在类错误中找不到列

Question

I'm trying to pull certain data out of a cassandra table, and then write it back to a different table in cassandra.

This is what I have:

JavaRDD<MeasuredValue> mvRDD = javaFunctions(sc).cassandraTable("SB1000_47130646", "Measured_Value", mapRowTo(MeasuredValue.class))
  .where ("\"Time_Key\" IN (1601823,1601824)")
  .select("Time_Key","Start_Frequency","Bandwidth", "Power");  

Then I write back to a new table with:

javaFunctions(mvRDD).writerBuilder("spark_reports","SB1000_47130646", mapToRow(MeasuredValue.class)).withColumnSelector(someColumns("Time_Key", "Start_Frequency", "Bandwidth", "Power")).saveToCassandra();

My MeasuredValue Class looks like this:

public static class MeasuredValue implements Serializable {


public MeasuredValue() { }

public MeasuredValue(Long Time_Key, Double Start_Frequency, Double Bandwidth, Float Power) {
    this.Time_Key = Time_Key;
    this.Start_Frequency = Start_Frequency;
    this.Bandwidth = Bandwidth;
    this.Power = Power;

}
private Long Time_Key;
public Long gettime_key() { return Time_Key; }
public void settime_key(Long Time_Key) { this.Time_Key = Time_Key; }

private Double Start_Frequency;
public Double getstart_frequency() { return Start_Frequency; }
public void setstart_frequency(Double Start_Frequency) { this.Start_Frequency = Start_Frequency; }

private Double Bandwidth;
public Double getbandwidth() { return Bandwidth; }
public void setbandwidth(Double Bandwidth) { this.Bandwidth = Bandwidth; }

private Float Power;    
public Float getpower() { return Power; }
public void setpower(Float Power) { this.Power = Power;
}

The error I get when running is:

Exception in thread "main" java.lang.IllegalArgumentException: requirement failed: Columns not found in class com.neutronis.spark_reports.Spark_Reports$MeasuredValue: [Time_Key, Start_Frequency, Bandwidth, Power]

Answer 1

I discovered that this is due to the fact that the getters/setters follow the JAVA naming scheme as far as capital letters and variables. Since the columns in my table were camel case I had too reconfigure the column names to a proper all lower case naming convention for it to work correctly.

In order to use capital letters I had to use a HashMap:

 HashMap<String,String> colmap = new HashMap<String,String>();
    colmap.put( "start_frequency", "Start_Frequency" );
    colmap.put( "bandwith", "Bandwidth" );
    colmap.put( "power", "Power" );
    RowReaderFactory<MeasuredValue> mapRowTo = mapRowTo(MeasuredValue.class, colmap);