编写Java代码，实现hive自定义函数，将MySQL数据写入hive表

好的，下面是Java代码实现hive自定义函数，将MySQL数据写入hive表的过程：

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

import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;

public class InsertMySQLDataToHive extends UDF {

    public Text evaluate() {

        String driver = "com.mysql.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/test";
        String user = "root";
        String password = "123456";

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

        String tableName = "hive_table";
        String mysqlTable = "mysql_table";

        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, user, password);
            stmt = conn.createStatement();
            rs = stmt.executeQuery("SELECT * FROM " + mysqlTable);

            while (rs.next()) {
                String column1 = rs.getString("column1");
                String column2 = rs.getString("column2");
                String column3 = rs.getString("column3");

                String insertSql = "INSERT INTO TABLE " + tableName + " VALUES ('" + column1 + "','" + column2 + "','" + column3 + "')";
                stmt.execute(insertSql);
            }

            return new Text("Insert MySQL data to Hive table successfully!");

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return new Text("ClassNotFoundException: " + e.getMessage());
        } catch (SQLException e) {
            e.printStackTrace();
            return new Text("SQLException: " + e.getMessage());
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (stmt != null) {
                    stmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
                return new Text("SQLException: " + e.getMessage());
            }
        }
    }
}

这个自定义函数连接到本地的MySQL数据库，从中读取数据并将其插入到Hive表中。在Hive中使用此自定义函数时，可以通过以下方式：

hive> ADD JAR /path/to/InsertMySQLDataToHive.jar;
hive> CREATE TEMPORARY FUNCTION insert_mysql_data_to_hive AS 'InsertMySQLDataToHive';
hive> SELECT insert_mysql_data_to_hive();

这将在Hive表中插入来自MySQL的数据，并在查询完成后返回“成功插入MySQL数据到Hive表！”。