Java或Scala從數據庫中檢索多列爲一行

Question

我想在一行中檢索數據庫中的多列。

實施例： -

CustomerId,AccountNumber 
1,AW0000001 

的Scala代碼我被寫出來吐涎列值到新的一行。

實施例： -

1 

AW0000001 

代碼： -

object SparkSQLServer { 

    class DbRow extends java.util.HashMap[java.lang.String,Object] { 

    } 


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

     Logger.getLogger("org").setLevel(Level.WARN) 
     Logger.getLogger("akka").setLevel(Level.WARN) 

     val conf = new SparkConf().setMaster("local[2]").setAppName("SparkProducerMSSQL") 
     val sc = new SparkContext(conf) 

     val driver = "com.microsoft.sqlserver.jdbc.SQLServerDriver" 
     val url = "jdbc:sqlserver://localhost;user=admin;password=oracle;database=AdventureWorks2014" 
     val username = "admin" 
     val password = "oracle" 

     var connection:Connection=null 

     Class.forName(driver) 
     connection=DriverManager.getConnection(url,username,password) 

     val statement=connection.createStatement() 
     val resultSet=statement.executeQuery("select top 10 CustomerID,AccountNumber from AdventureWorks2014.dbo.Customer") 
     resultSet.setFetchSize(10); 
     val columnnumber=resultSet.getMetaData().getColumnCount.toInt 

     val objcommand=("select top 10 CustomerID,AccountNumber from AdventureWorks2014.dbo.Customer",connection) 


     //var rows: Vector[DbRow]=Vector.empty 

     while (resultSet.next()) 
      { 

      //val row=new DbRow 

      var i=0.toInt; 
      for (i <- 1 to columnnumber.toInt) 
       { 

       val columnvalue=resultSet.getString(i); 
       val columnname=resultSet.getMetaData().getColumnName(i) 

       //row.put(columnname,resultSet.getObject(i)) 
       val test4=resultSet.getObject(i) 
       var list = new java.util.ArrayList[String]() 
       list.add(resultSet.getObject(i).toString()) 

       println(list) 

       } 
      //rows = rows :+ row 
      //print(row) 
      // print(rows.toString().replace("Vector","").replace(")","~")) 
      //print(rows.toString().replace("Vector","")) 
      // val test=sc.parallelize(List(row.toString().replace("{","").replace("}","~"))) 
      //val lines=test.flatMap(x=>x.split("~")) 
      //lines.collect().foreach(println) 



      //print(row) 
      // 
      //println(resultSet) 
      } 

     connection.close() 

    } 
} 

Answer 1

移動 「VAR列表=新java.util.ArrayListString」 和 「的println（列表）」 外面的for循環

var list = new java.util.ArrayList[String]() 
for .. { 

} 
println(list) 

和i t是更好地使用Java中的StringBuilder

StringBuilder sb=new StringBuilder(100); 
for { 
sb.append(resultSet.getObject(i).toString()); 
sb.append(","); 
} 
println(sb.toString()) 

Answer 2

完整的示例：

final String url  = "jdbc:sqlserver://localhost;user=admin;password=oracle;database=AdventureWorks2014"; 
final String username = "admin"; 
final String password = "oracle"; 
final String sql  = "select top 10 CustomerID,AccountNumber from AdventureWorks2014.dbo.Customer"; 
try (Connection connection = DriverManager.getConnection(url,username,password); 
    Statement statement = connection.createStatement(); 
    ResultSet resultSet = statement.executeQuery(sql)) { 

    final ResultSetMetaData metaData = resultSet.getMetaData(); 
    final int columnCount = metaData.getColumnCount(); 
    for (int i = 1; i <= columnCount; i++) { 
     if (i > 1) 
      System.out.print(','); 
     System.out.print(metaData.getColumnName(i)); 
    } 
    System.out.println(); 

    while (resultSet.next()) { 
     for (int i = 1; i <= columnCount; i++) { 
      if (i > 1) 
       System.out.print(','); 
      System.out.print(resultSet.getString(i)); 
     } 
     System.out.println(); 
    } 
}