今天簡單說下Spark和Mysql的整合開發,首先要知道:在Spark中提供了一個JdbcRDD類,該RDD就是讀取JDBC中的數據並轉換成RDD,以後咱們就能夠對該RDD進行各類的操做,該類的構造函數以下:java
JdbcRDD[T: ClassTag]( sc: SparkContext, getConnection: () => Connection, sql: String, lowerBound: Long, upperBound: Long, numPartitions: Int, mapRow: (ResultSet) => T = JdbcRDD.resultSetToObjectArray _)
參數:mysql
(1)getConnection 返回一個已經打開的結構化數據庫鏈接,JdbcRDD會自動維護關閉。
(2)sql 是查詢語句,此查詢語句必須包含兩處佔位符?來做爲分割數據庫ResulSet的參數,例如:"select title, author from books where ? < = id and id <= ?"
(3)lowerBound, upperBound, numPartitions 分別爲第1、第二佔位符,partition的個數。例如,給出lowebound 1,upperbound 20, numpartitions 2,則查詢分別爲(1, 10)與(11, 20)
(4)mapRow 是轉換函數,將返回的ResultSet轉成RDD需用的單行數據,此處能夠選擇Array或其餘,也能夠是自定義的case class。默認的是將ResultSet 轉換成一個Object數組。web
下面是動手實踐,個人開發環境是:sql
虛擬機CentOs7系統,IDEA,JDK8,Scala 2.11,Spark 2.0.1,一些基本環境問題這裏就再也不敘述了。數據庫
本人使用的是maven,建立maven項目,初始化並添加依賴,下面是pom.xml:apache
<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/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>JdbcRdd</groupId> <artifactId>Demo</artifactId> <version>1.0-SNAPSHOT</version> <inceptionYear>2018</inceptionYear> <properties> <scala.version>2.11.8</scala.version> </properties> <repositories> <repository> <id>scala-tools.org</id> <name>Scala-Tools Maven2 Repository</name> <url>http://scala-tools.org/repo-releases</url> </repository> </repositories> <pluginRepositories> <pluginRepository> <id>scala-tools.org</id> <name>Scala-Tools Maven2 Repository</name> <url>http://scala-tools.org/repo-releases</url> </pluginRepository> </pluginRepositories> <dependencies> <dependency> <groupId>org.scala-lang</groupId> <artifactId>scala-library</artifactId> <version>${scala.version}</version> </dependency> <dependency> <groupId>org.apache.spark</groupId> <artifactId>spark-core_2.11</artifactId> <version>2.0.1</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.25</version> </dependency> </dependencies> <build> <sourceDirectory>src/main/scala</sourceDirectory> <testSourceDirectory>src/test/scala</testSourceDirectory> <plugins> <plugin> <groupId>org.scala-tools</groupId> <artifactId>maven-scala-plugin</artifactId> <executions> <execution> <goals> <goal>compile</goal> <goal>testCompile</goal> </goals> </execution> </executions> <configuration> <scalaVersion>${scala.version}</scalaVersion> <args> <arg>-target:jvm-1.5</arg> </args> </configuration> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-eclipse-plugin</artifactId> <configuration> <downloadSources>true</downloadSources> <buildcommands> <buildcommand>ch.epfl.lamp.sdt.core.scalabuilder</buildcommand> </buildcommands> <additionalProjectnatures> <projectnature>ch.epfl.lamp.sdt.core.scalanature</projectnature> </additionalProjectnatures> <classpathContainers> <classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER</classpathContainer> <classpathContainer>ch.epfl.lamp.sdt.launching.SCALA_CONTAINER</classpathContainer> </classpathContainers> </configuration> </plugin> </plugins> </build> <reporting> <plugins> <plugin> <groupId>org.scala-tools</groupId> <artifactId>maven-scala-plugin</artifactId> <configuration> <scalaVersion>${scala.version}</scalaVersion> </configuration> </plugin> </plugins> </reporting> </project>
新建scala的Object類,以下:數組
package JdbcRdd import java.sql.DriverManager import org.apache.spark.{SparkConf, SparkContext} import org.apache.spark.rdd.JdbcRDD object SparkToJdbc { def main(args: Array[String]): Unit = { val conf = new SparkConf().setAppName("mysql").setMaster("local") val sc = new SparkContext(conf) val rdd = new JdbcRDD( sc,()=>{ Class.forName("com.mysql.jdbc.Driver").newInstance() DriverManager.getConnection("jdbc:mysql://鏈接的IP:3306/鏈接的數據庫名", "用戶名", "密碼") }, "SELECT CATEGORY FROM nyw_knowledges WHERE COMPANY_CODE >= ? AND COMPANY_CODE <= ?", 1000, 1200, 3, r => r.getString(1)).cache() val rd = rdd.filter(_.contains("諮詢")).count() println(rd) sc.stop() } }
這裏基本的代碼就這些,鏈接數據庫後對錶進行操做。eclipse
注意:這裏可能會出現幾個問題,須要慎重處理:jvm
(1)內存問題:若是內存不夠,則須要從新設置,本人使用的是運行時配置:maven
也能夠用另外一種方式,在代碼中配置,
可參考:http://blog.csdn.net/qingyang0320/article/details/50787550。
(2)數據庫訪問限制問題
報錯:java.sql.SQLException: null, message from server: 「Host ‘xxx’ is not allowed to connect,該問題是因爲本機的訪問權限未開放,須要進行設置。
可參考:http://blog.csdn.net/xionglangs/article/details/50385057。
(3)mysql Driver依賴未添加報錯
<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.25</version> </dependency>
結果:
經過訪問Spark web UI的地址:localhost:4040可以清楚的查看具體的spark參數,大功告成。