初始化sparksession，底層初始化sparkcontext，相當於spark任務的入口。
val sparksession = sparksession.
builder()
.("sparktest").
master
("local[2]").
getorcreate()
val sparkcontext = sparksession.sparkcontext
val log = sparkcontext.
textfile
("/users/mike/desktop/test.txt"
)
case
class
person
(name:string,age:int)
//轉化為rdd[person]
val rowrdd = log.
map(_.
split
(" "))
.map
(x =
>
person(x
(0),
x(1)
.toint)
)import sparksession.implicits._
val df = rowrdd.
todf()
df.show()
sparksession.
stop
()
val schemafiled =
"name,age"
val schemastring = schemafiled.
split
(","
)val schema =
structtype
(array
(structfield
(schemastring(0
), stringtype, nullable =
true),
structfield
(schemastring(1
), integertype, nullable =
true))
)//生成rdd[row]
val rowrdd = log.
map(_.
split
(" "))
.map
(x =
>
row(x(
0),x
(1).toint)
)//格式和rdd 構造dataframe
val df = sparksession.
createdataframe
(rowrdd, schema)
df.show()
sparksession.
stop
()
todf()將dataset轉化為dataframe
df.as[person]將dataframe轉化為dataset
***.rdd()將其他格式的資料轉化為rdd
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