org.apache.avro.generic

Class GenericDatumReader<D>

java.lang.Object

org.apache.avro.generic.GenericDatumReader<D>

All Implemented Interfaces:

DatumReader<D>

Direct Known Subclasses:

ProtobufDatumReader, SpecificDatumReader, ThriftDatumReader

public class GenericDatumReader<D>
extends Object
implements DatumReader<D>

DatumReader for generic Java objects.

Constructor Summary

Constructors

Modifier	Constructor and Description
	GenericDatumReader()
protected	GenericDatumReader(GenericData data)
	GenericDatumReader(Schema schema) Construct where the writer's and reader's schemas are the same.
	GenericDatumReader(Schema writer, Schema reader) Construct given writer's and reader's schema.
	GenericDatumReader(Schema writer, Schema reader, GenericData data)

Method Summary

Methods

Modifier and Type	Method and Description
protected void	addToArray(Object array, long pos, Object e) Called by the default implementation of readArray(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to add a value.
protected void	addToMap(Object map, Object key, Object value) Called by the default implementation of readMap(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to add a key/value pair.
protected Object	createBytes(byte[] value) Called to create byte arrays from default values.
protected Object	createEnum(String symbol, Schema schema) Called to create an enum value.
protected Object	createFixed(Object old, byte[] bytes, Schema schema) Deprecated. As of Avro 1.6.0 this method has been moved to GenericData.createFixed(Object, byte[], Schema)
protected Object	createFixed(Object old, Schema schema) Deprecated. As of Avro 1.6.0 this method has been moved to GenericData.createFixed(Object, Schema)
protected Object	createString(String value) Called to create a string from a default value.
protected Class	findStringClass(Schema schema) Determines the class to used to represent a string Schema.
GenericData	getData() Return the GenericData implementation.
Schema	getExpected() Get the reader's schema.
protected ResolvingDecoder	getResolver(Schema actual, Schema expected) Gets a resolving decoder for use by this GenericDatumReader.
Schema	getSchema() Return the writer's schema.
protected Object	newArray(Object old, int size, Schema schema) Called to create new array instances.
protected Object	newInstanceFromString(Class c, String s)
protected Object	newMap(Object old, int size) Called to create new array instances.
protected Object	newRecord(Object old, Schema schema) Deprecated. As of Avro 1.6.0 this method has been moved to GenericData.newRecord(Object, Schema)
protected Object	peekArray(Object array) Called by the default implementation of readArray(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to retrieve a value from a reused instance.
D	read(D reuse, Decoder in) Read a datum.
protected Object	read(Object old, Schema expected, ResolvingDecoder in) Called to read data.
protected Object	readArray(Object old, Schema expected, ResolvingDecoder in) Called to read an array instance.
protected Object	readBytes(Object old, Decoder in) Called to read byte arrays.
protected Object	readBytes(Object old, Schema s, Decoder in) Called to read byte arrays.
protected Object	readEnum(Schema expected, Decoder in) Called to read an enum value.
protected void	readField(Object r, Schema.Field f, Object oldDatum, ResolvingDecoder in, Object state) Called to read a single field of a record.
protected Object	readFixed(Object old, Schema expected, Decoder in) Called to read a fixed value.
protected Object	readInt(Object old, Schema expected, Decoder in) Called to read integers.
protected Object	readMap(Object old, Schema expected, ResolvingDecoder in) Called to read a map instance.
protected Object	readMapKey(Object old, Schema expected, Decoder in) Called by the default implementation of readMap(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to read a key value.
protected Object	readRecord(Object old, Schema expected, ResolvingDecoder in) Called to read a record instance.
protected Object	readString(Object old, Decoder in) Called to read strings.
protected Object	readString(Object old, Schema expected, Decoder in) Called to read strings.
void	setExpected(Schema reader) Set the reader's schema.
void	setSchema(Schema writer) Set the writer's schema.
static void	skip(Schema schema, Decoder in) Skip an instance of a schema.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GenericDatumReader

public GenericDatumReader()

GenericDatumReader

public GenericDatumReader(Schema schema)

Construct where the writer's and reader's schemas are the same.

GenericDatumReader

public GenericDatumReader(Schema writer,
                  Schema reader)

Construct given writer's and reader's schema.

GenericDatumReader

public GenericDatumReader(Schema writer,
                  Schema reader,
                  GenericData data)

GenericDatumReader

protected GenericDatumReader(GenericData data)

Method Detail

getData

public GenericData getData()

Return the GenericData implementation.

getSchema

public Schema getSchema()

Return the writer's schema.

setSchema

public void setSchema(Schema writer)

Description copied from interface: DatumReader

Set the writer's schema.

Specified by:

setSchema in interface DatumReader<D>

getExpected

public Schema getExpected()

Get the reader's schema.

setExpected

public void setExpected(Schema reader)

Set the reader's schema.

getResolver

protected final ResolvingDecoder getResolver(Schema actual,
                           Schema expected)
                                      throws IOException

Gets a resolving decoder for use by this GenericDatumReader. Unstable API. Currently uses a thread local cache to prevent constructing the resolvers too often, because that is very expensive.

Throws:

IOException

read

public D read(D reuse,
     Decoder in)
       throws IOException

Description copied from interface: DatumReader

Read a datum. Traverse the schema, depth-first, reading all leaf values in the schema into a datum that is returned. If the provided datum is non-null it may be reused and returned.

Specified by:

read in interface DatumReader<D>

Throws:

IOException

read

protected Object read(Object old,
          Schema expected,
          ResolvingDecoder in)
               throws IOException

Called to read data.

Throws:

IOException

readRecord

protected Object readRecord(Object old,
                Schema expected,
                ResolvingDecoder in)
                     throws IOException

Called to read a record instance. May be overridden for alternate record representations.

Throws:

IOException

readField

protected void readField(Object r,
             Schema.Field f,
             Object oldDatum,
             ResolvingDecoder in,
             Object state)
                  throws IOException

Called to read a single field of a record. May be overridden for more efficient or alternate implementations.

Throws:

IOException

readEnum

protected Object readEnum(Schema expected,
              Decoder in)
                   throws IOException

Called to read an enum value. May be overridden for alternate enum representations. By default, returns a GenericEnumSymbol.

Throws:

IOException

createEnum

protected Object createEnum(String symbol,
                Schema schema)

Called to create an enum value. May be overridden for alternate enum representations. By default, returns a GenericEnumSymbol.

readArray

protected Object readArray(Object old,
               Schema expected,
               ResolvingDecoder in)
                    throws IOException

Called to read an array instance. May be overridden for alternate array representations.

Throws:

IOException

peekArray

protected Object peekArray(Object array)

Called by the default implementation of readArray(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to retrieve a value from a reused instance. The default implementation is for GenericArray.

addToArray

protected void addToArray(Object array,
              long pos,
              Object e)

Called by the default implementation of readArray(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to add a value. The default implementation is for Collection.

readMap

protected Object readMap(Object old,
             Schema expected,
             ResolvingDecoder in)
                  throws IOException

Called to read a map instance. May be overridden for alternate map representations.

Throws:

IOException

readMapKey

protected Object readMapKey(Object old,
                Schema expected,
                Decoder in)
                     throws IOException

Called by the default implementation of readMap(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to read a key value. The default implementation returns delegates to readString(Object, org.apache.avro.io.Decoder).

Throws:

IOException

addToMap

protected void addToMap(Object map,
            Object key,
            Object value)

Called by the default implementation of readMap(java.lang.Object, org.apache.avro.Schema, org.apache.avro.io.ResolvingDecoder) to add a key/value pair. The default implementation is for Map.

readFixed

protected Object readFixed(Object old,
               Schema expected,
               Decoder in)
                    throws IOException

Called to read a fixed value. May be overridden for alternate fixed representations. By default, returns GenericFixed.

Throws:

IOException

createFixed

@Deprecated
protected Object createFixed(Object old,
                            Schema schema)

Deprecated. As of Avro 1.6.0 this method has been moved to GenericData.createFixed(Object, Schema)

Called to create an fixed value. May be overridden for alternate fixed representations. By default, returns GenericFixed.

createFixed

@Deprecated
protected Object createFixed(Object old,
                            byte[] bytes,
                            Schema schema)

Deprecated. As of Avro 1.6.0 this method has been moved to GenericData.createFixed(Object, byte[], Schema)

Called to create an fixed value. May be overridden for alternate fixed representations. By default, returns GenericFixed.

newRecord

@Deprecated
protected Object newRecord(Object old,
                          Schema schema)

Deprecated. As of Avro 1.6.0 this method has been moved to GenericData.newRecord(Object, Schema)

Called to create new record instances. Subclasses may override to use a different record implementation. The returned instance must conform to the schema provided. If the old object contains fields not present in the schema, they should either be removed from the old object, or it should create a new instance that conforms to the schema. By default, this returns a GenericData.Record.

newArray

protected Object newArray(Object old,
              int size,
              Schema schema)

Called to create new array instances. Subclasses may override to use a different array implementation. By default, this returns a GenericData.Array.

newMap

protected Object newMap(Object old,
            int size)

Called to create new array instances. Subclasses may override to use a different map implementation. By default, this returns a HashMap.

readString

protected Object readString(Object old,
                Schema expected,
                Decoder in)
                     throws IOException

Called to read strings. Subclasses may override to use a different string representation. By default, this calls readString(Object,Decoder).

Throws:

IOException

readString

protected Object readString(Object old,
                Decoder in)
                     throws IOException

Called to read strings. Subclasses may override to use a different string representation. By default, this calls Decoder.readString(Utf8).

Throws:

IOException

createString

protected Object createString(String value)

Called to create a string from a default value. Subclasses may override to use a different string representation. By default, this calls Utf8.Utf8(String).

findStringClass

protected Class findStringClass(Schema schema)

Determines the class to used to represent a string Schema. By default uses GenericData.STRING_PROP to determine whether Utf8 or String is used. Subclasses may override for alternate representations.

newInstanceFromString

protected Object newInstanceFromString(Class c,
                           String s)

readBytes

protected Object readBytes(Object old,
               Schema s,
               Decoder in)
                    throws IOException

Called to read byte arrays. Subclasses may override to use a different byte array representation. By default, this calls Decoder.readBytes(ByteBuffer).

Throws:

IOException

readBytes

protected Object readBytes(Object old,
               Decoder in)
                    throws IOException

Called to read byte arrays. Subclasses may override to use a different byte array representation. By default, this calls Decoder.readBytes(ByteBuffer).

Throws:

IOException

readInt

protected Object readInt(Object old,
             Schema expected,
             Decoder in)
                  throws IOException

Called to read integers. Subclasses may override to use a different integer representation. By default, this calls Decoder.readInt().

Throws:

IOException

createBytes

protected Object createBytes(byte[] value)

Called to create byte arrays from default values. Subclasses may override to use a different byte array representation. By default, this calls ByteBuffer.wrap(byte[]).

skip

public static void skip(Schema schema,
        Decoder in)
                 throws IOException

Skip an instance of a schema.

Throws:

IOException