Writable

A writable interface allows you to specify multicolumn key/value types. The getStorageTypesList() method returns a list of classes that can be mapped by the framework to types of database columns. The following table shows the mapping:

The following example of a custom Writable consists of three fields: int, float, and boolean. The getStorageTypesList() method used in the example returns a list of corresponding java classes: Integer.class, Float.class, Boolean.class. The method allows the framework to create appropriate readers and writers.

public class CustomWritable implements Writable {
private int a;
private float b;
private boolean c;
@Override
public void write(RecordOutput out) throws IOException {
out.writeInt(a);
out.writeFloat(b);
out.writeBoolean(c);
}
@Override
public void readFields(RecordInput in) throws IOException {
a = in.readInt();
b = in.readFloat();
c = in.readBoolean();
}
@Override
public List<Class<?>> getStorageTypesList() {
List<Class<?>> ret = new ArrayList<Class<?>>();
ret.add(Integer.class);
ret.add(Float.class);
ret.add(Boolean.class);
return ret;
}
}

Output database types are strictly determined by Writable's storage types defined in getStorageTypesList() method. However, the framework supports the following automatic conversions while reading data from database records to Writable types.

	Boolean	Integer	Long	Float	Double	Text	Ntext
BOOL	YES					YES	YES
FLOAT				YES	YES	YES	YES
DOUBLE					YES	YES	YES
BYTEINT		YES	YES		YES	YES	YES
SMALLINT		YES	YES	YES	YES	YES	YES
INTEGER		YES	YES	YES	YES	YES	YES
BIGINT			YES	YES	YES	YES	YES
NUMERIC						YES	YES
CHAR	YES	YES	YES	YES	YES	YES	YES
VARCHAR	YES	YES	YES	YES	YES	YES	YES
NCHAR	YES	YES	YES	YES	YES	YES	YES
NVARCHAR	YES	YES	YES	YES	YES	YES	YES
DATE						YES	YES
TIME						YES	YES
TIMESTAMP						YES	YES
TIMETZ						YES	YES
INTERVAL						YES	YES