HBase基础知识（四）：HBase API

HBase还提供了API，我们可以通过编程的方式来进行对HBase的操作。

1. 环境准备

新建项目后在 pom.xml 中添加依赖：

<dependencies>
    <dependency>
        <groupId>org.apache.hbase</groupId>
        <artifactId>hbase-server</artifactId>
        <version>1.3.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hbase</groupId>
        <artifactId>hbase-client</artifactId>
        <version>1.3.1</version>
    </dependency>
</dependencies>

2. HBase API

2.1 获取 Configuration 对象

 public static Connection connection = null;
    public static Admin admin = null;

    static {
        try {
            //1. 获取配置信息
            Configuration configuration = HBaseConfiguration.create();

            //2. 创建连接对象
            connection = ConnectionFactory.createConnection(configuration);

            //3. 创建admin对象
            admin = connection.getAdmin();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

2.2 判断表是否存在

 //2.判断表明是否存在
    public static boolean isTableExistByNewFun(String tableName) throws IOException {

        //3. 判断表是否存在
        return admin.tableExists(TableName.valueOf(tableName));
    }

2.3 DDL

package com.atguigu.DDL;

import com.atguigu.HbaseAPI;
import com.atguigu.test;
import org.apache.hadoop.hbase.*;
import org.apache.hadoop.hbase.client.Admin;

import java.io.IOException;

public class createTable {

    public static void main(String[] args) throws IOException {

        createTable table = new createTable();

        System.out.println(HbaseAPI.isTableExistByNewFun("0408:stu5"));

        //1. 创建表测试,在命名空间0408下面创建表
        table.createTable("0408:stu5","info1","info2");

        System.out.println(HbaseAPI.isTableExistByNewFun("0408:stu5"));

        /*//2.删除表
        table.dropTable("stu5");*/

        //4.创建命名空间 hbase(main):004:0> list_namespace
        //NAMESPACE
        //0408
        //default
        //hbase
        //3 row(s) in 0.3890 seconds
        table.createNameSpace("0408");

        //2.关闭资源
        HbaseAPI.close();
    }

    //1.创建表
    public void createTable (String tableName , String... cfs) throws IOException {
        //1.判断是否存在列族信息
        if (cfs.length <= 0){
            System.out.println("请设置列族信息");
            return;
        }

        //2. 判断表是否存在
        if (HbaseAPI.isTableExistByNewFun(tableName)){
            System.out.println(tableName + "表已存在");
            return;
        }

        //2.5 创建表描述器
        HTableDescriptor hTableDescriptor = new HTableDescriptor(TableName.valueOf(tableName));

        //2.6 循环添加列族信息
        for (String cf : cfs) {
            //2.7 创建列族描述器
            HColumnDescriptor hColumnDescriptor = new HColumnDescriptor(cf);

            //2.8 添加具体的列族信息
            hTableDescriptor.addFamily(hColumnDescriptor);
        }

        //3.创建表
        HbaseAPI.admin.createTable(hTableDescriptor);
    }

    //2.删除表
    public void dropTable (String tableName) throws IOException {
        System.out.println("++++++++++++++++++++表的删除操作++++++++++++++++");
        //1.先判断表是否存在
        if (HbaseAPI.isTableExistByNewFun(tableName)){
            System.out.println(tableName+": 表存在");
        }else{
            System.out.println(tableName+":不存在");
            return;
        }

        //2. 使表下线
        HbaseAPI.admin.disableTable(TableName.valueOf(tableName));

        //3.删除表
        HbaseAPI.admin.deleteTable(TableName.valueOf(tableName));
    }

    //3. 创建命名空间
    public void createNameSpace(String ns){

        //1.创建命令空间描述器
        NamespaceDescriptor namespaceDescriptor = NamespaceDescriptor.create(ns).build();

        //2.创建命名空间
        try {
            HbaseAPI.admin.createNamespace(namespaceDescriptor);
        }catch (NamespaceExistException e){
            System.out.println(ns+":命名空间已存在");
        }catch (Exception e){
            e.printStackTrace();
        }

        System.out.println("命名空间存在，方法运行结束");
    }
}

续：

package com.atguigu.DML;

import com.atguigu.HbaseAPI;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.*;
import org.apache.hadoop.hbase.util.Bytes;

import java.io.IOException;
import java.util.List;

public class Table_DML {
    public static void main(String[] args) throws IOException {
        Table_DML table = new Table_DML();
        /*//1.创建数据测试
        table.putData("stu","1002","info","name","TS");
*/

        //2.获取单行数据
        /*table.getData("stu","1001","info","name");*/

        //3.查询表中的数据
        /*table.ScanData("stu");*/

        //4.测试删除
        table.deleteData("stu","1006","info","name");


        HbaseAPI.close();

    }

    //1.向表内插入数据
    public void putData(String tableName,String rowKey , String cf , String cn , String value) throws IOException {
        //1.获取表对象
        Table table = HbaseAPI.connection.getTable(TableName.valueOf(tableName));

        //2.创建put对象
        Put put = new Put(Bytes.toBytes(rowKey));

        //3.给put对象赋值
        put.addColumn(Bytes.toBytes(cf),Bytes.toBytes(cn),Bytes.toBytes(value));

        //多个数据插入
        //table.put(new List<Put>);

        //4.插入数据
        table.put(put);

    }

    //2.获取数据（get）
    public void getData(String tableName , String rowKey , String cf , String cn) throws IOException {

        //1.获取表对象
        Table table = HbaseAPI.connection.getTable(TableName.valueOf(tableName));

        //2.创建Get对象
        Get get = new Get(Bytes.toBytes(rowKey));

        //2.1 指定获取的列族
        get.addFamily(Bytes.toBytes(cf));

        //2.2 指定列族和列
        get.addColumn(Bytes.toBytes(cf),Bytes.toBytes(cn));

        //2.3 设置获取数据的版本数
        get.setMaxVersions();


        //3.获取数据
        Result result = table.get(get);

        //4.解析result并打印
        for (Cell cell : result.rawCells()) {
            //5.打印数据
            System.out.println( "CF: " + Bytes.toString(CellUtil.cloneFamily(cell)) +
                    " CN: "+ Bytes.toString(CellUtil.cloneQualifier(cell)) +
                    " Value: "+ Bytes.toString(CellUtil.cloneValue(cell))
                    );
        }

        table.close();
    }

    //3.获取数据（scan）
    public void ScanData (String tableName) throws IOException {
         //1.获取表的连接
        Table table = HbaseAPI.connection.getTable(TableName.valueOf(tableName));

        //2. 构建Scan对象
        Scan scan = new Scan();
        /*获取范围id的值*/
        //Scan scan = new Scan(Bytes.toBytes("1001"),Bytes.toBytes("1003"));

        //3.扫描表
        ResultScanner resultScanner = table.getScanner(scan);

        //4.解析resultScanner
        for (Result result : resultScanner) {

            //5.打印数据
            for (Cell cell : result.rawCells()) {
                //5.打印数据
                System.out.println( "CF: " + Bytes.toString(CellUtil.cloneFamily(cell)) +
                        " CN: "+ Bytes.toString(CellUtil.cloneQualifier(cell)) +
                        " Value: "+ Bytes.toString(CellUtil.cloneValue(cell))
                );
            }
        }

        //5.关闭资源
        table.close();
    }

    //4.删除数据
    /*
     * @author: 左先生
     * @date: 2022-01-15 17:08
     * @description:总结：
     */
    public void deleteData(String tableName , String rowKey , String cf , String cn) throws IOException {
        //1.获取表的连接
        Table table = HbaseAPI.connection.getTable(TableName.valueOf(tableName));

        //2.构建删除对象
        Delete delete = new Delete(Bytes.toBytes(rowKey));

        //2.1 设置删除的列,该设置可以删除指定的info以及列信息，进行单个删除，里面的timestamp参数可加可不加
        delete.addColumns(Bytes.toBytes(cf),Bytes.toBytes(cn),1642236880388L);

        //2.2 删除指定的列族
        //delete.addFamily(Bytes.toBytes(cf));


        //3.执行删除操作
        table.delete(delete);

        //4.关闭连接
        table.close();

    }
}