Scala

[Scala]03 Scala学习笔记

Scala 读取文件及网络数据、Scala读取MySQL数据、Scala操作XML文件

Posted by 李玉坤 on 2018-03-20

Scala 操作外部数据

Scala 读取文件及网络数据

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import scala.io.Source

object FileApp {

  def main(args: Array[String]): Unit = {

    val file = Source.fromFile("/home/hadoop/hello.txt")(scala.io.Codec.ISO8859)

按照行读取文件：
    def readLine(): Unit ={
      for(line <- file.getLines()){
        println(line)
      }
    }

    readLine()

按照字符读取文件：
    def readChar(): Unit ={
      for(ele <- file) {
        println(ele)
      }
    }

    readChar()

按照url读取文件：
    def readNet(): Unit ={
      val file = Source.fromURL("http://www.baidu.com")
      for(line <- file.getLines()){
        println(line)
      }
    }

    readNet()

  }

}

Scala读取MySQL数据

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<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
</dependency>
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import java.sql.{Connection, DriverManager}

object MySQLApp {

  def main(args: Array[String]): Unit = {

    val url = "jdbc:mysql://localhost:3306/mysql"
    val username = "root"
    val password = "root"

    var connection:Connection = null
    try{

      // make the connection
      classOf[com.mysql.jdbc.Driver]

      connection = DriverManager.getConnection(url, username, password)

      // create the statement, and run the select query
      val statement = connection.createStatement()
      val resultSet = statement.executeQuery("select host,user from user")
      while(resultSet.next()){
        val host = resultSet.getString("host")
        val user = resultSet.getString("user")

        println(s"$host, $user")
      }
    } catch {
      case e:Exception => e.printStackTrace()
    } finally {
      // free
      if(connection == null) {
        connection.close()
      }
    }

  }

}

Scala操作XML文件

xml文件

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<bookshelf>
    <book id="002-new">
        <name>Spark Programming</name>
    </book>
    <book id="001-new">
        <name>Scala Programming</name>
    </book>
</bookshelf>

读取XML文件

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import java.io.{FileInputStream, InputStreamReader}

import scala.xml.XML

object XMLApp {

  def main(args: Array[String]): Unit = {

   loadXML()

  }

  def loadXML(): Unit = {
//获取 Resource 下的xml文件
    val xml = XML.load(this.getClass.getClassLoader.getResource("test.xml"))
    println(xml)

//指定url路径 获取xml文件 绝对路径
    val xml = XML.load(new FileInputStream(".../scala-train/src/main/resources/test.xml"))
    println(xml)

//指定url路径 获取xml文件 绝对路径
    val xml = XML.load(
      new InputStreamReader(
        new FileInputStream(".../scala-train/src/main/resources/test.xml")
      )
    )
    println(xml)
  }

}

读取XML属性内容

test.xml文件

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<fix major="4" minor="2">
    <header>
        <field name="BeginString" required="Y">FIX4.2</field>
        <field name="MsgType" required="Y">Test</field>
    </header>

    <trailer>
        <field name="Signature" required="N"/>
        <field name="CheckSum" required="Y"/>
    </trailer>

    <messages>
        <message name="Logon" msgtype="A" msgcat="admin">
            <field name="ResetSeqNumFlag" required="N"/>
            <field name="MaxMessageSize" required="N"/>
            <group name="NoMsgTypes" required="N">
                <field name="RefMsgType" required="N"/>
                <field name="MsgDirection" required="N"/>
            </group>
        </message>
        <message name="ResendRequest" msgtype="2" msgcat="admin">
            <field name="BeginSeqNo" required="Y"/>
            <field name="EndSeqNo" required="Y"/>
        </message>
    </messages>

    <fields>
        <field number="1" name="TradingEntityId" type="STRING"/>
        <field number="4" name="AdvSide" type="STRING">
            <value enum="X" description="CROSS"/>
            <value enum="T" description="TRADE"/>
        </field>
        <field number="5" name="AdvTransType" type="STRING">
            <value enum="N" description="NEW"/>
        </field>
    </fields>
</fix>
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  def readXMLAttr(): Unit = {
    val xml = XML.load(this.getClass.getClassLoader.getResource("test.xml"))
        println(xml)

// header/field
        val headerField = xml \ "header" \ "field"
        println(headerField)

// all field
        val fields = xml \\ "field"
        for (field <- fields) {
          println(field)
        }

// header/field/name
        val fieldAttributes = (xml \ "header" \ "field").map(_ \ "@name")
        val fieldAttributes = (xml \ "header" \ "field" \\ "@name")
        for (fieldAttribute <- fieldAttributes) {
          println(fieldAttribute)
        }


//name="Logon"的message
    val filters = (xml \\ "message")
      .filter(_.attribute("name").exists(_.text.equals("Logon")))

    val filters = (xml \\ "message")
      .filter(x => ((x \ "@name").text).equals("Logon"))
	  
	  
   for (filter <- filters) {
      println(filter)
    }

// header/field  内容
    (xml \ "header" \ "field")
      .map(x => (x \ "@name", x.text, x \ "@required"))
      .foreach(println)
  }

修改XML属性内容

books.xml文件

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<bookshelf>
    <book id="001">
        <name>Scala</name>
        <author>PK</author>
    </book>

    <book id="002">
        <name>Spark</name>
        <author>pk</author>
    </book>
</bookshelf>
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def updateXML(): Unit ={
    val xml = XML.load(this.getClass.getClassLoader.getResource("books.xml"))
    println(xml)
	
    val bookMap = scala.collection.mutable.HashMap[String,String]()

//将xml赋值给bookMap
    (xml \ "book").map(x => {
      val id = (x \ "@id").toString()
      val name = (x \ "name").text.toString
      bookMap(id) = name
    })

//遍历出bookMap
    for((key,value) <- bookMap) {
      println(s"$key : $value")
    }

    val newXml = <bookshelf>{bookMap.map(updateXmlFile)}</bookshelf>

//    println(newXml)
    XML.save("newBooks.xml", newXml)
  }

//修改方法
  def updateXmlFile(ele:(String,String)) = {
    val (id, oldName) = ele

    <book id={id + "-new"}>
      <name>{oldName + " Programming"}</name>
    </book>
  }



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