the “Systems” view. We can edit the authentication model using both ways.
This concludes this first post of the series. Next we will see how to create our data definition (aka persistence model) beyond the creation of the schema that was illustrated above, creating tables and sequences:
- SAP Managed Tags:
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