6.3 创建表

涉及到表的元数据操作的都需要用 Admin 对象, 所以,我们把 Admin 对象提出来.

package com.atguigu.hbase;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HColumnDescriptor;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.Admin;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.ConnectionFactory;

import java.io.IOException;

public class HBaseDemo {

    private static Configuration conf;
    private static Connection conn;
    private static Admin admin;

    // 为了方便, 我们使用静态代码块来获取 HBaseConfiguration 对象
    static {
        // 创建 Configuration 对象
        conf = HBaseConfiguration.create();
        // 配置 Zookeeper
        conf.set("hbase.zookeeper.quorum", "hadoop201");
        conf.set("hbase.zookeeper.property.clientPort", "2181");


        try {
            conn = ConnectionFactory.createConnection(conf);
            admin = conn.getAdmin();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    public static void main(String[] args) throws IOException {
        System.out.println(isTableExists("person"));
        createTable("person", "info");
        System.out.println(isTableExists("person"));
        close();
    }

    /**
     * @param tableName 表名
     * @param cfs       多个列族
     */
    private static void createTable(String tableName, String... cfs) throws IOException {
        if(isTableExists(tableName)) return;  // 表如果存在就直接结束方法
        HTableDescriptor descriptor = new HTableDescriptor(TableName.valueOf(tableName));
        for (String cf : cfs) {
            descriptor.addFamily(new HColumnDescriptor(cf));
        }
        admin.createTable(descriptor);
        System.out.println("表:" + tableName + "创建成功!");
    }


    /**
     * 判断指定的表是否存在
     *
     * @param tableName
     * @return
     * @throws IOException
     */
    private static boolean isTableExists(String tableName) throws IOException {
        // 创建一个连接对象
        boolean isExists = admin.tableExists(TableName.valueOf(tableName));
        return isExists;
    }

    /**
     * 关闭 Admin和 Connection 对象
     */

    private static void close() {
        if (admin != null) {
            try {
                admin.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }


}