使用應用程序(Java/Python)訪問MaxCompute Lightning進行數據開發

MaxCompute Lightning是MaxCompute產品的交互式查詢服務，支持以PostgreSQL協議及語法鏈接訪問Maxcompute項目，讓您使用熟悉的工具以標準 SQL查詢分析MaxCompute項目中的數據，快速獲取查詢結果。
不少開發者但願利用Lightning的特性來開發數據應用，本文將結合示例來介紹Java和Python如何鏈接訪問Lightning進行應用開發(參考時須要替換爲您項目所在region的Endpoint及用戶認證信息)。
1、Java使用JDBC訪問Lightning
示例以下：

import java.sql.*;

public class Main {

    private static Connection connection;

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

        String url = "jdbc:postgresql://lightning.cn-shanghai.maxcompute.aliyun.com:443/your_project_name?prepareThreshold=0&sslmode=require";
        String accessId = "<your_maxcompute_access_id>";
        String accessKey = "<your_maxcompute_access_key>";
        String sql = "select * from dual";

        try {
            Connection conn = getCon(url, accessId, accessKey);
            Statement st = conn.createStatement();
            System.out.println("Send Lightning query");
            ResultSet rs = st.executeQuery(sql);
            while (rs.next()) {
                System.out.println(rs.getString(1)+ "\t");
            }
            System.out.println("End Lightning query");
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static Connection getCon(String lightningsHost, String lightningUser, String lightningPwd) {
        try {
            if (connection == null || connection.isClosed()) {
                try {
                    Class.forName("org.postgresql.Driver").newInstance();
                    DriverManager.setLoginTimeout(1);
                    connection = DriverManager.getConnection(lightningsHost, lightningUser, lightningPwd);
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return connection;
    }
}複製代碼

2、Java使用druid訪問Lightning
1.pom依賴

<dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.23</version>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>9.3-1101-jdbc4</version>
        </dependency>
複製代碼

2.spring配置

<bean id="LightningDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="url" value="jdbc:postgresql://lightning.cn-shanghai.maxcompute.aliyun.com:443/project_name?prepareThreshold=0&sslmode=require」/> <!--替換成本身project所在region的Endpoint—> <property name="username" value=「訪問用戶的Access Key ID"/>
        <property name="password" value="訪問用戶的Access Key Secret"/>
        <property name="driverClassName" value="org.postgresql.Driver"/>
        <property name="dbType" value="postgresql"/>
        <property name="initialSize" value="1" />  
        <property name="minIdle" value="1" />
        <property name="maxActive" value="5" />  <!—Lightning服務每一個project的鏈接數限制20，因此不要配置過大，按需配置，不然容易出現query_wait_timeout錯誤 -->
 
        <!--如下兩個配置，檢測鏈接有效性，修復偶爾出現create connection holder error錯誤 -->
        <property name="testWhileIdle" value="true" />
        <property name="validationQuery" value="SELECT 1" />
    </bean>

  <bean class="com.xxx.xxx.LightningProvider">
    <property name="druidDataSource" ref="LightningDataSource"/>
  </bean>複製代碼

3.代碼訪問

public class LightningProvider {

    DruidDataSource druidDataSource;
    /**
     * 執行sql
     * @param sql
     * @return
     * @throws Exception
     */
    public void execute(String sql) throws SQLException {
        DruidPooledConnection connection = null ;
        Statement st = null;
        try{
            connection = druidDataSource.getConnection();
            st = connection.createStatement();

            ResultSet resultSet = st.executeQuery(sql);
            //對返回值的解析和處理的代碼
            //按行處理，每行的數據放到一個map中
            ResultSetMetaData metaData = resultSet.getMetaData();
            int columnCount = metaData.getColumnCount();
            List<LinkedHashMap> rows = Lists.newArrayList();
            while(resultSet.next()){
            LinkedHashMap map = Maps.newLinkedHashMap();
            for(int i=1;i<=columnCount;i++){
                String label = resultSet.getMetaData().getColumnLabel(i);
                map.put(label,resultSet.getString(i));
            }
            rows.add(map);
        }   
        }catch (Exception e){
             e.printStackTrace();
        }finally {
            try {
                if(st!=null) {
                    st.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }

            try {
                if(connection!=null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}複製代碼

3、Python使用pyscopg2訪問Lightning
示例以下：

#!/usr/bin/env python
# coding=utf-8

import psycopg2
import sys

def query_lightning(lightning_conf, sql):
    """Query data through Lightning by sql Args: lightning_conf: a map contains settings of 'dbname', 'user', 'password', 'host', 'port' sql: query submit to Lightning Returns: result: the query result in format of list of rows """
    result = None
    conn = None
    conn_str = None
    try:
        conn_str = ("dbname={dbname} "
                    "user={user} "
                    "password={password} "
                    "host={host} "
                    "port={port}").format(**lightning_conf)
    except Exception, e:
        print >> sys.stderr, ("Invalid Lightning' configuration "
                       "{}".format(e))
        sys.exit(1)

    try:
        conn = psycopg2.connect(conn_str)
        conn.set_session(autocommit=True) # This will disable transaction
                                   # started with keyword BEGIN,
                                   # which is currently not
                                   # supported by Lightning’ public service

        cur = conn.cursor()
        # execute Lightning' query
        cur.execute(sql)
        # get result
        result = cur.fetchall()
    except Exception, e:
        print >> sys.stderr, ("Failed to query data through "
                       "Lightning: {}".format(e))
    finally:
        if conn:
            conn.close()

    return result

if __name__ == "__main__":
    # step1. setup configuration
    lightning_conf = {
        "dbname": 「your_project_name」,
        "user": "<your_maxcompute_access_id>", 
        "password": "<your_maxcompute_access_key>", 
        "host": "lightning.cn-shanghai.maxcompute.aliyun.com",  #your region lightning endpoint
        "port": 443
    }

    # step2. issue a query
    result = query_lightning(lightning_conf, "select * from test」) # step3. print result if result: for i in xrange(0, len(result)): print "Got %d row from Lightning:%s" % (i + 1, result[i])複製代碼

4、Python使用ODBC訪問Lightning
您須要如今電腦上安裝並和配置odbc驅動。代碼示例以下：

import pyodbc
conn_str = (
    "DRIVER={PostgreSQL Unicode};"
    "DATABASE=your_project_name;"
    "UID=your_maxcompute_access_id;"
    "PWD=your_maxcompute_access_key;"
    "SERVER=lightning.cn-shanghai.maxcompute.aliyun.com;" #your region lightning endpoint
    "PORT=443;"
    )
conn = pyodbc.connect(conn_str)
crsr = conn.execute("SELECT * from test」) row = crsr.fetchone() print(row) crsr.close() conn.close()複製代碼

因爲Lightning提供了PostgreSQL兼容的接口，您能夠像開發PostgreSQL的應用同樣開發Lightning應用程序。

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