实验目的

熟悉如何使用Java API操作Hive

实验原理

Hive有两种操作方式，Shell和Java API。

NOTE。步骤2-9必须按照严格的顺序执行，后面的步骤基于前面的步骤的结果，如果哪一步出错且对数据库造成影响，建议执行步骤8,9后再从步骤2开始。

实验步骤

步骤1.启动Hadoop和Hive.

#start-dfs.sh

进入Hive目录后，开启Hive远程接口。执行完之后不能关闭终端。

#cd /usr/local/hive
#bin/hive --service hiveserver2

步骤2.打开eclipse,在eclipse中File->New->Other->Map/Reduce->Map/Reduce Project，新建项目HiveWithJDBC，然后新建包hiveexamples.选中HiveWithJDBC，右键Properties->Java Build Path->Libraries->Add External JARs，将/usr/local/hivejars文件夹下的所有jar包导入，然后Apply and Close。

步骤3.新建文件HiveCreateDb.java，编写Java代码通过JDBC创建数据库。

package hiveexamples;

import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveCreateDb {
   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

   public static void main(String[] args) throws SQLException {
      // Register driver and create driver instance

      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
      // get connection

      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/default", "", "");
      Statement stmt = con.createStatement();

      stmt.execute("CREATE DATABASE userdb");
      System.out.println("Database userdb created successfully.");

      con.close();
   }
}

步骤4.测试。

选择，右键Run as->Run on Hadoop，查看输出结果。如果输出Database userdb created successfully.则成功执行。

步骤5.新建文件HiveCreateTable.java，编写Java代码通过JDBC新建表。

package hiveexamples;
import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveCreateTable {
   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

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

      // Register driver and create driver instance
      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

      // get connection
      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/userdb", "", "");

      // create statement
      Statement stmt = con.createStatement();

      // execute statement
      stmt.execute("CREATE TABLE IF NOT EXISTS "
         +" employee ( eid int, name String, "
         +" salary String, destignation String)"
         +" COMMENT 'Employee details'"
         +" ROW FORMAT DELIMITED"
         +" FIELDS TERMINATED BY '\t'"
         +" LINES TERMINATED BY '\n'"
         +" STORED AS TEXTFILE");

      System.out.println("Table employee created.");
      con.close();
   }
}

重复步骤4测试。

步骤6.新建文件HiveLoadData.java，编写Java代码通过JDBC加载数据到表中。

package hiveexamples;

import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveLoadData {

   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

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

      // Register driver and create driver instance
      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

      // get connection
      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/userdb", "", "");

      // create statement
      Statement stmt = con.createStatement();

      // execute statement
      stmt.execute("LOAD DATA LOCAL INPATH '/usr/local/hive/sample.txt'" + "OVERWRITE INTO TABLE employee");
      System.out.println("Load Data into employee successful");

      con.close();
   }
}

在开始执行之前，先要创建加载的数据文件。在/usr/local/hive下创建文件sample.txt。

# cd /usr/local/hive
# touch sample.txt
# gedit sample.txt

在打开的文件中输入以下内容，以tap键作为分隔符：

1    zhao    3300    manager
2    qian    1200    assistant
3    li    1200    assistant

重复步骤4测试。

步骤7.编写Java代码通过JDBC修改表。

新建文件HiveAlterAddColumn.java，实现添加列的功能。

package hiveexamples;
import java.sql.SQLException;


import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveAlterAddColumn {
   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

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

      // Register driver and create driver instance
      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

      // get connection
      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/userdb", "", "");

      // create statement
      Statement stmt = con.createStatement();

      // execute statement
      stmt.execute("ALTER TABLE employee ADD COLUMNS " + " (dept STRING COMMENT 'Department name')");
      System.out.println("Add column successful.");

      con.close();
   }
}

重复步骤4测试。

新建文件HiveAlterChangeColumn.java，实现更改列名的功能。

package hiveexamples;

import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveAlterChangeColumn {
   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

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

      // Register driver and create driver instance
      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

      // get connection
      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/userdb", "", "");

      // create statement
      Statement stmt = con.createStatement();

      // execute statement
      stmt.execute("ALTER TABLE employee CHANGE name ename String");
      stmt.execute("ALTER TABLE employee CHANGE salary salary Double");

      System.out.println("Change column successful.");
      con.close();
   }
}

重复步骤4测试。

新建文件HiveAlterRenameTo.java，实现重命名表的功能。

package hiveexamples;

import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet; 
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveAlterRenameTo {
   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

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

      // Register driver and create driver instance
      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

      // get connection
      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/userdb", "", "");

      // create statement
      Statement stmt = con.createStatement();

      // execute statement
      stmt.execute("ALTER TABLE employee RENAME TO empl");
      System.out.println("Table Renamed Successfully");
      con.close();
   }
}

重复步骤4测试。

步骤8.新建文件HiveDropTable.java，编写Java代码通过JDBC删除表。

package hiveexamples;

import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveDropTable {

   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

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

      // Register driver and create driver instance
      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

      // get connection
      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/userdb", "", "");

      // create statement
      Statement stmt = con.createStatement();

      // execute statement
      stmt.execute("DROP TABLE IF EXISTS empl");
      System.out.println("Drop table successful.");

      con.close();
   }
}

重复步骤4.

步骤9.新建文件HiveDropDb.java，编写Java代码通过JDBC删除数据库。

package hiveexamples;

import java.sql.SQLException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.DriverManager;

public class HiveDropDb {
   private static String driverName = "org.apache.hive.jdbc.HiveDriver";

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

      // Register driver and create driver instance
      try {
        Class.forName(driverName);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

      // get connection
      Connection con = DriverManager.getConnection("jdbc:hive2://localhost:10000/default", "", "");
      Statement stmt = con.createStatement();
      stmt.execute("DROP DATABASE userdb");

      System.out.println("Drop userdb database successful.");

      con.close();
   }
}

步骤10.新建文件hiveJDBC.java，该文件是总结性的测试代码。

package hiveexamples;

import java.sql.Connection;  
import java.sql.DriverManager;  
import java.sql.ResultSet;  
import java.sql.SQLException;  
import java.sql.Statement;  

import org.apache.log4j.Logger;  

/** 
 * Hive的JavaApi 
 *  
 * 启动hive的远程服务接口命令行执行：hive --service hiveserver2 
 * 
 *  
 */  
public class hiveJDBC {  

    private static String driverName = "org.apache.hive.jdbc.HiveDriver";  
    private static String url = "jdbc:hive2://localhost:10000/default";  
    private static String user = "";  
    private static String password = "";  
    private static String sql = "";  
    private static ResultSet res;  
    private static final Logger log = Logger.getLogger(hiveJDBC.class);  

    public static void main(String[] args) {  
        Connection conn = null;  
        Statement stmt = null;  
        try {  
            conn = getConn();  
            stmt = conn.createStatement();  

            // 第一步:存在就先删除  
            String tableName = dropTable(stmt);  

            // 第二步:不存在就创建  
            createTable(stmt, tableName);  

            // 第三步:查看创建的表  
            showTables(stmt, tableName);  

            // 执行describe table操作  
            describeTables(stmt, tableName);  

            // 执行load data into table操作  
            loadData(stmt, tableName);  

            // 执行 select * query 操作  
            selectData(stmt, tableName);  

            // 执行 regular hive query 统计操作  
            countData(stmt, tableName);  

        } catch (ClassNotFoundException e) {  
            e.printStackTrace();  
            log.error(driverName + " not found!", e);  
            System.exit(1);  
        } catch (SQLException e) {  
            e.printStackTrace();  
            log.error("Connection error!", e);  
            System.exit(1);  
        } finally {  
            try {  
                if (conn != null) {  
                    conn.close();  
                    conn = null;  
                }  

            } catch (SQLException e) {  
                e.printStackTrace();  
            }  
        }  
    }  

    private static void countData(Statement stmt, String tableName)  
            throws SQLException {  
        sql = "select count(1) from " + tableName;  
        System.out.println("Running:" + sql);  
        res = stmt.executeQuery(sql);  
        System.out.println("执行“regular hive query”运行结果:");  
        while (res.next()) {  
            System.out.println("count ------>" + res.getString(1));  
        }  
    }  

    private static void selectData(Statement stmt, String tableName)  
            throws SQLException {  
        sql = "select * from " + tableName;  
        System.out.println("Running:" + sql);  
        res = stmt.executeQuery(sql);  
        System.out.println("执行 select * query 运行结果:");  
        while (res.next()) {  
            System.out.println(res.getInt(1) + "\t" + res.getString(2));  
        }  
    }  

    private static void loadData(Statement stmt, String tableName)  
            throws SQLException {  
        String filepath = "/usr/local/hadoop/input.txt";  
        sql = "load data local inpath '" + filepath + "' into table "  
                + tableName;  
        System.out.println("Running:" + sql);  
        stmt.execute(sql);  
    }  

    private static void describeTables(Statement stmt, String tableName)  
            throws SQLException {  
        sql = "describe " + tableName;  
        System.out.println("Running:" + sql);  
        res = stmt.executeQuery(sql);  
        System.out.println("执行 describe table 运行结果:");  
        while (res.next()) {  
            System.out.println(res.getString(1) + "\t" + res.getString(2));  
        }  
    }  

    private static void showTables(Statement stmt, String tableName)  
            throws SQLException {  
        sql = "show tables '" + tableName + "'";  
        System.out.println("Running:" + sql);  
        res = stmt.executeQuery(sql);  
        System.out.println("执行 show tables 运行结果:");  
        if (res.next()) {  
            System.out.println(res.getString(1));  
        }  
    }  

    private static void createTable(Statement stmt, String tableName)  
            throws SQLException {  
        sql = "create table "  
                + tableName  
                + " (key int, value string)  row format delimited fields terminated by '\t'";  
        stmt.execute(sql);  
    }  

    private static String dropTable(Statement stmt) throws SQLException {  
        // 创建的表名  
        String tableName = "testHive";  
        sql = "drop table " + tableName;  
        stmt.execute(sql);  
        return tableName;  
    }  

    private static Connection getConn() throws ClassNotFoundException,  
            SQLException {  
        Class.forName(driverName);  
        Connection conn = DriverManager.getConnection(url, user, password);  
        return conn;  
    }  

}

步骤11.重复步骤4，查看结果。