Author: Rudramani Pandey

Get Token from SAP Cloud Platform Service

Preface – This post is part of the ABAP Programs series.

In this step we will call the service to get the token and store that token in a global variable for later use.

METHOD get_token.
    DATA: lo_http_client TYPE REF TO if_http_client.
    DATA: response TYPE string,
          lv_url   TYPE string.
    CONSTANTS: lv_initial_url TYPE string VALUE '<Blockchain Service Link>',
               lv_auth        TYPE string VALUE 'Basic <your login credentials>'.
    "create HTTP client by url
    CALL METHOD cl_http_client=>create_by_url
      EXPORTING
        url                = lv_initial_url
      IMPORTING
        client             = lo_http_client
      EXCEPTIONS
        argument_not_found = 1
        plugin_not_active  = 2
        internal_error     = 3
        OTHERS             = 4.
    "Available API Endpoints
    "https://blockchain-service.cfapps.sap.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    "https://blockchain-service.cfapps.eu10.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    "https://blockchain-service.cfapps.us10.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    IF sy-subrc <> 0.
      "error handling
    ENDIF.
    "setting request method
    lo_http_client->request->set_method('GET').
    "adding headers
    lo_http_client->request->set_header_field( name = 'Authorization' value = lv_auth ).
    "Available Security Schemes for productive API Endpoints
    "OAuth 2.0
    CALL METHOD lo_http_client->send
      EXCEPTIONS
        http_communication_failure = 1
        http_invalid_state         = 2
        http_processing_failed     = 3
        http_invalid_timeout       = 4
        OTHERS                     = 5.
    IF sy-subrc = 0.
      CALL METHOD lo_http_client->receive
        EXCEPTIONS
          http_communication_failure = 1
          http_invalid_state         = 2
          http_processing_failed     = 3
          OTHERS                     = 5.
    ENDIF.
    IF sy-subrc <> 0.
      "error handling
    ENDIF.
    response = lo_http_client->response->get_cdata( ).
   GV_TOKEN = response. "Global Variable
  ENDMETHOD.

December 29, 2019

Calculate a hash in ABAP

Preface – This post is part of the ABAP Programs series.

In ABAP we can perform the following:

calculate_hash_for_raw

METHOD calculate_hash_for_raw.

    TRY.
        cl_abap_message_digest=>calculate_hash_for_raw(
          EXPORTING
            if_algorithm = 'SHA256'
            if_data      = iv_data
          IMPORTING
            ef_hashstring = ev_sha256
        ).
      CATCH cx_root.
        " Eh, what're you gonna do?
    ENDTRY.
  ENDMETHOD.

calculate_hash_for_string

METHOD calculate_hash_for_string.

    TRY.
        cl_abap_message_digest=>calculate_hash_for_char(
          EXPORTING
            if_algorithm = 'SHA256'
            if_data      = iv_data
          IMPORTING
            ef_hashstring = ev_sha256
        ).
      CATCH cx_root.
        " Eh, what're you gonna do?
    ENDTRY.
  ENDMETHOD.

December 29, 2019

Navigate between Views in Web Dynpro
Preface – This post is part of the SAP ABAP Web Dynpro series.

Introduction

In our previous articles we have already seen how to create a view in Web Dynpro. In Web Dynpro we can create multiple views under a component. It is also important to embed that view in the window to make it visible. In this article we will explore how to navigate between Views in Web Dynpro. Before jumping directly to the navigation concept, we will start with the concept of plugs in Web Dynpro.

Navigate between Views in Web Dynpro

A Web Dynpro application needs following to navigate between two views within a window:
1. Views: At least two views which will have the navigation concept implemented.
2. Navigation Links: A Navigation link is the connection between the above views.
3. Plugs: A plug is the port that exists at both the ends of the Navigation link.
The above concepts can be understood with the diagram shown below:

Plugs

A plug is a junction used for accessing or existing a view. Either you will access a view or exist a view; and for both case we have two different plugs. These are:

Inbound Plug

This is a plug which is used to enter a view. Every inbound plug must be linked to an outbound plug else it produces errors.

Outbound Plug

This is a plug which is used to exit a view. Every outbound plug must be linked to an inbound plug else it produces errors.

Navigation Link

A Navigation link is the connection between two views. It needs plugs to execute a navigation.

Step by step process to create a Navigation between views

Step 1: Go to SE80, create a web Dynpro component ZTest_PLUGS.

Step 2: Go to main view, insert a button, provide button text as ‘Press’, and create action method for button ON_PRESS.

Step 3: Right click on component -> create -> view, provide name as DETAILS_VIEW and enter.

Step 4: Go to “DETAILS_VIEW” view, insert a button, provide button text as ‘Back’, create action method for button ON_BACK.

Step 5: Go to main view, outbound plugs tab, add outbound plug as GOTO_DETAILS_VIEW and inbound plugs tab add inbound plug as IN_MAIN.

Step 6: Go to DETAILS_VIEW view, outbound plugs tab, add outbound plug as GOTO_MAIN and inbound plugs tab add inbound plug as IN_DETAILS.

Step 7: Expand window, drag and drop MAIN, “DETAILS_VIEW” view into window.

Step 8: Expand two views, right click on GOTO_ DETAILS_VIEW -> Create Navigation Link, press F4, select destination view as DETAILS_VIEW and enter.

Step 9: Right click on GOTO_MAIN -> Create Navigation Link, press F4, select destination view as MAIN and enter.

Step 10: Go to main view actions tab, double click on ON_PRESS method and add below code.

wd_this->FIRE_GOTO_ DETAILS_VIEW_PLG( );

Step 11: Go to DETAILS_VIEW view actions tab, double click on ON_BACK method and add below code.

wd_this->FIRE_GOTO_MAIN_PLG( );

Step 12: Save and Activate the components.

Step 13: Run and Test the components.
December 29, 2019
Data Binding in Web Dynpro
Preface – This post is part of the SAP ABAP Web Dynpro series.

Introduction

A Web Dynpro Application is developed using MVC (Model View Controller) Architecture. It means whatever data model is there that requires binding with the View elements (e.g. Input Field, Check box, Table, etc.). This binding can be achieved using view and controller. In this article we will explore data binding in Web Dynpro.

Data Binding in Web Dynpro

In Web Dynpro, we have multiple components. In our previous article, we have already discussed that we have something called Context which is a data container which stores data at runtime. A context can have multiple nodes e.g. Table nodes which will store table data. These nodes can have multiple Attributes that are the fields of the table.

Definition

Binding of the attributes or nodes of a context with UI elements (e.g. Table, Input Fields, etc.) is known as Data Binding in Web Dynpro.

Why we need Data Binding
1. To show Customer Data on the Web Dynpro screen
2. To auto fill the input fields based on pre-defined selections
3. To provide search helps for an input element
4. To maintain/provide conditions on UI based on backend data
Types of Data Binding
1. Internal Mapping
  It is a mapping between contexts of single component.
2. External Mapping
  It is a mapping between multiple contexts using their interface controller.
Setup and Coding for Data Binding

In our previous articles we have already shared steps to create a Web Dynpro View and publish it as an application. You can follow steps and code mentioned here to convert that application in an Application which utilizes data binding.
December 29, 2019

Blockchain Implementation in ABAP

Preface – This post is part of the Blockchain on SAP Cloud Platform series.

Introduction

With the introduction of Blockchain in SAP Cloud Platform, the important questions for SAP developers was its implementation in SAP ABAP. All the client information of SAP is mainly on premise based. The major amount of data is already stored in backend system and if we cannot push this data on blockchain then the Blockchain on SAP Cloud Platform is of no use. In this article we will explain the Blockchain Implementation in ABAP.

Blockchain on SAP Cloud Platform

In our previous articles we have already explained the blockchain services (mainly Hyperledger, Multichain and Quorum) on SAP Cloud Platform. These instances are connected with SAP Blockchain enablement services, which acts as an interface between these blockchain services and other SAP services.

Blockchain Implementation in ABAP

We can easily understand the blockchain implementation in ABAP using the given block diagram:

Blockchain Implementation in ABAP

In the diagram above, you can see that the SAP ABAP interacts with Blockchain Enablement services and the HANA Database. This application can be either displayed using Classical ABAP Report or using Fiori Application which will then use OData to interact with SAP ABAP methods.

To call any service in SAP Cloud platform, we need to do the following:

Get Token from the service using a read call.
Perform CRUD operation on the service using the token received above.

Let us understand these steps with respect to the blockchain services.

Get Token from the Blockchain Service

In this step we will call the service to get the token and store that token in a global variable for later use.

METHOD get_token.
    DATA: lo_http_client TYPE REF TO if_http_client.
    DATA: response TYPE string,
          lv_url   TYPE string.
    CONSTANTS: lv_initial_url TYPE string VALUE '<Blockchain Service Link>',
               lv_auth        TYPE string VALUE 'Basic <your login credentials>'.


    "create HTTP client by url
    CALL METHOD cl_http_client=>create_by_url
      EXPORTING
        url                = lv_initial_url
      IMPORTING
        client             = lo_http_client
      EXCEPTIONS
        argument_not_found = 1
        plugin_not_active  = 2
        internal_error     = 3
        OTHERS             = 4.

    "Available API Endpoints
    "https://blockchain-service.cfapps.sap.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    "https://blockchain-service.cfapps.eu10.hana.ondemand.com/blockchain/proofOfHistory/api/v1
    "https://blockchain-service.cfapps.us10.hana.ondemand.com/blockchain/proofOfHistory/api/v1

    IF sy-subrc <> 0.
      "error handling
    ENDIF.

    "setting request method
    lo_http_client->request->set_method('GET').

    "adding headers
    lo_http_client->request->set_header_field( name = 'Authorization' value = lv_auth ).


    "Available Security Schemes for productive API Endpoints
    "OAuth 2.0

    CALL METHOD lo_http_client->send
      EXCEPTIONS
        http_communication_failure = 1
        http_invalid_state         = 2
        http_processing_failed     = 3
        http_invalid_timeout       = 4
        OTHERS                     = 5.

    IF sy-subrc = 0.
      CALL METHOD lo_http_client->receive
        EXCEPTIONS
          http_communication_failure = 1
          http_invalid_state         = 2
          http_processing_failed     = 3
          OTHERS                     = 5.
    ENDIF.

    IF sy-subrc <> 0.
      "error handling
    ENDIF.

    response = lo_http_client->response->get_cdata( ).

   GV_TOKEN = response. "Global Variable
  ENDMETHOD.

Get Proof history from the Blockchain Service

In this step we will call the blockchain service again using the token that we have stored in above step. And then we will receive the history of transactions from blockchain.

METHOD get_proof_history.
    DATA: lo_http_client TYPE REF TO if_http_client.
    DATA: response TYPE string,
          lv_url   TYPE string,
          lv_auth  TYPE string,
          lv_auth2 TYPE string.

    CONSTANTS : lv_initial_url TYPE string VALUE '<Your Service>'.

    IF iv_object_id IS NOT INITIAL.

*** Getting Token
      TYPES:
        BEGIN OF t_entry,
          access_token TYPE string,
          token_type   TYPE string,
          expires_in   TYPE n LENGTH 8,
          scope        TYPE string,
          jti          TYPE string,
        END OF t_entry .
      TYPES:
        t_entry_map TYPE SORTED TABLE OF t_entry WITH UNIQUE KEY access_token.
      DATA: m_entries TYPE t_entry.

      DATA: lr_instance  TYPE REF TO  /ui5/cl_json_parser.
      CREATE OBJECT lr_instance.
      CALL METHOD me->get_token.
      IF gv_token IS NOT INITIAL.

*        data: itab TYPE TABLE OF string.
*        data: access_tok type string.
*        SPLIT gv_token at '"' INTO TABLE itab.
*        try.
*            lv_auth2 = itab[ 4 ].
*          catch cx_sy_itab_line_not_found.
*        ENDTRY.

        /ui2/cl_json=>deserialize(
        EXPORTING json = gv_token pretty_name = /ui2/cl_json=>pretty_mode-camel_case CHANGING data = m_entries ).
        lv_auth2 = m_entries-access_token.
        gv_token = gv_token+17.

        CONCATENATE 'Bearer' lv_auth2 INTO lv_auth SEPARATED BY space.

      ENDIF.
      DATA lv_object_id TYPE string.
      lv_object_id = iv_object_id.
      TRANSLATE lv_object_id TO LOWER CASE.

      CONCATENATE lv_initial_url lv_object_id INTO lv_url. "Appending Fix URL and the Object ID to get the Request URL

      "create HTTP client by url
      CALL METHOD cl_http_client=>create_by_url
        EXPORTING
          url                = lv_url
        IMPORTING
          client             = lo_http_client
        EXCEPTIONS
          argument_not_found = 1
          plugin_not_active  = 2
          internal_error     = 3
          OTHERS             = 4.

      "Available API Endpoints
      "https://blockchain-service.cfapps.sap.hana.ondemand.com/blockchain/proofOfHistory/api/v1
      "https://blockchain-service.cfapps.eu10.hana.ondemand.com/blockchain/proofOfHistory/api/v1
      "https://blockchain-service.cfapps.us10.hana.ondemand.com/blockchain/proofOfHistory/api/v1

      IF sy-subrc <> 0.
        "error handling
      ENDIF.

      "setting request method
      lo_http_client->request->set_method('GET').

      "creatung Auth value
*       lv_auth2 = 'Basic <Your Login Credentials>'.

      "adding headers
*      lo_http_client->request->set_header_field( name = 'Content-Type' value = 'application/x-www-form-urlencoded' ).
      lo_http_client->request->set_header_field( name = 'Accept' value = 'application/json' ).
      lo_http_client->request->set_header_field( name = 'Authorization' value = lv_auth ).
*      lo_http_client->request->set_header_field( name = 'APIKey' value = 'zBoCpDtkaT9jexRjtMk0J98Rs8izmQi1' ).


      "Available Security Schemes for productive API Endpoints
      "OAuth 2.0

      CALL METHOD lo_http_client->send
        EXCEPTIONS
          http_communication_failure = 1
          http_invalid_state         = 2
          http_processing_failed     = 3
          http_invalid_timeout       = 4
          OTHERS                     = 5.

      IF sy-subrc = 0.
        CALL METHOD lo_http_client->receive
          EXCEPTIONS
            http_communication_failure = 1
            http_invalid_state         = 2
            http_processing_failed     = 3
            OTHERS                     = 5.
      ENDIF.

      IF sy-subrc = 1.
        "error handling
        ev_response = 'http_communication_failure'.
      ELSEIF sy-subrc = 2.
        ev_response = 'http_invalid_state'.
      ELSEIF sy-subrc = 3.
        ev_response = 'http_processing_failed'.
      ELSEIF sy-subrc = 0.
        response = lo_http_client->response->get_cdata( ).
*WRITE: 'response: ', response.
        ev_response = response.
      ELSE.
        ev_response = 'Unknown Error'.
      ENDIF.
    ENDIF.
  ENDMETHOD.

December 27, 2019

Components in Web Dynpro
Preface – This post is part of the SAP ABAP Web Dynpro series.

Introduction

Web Dynpro is a SAP based technology which is used to create web-based Application. To develop a web based application we need multiple components and interfaces. In this article we will explain Components in Web Dynpro in detail.

Components in Web Dynpro

A Web Dynpro component is a reusable entity. The creation of Components in Web Dynpro is a mandatory process. A Web Dynpro component can even contain another Web Dynpro Component. The lifetime of Web Dynpro component begins at runtime of the application and end with the lifetime of Web Dynpro Application.

Context

It is a data container (or a temporary storage area) where we store data during runtime of Web Dynpro Application.

UI Element

It is the most important element of Web Dynpro. It is a display/screen element. Using it, we can display any information on the screen. It include Text View, Radio Buttons, Drop Down, Check Boxes, Tables, etc.

View

Like HTML websites, it is the screen that is visible on the browser. It is the same view that we have discussed in the MVC concept of Web Dynpro earlier.

Window

The window is the container that holds multiple view altogether.

Methods

It is the section that contains the business logic of our Web Dynpro Application. Like SAP ABAP, we include Select statements, Function Module, other code blocks here.

Controller

As we have discussed about MVC architecture of Web Dynpro, a controller is used to communicate between views and models (data). These models are extracted from the Methods.

Navigation Plugs

A navigation plug, as its name suggests is used to navigate between multiple views.

Application

Once we are done with all the component creation, modelling and coding, we need to get an executable link which is extracted from Web Dynpro Application.

Advantage of Components in Web Dynpro

Following are the advantages of Components in Web Dynpro:
1. It helps in Structuring the programming
2. It helps in creating blocks which are easily manageable
3. It creates blocks which are reusable
December 27, 2019
Setup of SAP Web Dynpro Application

Preface – This post is part of the SAP ABAP Web Dynpro series.

Introduction

Web Dynpro in SAP ABAP is a standard technology which is used to create web-based applications using ABAP programing language. Web Dynpro includes many graphical development tools which are included in ABAP workbench. Because of the use of a graphical tool, it seems to be more user-friendly. In this article we will learn about the setup of SAP Web Dynpro Application.

Setup of SAP Web Dynpro Application

Step 01: Goto the transaction SE80

Step 02: Click Repository Browser

Step 03: Select Create web Dynpro component and assign it a name as shown above. On Clicking enter it will open a pop up as shown below:

Step 04: Enter the description, chose the type and Assign Window and View name as shown below:

Step 05: Now a view is created as shown below:

Step 06: Double click the view to open it, as shown below. Choose the layout option here:

Step 07: In the right hand side, you will see two options, choose Root Element Container, as shown below:

Step 08: In above step, choose Insert Element:

Step 09: Provide ID and TYPE of the element, as shown below:

Step 10: For the element “Page Header” you have just created, define the properties available in the right pane:

The title that we have provided above will be the header of the Web Dynpro Application. It is suggested to give a meaning title, unlike the one we have mentioned.

Step 11: To save your application, click CTRL + S

Step 12: Now activate your application, by right clicking the application name from left pane and clicking “Activate”, as shown below:

Step 13: Whatever, we have done is just the creation of Web Dynpro Interface/Component. To get an executable Application, right click and under Create option, choose “Web Dynpro Application”.

Provide the name of the application and meaningful description. The application you have just created will appear just below the “Windows” option above. Now right click the Web Dynpro Application and click test to open your application. The application will open in Internet Explorer.

December 27, 2019
R3 Corda Platform Introduction
Preface – This post is part of the Blockchain Basics series.

Introduction

Corda is an open source private blockchain platform, introduced by R3 that integrates the existing proven technologies such as relational database, Java Machine (JVM) in blockchain for ERP and business solutions.

Corda has published a whitepaper to discuss the underline technologies; you can read the Corda: A distributed ledger Whitepaper here.

How R3 Corda Works

In Corda network, a node firstly undergoes a KYC process to obtain identity certificate. When this node joins the network, they publish this certificate including their legal name, their IP address, public key and some other information. Then the nodes communicate point-to-point using TLS encrypted messaging.

R3 Corda Use Cases

R3 Codra is one of the most used Enterprise based blockchain network. Following are some of the common use cases:
1. International Bank Transaction
To implement cross border payment without any third party involvement, a bank can use R3 Corda based network to implement it.
1. Construction Industry
To share information between multiple sub-contractors, we can submit the information related to construction on Corda Blockchain.
1. Healthcare Industry
Healthcare Industry has following two possible use cases to implement blockchain:
1. Health records exchange
2. Health Claims management
Merits of Corda Blockchain

Following are the merits of Corda Blockchain Network:
1. Privacy
2. Agile and flexible
3. Interoperability
4. Open development
5. Open design
Demerits of Corda Blockchain

Following are the demerits of Quorum blockchain:
1. Anonymity
2. Questionable affair for many companies
December 10, 2019
Quorum Introduction
Preface – This post is part of the Blockchain Basics series.

Introduction

Quorum is a private and permissioned blockchain developed on top of Go and Ethereum technology mainly for Enterprise based solution. An Ethereum is a decentralized platform which is used to run smart contracts. In this Quorum Introduction we will explore more about it.

Quorum has its Whitepaper published here. Apart from Quorum Introduction, it discusses the core architecture and end to end implementation of Quorum technology.

How Quorum Works

Quorum Application are based on three layered structure. The initial layer is the go-Ethereum where all the transaction happens. The second layer is of Quorum where all the logics are implemented which also includes Transaction Manager, Crypto Enclave, consensus and network manager. The last layer includes the distributed blockchain applications.

Quorum Use Cases

With its permissioned blockchain paradigm, Quorum can be implemented easily in given use cases:
1. Financial Applications
To ensure the transactions between two parties and two financial institutions are secure, private and not revealed to any other financial institutions, then implementing it via a permissioned network like Quorum is a right decision. Quorum supports both client privacy as well as meet legal and regularity requirements.
1. Payment Applications
To implement payment across various parties based on various pre-defined conditions might include the implementation of smart contracts. The use of Quorum network helps us to implement the transaction on a common protocol.

Merits of Quorum Blockchain

Following are the merits of Quorum blockchain:
1. Private and Permissioned Network
2. Alternative Consensus Mechanism
3. Peer permissioning
4. Higher performance
Demerits of Quorum Blockchain

Following are the demerits of Quorum blockchain:
1. Anonymity
2. Questionable affair for many companies
December 9, 2019
Multichain Introduction
Preface – This post is part of the Blockchain Basics series.

Introduction

Multichain is off-the-shelf private blockchain platform developed primarily for institutional financial sectors. It provides privacy, openness and control to the network administrator (that can be either miner of the first “genesis” block or a predefined miners set as Admin by previous Admin). Multichain has published a whitepaper to discuss the underline technologies; you can read the Multichain Private Blockchain Whitepaper here. In this article we will explore the Multichain Introduction with some of its use cases.

How Multichain Works

In a Multichain bases blockchain network, the administrator grants privileges to other users in the network. The mining (block validation) in a Multichain is just like a round robin schedule, which means each miner/user in the network must create blocks in rotation to generate an authentic blockchain.

Multichain Use Cases

Multichain is one of the widely used blockchain technologies that are being utilized by enterprises and small industries. Following are some of the accepted use cases by Multichain:
1. Centralized Currency Settlement System
This is a very generic use case where all the currency exchange system can be scrutinized under blockchain methodology.
1. Bond Issuance System
Issuance of bond in a systematic manner becomes a tedious job. Multichain can become a secure solution to this problem.
1. Peer-to-peer Trading System
Stock trading is not a peer-to-peer system but it can be like bitcoin trading system. This can be easily achieved with the help of Multichain.
1. Consumer facing reward scheme
It is also a generic scenario where blockchain can be used to win trust and bring fair results in the reward scheme.

Merits of Multichain Blockchain

Multichain Introduction on top of Bitcoin brings following merits:
- Unlimited capacity
- Very less or no transaction cost (based on subscription)
- Relevant Data storage
- Reduced Mining risks
- Higher privacy features
- Openness
Demerits of Multichain Blockchain

Although Multichain provides additional features on top of Bitcoin and is better than many permissioned blockchain technology, still it comes with following demerits:
- No support to smart contracts
- Typical consensus mechanism
November 29, 2019