Create a user-defined input node in C to receive messages into a message flow.
A loadable implementation library, or LIL, is the implementation module for a C node. A LIL is implemented as a shared or dynamic link library (DLL), but has the file extension .lil not .dll.
The implementation functions that you write for the node are listed in C node implementation functions. You can call utility functions, implemented in the runtime integration node, to help with the node operation; these functions are listed in C node utility functions.
IBM® Integration Bus provides the source for two sample user-defined nodes called SwitchNode and TransformNode. You can use these nodes in their current state, or you can modify them.
To declare and define a user-defined node to the integration node, include an initialization function, bipGetMessageflowNodeFactory, in your LIL. The following steps outline how the integration node calls your initialization function, and how your initialization function declares and defines the user-defined node:
To instantiate your node:
Attributes are set whenever you start the integration node, or when you redeploy the message flow with new values.
{
const CciChar* ucsAttr = CciString("nodeTraceSetting", BIP_DEF_COMP_CCSID) ;
insAttrTblEntry(p, (CciChar*)ucsAttr, CNI_TYPE_INTEGER);
_setAttribute(p, (CciChar*)ucsAttr, (CciChar*)constZero);
free((void *)ucsAttr) ;
}
{
const CciChar* ucsAttr = CciString("nodeTraceOutfile", BIP_DEF_COMP_CCSID) ;
insAttrTblEntry(p, (CciChar*)ucsAttr, CNI_TYPE_STRING);
_setAttribute(p, (CciChar*)ucsAttr, (CciChar*)constSwitchTraceLocation);
free((void *)ucsAttr) ;
}
When the integration node knows that it has an input node, it calls the cniRun function of this node at regular intervals. The cniRun function must then decide what course of action it must take. If data is available for processing, the cniRun function can propagate the message. If no data is available for processing, the cniRun function must return with CCI_TIMEOUT so that the integration node can continue configuration changes.
If ( anything to do )
CniDispatchThread;
/* do the work */
If ( work done O.K.)
Return CCI_SUCCESS_CONTINUE;
Else
Return CCI_FAILURE_CONTINUE;
Else
Return CCI_TIMEOUT;
An input node implementation typically determines what message parser initially parses an input message. For example, the MQInput node dictates that an MQMD parser is required to parse the MQMD header. A user-defined input node can select an appropriate header or message parser, and the mode in which the parsing is controlled, by using or overriding the following attributes that are included as default:
CciFactory LilFactoryExportPrefix * LilFactoryExportSuffix bipGetMessageflowNodeFactory()
{
....
CciFactory* factoryObject;
....
factoryObject = cniCreateNodeFactory(0, (unsigned short *)constPluginNodeFactory);
...
vftable.iFpCreateNodeContext = _createNodeContext;
vftable.iFpSetAttribute = _setAttribute;
vftable.iFpGetAttribute = _getAttribute;
...
cniDefineNodeClass(&rc, factoryObject, (CciChar*)constSwitchNode, &vftable);
...
return(factoryObject);
}
CciContext* _createNodeContext(
CciFactory* factoryObject,
CciChar* nodeName,
CciNode* nodeObject
){
NODE_CONTEXT_ST* p;
...
/* Allocate a pointer to the local context */
p = (NODE_CONTEXT_ST *)malloc(sizeof(NODE_CONTEXT_ST));
/* Create attributes and set default values */
{
const CciChar* ucsAttrName = CciString("firstParserClassName", BIP_DEF_COMP_CCSID);
const CciChar* ucsAttrValue = CciString("MYPARSER", BIP_DEF_COMP_CCSID) ;
insAttrTblEntry(p, (CciChar*)ucsAttrName, CNI_TYPE_INTEGER);
/*see sample BipSampPluginNode.c for implementation of insAttrTblEntry*/
_setAttribute(p, (CciChar*)ucsAttrName, (CciChar*)ucsAttrValue);
free((void *)ucsAttrName) ;
free((void *)ucsAttrValue) ;
}
In the code example above, the insAttrTblEntry method
is called. This method is declared in the SwitchNode and TransformNode
sample user-defined nodes.Nodes are destroyed when a message flow is redeployed, or when the integration server process is stopped (using the mqsistop command). When a node is destroyed, you must call the cniDeleteNodeContext function to free all used memory and release all held resources. For example:
void _deleteNodeContext(
CciContext* context
){
static char* functionName = (char *)"_deleteNodeContext()";
return;
}