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Ada and HANA playing together

former_member182779
Active Contributor
‎2015 Nov 02 8:16 PM
0 Kudos
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Ada is a structured, statically typed, imperative, wide-spectrum and object-oriented programming language, extended from Pascal and other languages.

It was originally developed for the United States Department of Defense. And it was named after Ada Lovelace (1815-1852), who was the first computer programmer.

Ada is a language that simply would not allow you to fail…as it have mechanisms for compile and execution time checks…getting rid of most of the bugs that your application could ever produce…

So…no example or demonstration would be complete if we didn’t hook it up with SAP HANA, right? So…let’s go and do it -;)

First, we need to create a Calculation View and call it “FLIGHTS_BY_CARRIER”. It will be composed of two tables, SCARR and SFLIGHT.

First, we need to create a Join object and link the table by MANDT and CARRID. From here select the following fields as output MANDT, CARRID, CARRNAME, PRICE and CURRENCY.

Then create an Aggregation object selecting the fields CARRNAME, PRICE (As Aggregated Column) and CURRENCY. Filter the CURRENCY field by ‘USD’.

Then create a Projection object and select only PRICE and CARRNAME.


On the Semantics object make sure to select “CROSS CLIENT” as the Default Client.

Now, switch to the SAP HANA Development View and create a new repository. Call it “Flights”.

Create a new “XS Engine” project and call it “Flights” as well. Link it to the “Flights” repository.

Create an empty “.xsapp” file.

Create a file called “.xsaccess” with the following code.

.xsaccess

{

"exposed" : true,

"authentication" : [ { "method" : "Basic" } ]

}

Finally create a file called “flights.xsodata” with the following code

flights.xsodata

service {

          "Blag/FLIGHTS_BY_CARRIER.calculationview" as "FLIGHTS" keys generate local "Id";

}


Activate your project and launch it on your browser, you should see something like this…


The SAP HANA part is done…so we can move into the Ada part…

Ada comes installed in most Linux-based distros…but the version can be old…so it’s better to download and install a more recent version…so please just do this on a terminal session…

sudo apt-get install gnat

sudo apt-get install libaws-bin libaws3.2.0-dev

To install both Ada and AWS (Nope…not that one…but Ada Web Server)…


Also, we will need to download and install XML/Ada

tar zxvf xmlada-gpl-4.3-src.tgz

cd xmlada-4.3-src/

./configure --prefix=/usr/gnat

PROCESSORS=4 make all

make docs

make install

Then, you will need to update your .bashrc file in order to have the right paths…


PATH=/usr/gnat/lib/gnat:$PATH

export PATH

GPR_PROJECT_PATH=/usr/gnat/lib/gnat:$GPR_PROJECT_PATH

export GPR_PROJECT_PATH

ADA_PROJECT_PATH=$ADA_PROJECT_PATH:/usr/gnat/lib/gnat

export ADA_PROJECT_PATH

ADA_OBJECTS_PATH=$ADA_OBJECTS_PATH:/usr/gnat/lib/gnat

export ADA_OBJECTS_PATH

ADA_INCLUDE_PATH=$ADA_INCLUDE_PATH:/usr/gnat/lib/gnat

export ADA_INCLUDE_PATH

The create a file called ada_hana.adb on your favorite editor and copy the following code

Ada_HANA.adb

with Ada.Text_IO; use Ada.Text_IO;

with AWS.Client;

with AWS.Response;

with Input_Sources.Strings;

with Unicode.CES.Utf8;

with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;

with Sax.Readers;        use Sax.Readers;

with DOM.Readers;        use DOM.Readers;

with DOM.Core;           use DOM.Core;

with DOM.Core.Documents; use DOM.Core.Documents;

with DOM.Core.Nodes;     use DOM.Core.Nodes;

with DOM.Core.Attrs;     use DOM.Core.Attrs;

procedure Ada_Hana is

  Flights : Unbounded_String;

  Input : Input_Sources.Strings.String_Input;

  Reader : Tree_Reader;

  Doc    : Document;

  C_List   : Node_List;

  P_List   : Node_List;

  C_N      : Node;

  P_N      : Node;

begin

  Flights := AWS.Response.Message_Body (AWS.Client.Get (URL => "http://YourServer:8000/Flights/flights.xsodata/FLIGHTS",

                                                                                           User => "SYSTEM", Pwd => "YourPassword"));

  Input_Sources.Strings.Open (To_String(Flights), Unicode.CES.Utf8.Utf8_Encoding, Input);

  DOM.Readers.Parse (Reader, Input);

  Doc := Get_Tree (Reader);

  C_List := Get_Elements_By_Tag_Name (Doc, "d:CARRNAME");

  P_List := Get_Elements_By_Tag_Name (Doc, "d:PRICE");

   for Index in 1 .. Length (C_List) loop

      C_N := Item (C_List, Index - 1);

      P_N := Item (P_List, Index - 1);

      Put_Line (Node_Value(First_Child(C_N)) & ": " & Node_Value(First_Child(P_N)));

   end loop;

   Free (C_List);

   Free (P_List);

   Free (Reader);

end Ada_Hana;

To compile this application we need to create another file…called compile_ada_hana.gpr


ada_hana.gpr

with "aws";

project Compile_Ada_HANA is

for Main use ("ada_hana.adb");

end Compile_Ada_HANA;


And run it like this…


sudo gprbuild compile_ada_hana.gpr

One the executable is done…we can run it like this…

./ada_hana

If you are wondering…why didn’t I use JSON instead of XML? Well…there’s an easy explanation for that :smile: The JSON library is nice…but I had some troubles compiling it and there’s not much examples on how to retrieve the data from a complex JSON…so using XML looked like an easier and better choice :wink: