大数据入门教程系列之Hive的Java API 操作

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Java 想要访问Hive，需要通过beeline的方式连接Hive，hiveserver2提供了一个新的命令行工具beeline，hiveserver2 对 之前的hive做了升级，功能更加强大，它增加了权限控制，要使用beeline需要先启动hiverserver2，再使用beeline连接

操作步骤：

①、修改hadoop的core-site.xml配置文件

②、启动hadoop

③、启动hiverserver2

④、打开一个新窗口使用beeline连接(注意这里的javaapidb需要提前建立好)

⑤、新建java项目(maven)

 

 

详细步骤：

一、修改hadoop的core-site.xml配置文件

[code]<property>
<name>hadoop.proxyuser.hadoop.hosts</name>
<value>*</value>
</property>
<property>
<name>hadoop.proxyuser.hadoop.groups</name>
<value>*</value>
</property>

否则使用beeline连接时会报如下错

hadoop is not allowed to impersonate hadoop (state=08S01,code=0)

原因：hiveserver2增加了权限控制，需要在hadoop的配置文件中配置

解决方法：在hadoop的core-site.xml中添加如下内容，然后重启hadoop，再使用beeline连接即可

参考官网：

https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/Superusers.html

 

二、启动hadoop

[code]start-sll.sh

 

三、启动hiverserver2

[code]hiveserver2

jps看到这个进程说明启动成功了

 

四、打开一个新窗口使用beeline连接(注意这里的javaapidb需要提前建立好)

[code]beeline -u jdbc:hive2://node1:10000/javaapidb -n hadoop -p

参数解释： 

-u：连接url，可以使用IP，也可以使用主机名，端口默认为10000 

-n：连接的用户名（注：不是登录hive的用户名，是hive所在服务器登录用户名） 

-p：密码，可以不用输入

启动中密码处可以直接回车，启动后我们查询一下数据库即可看到是否启动成功

 

五、新建java项目(maven)

1、修改pom

[code]
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.demo</groupId>
<artifactId>java-api-hive</artifactId>
<version>1.0-SNAPSHOT</version>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

<dependencies>
<dependency>
<groupId>org.apache.hive</groupId>
<artifactId>hive-jdbc</artifactId>
<version>2.3.0</version>
</dependency>

<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.9</version>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>

</project>

2、创建测试类HiveJDBC，代码如下 

官网参考：https://cwiki.apache.org/confluence/display/Hive/HiveServer2+Clients

演示了一个查询

完整代码： 

[code]package hiveapi;

/**
* Created by zhoujh on 2018/8/15.
*/

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.sql.*;

/**
* JDBC 操作 Hive（注：JDBC 访问 Hive 前需要先启动HiveServer2）
*/
public class HiveJDBC {

private static String driverName = "org.apache.hive.jdbc.HiveDriver";
private static String url = "jdbc:hive2://node1:10000/javaapidb";
private static String user = "hadoop";
private static String password = "";

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

// 加载驱动、创建连接
@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 testdb";
System.out.println("Running: " + sql);
stmt.execute(sql);
}

// 查询所有数据库
@Test
public void showDatabases() throws Exception {
String sql = "show databases";
System.out.println("Running: " + 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 emp(\n" +
"empno int,\n" +
"ename string,\n" +
"job string,\n" +
"mgr int,\n" +
"hiredate string,\n" +
"sal double,\n" +
"comm double,\n" +
"deptno int\n" +
")\n" +
"row format delimited fields terminated by '\\t'";
System.out.println("Running: " + sql);
stmt.execute(sql);
}

// 查询所有表
@Test
public void showTables() throws Exception {
String sql = "show tables";
System.out.println("Running: " + 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";
System.out.println("Running: " + 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 emp";
System.out.println("Running: " + sql);
stmt.execute(sql);
}

// 查询数据
@Test
public void selectData() throws Exception {
String sql = "select * from emp";
System.out.println("Running: " + sql);
rs = stmt.executeQuery(sql);
System.out.println("员工编号" + "\t" + "员工姓名" + "\t" + "工作岗位");
while (rs.next()) {
System.out.println(rs.getString("empno") + "\t\t" + rs.getString("ename") + "\t\t" + rs.getString("job"));
}
}

// 统计查询（会运行mapreduce作业）
@Test
public void countData() throws Exception {
String sql = "select count(1) from emp";
System.out.println("Running: " + 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 hive_jdbc_test";
System.out.println("Running: " + sql);
stmt.execute(sql);
}

// 删除数据库表
@Test
public void deopTable() throws Exception {
String sql = "drop table if exists emp";
System.out.println("Running: " + 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();
}
}
}