public class ResolvingDecoder extends ValidatingDecoder
Decoder that performs type-resolution between the reader's and
writer's schemas.
When resolving schemas, this class will return the values of fields in
_writer's_ order, not the reader's order. (However, it returns _only_ the
reader's fields, not any extra fields the writer may have written.) To help
clients handle fields that appear to be coming out of order, this class
defines the method readFieldOrder().
See the parser documentation for information on how this works.
inparser| Modifier and Type | Method and Description |
|---|---|
Symbol |
doAction(Symbol input,
Symbol top)
Handle the action symbol top when the input is sought to be
taken off the stack.
|
void |
drain()
Consume any more data that has been written by the writer but not needed by
the reader so that the the underlying decoder is in proper shape for the next
record.
|
ByteBuffer |
readBytes(ByteBuffer old)
Reads a byte-string written by
Encoder.writeBytes(java.nio.ByteBuffer). |
double |
readDouble()
Reads a double written by
Encoder.writeDouble(double). |
int |
readEnum()
Reads an enumeration.
|
Schema.Field[] |
readFieldOrder()
Returns the actual order in which the reader's fields will be returned to the
reader.
|
Schema.Field[] |
readFieldOrderIfDiff()
Same as
readFieldOrder() except that it returns null if there
was no reordering of fields, i.e., if the correct thing for the reader to do
is to read (all) of its fields in the order specified by its own schema
(useful for optimizations). |
float |
readFloat()
Reads a float written by
Encoder.writeFloat(float). |
int |
readIndex()
Reads the tag of a union written by
Encoder.writeIndex(int). |
long |
readLong()
Reads a long written by
Encoder.writeLong(long). |
String |
readString()
Reads a char-string written by
Encoder.writeString(org.apache.avro.util.Utf8). |
Utf8 |
readString(Utf8 old)
Reads a char-string written by
Encoder.writeString(org.apache.avro.util.Utf8). |
static Object |
resolve(Schema writer,
Schema reader)
Produces an opaque resolver that can be used to construct a new
ResolvingDecoder(Object, Decoder). |
void |
skipAction()
Skips the action at the top of the stack.
|
void |
skipBytes()
Discards a byte-string written by
Encoder.writeBytes(java.nio.ByteBuffer). |
void |
skipString()
Discards a char-string written by
Encoder.writeString(org.apache.avro.util.Utf8). |
arrayNext, configure, mapNext, readArrayStart, readBoolean, readFixed, readInt, readMapStart, readNull, skipArray, skipFixed, skipFixed, skipMapskipTopSymbolpublic static Object resolve(Schema writer, Schema reader) throws IOException
ResolvingDecoder(Object, Decoder). The returned
Object is immutable and hence can be simultaneously used in many
ResolvingDecoders. This method is reasonably expensive, the users are
encouraged to cache the result.writer - The writer's schema. Cannot be null.reader - The reader's schema. Cannot be null.IOExceptionNullPointerException - if writer or reader is
nullpublic final Schema.Field[] readFieldOrder() throws IOException
ResolvingDecoder returns values in the
order written by the writer, rather than the order expected by the reader.
This method allows readers to figure out what fields to expect. Let's say the
reader is expecting a three-field record, the first field is a long, the
second a string, and the third an array. In this case, a typical usage might
be as follows:
Schema.Fields[] fieldOrder = in.readFieldOrder();
for (int i = 0; i < 3; i++) {
switch (fieldOrder[i].pos()) {
case 1:
foo(in.readLong());
break;
case 2:
someVariable = in.readString();
break;
case 3:
bar(in); // The code of "bar" will read an array-of-int
break;
}
Note that ResolvingDecoder will return only the fields expected by
the reader, not other fields that may have been written by the writer. Thus,
the iteration-count of "3" in the above loop will always be correct.
Throws a runtime exception if we're not just about to read the first field of
a record. (If the client knows the order of incoming fields, then the client
does not need to call this method but rather can just start reading
the field values.)AvroTypeException - If we're not starting a new recordIOExceptionpublic final Schema.Field[] readFieldOrderIfDiff() throws IOException
readFieldOrder() except that it returns null if there
was no reordering of fields, i.e., if the correct thing for the reader to do
is to read (all) of its fields in the order specified by its own schema
(useful for optimizations).IOExceptionpublic final void drain()
throws IOException
IOExceptionpublic long readLong()
throws IOException
DecoderEncoder.writeLong(long).readLong in class ValidatingDecoderIOExceptionpublic float readFloat()
throws IOException
DecoderEncoder.writeFloat(float).readFloat in class ValidatingDecoderIOExceptionpublic double readDouble()
throws IOException
DecoderEncoder.writeDouble(double).readDouble in class ValidatingDecoderIOExceptionpublic Utf8 readString(Utf8 old) throws IOException
DecoderEncoder.writeString(org.apache.avro.util.Utf8).readString in class ValidatingDecoderIOExceptionpublic String readString() throws IOException
DecoderEncoder.writeString(org.apache.avro.util.Utf8).readString in class ValidatingDecoderIOExceptionpublic void skipString()
throws IOException
DecoderEncoder.writeString(org.apache.avro.util.Utf8).skipString in class ValidatingDecoderIOExceptionpublic ByteBuffer readBytes(ByteBuffer old) throws IOException
DecoderEncoder.writeBytes(java.nio.ByteBuffer). if old is
not null and has sufficient capacity to take in the bytes being read, the
bytes are returned in old.readBytes in class ValidatingDecoderIOExceptionpublic void skipBytes()
throws IOException
DecoderEncoder.writeBytes(java.nio.ByteBuffer).skipBytes in class ValidatingDecoderIOExceptionpublic int readEnum()
throws IOException
DecoderreadEnum in class ValidatingDecoderIOExceptionpublic int readIndex()
throws IOException
DecoderEncoder.writeIndex(int).readIndex in class ValidatingDecoderIOExceptionpublic Symbol doAction(Symbol input, Symbol top) throws IOException
Parser.ActionHandlerdoAction in interface Parser.ActionHandlerdoAction in class ValidatingDecoderinput - The input symbol from the caller of advancetop - The symbol at the top the stack.IOExceptionpublic void skipAction()
throws IOException
SkipParser.SkipHandlerskipAction in interface SkipParser.SkipHandlerskipAction in class ParsingDecoderIOExceptionCopyright © 2009–2023 The Apache Software Foundation. All rights reserved.