You might be curious what the simplest Java program to talk to Couchbase might look like, and how you might compile and run it using just the Java command line tools. Follow along if you like and look at Listing 1.

Listing 1: Main.java

import java.net.URI;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.TimeUnit;

import com.couchbase.client.CouchbaseClient;
import net.spy.memcached.internal.GetFuture;
import net.spy.memcached.internal.OperationFuture;

public class Main {
  public static final int EXP_TIME = 10;
  public static final String KEY = "spoon";
  public static final String VALUE = "Hello World!";

  public static void main(String args[]) {
    // Set the URIs and get a client
    List<URI> uris = new LinkedList<URI>();

    Boolean do_delete = false;

    // Connect to localhost or to the appropriate URI
    uris.add(URI.create("http://127.0.0.1:8091/pools"));

    CouchbaseClient client = null;
    try {
      client = new CouchbaseClient(uris, "default", "");
    } catch (Exception e) {
      System.err.println("Error connecting to Couchbase: "
        + e.getMessage());
      System.exit(0);
    }
    // Do a synchrononous get
    Object getObject = client.get(KEY);
    // Do an asynchronous set
    OperationFuture<Boolean> setOp = client.set(KEY, EXP_TIME, VALUE);
    // Do an asynchronous get
    GetFuture getOp = client.asyncGet(KEY);
    // Do an asynchronous delete
    OperationFuture<Boolean> delOp = null;
    if (do_delete) {
      delOp = client.delete(KEY);
    }
    // Shutdown the client
    client.shutdown(3, TimeUnit.SECONDS);
    // Now we want to see what happened with our data
    // Check to see if our set succeeded
    try {
      if (setOp.get().booleanValue()) {
        System.out.println("Set Succeeded");
      } else {
        System.err.println("Set failed: "
            + setOp.getStatus().getMessage());
      }
    } catch (Exception e) {
      System.err.println("Exception while doing set: "
          + e.getMessage());
    }
    // Print the value from synchronous get
    if (getObject != null) {
      System.out.println("Synchronous Get Suceeded: "
          + (String) getObject);
    } else {
      System.err.println("Synchronous Get failed");
    }
    // Check to see if ayncGet succeeded
    try {
      if ((getObject = getOp.get()) != null) {
        System.out.println("Asynchronous Get Succeeded: "
            + getObject);
      } else {
        System.err.println("Asynchronous Get failed: "
            + getOp.getStatus().getMessage());
      }
    } catch (Exception e) {
      System.err.println("Exception while doing Aynchronous Get: "
          + e.getMessage());
    }
    // Check to see if our delete succeeded
    if (do_delete) {
      try {
        if (delOp.get().booleanValue()) {
          System.out.println("Delete Succeeded");
        } else {
          System.err.println("Delete failed: " +
              delOp.getStatus().getMessage());
        }
      } catch (Exception e) {
        System.err.println("Exception while doing delete: "
            + e.getMessage());
      }
    }
  }
}

Of course, substitute your own Couchbase server IP address. If you are on Linux or MacOS replace the semi-colon in the second command-line with a colon. The program will produce the following output:

2012-01-16 15:06:29.265 INFO com.couchbase.client.CouchbaseConnection:  Added {QA sa=/127.0.0.1:11210, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
2012-01-16 15:06:29.277 INFO com.couchbase.client.CouchbaseConnection:  Connection state changed for sun.nio.ch.SelectionKeyImpl@1d3c468a
2012-01-16 15:06:29.420 INFO com.couchbase.client.CouchbaseConnection:  Shut down Couchbase client
Synchronous Get failed
Set Succeeded
Asynchronous Get Succeeded: Hello World!

Much of this output is logging statements produced by the client library, to inform you of what's going on inside the client library to help you diagnose issues. It says that a connection to Couchbase was added and that the connection state changed. Then the code shows that the key spoon did not exist in Couchbase which is why the Synchronous Get failed.

Running the program again, within 10 seconds will produce the following output:

2012-01-16 15:37:12.242 INFO com.couchbase.client.CouchbaseConnection:  Added {QA sa=/127.0.0.1:11210, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
2012-01-16 15:37:12.253 INFO com.couchbase.client.CouchbaseConnection:  Connection state changed for sun.nio.ch.SelectionKeyImpl@7f2ad19e
2012-01-16 15:37:12.439 INFO com.couchbase.client.CouchbaseConnection:  Shut down Couchbase client
Synchronous Get Succeeded: Hello World!
Set Succeeded
Asynchronous Get Succeeded: Hello World!

Again you see the log statements, followed by the indication that this time, the key spoon was found in Couchbase with the value "Hello World!" as evidenced in the Synchronous Get succeeding. Run the same piece of code after 10 seconds or set the do_delete flag to true and notice the changed behavior of the program. It is possible to get the precise message from the server in the case of a failure by calling the getOp.getStatus().getMessage() method on the Operation.

Congratulations, you've taken your first small step into a much larger world.