First, download the Java LTK from Sourceforge.
Make sure the .jar file is in your CLASSPATH.
Next, create a new class that implements the LLRPEndpoint interface. This class will contain all of our Java LTK code.
import java.util.List;
import org.llrp.ltk.generated.enumerations.*;
import org.llrp.ltk.generated.interfaces.*;
import org.llrp.ltk.generated.messages.*;
import org.llrp.ltk.generated.parameters.*;
import org.llrp.ltk.net.*;
import org.llrp.ltk.types.*;
public class HelloJavaLtk implements LLRPEndpoint
{
private LLRPConnection reader;
private static final int TIMEOUT_MS = 10000;
private static final int ROSPEC_ID = 123;
// Build the ROSpec.
// An ROSpec specifies start and stop triggers,
// tag report fields, antennas, etc.
public ROSpec buildROSpec()
{
System.out.println("Building the ROSpec.");
// Create a Reader Operation Spec (ROSpec).
ROSpec roSpec = new ROSpec();
roSpec.setPriority(new UnsignedByte(0));
roSpec.setCurrentState(new ROSpecState(ROSpecState.Disabled));
roSpec.setROSpecID(new UnsignedInteger(ROSPEC_ID));
// Set up the ROBoundarySpec
// This defines the start and stop triggers.
ROBoundarySpec roBoundarySpec = new ROBoundarySpec();
// Set the start trigger to null.
// This means the ROSpec will start as soon as it is enabled.
ROSpecStartTrigger startTrig = new ROSpecStartTrigger();
startTrig.setROSpecStartTriggerType
(new ROSpecStartTriggerType(ROSpecStartTriggerType.Null));
roBoundarySpec.setROSpecStartTrigger(startTrig);
// Set the stop trigger is null. This means the ROSpec
// will keep running until an STOP_ROSPEC message is sent.
ROSpecStopTrigger stopTrig = new ROSpecStopTrigger();
stopTrig.setDurationTriggerValue(new UnsignedInteger(0));
stopTrig.setROSpecStopTriggerType
(new ROSpecStopTriggerType(ROSpecStopTriggerType.Null));
roBoundarySpec.setROSpecStopTrigger(stopTrig);
roSpec.setROBoundarySpec(roBoundarySpec);
// Add an Antenna Inventory Spec (AISpec).
AISpec aispec = new AISpec();
// Set the AI stop trigger to null. This means that
// the AI spec will run until the ROSpec stops.
AISpecStopTrigger aiStopTrigger = new AISpecStopTrigger();
aiStopTrigger.setAISpecStopTriggerType
(new AISpecStopTriggerType(AISpecStopTriggerType.Null));
aiStopTrigger.setDurationTrigger(new UnsignedInteger(0));
aispec.setAISpecStopTrigger(aiStopTrigger);
// Select which antenna ports we want to use.
// Setting this property to zero means all antenna ports.
UnsignedShortArray antennaIDs = new UnsignedShortArray();
antennaIDs.add(new UnsignedShort(0));
aispec.setAntennaIDs(antennaIDs);
// Tell the reader that we're reading Gen2 tags.
InventoryParameterSpec inventoryParam = new InventoryParameterSpec();
inventoryParam.setProtocolID
(new AirProtocols(AirProtocols.EPCGlobalClass1Gen2));
inventoryParam.setInventoryParameterSpecID(new UnsignedShort(1));
aispec.addToInventoryParameterSpecList(inventoryParam);
roSpec.addToSpecParameterList(aispec);
// Specify what type of tag reports we want
// to receive and when we want to receive them.
ROReportSpec roReportSpec = new ROReportSpec();
// Receive a report every time a tag is read.
roReportSpec.setROReportTrigger(new ROReportTriggerType
(ROReportTriggerType.Upon_N_Tags_Or_End_Of_ROSpec));
roReportSpec.setN(new UnsignedShort(1));
TagReportContentSelector reportContent =
new TagReportContentSelector();
// Select which fields we want in the report.
reportContent.setEnableAccessSpecID(new Bit(0));
reportContent.setEnableAntennaID(new Bit(0));
reportContent.setEnableChannelIndex(new Bit(0));
reportContent.setEnableFirstSeenTimestamp(new Bit(0));
reportContent.setEnableInventoryParameterSpecID(new Bit(0));
reportContent.setEnableLastSeenTimestamp(new Bit(1));
reportContent.setEnablePeakRSSI(new Bit(0));
reportContent.setEnableROSpecID(new Bit(0));
reportContent.setEnableSpecIndex(new Bit(0));
reportContent.setEnableTagSeenCount(new Bit(0));
roReportSpec.setTagReportContentSelector(reportContent);
roSpec.setROReportSpec(roReportSpec);
return roSpec;
}
// Add the ROSpec to the reader.
public void addROSpec()
{
ADD_ROSPEC_RESPONSE response;
ROSpec roSpec = buildROSpec();
System.out.println("Adding the ROSpec.");
try
{
ADD_ROSPEC roSpecMsg = new ADD_ROSPEC();
roSpecMsg.setROSpec(roSpec);
response = (ADD_ROSPEC_RESPONSE)
reader.transact(roSpecMsg, TIMEOUT_MS);
System.out.println(response.toXMLString());
// Check if the we successfully added the ROSpec.
StatusCode status = response.getLLRPStatus().getStatusCode();
if (status.equals(new StatusCode("M_Success")))
{
System.out.println
("Successfully added ROSpec.");
}
else
{
System.out.println("Error adding ROSpec.");
System.exit(1);
}
}
catch (Exception e)
{
System.out.println("Error adding ROSpec.");
e.printStackTrace();
}
}
// Enable the ROSpec.
public void enableROSpec()
{
ENABLE_ROSPEC_RESPONSE response;
System.out.println("Enabling the ROSpec.");
ENABLE_ROSPEC enable = new ENABLE_ROSPEC();
enable.setROSpecID(new UnsignedInteger(ROSPEC_ID));
try
{
response = (ENABLE_ROSPEC_RESPONSE)
reader.transact(enable, TIMEOUT_MS);
System.out.println(response.toXMLString());
}
catch (Exception e)
{
System.out.println("Error enabling ROSpec.");
e.printStackTrace();
}
}
// Start the ROSpec.
public void startROSpec()
{
START_ROSPEC_RESPONSE response;
System.out.println("Starting the ROSpec.");
START_ROSPEC start = new START_ROSPEC();
start.setROSpecID(new UnsignedInteger(ROSPEC_ID));
try
{
response = (START_ROSPEC_RESPONSE)
reader.transact(start, TIMEOUT_MS);
System.out.println(response.toXMLString());
}
catch (Exception e)
{
System.out.println("Error deleting ROSpec.");
e.printStackTrace();
}
}
// Delete all ROSpecs from the reader.
public void deleteROSpecs()
{
DELETE_ROSPEC_RESPONSE response;
System.out.println("Deleting all ROSpecs.");
DELETE_ROSPEC del = new DELETE_ROSPEC();
// Use zero as the ROSpec ID.
// This means delete all ROSpecs.
del.setROSpecID(new UnsignedInteger(0));
try
{
response = (DELETE_ROSPEC_RESPONSE)
reader.transact(del, TIMEOUT_MS);
System.out.println(response.toXMLString());
}
catch (Exception e)
{
System.out.println("Error deleting ROSpec.");
e.printStackTrace();
}
}
// This function gets called asynchronously
// when a tag report is available.
public void messageReceived(LLRPMessage message)
{
if (message.getTypeNum() == RO_ACCESS_REPORT.TYPENUM)
{
// The message received is an Access Report.
RO_ACCESS_REPORT report = (RO_ACCESS_REPORT) message;
// Get a list of the tags read.
List <TagReportData> tags =
report.getTagReportDataList();
// Loop through the list and get the EPC of each tag.
for (TagReportData tag : tags)
{
System.out.println(tag.getEPCParameter());
System.out.println(tag.getLastSeenTimestampUTC());
}
}
}
// This function gets called asynchronously
// when an error occurs.
public void errorOccured(String s)
{
System.out.println("An error occurred: " + s);
}
// Connect to the reader
public void connect(String hostname)
{
// Create the reader object.
reader = new LLRPConnector(this, hostname);
// Try connecting to the reader.
try
{
System.out.println("Connecting to the reader.");
((LLRPConnector) reader).connect();
}
catch (LLRPConnectionAttemptFailedException e1)
{
e1.printStackTrace();
System.exit(1);
}
}
// Disconnect from the reader
public void disconnect()
{
((LLRPConnector) reader).disconnect();
}
// Connect to the reader, setup the ROSpec
// and run it.
public void run(String hostname)
{
connect(hostname);
deleteROSpecs();
addROSpec();
enableROSpec();
startROSpec();
}
// Cleanup. Delete all ROSpecs
// and disconnect from the reader.
public void stop()
{
deleteROSpecs();
disconnect();
}
}
Finally, we need an application class and Main function to start up our program. Make sure to change the reader hostname when you call the run function (highlighted below).
public class HelloJavaLtkMain
{
public static void main(String[] args) throws InterruptedException
{
HelloJavaLtk app = new HelloJavaLtk();
System.out.println("Starting reader.");
app.run("SpeedwayR-10-2E-63");
Thread.sleep(30000);
System.out.println("Stopping reader.");
app.stop();
System.out.println("Exiting application.");
System.exit(0);
}
}
If you're using a Java IDE like Eclipse, the build process is handled for you. If you're using the command line, first compile:
javac -cp ltkjava-1.0.0.6-with-dependencies.jar
HelloJavaLtkMain.java HelloJavaLtk.java
Then run:
java -cp :ltkjava-1.0.0.6-with-dependencies.jar HelloJavaLtkMain
