Json conversion: Convert one of the fields of the object as binary data
Problem statement: I had an object that I wanted to convert to JSON. However, one of the fields of this object was a serializable-blob and hence I wanted to save it in binary/byte-array format instead of String format.
Solution:
1. Write a custom JsonSerializer and JsonDeserializer as shown below
2. Annotate the getter/setter of the blob-field with this custom serializer/deserializer respectively.
Object:
public class TestObject {
private String name = null;
private MyBlob data = null;
public TestObject() {
super();
}
@JsonSerialize(using=ByteArraySerializer.class)
public MyBlob getData() {
return data;
}
@JsonDeserialize(as=MyBlob.class, using=ByteArrayDeserializer.class)
public void setData(MyBlob data) {
this.data = data;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
JsonSerializer:
//(You can find out some other object-serializer (or write your own) to avoid dependency over Cassandra-code)
import me.prettyprint.cassandra.serializers.ObjectSerializer;
import me.prettyprint.cassandra.serializers.ObjectSerializer;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.JsonSerializer;
import org.codehaus.jackson.map.SerializerProvider;
public class ByteArraySerializer extends JsonSerializer<Object> {
@Override
public void serialize(Object value, JsonGenerator jgen,
SerializerProvider provider) throws IOException,
JsonProcessingException {
byte[] bytes = ObjectSerializer.get().toBytes(value);
jgen.writeBinary(bytes);
}
}
JsonDeserializer:
import java.io.IOException;
//(You can find out some other object-deserializer (or write your own) to avoid dependency over Cassandra-code)
import me.prettyprint.cassandra.serializers.ObjectSerializer;
import me.prettyprint.cassandra.serializers.ObjectSerializer;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.DeserializationContext;
import org.codehaus.jackson.map.JsonDeserializer;
public class ByteArrayDeserializer extends JsonDeserializer<Object> {
@Override
public Object deserialize(JsonParser jp, DeserializationContext ctxt)
throws IOException, JsonProcessingException {
byte[] bytes = jp.getBinaryValue();
Object obj = ObjectSerializer.get().fromBytes(bytes);
return obj;
}
}
- Sarang Anajwala
