Putting it all together Example

Now that you’ve seen how to interact with HBase, let’s assemble what you know into a

working example. To start, define a simple model object for the User instances, as in

the next listing.

<span style="font-size:14px;">package HBaseIA.TwitBase.model;
public abstract class User {
public String user;
public String name;
public String email;
public String password;
@Override
public String toString() {
return String.format("<User: %s, %s, %s>", user, name, email);
}
}</span>
 

Let’s wrap all the user-centric HBase interactions in a single class. Start by declaring

the commonly used byte[] constants. Then define some helper methods to encapsulate

command creation. Follow that with the public interfaces and a private implementation

of the User model, as shown next.

<span style="font-size:14px;"><pre name="code" class="java">package HBaseIA.TwitBase.hbase;


//...
public class UsersDAO {
    public static final byte[] TABLE_NAME = Bytes.toBytes("users");
    public static final byte[] INFO_FAM = Bytes.toBytes("info");
    private static final byte[] USER_COL = Bytes.toBytes("user");
    private static final byte[] NAME_COL = Bytes.toBytes("name");
    private static final byte[] EMAIL_COL = Bytes.toBytes("email");
    private static final byte[] PASS_COL = Bytes.toBytes("password");
    public static final byte[] TWEETS_COL = Bytes.toBytes("tweet_count");
    private HTablePool pool;


    public UsersDAO(HTablePool pool) {
        this.pool = pool;
    }


    private static Get mkGet(String user) {
        Get g = new Get(Bytes.toBytes(user));
        g.addFamily(INFO_FAM);


        return g;
    }


    private static Put mkPut(User u) {
        Put p = new Put(Bytes.toBytes(u.user));
        p.add(INFO_FAM, USER_COL, Bytes.toBytes(u.user));
        p.add(INFO_FAM, NAME_COL, Bytes.toBytes(u.name));
        p.add(INFO_FAM, EMAIL_COL, Bytes.toBytes(u.email));
        p.add(INFO_FAM, PASS_COL, Bytes.toBytes(u.password));


        return p;
    }


    private static Delete mkDel(String user) {
        Delete d = new Delete(Bytes.toBytes(user));


        return d;
    }


    public void addUser(String user, String name, String email, String password)
        throws IOException {
        HTableInterface users = pool.getTable(TABLE_NAME);
        Put p = mkPut(new User(user, name, email, password));
        users.put(p);
        users.close();
    }


    public HBaseIA.TwitBase.model.User getUser(String user)
        throws IOException {
        HTableInterface users = pool.getTable(TABLE_NAME);
        Get g = mkGet(user);
        Result result = users.get(g);


        if (result.isEmpty()) {
            return null;
        }


        User u = new User(result);
        users.close();


        return u;
    }


    public void deleteUser(String user) throws IOException {
        HTableInterface users = pool.getTable(TABLE_NAME);
        Delete d = mkDel(user);
        users.delete(d);
        users.close();
    }


    private static class User extends HBaseIA.TwitBase.model.User {
        private User(Result r) {
            this(r.getValue(INFO_FAM, USER_COL),
                r.getValue(INFO_FAM, NAME_COL),
                r.getValue(INFO_FAM, EMAIL_COL),
                r.getValue(INFO_FAM, PASS_COL),
                (r.getValue(INFO_FAM, TWEETS_COL) == null) ? Bytes.toBytes(0L)
                                                           : r.getValue(
                    INFO_FAM, TWEETS_COL));
        }


        private User(byte[] user, byte[] name, byte[] email, byte[] password,
            byte[] tweetCount) {
            this(Bytes.toString(user), Bytes.toString(name),
                Bytes.toString(email), Bytes.toString(password));
            this.tweetCount = Bytes.toLong(tweetCount);
        }


        private User(String user, String name, String email, String password) {
            this.user = user;
            this.name = name;
            this.email = email;
            this.password = password;
        }
    }
}
</span>
 

Listing 2.1 Userdata model

Listing 2.2 CRUD operations in UsersDAO.

The last piece of this puzzle is a main() method. Let’s make a UsersTool, shown in the

next listing, to simplify interaction with the users table in HBase.

<span style="font-size:14px;">package HBaseIA.TwitBase;

//...
public class UsersTool {
    public static final String usage = "UsersTool action ...\n" +
        " help - print this message and exit.\n" +
        " add user name email password" + " - add a new user.\n" +
        " get user - retrieve a specific user.\n" +
        " list - list all installed users.\n";

    public static void main(String[] args) throws IOException {
        if ((args.length == 0) || "help".equals(args[0])) {
            System.out.println(usage);
            System.exit(0);
        }

        HTablePool pool = new HTablePool();
        UsersDAO dao = new UsersDAO(pool);

        if ("get".equals(args[0])) {
            System.out.println("Getting user " + args[1]);

            User u = dao.getUser(args[1]);
            System.out.println(u);
        }

        if ("add".equals(args[0])) {
            System.out.println("Adding user...");
            dao.addUser(args[1], args[2], args[3], args[4]);

            User u = dao.getUser(args[1]);
            System.out.println("Successfully added user " + u);
        }

        if ("list".equals(args[0])) {
            for (User u : dao.getUsers()) {
                System.out.println(u);
            }
        }

        pool.closeTablePool(UsersDAO.TABLE_NAME);
    }
}
</span>
 

With all the code available, you can try the whole thing. In the root directory of this

book’s source code, compile the application jar:

<span style="font-size:14px;">$ mvn package
...
[INFO] -----------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] -----------------------------------------------------
[INFO] Total time: 20.467s</span>

This produces a twitbase-1.0.0.jar file in the target directory.

Using UsersTool to add Mark to the users table is easy:

$ java -cp target/twitbase-1.0.0.jar \

<span style="font-size:14px;">HBaseIA.TwitBase.UsersTool \
add \
TheRealMT \
"Mark Twain" \
[email protected] \
abc123
Successfully added user <User: TheRealMT></span>

You can list the contents of your table:

<span style="font-size:14px;">$ java -cp target/twitbase-1.0.0.jar \
HBaseIA.TwitBase.UsersTool \
list
21:49:30 INFO cli.UsersTool: Found 1 users.
<User: TheRealMT></span>

Now that you’ve seen a little of how to interact with HBase, let’s better understand the

logical and physical data models present in HBase.