本文仅仅介绍通过java api访问hive的数据。
本文依赖hive环境可用，特别是HiveServer2。
本文比较简单，仅仅为示例。

一、pom.xml

    <dependency>
        <groupId>org.apache.hive</groupId>
        <artifactId>hive-jdbc</artifactId>
        <version>3.1.2</version>
    </dependency>

二、java 类
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import lombok.extern.slf4j.Slf4j;

/**
* JDBC 操作 Hive
*
*/
@Slf4j
public class App {

    private static String driverName = "org.apache.hive.jdbc.HiveDriver";
    private static String url = "jdbc:hive2://server4:10000/default";// default 是默認數據庫名稱
    private static String user = "alanchan";// hadoop中可以訪問hdfs的用戶
    private static String password = "123456";// 該用戶的密碼

    private static Connection conn = null;
    private static Statement stmt = null;
    private static ResultSet rs = null;

    @Before
    public void init() throws Exception {
        Class.forName(driverName);
        conn = DriverManager.getConnection(url, user, password);
        stmt = conn.createStatement();
    }

    // 创建数据库
    @Test
    public void createDatabase() throws Exception {
        String sql = "create database test";
        log.info("sql:{}", sql);
        stmt.execute(sql);
    }

    // 查询所有数据库
    @Test
    public void showDatabases() throws Exception {
        String sql = "show databases";
        log.info("sql:{}", sql);
        rs = stmt.executeQuery(sql);
        while (rs.next()) {
            System.out.println(rs.getString(1));
        }
    }

    // 创建表
    @Test
    public void createTable() throws Exception {
        String sql = "create table test (id int ,name string) row format delimited fields terminated by '\\t' ";
        log.info("sql:{}", sql);
        stmt.execute(sql);
    }

    // 查询所有表
    @Test
    public void showTables() throws Exception {
        String sql = "show tables";
        log.info("sql:{}", sql);
        rs = stmt.executeQuery(sql);
        while (rs.next()) {
            System.out.println(rs.getString(1));
        }
    }

    // 查看表结构
    @Test
    public void descTable() throws Exception {
        String sql = "desc emp";
        log.info("sql:{}", sql);
        rs = stmt.executeQuery(sql);
        while (rs.next()) {
            System.out.println(rs.getString(1) + "\t" + rs.getString(2));
        }
    }

    // 加载数据
    @Test
    public void loadData() throws Exception {
        String filePath = "/home/hadoop/data/emp.txt";
        String sql = "load data local inpath '" + filePath + "' overwrite into table test";
        log.info("sql:{}", sql);
        stmt.execute(sql);
    }

    // 查询数据
    @Test
    public void selectData() throws Exception {
        String sql = "select * from test";
        log.info("sql:{}", sql);
        rs = stmt.executeQuery(sql);

        while (rs.next()) {
            System.out.println(rs.getInt("id") + "\t\t" + rs.getString("name"));
        }
    }

    // 统计查询（会运行mapreduce作业）
    @Test
    public void countData() throws Exception {
        String sql = "select count(1) from test";
        log.info("sql:{}", sql);
        rs = stmt.executeQuery(sql);
        while (rs.next()) {
            System.out.println(rs.getInt(1));
        }
    }

    // 删除数据库
    @Test
    public void dropDatabase() throws Exception {
        String sql = "drop database if exists test";
        log.info("sql:{}", sql);
        stmt.execute(sql);
    }

    // 删除数据库表
    @Test
    public void deopTable() throws Exception {
        String sql = "drop table if exists test";
        log.info("sql:{}", sql);
        stmt.execute(sql);
    }

    // 释放资源
    @After
    public void destory() throws Exception {
        if (rs != null) {
            rs.close();
        }
        if (stmt != null) {
            stmt.close();
        }
        if (conn != null) {
            conn.close();
        }
    }

}

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