Reading BigQuery Table Data into Java Classes(Pojo) Directly

While Developing my code I used the below code snippet to read the table data from BigQuery.

 
```

PCollection gpseEftReasonCodes = input
.apply("Reading xxyyzz",
BigQueryIO

.read(new ReadTable(ReasonCode.class))
.withoutValidation()

.withTemplateCompatibility()
.fromQuery("Select * from dataset.xxyyzz")

.usingStandardSql()
.withCoder(SerializableCoder.of(xxyyzz.class))

```

Read Table Class:

```

@DefaultSchema(JavaBeanSchema.class)
public class ReadTable implements SerializableFunction {
private static final long serialVersionUID = 1L;
private static Gson gson = new Gson();

public static final Logger LOG = LoggerFactory.getLogger(ReadTable.class); private final Counter countingRecords
=
Metrics.counter(ReadTable.class, "Reading Records EFT Report");
private Class class1;

public ReadTable(Class class1) { this.class1 = class1; }
 
public T apply(SchemaAndRecord
schemaAndRecord) {
Map mapping = new HashMap<>();
int counter = 0;
try
{
GenericRecord s = schemaAndRecord.getRecord();
org.apache.avro.Schema s1 = s.getSchema();

for (Field f : s1.getFields()) {
counter++;
mapping.put(f.name(), null==s.get(f.name())
? null : String.valueOf(s.get(counter)));
}
countingRecords.inc();
JsonElement
jsonElement = gson.toJsonTree(mapping);
return gson.fromJson(jsonElement, class1);
} catch
(Exception mp) {
LOG.error("Found Wrong Mapping for the Record: "+mapping); mp.printStackTrace();
return null; }
}
}

```

So After Reading the data from Bigquery I was mapping data from SchemaAndRecord to pojo I was getting value for columns whose Data type is Numeric mention below.

```

last_update_amount=java.nio.HeapByteBuffer[pos=0 lim=16 cap=16]

```

My Expectation was I will get exact value but getting the HyperByte Buffer the version I am using is Apache beam 2.12.0. If any more information is needed then please let me know.

Way 2 Tried:

```

GenericRecord s = schemaAndRecord.getRecord();
org.apache.avro.Schema s1 = s.getSchema();
for (Field
f : s1.getFields()) {
counter++;
mapping.put(f.name(), null==s.get(f.name()) ? null : String.valueOf(s.get(counter)));

if(f.name().equalsIgnoreCase("reason_code_id")) {
BigDecimal numericValue = new Conversions.DecimalConversion()

.fromBytes((ByteBuffer) s.get(f.name()), Schema.create(s1.getType()), s1.getLogicalType());

System.out.println("Numeric Con"+numericValue);
} else {
System.out.println("Else Condition
"+f.name());
}

```

Facing Issue:

```

2019-05-24 (14:10:37) org.apache.avro.AvroRuntimeException: Can't create a: RECORD

```

 

It would be Great if we have a method which maps all the BigQuery Data with Pojo Schema which Means if I have 10 Columns in BQ and in my Pojo I need only 5 Column then, in that case, BigQueryIO should map only that 5 Data values into Java Class and Rest will be Rejected As I am Doing After So much Effort.
Numeric Data Type must be Deserialize by itself while fetching data like TableRow.

 

Imported from Jira [BEAM-7425](https://issues.apache.org/jira/browse/BEAM-7425). Original Jira may contain additional context.
Reported by: KishanK.