scala - 尽管使用了 import sqlContext.implicits._，但 toDF 无法编译

Question

当我想使用 toDF 将 RDD 传递到 DataFrame 时，我在编译 Spark Scala 代码时遇到了一些问题。我检查了Spark 2.0.0和1.6.2，问题都是一样的。 下面我提供我的 POM 文件和代码段:

POM.xml

<?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>org.test</groupId>
    <artifactId>test_service</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

        <java.version>1.8</java.version>
        <scala.version>2.10.6</scala.version>
        <spark.version>2.0.0</spark.version>
        <jackson.version>2.8.3</jackson.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>${scala.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-streaming-kafka_2.10</artifactId>
            <version>1.6.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-sql_2.10</artifactId>
            <version>${spark.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_2.10</artifactId>
            <version>${spark.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-streaming_2.10</artifactId>
            <version>${spark.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-mllib_2.10</artifactId>
            <version>${spark.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-scala_2.10</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-scala_2.10</artifactId>
            <version>2.8.3</version>
        </dependency>
        <dependency>
            <groupId>org.sedis</groupId>
            <artifactId>sedis_2.10</artifactId>
            <version>1.2.2</version>
        </dependency>
        <dependency>
            <groupId>com.lambdaworks</groupId>
            <artifactId>jacks_2.10</artifactId>
            <version>2.3.3</version>
        </dependency>
        <dependency>
            <groupId>com.github.nscala-time</groupId>
            <artifactId>nscala-time_2.10</artifactId>
            <version>2.12.0</version>
        </dependency>
        <dependency>
            <groupId>com.typesafe</groupId>
            <artifactId>config</artifactId>
            <version>1.3.1</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-java-sdk-s3</artifactId>
            <version>1.11.53</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <executions>
                    <execution>
                        <id>build-a</id>
                        <configuration>
                            <archive>
                                <manifest>
                                    <mainClass>org.test.Runner1</mainClass>
                                </manifest>
                            </archive>
                            <descriptorRefs>
                                <descriptorRef>jar-with-dependencies</descriptorRef>
                            </descriptorRefs>
                            <finalName>runner1</finalName>
                        </configuration>
                        <phase>package</phase>
                        <goals>
                            <goal>assembly</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>build-b</id>
                        <configuration>
                            <archive>
                                <manifest>
                                    <mainClass>org.test.Runner2</mainClass>
                                </manifest>
                            </archive>
                            <descriptorRefs>
                                <descriptorRef>jar-with-dependencies</descriptorRef>
                            </descriptorRefs>
                            <finalName>runner2</finalName>
                        </configuration>
                        <phase>package</phase>
                        <goals>
                            <goal>assembly</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <!-- Configure maven-compiler-plugin to use the desired Java version -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>

            <!-- Use build-helper-maven-plugin to add Scala source and test source directories -->
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>build-helper-maven-plugin</artifactId>
                <version>1.10</version>
                <executions>
                    <execution>
                        <id>add-source</id>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>add-source</goal>
                        </goals>
                        <configuration>
                            <sources>
                                <source>src/main/scala</source>
                            </sources>
                        </configuration>
                    </execution>
                    <execution>
                        <id>add-test-source</id>
                        <phase>generate-test-sources</phase>
                        <goals>
                            <goal>add-test-source</goal>
                        </goals>
                        <configuration>
                            <sources>
                                <source>src/test/scala</source>
                            </sources>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

            <!-- Use scala-maven-plugin for Scala support -->
            <plugin>
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.2.2</version>
                <executions>
                    <execution>
                        <goals>
                            <!-- Need to specify this explicitly, otherwise plugin won't be called when doing e.g. mvn compile -->
                            <goal>compile</goal>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

一段提供错误的代码(rdd -> RDD[Map[String,Any]]):

import org.apache.spark.sql.SQLContext
import org.apache.spark.streaming.kafka.KafkaUtils
import org.apache.spark.streaming.{Seconds, StreamingContext}
import org.apache.spark.{SparkConf, SparkContext}

    val sqlContext = new org.apache.spark.sql.SQLContext(sc)
    import sqlContext.implicits._

    myDStream.foreachRDD { rdd =>

        val features = rdd.map(line => line.keySet).first().toList
        val myDF = filtered.toDF(features: _*) // toDF is not recognized!!!

}

Answer 1

这是预期的。 RDD[Map[String,Any]] 无法转换为 DataFrame:

• 没有隐式转换 https://spark.apache.org/docs/1.6.0/api/scala/index.html#org.apache.spark.sql.SQLContext $隐式$
• DataFrame 不支持Any。