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Runtimes
Descriptions of Link runtime services.
SDK
The LNK programming interface includes language-specific methods and objects that provide common functionality across multiple environments.
C API
The C API enables applications to invoke maps and to develop adapters to use with HCL Link.
Custom adapters
The custom adapters interface makes it possible for users to develop adapters with as much functionality as those provided with the product.
Methods provided by adapter
Source and target interface
Source and target interface methods are called to get data from a resource, to put data to a resource, and to control a transaction while developing custom adapters.
Get
The Get method is called to obtain data from a resource for input to a map.

Runtimes
Descriptions of Link runtime services.
- REST API
  The REST Runtme provides a REST API used to run maps and flows that have been deployed.
- Flow Command Server
  Deploy a flow from the HCL Link to the local filesystem using Execution flow server definition.
- Map Command Server
  To use the Map Command Server to execute a map, you will prepare the maps for execution.
- SDK
  The LNK programming interface includes language-specific methods and objects that provide common functionality across multiple environments.
  - Link programming interface overview
    The Link programming interface is an object-oriented approach that enables applications to invoke HCL Link maps, thus removing reliance on command lines.
  - C API
    The C API enables applications to invoke maps and to develop adapters to use with HCL Link.
    - C API interface methods overview
      The map, card, and adapter object properties define the properties that can be set for each object. Use the C API interface methods to GET or SET the adapter object properties.
    - Object methods
    - Loading, running, and controlling maps
      There are various methods you can use to load, run, and control maps when you use APIs with HCL Link.
    - Custom adapters
      The custom adapters interface makes it possible for users to develop adapters with as much functionality as those provided with the product.
      - Developing custom adapters
        The custom adapters interface makes it possible for users to develop adapters with as much functionality as those provided with the product.
      - Adapter registration and the library virtual table
        The first step required to develop an adapter is to add the adapter to the adapters.xml registration file.
      - Initializing the adapter
        InitializeLibrary provides an entry point by which any global structures, critical sections, or lists that are required by the adapter can be initialized.
      - Point to adapter methods
        After your adapter is loaded, you call the virtual table (vtable) structure to obtain pointers to the methods.
      - Adapter registration file
        The adapters.xml registration file contains a single tag for each adapter, including a number of attributes to provide information about the adapter.
      - Vtable adapter library
      - Methods provided by adapter
        Methods provided by an adapter
        Various methods must be provided by an adapter.
        Adapter methods used post-instance creation
        After you create an instance of the adapter and connection objects, the map can use these objects to get data, put data, or to listen for events. The adapter virtual table, MPI_ADAPTER_VTABLE, points to a number of methods that are provided by the adapter.
        Adapter instance overview
        When a map executes, there are a number of objects created (for example, map and card). Each card has an associated adapter instance. The adapter instance contains a number of properties that determine the behavior of the adapter. The number and type of these properties are defined through the mpiObjectNewPropColl method.
        Connection instance overview
        Instances of connection objects are created in the same way as adapter instances. When a new connection is required, a connection instance is created.
        Connection interface
        The connection interface methods are called to connect to a resource and to control connection pooling.
        Library initialization and termination methods
        The InitializeLibrary and DestroyLibrary custom adapter methods are called to perform one-time initialization tasks and to clean up from these tasks.
        Listener interface
        The Listener interface uses the Listen, CombinedListen, and CompareWatches methods to listen for single or multiple events from the resource.
        Method invocation
        The method invocation examples demonstrate the sequence of calls made to an adapter.
        Source and target interface
        Source and target interface methods are called to get data from a resource, to put data to a resource, and to control a transaction while developing custom adapters.
        Get
        The Get method is called to obtain data from a resource for input to a map.
        Put
        The Put method is called to send data to a resource for output from a map.
        OnNotify
        The OnNotify method is called to notify an adapter about the progress of the map as related to the adapter.
        BeginTransaction
        The BeginTransaction method is called to explicitly start a transaction.
        EndTransaction
        The EndTransaction method is called at the end of the transaction to complete the transaction.
        Property interface
        The ValidateProperties custom adapter method is called to validate the adapter’s properties.
        C API return codes
        There are three types of C API return codes: success, warning, or error.
      - Additional adapter methods
        There are a number of additional methods that are part of the HCL Link Programming Interface library that are of particular relevance to adapter developers.
      - Passing data to and from maps
        Data is passed between adapters and the engine through stream objects. From the adapter perspective, there is no need to create these stream objects; they are already created when either the Get or Put method is called.
      - Threads, connections, and transactions overview
        It is important to understand how threads, connections, and transactions interact.
  - Python API
    Use the Python API to create, edit, and run maps and schemas from a Python program. For details, see the documentation installed in install_dir/python/api/hip/docs/html/index.html. Examples of the Python API are installed in install_dir/python/api/examples. Documentation for the Python API examples is available in install_dir/python/api/docs/html/examples.html.
  - Java API
    The Java API interfaces enable you to create, edit, and run maps and schemas from a Java™ program.
  - Java Tools
    The Java™ Tools provide objects and JNI utilities that you can use to get information about your map instances.

Get method overview

The Get method is called to obtain data from a resource for input to a map.

The Get method is called for an input card, GET function, or for a DBLOOKUP and DBQUERY if the source is a database. The call accesses the resource for which the hConnection handle is associated and returns data. This data is passed to the map server through a stream object.

MPIRC Get (HMPIADAPT  hAdapter,HMPICONNECT  
hConnection)

Inputs

hAdapter: Adapter handle
hConnection: Connection handle

Outputs

None

Returns

Success status

The method should get a single unit of work from the input (for example, a result set from a database query, a file, or a message from a queue), and return the unit of work through a stream object associated with the MPIP_ADAPTER_DATA_FROM_ADAPT property. For example:

mpiPropertyGetObject (hAdapter, 
MPIP_ADAPTER_DATA_FROM_ADAPT, 0, &hStream);   
mpiStreamNewPage(hStream, &hPage, iSize);   
mpiStreamPageGetInfo(hPage, &pData, &iSize);   
get data into pData   
mpiStreamWritePage(hStream, hPage);

Quantity or FetchUnit values do not affect the adapter; this is handled by the Resource Manager. Each call to Get should return a single unit of work.

If Get is called from the GET mapping function (the MPIP_ADAPTER_CONTEXT will be set to MPI_CONTEXT_GET), data might be passed to the Get call from the third parameter in the GET mapping function. This applies to adapters that require data to be sent out in the form of a request, such that the corresponding reply is returned from the Get call.

To determine whether any data has been passed, the adapter should get the MPIP_ADAPTER_DATA_TO_ADAPT property. If this returns an MPIRC_NULL_OBJECT error, it means that no data was passed to the Get. If data was passed, use the stream object to get the data.

If Get is called as the result of an input event (the MPIP_ADAPTER_CONTEXT property is MPI_CONTEXT_SOURCE_EVENT), information about the event or events is obtained from the MPIP_ADAPTER_MSG_COLLECTION property by repeatedly calling mpiMsgCollGetNext until there are no more messages in the collection. These messages have previously been added to a collection by the adapter's Listen method.