Creating an input node in Java

Before you can create Java nodes in the IBM® Integration Toolkit, you must create a Java project:

Every class that implements MbInputNodeInterface and is contained in the integration node LIL path is registered with the integration node as an input node. When you implement MbInputNodeInterface, you must also implement a run method for this class. The run method represents the start of the message flow, contains the data that formulates the message, and propagates it down the flow. The integration node calls the run method when threads become available in accordance with your specified threading model.

The class name must end with the word "Node". For example, if the name is BasicInput in the IBM Integration Toolkit, the class name must be BasicInputNode.

For example, to declare the input node class:

package com.ibm.jplugins;

import com.ibm.broker.plugin.*;

public class BasicInputNode extends MbInputNode implements MbInputNodeInterface
{
...

Follow these steps to complete this action in the IBM Integration Toolkit:

When the node is instantiated, the constructor of the node class is called. This class is where you create the terminals of the node, and initialize the default values for the attributes.

An input node has a number of output terminals associated with it, but does not typically have any input terminals. Use the createOutputTerminal method to add output terminals to a node when the node is instantiated. For example, to create a node with three output terminals:

public BasicInputNode() throws MbException
{
	createOutputTerminal ("out");
	createOutputTerminal ("failure");
	createOutputTerminal ("catch");
	setAttribute ("firstParserClassName","myParser");
	attributeVariable  = "none"; 
}

An input node can receive data from any type of external source, such as a file system, a queue, or a database, in the same way as all other Java programs, if the output from the node is in the correct format.

Provide an input buffer (or bit stream) to contain input data, and associate it with a message object. Create a message from a byte array by using the createMessage method of the MbInputNode class, and then generate a valid message assembly from this message. For example, to read the input data from a file:

After creating a message assembly, you can propagate it to one of the output terminals that are defined on the node.

MbOutputTerminal out = getOutputTerminal("out");
out.propagate(newAssembly);

msg.clearMessage();

To clear the memory that is allocated for the message tree, call the clearMessage() function within the finally block of try/catch.

The integration node infrastructure handles transaction issues such as controlling the commit of a WebSphere® MQ or database unit of work when message processing has completed. However, resources modified from within a user-defined node are not necessarily under the transactional control of the integration node.

Each message flow thread is allocated from a pool of threads maintained for each message flow, and starts in the run method.

The user-defined node uses return values to indicate whether a transaction is successful, to control whether transactions are committed or rolled back, and to control when the thread is returned to the pool. The integration node infrastructure catches all unhandled exceptions, and rolls back the transaction.

You determine the behavior of transactions and threads by using the appropriate return value:

public int run( MbMessageAssembly assembly ) throws MbException
{
  byte[] data = getDataWithTimeout();  // user supplied method
                                       // returns null if timeout
  if( data == null )
    return TIMEOUT;

  MbMessage msg = createMessage( data );
  msg.finalizeMessage( MbMessage.FINALIZE_VALIDATE );
  MbMessageAssembly newAssembly =
       new MbMessageAssembly( assembly, msg );

  dispatchThread();

  getOutputTerminal( "out" ).propagate( newAssembly );

  return SUCCESS_RETURN;
}

You must declare the name of the node for use and identification by the IBM Integration Toolkit. All node names must end with the characters "Node". Declare the name by using the following method:

public static String getNodeName()
{
   return "BasicInputNode";
}

package com.ibm.pluginsamples;
public class BasicInputNode extends MbInputNode implements MbInputNodeInterface
{
   ...

Declare node attributes by using the same method that you use for Java bean properties. You are responsible for writing get and set methods for the attributes; the API framework infers the attribute names by using the Java bean introspection rules. For example, if you declare the following two methods:

private String attributeVariable;

public String getFirstAttribute()
{
  return attributeVariable;
}

public void setFirstAttribute(String value)
{
  attributeVariable = value;
}

The integration node infers that this node has an attribute called firstAttribute. This name is derived from the names of the get or set methods, not from the variable names of any internal class members. Attributes can be exposed only as strings, so convert numeric types to and from strings in the get or set methods. For example, the following method defines an attribute called timeInSeconds:

int seconds;

public String getTimeInSeconds()
{
  return Integer.toString(seconds);
}

public void setTimeInSeconds(String value)
{
  seconds = Integer.parseInt(value);
}

As already described, the run method is called by the integration node to create the input message. This method must provide all the processing function for the input node.

An input node implementation normally determines which message parser initially parses an input message. For example, the built-in 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 the following default attributes that are included, which you can override:

rootParserClassName

Defines the name of the root parser that parses message formats supported by the user-defined input node. It defaults to GenericRoot, a supplied root parser that causes the integration node to allocate and chain parsers together. It is unlikely that a node would have to modify this attribute value.

firstParserClassName

Defines the name of the first parser, in what might be a chain of parsers that are responsible for parsing the bit stream. It defaults to XML.

messageDomainProperty

An optional attribute that defines the name of the message parser required to parse the input message. The supported values are the same as the values that are supported by the MQInput node.

messageSetProperty

An optional attribute that defines the message set identifier, or the message set name, in the Message Set field, only if the MRM parser was specified by the messageDomainProperty attribute.

messageTypeProperty

An optional attribute that defines the identifier of the message in the MessageType field, only if the MRM parser was specified by the messageDomainProperty attribute.

messageFormatProperty

An optional attribute that defines the format of the message in the Message Format field, only if the MRM parser was specified by the messageDomainProperty attribute.

Implement the onDelete method as follows:

public void onDelete()
{
  // perform node cleanup if necessary
}