Hbase 学习笔记一 》Example
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.