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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
Listener interface
The Listener interface uses the Listen, CombinedListen, and CompareWatches methods to listen for single or multiple events from the resource.
CompareWatches
The CompareWatches method compares two watches to see whether they are equivalent. This method is equivalent to CompareConnection method.

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.
        Listen
        The Listen method listens for events and returns when an event has occurred.
        CombinedListen
        The CombinedListen method is generally the same as the Listen method. The difference is that the CombinedListen method listens for multiple watches.
        CompareWatches
        The CompareWatches method compares two watches to see whether they are equivalent. This method is equivalent to CompareConnection method.
        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.
        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.

CompareWatches method

The CompareWatches method compares two watches to see whether they are equivalent. This method is equivalent to CompareConnection method.

MPIRC CompareWatches (HMPIADAPT  
hAdapter1, HMPIADAPT  hAdapter2,MPICOMP  
*peComp)

Inputs

hAdapter1: Adapter handle
hAdapter2: Adapter handle

Outputs

peComp

MPI_CMP_EQUAL: Watches correspond
MPI_CMP_DIFFER: Watches do not correspond
MPI_CMP_LESS: Watch1 is less than Watch2
MPI_CMP_GREATER: Watch1 is greater than Watch2

Returns

Success status

If the adapter does not combine listeners, that is provides Listen as opposed to the CombinedListen method, there is no need to provide a CompareWatches method.

If the method returns MPI_CMP_EQUAL, only one listener thread is created to handle multiple equivalent watches, and the CombinedListen method will be called to handle the multiple combined watches.

If wildcards are part of the command, it might not be possible to combine watches. For example, if there are two commands, to the same queue but one has MID="FRED" and the other MID="*", in some instances, the resource is the same, but not in others.

In this instance, the adapter might handle both events, returning MPI_CMP_EQUAL from this call, or two separate listeners might be spawned, returning MPI_CMP_DIFFER, MPI_CMP_LESS or MPI_CMP_GREATER from this method. The determination of the path to follow can be determined by performance reasons or limitation in the resource's API.

If the sense of ordering in comparisons can be made, the number of comparisons can be reduced because every existing watch does not have to be compared when searching for a valid connection to use.

The following example shows a resource identified by QueueManager:

mpiPropertyGetText(hAdapter1, MYPROP_Q_MGR, 0, &pAdapt1QMgr, &iLen);
mpiPropertyGetText(hAdapter2, MYPROP_Q_MGR, 0, &pAdapt1QMgr, &iLen);
rc = strcmp(pAdapt1QMgr, pAdapt2QMgr);
if (rc == 0)
  return MPI_CMP_EQUAL;
else if (rc < 0)
  return MPI_CMP_LESS;
else 
  return MPI_CMP_GREATER;