上代码：
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<hive.version>1.1.0</hive.version>
<hadoop.version>2.6.0</hadoop.version>
<mysql.version>5.1.34</mysql.version>
</properties>
<dependencies>
<dependency>
<groupId>org.apache.hive</groupId>
<artifactId>hive-exec</artifactId>
<version>${hive.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>${hadoop.version}</version>
<exclusions>
<exclusion>
<groupId>jdk.tools</groupId>
<artifactId>jdk.tools</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql.version}</version>
</dependency>
</dependencies>
java代码：
import java.io.IOException;
import java.net.URI;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hive.ql.exec.UDF;
public class GetNextTradeDate extends UDF{
public String evaluate (){
Properties p=null;
try {
p = getPro();
} catch (Exception e1) {
e1.printStackTrace();
}
String DB_URL=p.getProperty("DB_URL");
String JDBC_DRIVER=p.getProperty("JDBC_DRIVER");
String USER=p.getProperty("USER");
String PASS=p.getProperty("PASS");
Connection conn = null;
Statement stmt = null;
String init_date = "";
try{
Class.forName(JDBC_DRIVER);
conn = DriverManager.getConnection(DB_URL,USER,PASS);
stmt = conn.createStatement();
String sql = "SELECT date FROM xxx.xxx limit 1";
ResultSet rs = stmt.executeQuery(sql);
while(rs.next()){
init_date= rs.getString("date");
}
rs.close();
stmt.close();
conn.close();
}catch(SQLException se){
se.printStackTrace();
}catch(Exception e){
e.printStackTrace();
}finally{
try{
if(stmt!=null) stmt.close();
}catch(SQLException se2){
}
try{
if(conn!=null) conn.close();
}catch(SQLException se){
se.printStackTrace();
}
}
return init_date;
}
private Properties getPro() throws Exception{
String dsf= "/user/xxx/mysql-for-hive.properties";
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(dsf),conf);
FSDataInputStream inputStream = fs.open(new Path(dsf));
Properties p = new Properties();
try {
p.load(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
return p;
}
}
将上述代码导出为jar包。
配置文件mysql-for-hive.properties内容如下：
JDBC_DRIVER=com.mysql.jdbc.Driver
DB_URL=jdbc:mysql://192.168.xxx.xxx:3306/xxx
USER=xxxx
PASS=xxxx
这种是创建永久UDF函数，需要把jar包和配置文件上传hdfs；
hdfs dfs -put -p getNextTradeDate.jar /user/xxx
hdfs dfs -put -p mysql-for-hive.properties /user/xxx
创建函数
CREATE FUNCTION getNextTradeDate AS 'com.xxx.xxx.xxx.GetNextTradeDate' USING JAR 'hdfs://xxxx:8020/user/xxxx/getNextTradeDate.jar';
删除函数
drop function getNextTradeDate;
测试函数：
select getNextTradeDate() tradeDate from xxxx.xxxx;
创建临时函数略有不同，临时函数当前session有效：
如果你的临时函数没有输入，只有输出，会被hive优化为本地执行，不需要集群，这时候读取配置文件就可以读本地，add file后，直接用getResourceAsStream读本地文件即可，不再采用从集群中读取配置文件的方式。
读入配置文件的语句修改如下：
InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("./mysql-for-hive.properties");
然后再Properties p = new Properties(); p.load(inputStream); .........
打jar包上传，然后打开hive，输入：
add file /home/mysql-for-hive.properties;
add jar /home/getNextTradeDate.jar;
create temporary function getNextTradeDate as "com.xxx.xxx.xxx.GetNextTradeDate";
select getNextTradeDate() tradeDate from xxxx.xxxx;
有结果的话就测试成功。
删除临时函数
drop temporary function getNextTradeDate;
