前言
本文主要给出Spark创建空的DataFrame的代码示例，这里讲的空的DataFrame主要指有列名（可以自己随意指定），但是没有行的DataFrame，因为自己在开发过程中有这个需求，之前并不知道怎么创建，就查了一下，发现资料并不多，不知道因为太简单还是用的人少，至于具体什么需求就不阐述了，主要给有这方面需求的小伙伴参考一下。还有另一种空的DataFrame就是没有任何行任何列的DataFrame，不知道有什么用，反正贴在代码里，万一有人用呢
1、代码
代码较简单，如下
import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.types._
import org.apache.spark.sql.Row
import org.apache.spark.rdd.EmptyRDD
/**
* Spark创建空DataFrame示例
*/
object EmptyDataFrame {
def main(args: Array[String]): Unit = {
val spark = SparkSession.builder().appName("EmptyDataFrame").master("local").getOrCreate()
/**
* 创建一个空的DataFrame，代表用户
* 有四列，分别代表ID、名字、年龄、生日
*/
val colNames = Array("id", "name", "age", "birth")
//为了简单起见，字段类型都为String
val schema = StructType(colNames.map(fieldName => StructField(fieldName, StringType, true)))
//主要是利用了spark.sparkContext.emptyRDD
val emptyDf = spark.createDataFrame(spark.sparkContext.emptyRDD[Row], schema)
emptyDf.show
/**
* 也可以给每列指定相对应的类型
*/
val schema1 = StructType(
Seq(
StructField("id", IntegerType, true),
StructField("name", StringType, true),
StructField("age", IntegerType, true),
StructField("birth", StringType, true)))
val emptyDf1 = spark.createDataFrame(spark.sparkContext.emptyRDD[Row], schema1)
emptyDf1.show
//还有一种空的DataFrame，没有任何行任何列
spark.emptyDataFrame.show
spark.stop()
}
}
2、结果
D:devtoolsJavajdk1.8.0_191injava.exe "-javaagent:D:devtoolsIntelliJ IDEA Community Edition 2018.2.6libidea_rt.jar=64870:D:devtoolsIntelliJ IDEA Community Edition 2018.2.6in" -Dfile.encoding=UTF-8 -classpath D:devtoolsJavajdk1.8.0_191jrelibcharsets.jar;D:devtoolsJavajdk1.8.0_191jrelibdeploy.jar;D:devtoolsJavajdk1.8.0_191jrelibextaccess-bridge-64.jar;D:devtoolsJavajdk1.8.0_191jrelibextcldrdata.jar;D:devtoolsJavajdk1.8.0_191jrelibextdnsns.jar;D:devtoolsJavajdk1.8.0_191jrelibextjaccess.jar;D:devtoolsJavajdk1.8.0_191jrelibextjfxrt.jar;D:devtoolsJavajdk1.8.0_191jrelibextlocaledata.jar;D:devtoolsJavajdk1.8.0_191jrelibext
ashorn.jar;D:devtoolsJavajdk1.8.0_191jrelibextsunec.jar;D:devtoolsJavajdk1.8.0_191jrelibextsunjce_provider.jar;D:devtoolsJavajdk1.8.0_191jrelibextsunmscapi.jar;D:devtoolsJavajdk1.8.0_191jrelibextsunpkcs11.jar;D:devtoolsJavajdk1.8.0_191jrelibextzipfs.jar;D:devtoolsJavajdk1.8.0_191jrelibjavaws.jar;D:devtoolsJavajdk1.8.0_191jrelibjce.jar;D:devtoolsJavajdk1.8.0_191jrelibjfr.jar;D:devtoolsJavajdk1.8.0_191jrelibjfxswt.jar;D:devtoolsJavajdk1.8.0_191jrelibjsse.jar;D:devtoolsJavajdk1.8.0_191jrelibmanagement-agent.jar;D:devtoolsJavajdk1.8.0_191jrelibplugin.jar;D:devtoolsJavajdk1.8.0_191jrelib
esources.jar;D:devtoolsJavajdk1.8.0_191jrelib
t.jar;D:workspaceSpark_Test argetclasses;C:Users一期一会.m2
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epositoryorgcodehausjacksonjackson-mapper-asl1.9.13jackson-mapper-asl-1.9.13.jar;C:Users一期一会.m2
epositorycom houghtworksparanamerparanamer2.7paranamer-2.7.jar;C:Users一期一会.m2
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epositoryorgapachehadoophadoop-mapreduce-client-shuffle2.6.5hadoop-mapreduce-client-shuffle-2.6.5.jar;C:Users一期一会.m2
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epositoryorgapachehadoophadoop-mapreduce-client-core2.6.5hadoop-mapreduce-client-core-2.6.5.jar;C:Users一期一会.m2
epositoryorgapachehadoophadoop-yarn-common2.6.5hadoop-yarn-common-2.6.5.jar;C:Users一期一会.m2
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epositoryorgcodehausjacksonjackson-jaxrs1.9.13jackson-jaxrs-1.9.13.jar;C:Users一期一会.m2
epositoryorgcodehausjacksonjackson-xc1.9.13jackson-xc-1.9.13.jar;C:Users一期一会.m2
epositoryorgapachehadoophadoop-mapreduce-client-jobclient2.6.5hadoop-mapreduce-client-jobclient-2.6.5.jar;C:Users一期一会.m2
epositoryorgapachehadoophadoop-annotations2.6.5hadoop-annotations-2.6.5.jar;C:Users一期一会.m2
epositoryorgapachesparkspark-launcher_2.112.4.0spark-launcher_2.11-2.4.0.jar;C:Users一期一会.m2
epositoryorgapachesparkspark-kvstore_2.112.4.0spark-kvstore_2.11-2.4.0.jar;C:Users一期一会.m2
epositoryorgfusesourceleveldbjnileveldbjni-all1.8leveldbjni-all-1.8.jar;C:Users一期一会.m2
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epositoryorgapachesparkspark-network-common_2.112.4.0spark-network-common_2.11-2.4.0.jar;C:Users一期一会.m2
epositoryorgapachesparkspark-network-shuffle_2.112.4.0spark-network-shuffle_2.11-2.4.0.jar;C:Users一期一会.m2
epositoryorgapachesparkspark-unsafe_2.112.4.0spark-unsafe_2.11-2.4.0.jar;C:Users一期一会.m2
epositoryjavaxactivationactivation1.1.1activation-1.1.1.jar;C:Users一期一会.m2
epositoryorgapachecuratorcurator-recipes2.6.0curator-recipes-2.6.0.jar;C:Users一期一会.m2
epositoryorgapachecuratorcurator-framework2.6.0curator-framework-2.6.0.jar;C:Users一期一会.m2
epositorycomgoogleguavaguava16.0.1guava-16.0.1.jar;C:Users一期一会.m2
epositoryorgapachezookeeperzookeeper3.4.6zookeeper-3.4.6.jar;C:Users一期一会.m2
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epositoryorgapachecommonscommons-lang33.5commons-lang3-3.5.jar;C:Users一期一会.m2
epositoryorgapachecommonscommons-math33.4.1commons-math3-3.4.1.jar;C:Users一期一会.m2
epositorycomgooglecodefindbugsjsr3051.3.9jsr305-1.3.9.jar;C:Users一期一会.m2
epositoryorgslf4jslf4j-api1.7.16slf4j-api-1.7.16.jar;C:Users一期一会.m2
epositoryorgslf4jjul-to-slf4j1.7.16jul-to-slf4j-1.7.16.jar;C:Users一期一会.m2
epositoryorgslf4jjcl-over-slf4j1.7.16jcl-over-slf4j-1.7.16.jar;C:Users一期一会.m2
epositorylog4jlog4j1.2.17log4j-1.2.17.jar;C:Users一期一会.m2
epositoryorgslf4jslf4j-log4j121.7.16slf4j-log4j12-1.7.16.jar;C:Users一期一会.m2
epositorycom
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epositoryorgxerialsnappysnappy-java1.1.7.1snappy-java-1.1.7.1.jar;C:Users一期一会.m2
epositoryorglz4lz4-java1.4.0lz4-java-1.4.0.jar;C:Users一期一会.m2
epositorycomgithublubenzstd-jni1.3.2-2zstd-jni-1.3.2-2.jar;C:Users一期一会.m2
epositoryorg
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epositorycommons-netcommons-net3.1commons-net-3.1.jar;C:Users一期一会.m2
epositoryorgjson4sjson4s-jackson_2.113.5.3json4s-jackson_2.11-3.5.3.jar;C:Users一期一会.m2
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epositoryorgjson4sjson4s-scalap_2.113.5.3json4s-scalap_2.11-3.5.3.jar;C:Users一期一会.m2
epositoryorgscala-langmodulesscala-xml_2.111.0.6scala-xml_2.11-1.0.6.jar;C:Users一期一会.m2
epositoryorgglassfishjerseycorejersey-client2.22.2jersey-client-2.22.2.jar;C:Users一期一会.m2
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epositoryorgglassfishhk2hk2-locator2.4.0-b34hk2-locator-2.4.0-b34.jar;C:Users一期一会.m2
epositoryorgjavassistjavassist3.18.1-GAjavassist-3.18.1-GA.jar;C:Users一期一会.m2
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epositoryorgglassfishjerseyundles
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epositoryorgglassfishjerseymediajersey-media-jaxb2.22.2jersey-media-jaxb-2.22.2.jar;C:Users一期一会.m2
epositoryjavaxvalidationvalidation-api1.1.0.Finalvalidation-api-1.1.0.Final.jar;C:Users一期一会.m2
epositoryorgglassfishjerseycontainersjersey-container-servlet2.22.2jersey-container-servlet-2.22.2.jar;C:Users一期一会.m2
epositoryorgglassfishjerseycontainersjersey-container-servlet-core2.22.2jersey-container-servlet-core-2.22.2.jar;C:Users一期一会.m2
epositoryio
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epositoryio
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epositorycomclearspringanalyticsstream2.7.0stream-2.7.0.jar;C:Users一期一会.m2
epositoryiodropwizardmetricsmetrics-core3.1.5metrics-core-3.1.5.jar;C:Users一期一会.m2
epositoryiodropwizardmetricsmetrics-jvm3.1.5metrics-jvm-3.1.5.jar;C:Users一期一会.m2
epositoryiodropwizardmetricsmetrics-json3.1.5metrics-json-3.1.5.jar;C:Users一期一会.m2
epositoryiodropwizardmetricsmetrics-graphite3.1.5metrics-graphite-3.1.5.jar;C:Users一期一会.m2
epositorycomfasterxmljacksoncorejackson-databind2.6.7.1jackson-databind-2.6.7.1.jar;C:Users一期一会.m2
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epositoryorgscala-langscala-reflect2.11.8scala-reflect-2.11.8.jar;C:Users一期一会.m2
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epositoryorgapacheivyivy2.4.0ivy-2.4.0.jar;C:Users一期一会.m2
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epositoryorgapachecommonscommons-crypto1.0.0commons-crypto-1.0.0.jar;C:Users一期一会.m2
epositoryorgspark-projectsparkunused1.0.0unused-1.0.0.jar;C:Users一期一会.m2
epositoryorgapachesparkspark-sql_2.112.4.0spark-sql_2.11-2.4.0.jar;C:Users一期一会.m2
epositorycomunivocityunivocity-parsers2.7.3univocity-parsers-2.7.3.jar;C:Users一期一会.m2
epositoryorgapachesparkspark-sketch_2.112.4.0spark-sketch_2.11-2.4.0.jar;C:Users一期一会.m2
epositoryorgapachesparkspark-catalyst_2.112.4.0spark-catalyst_2.11-2.4.0.jar;C:Users一期一会.m2
epositoryorgscala-langmodulesscala-parser-combinators_2.111.1.0scala-parser-combinators_2.11-1.1.0.jar;C:Users一期一会.m2
epositoryorgcodehausjaninojanino3.0.9janino-3.0.9.jar;C:Users一期一会.m2
epositoryorgcodehausjaninocommons-compiler3.0.9commons-compiler-3.0.9.jar;C:Users一期一会.m2
epositoryorgantlrantlr4-runtime4.7antlr4-runtime-4.7.jar;C:Users一期一会.m2
epositoryorgapacheorcorc-core1.5.2orc-core-1.5.2-nohive.jar;C:Users一期一会.m2
epositoryorgapacheorcorc-shims1.5.2orc-shims-1.5.2.jar;C:Users一期一会.m2
epositorycomgoogleprotobufprotobuf-java2.5.0protobuf-java-2.5.0.jar;C:Users一期一会.m2
epositorycommons-langcommons-lang2.6commons-lang-2.6.jar;C:Users一期一会.m2
epositoryioairliftaircompressor0.10aircompressor-0.10.jar;C:Users一期一会.m2
epositoryorgapacheorcorc-mapreduce1.5.2orc-mapreduce-1.5.2-nohive.jar;C:Users一期一会.m2
epositoryorgapacheparquetparquet-column1.10.0parquet-column-1.10.0.jar;C:Users一期一会.m2
epositoryorgapacheparquetparquet-common1.10.0parquet-common-1.10.0.jar;C:Users一期一会.m2
epositoryorgapacheparquetparquet-encoding1.10.0parquet-encoding-1.10.0.jar;C:Users一期一会.m2
epositoryorgapacheparquetparquet-hadoop1.10.0parquet-hadoop-1.10.0.jar;C:Users一期一会.m2
epositoryorgapacheparquetparquet-format2.4.0parquet-format-2.4.0.jar;C:Users一期一会.m2
epositoryorgapacheparquetparquet-jackson1.10.0parquet-jackson-1.10.0.jar;C:Users一期一会.m2
epositoryorgapachearrowarrow-vector0.10.0arrow-vector-0.10.0.jar;C:Users一期一会.m2
epositoryorgapachearrowarrow-format0.10.0arrow-format-0.10.0.jar;C:Users一期一会.m2
epositoryorgapachearrowarrow-memory0.10.0arrow-memory-0.10.0.jar;C:Users一期一会.m2
epositoryjoda-timejoda-time2.9.9joda-time-2.9.9.jar;C:Users一期一会.m2
epositorycomcarrotsearchhppc0.7.2hppc-0.7.2.jar;C:Users一期一会.m2
epositorycomvlkanflatbuffers1.2.0-3f79e055flatbuffers-1.2.0-3f79e055.jar;C:Users一期一会.m2
epositoryorgscala-langscala-library2.11.0scala-library-2.11.0.jar com.hikvision.learn.TestEmptyDataFrame
+---+----+---+-----+
| id|name|age|birth|
+---+----+---+-----+
+---+----+---+-----+
+---+----+---+-----+
| id|name|age|birth|
+---+----+---+-----+
+---+----+---+-----+
++
||
++
++
Process finished with exit code 0