org.apache.avro.io
Class JsonDecoder

java.lang.Object
  org.apache.avro.io.Decoder
      org.apache.avro.io.ParsingDecoder
          org.apache.avro.io.JsonDecoder

All Implemented Interfaces:

Parser.ActionHandler, SkipParser.SkipHandler

public class JsonDecoder
extends ParsingDecoder
implements Parser.ActionHandler

A Decoder for Avro's JSON data encoding.

Field Summary

Fields inherited from class org.apache.avro.io.ParsingDecoder

parser

Constructor Summary

JsonDecoder(Schema schema, InputStream in)
Creates a new JsonDecoder based on an InputStream.

JsonDecoder(Schema schema, String in)
Creates a new JsonDecoder based on a String input.

Method Summary

long	arrayNext() Processes the next block of an array andreturns the number of items in the block and let's the caller read those items.
Symbol	doAction(Symbol input, Symbol top) Handle the action symbol top when the input is sought to be taken off the stack.
void	init(InputStream in) Start reading against a different input stream.
void	init(String in) Re-initializes to start reading from a new String input.
long	mapNext() Processes the next block of map entries and returns the count of them.
long	readArrayStart() Reads and returns the size of the first block of an array.
boolean	readBoolean() Reads a boolean value written by Encoder.writeBoolean(boolean).
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.
void	readFixed(byte[] bytes, int start, int len) Reads fixed sized binary object.
float	readFloat() Reads a float written by Encoder.writeFloat(float).
int	readIndex() Reads the tag of a union written by Encoder.writeIndex(int).
int	readInt() Reads an integer written by Encoder.writeInt(int).
long	readLong() Reads a long written by Encoder.writeLong(long).
long	readMapStart() Reads and returns the size of the next block of map-entries.
void	readNull() "Reads" a null value.
Utf8	readString(Utf8 old) Reads a char-string written by Encoder.writeString(org.apache.avro.util.Utf8).
void	setItemCount(long itemCount)
long	skipArray() Used for quickly skipping through an array.
void	skipBytes() Discards a byte-string written by Encoder.writeBytes(java.nio.ByteBuffer).
protected void	skipFixed()
void	skipFixed(int length) Discards fixed sized binary object.
long	skipMap() Support for quickly skipping through a map similar to Decoder.skipArray().
void	skipString() Discards a char-string written by Encoder.writeString(org.apache.avro.util.Utf8).

Methods inherited from class org.apache.avro.io.ParsingDecoder

skipAction, skipTopSymbol

Methods inherited from class org.apache.avro.io.Decoder

readFixed

Methods inherited from class java.lang.Object

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

Constructor Detail

JsonDecoder

public JsonDecoder(Schema schema,
                   InputStream in)
            throws IOException

Creates a new JsonDecoder based on an InputStream.

Throws:

IOException

JsonDecoder

public JsonDecoder(Schema schema,
                   String in)
            throws IOException

Creates a new JsonDecoder based on a String input.

Throws:

IOException

Method Detail

init

public void init(InputStream in)
          throws IOException

Description copied from class: Decoder

Start reading against a different input stream. Stateful subclasses will reset their states to their initial state.

A Decoder may read ahead beyond the minimum bytes necessary, similar to a BufferedInputStream. In order to interleave reads on this stream's data between Decoder and another reader, the other reader must use the buffer-aware input stream returned by the Decoder implementation, if applicable.

Specified by:

init in class Decoder

Throws:

IOException

init

public void init(String in)
          throws IOException

Re-initializes to start reading from a new String input.

Throws:

IOException

readNull

public void readNull()
              throws IOException

Description copied from class: Decoder

"Reads" a null value. (Doesn't actually read anything, but advances the state of the parser if the implementation is stateful.)

Specified by:

readNull in class Decoder

Throws:

IOException

readBoolean

public boolean readBoolean()
                    throws IOException

Description copied from class: Decoder

Reads a boolean value written by Encoder.writeBoolean(boolean).

Specified by:

readBoolean in class Decoder

Throws:

IOException

readInt

public int readInt()
            throws IOException

Description copied from class: Decoder

Reads an integer written by Encoder.writeInt(int).

Specified by:

readInt in class Decoder

Throws:

IOException

readLong

public long readLong()
              throws IOException

Description copied from class: Decoder

Reads a long written by Encoder.writeLong(long).

Specified by:

readLong in class Decoder

Throws:

IOException

readFloat

public float readFloat()
                throws IOException

Description copied from class: Decoder

Reads a float written by Encoder.writeFloat(float).

Specified by:

readFloat in class Decoder

Throws:

IOException

readDouble

public double readDouble()
                  throws IOException

Description copied from class: Decoder

Reads a double written by Encoder.writeDouble(double).

Specified by:

readDouble in class Decoder

Throws:

IOException

readString

public Utf8 readString(Utf8 old)
                throws IOException

Description copied from class: Decoder

Reads a char-string written by Encoder.writeString(org.apache.avro.util.Utf8).

Specified by:

readString in class Decoder

Throws:

IOException

skipString

public void skipString()
                throws IOException

Description copied from class: Decoder

Discards a char-string written by Encoder.writeString(org.apache.avro.util.Utf8).

Specified by:

skipString in class Decoder

Throws:

IOException

readBytes

public ByteBuffer readBytes(ByteBuffer old)
                     throws IOException

Description copied from class: Decoder

Reads a byte-string written by Encoder.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.

Specified by:

readBytes in class Decoder

Throws:

IOException

skipBytes

public void skipBytes()
               throws IOException

Description copied from class: Decoder

Discards a byte-string written by Encoder.writeBytes(java.nio.ByteBuffer).

Specified by:

skipBytes in class Decoder

Throws:

IOException

readFixed

public void readFixed(byte[] bytes,
                      int start,
                      int len)
               throws IOException

Description copied from class: Decoder

Reads fixed sized binary object.

Specified by:

readFixed in class Decoder

Parameters:

bytes - The buffer to store the contents being read.

start - The position where the data needs to be written.

len - The size of the binary object.

Throws:

IOException

skipFixed

public void skipFixed(int length)
               throws IOException

Description copied from class: Decoder

Discards fixed sized binary object.

Specified by:

skipFixed in class Decoder

Parameters:

length - The size of the binary object to be skipped.

Throws:

IOException

skipFixed

protected void skipFixed()
                  throws IOException

Specified by:

skipFixed in class ParsingDecoder

Throws:

IOException

readEnum

public int readEnum()
             throws IOException

Description copied from class: Decoder

Reads an enumeration.

Specified by:

readEnum in class Decoder

Returns:

The enumeration's value.

Throws:

IOException

readArrayStart

public long readArrayStart()
                    throws IOException

Description copied from class: Decoder

Reads and returns the size of the first block of an array. If this method returns non-zero, then the caller should read the indicated number of items, and then call Decoder.arrayNext() to find out the number of items in the next block. The typical pattern for consuming an array looks like:

   for(long i = in.readArrayStart(); i != 0; i = in.arrayNext()) {
     for (long j = 0; j < i; j++) {
       read next element of the array;
     }
   }
 

Specified by:

readArrayStart in class Decoder

Throws:

IOException

arrayNext

public long arrayNext()
               throws IOException

Description copied from class: Decoder

Processes the next block of an array andreturns the number of items in the block and let's the caller read those items.

Specified by:

arrayNext in class Decoder

Throws:

IOException

skipArray

public long skipArray()
               throws IOException

Description copied from class: Decoder

Used for quickly skipping through an array. Note you can either skip the entire array, or read the entire array (with Decoder.readArrayStart()), but you can't mix the two on the same array. This method will skip through as many items as it can, all of them if possible. It will return zero if there are no more items to skip through, or an item count if it needs the client's help in skipping. The typical usage pattern is:

   for(long i = in.skipArray(); i != 0; i = i.skipArray()) {
     for (long j = 0; j < i; j++) {
       read and discard the next element of the array;
     }
   }
 

Note that this method can automatically skip through items if a byte-count is found in the underlying data, or if a schema has been provided to the implementation, but otherwise the client will have to skip through items itself.

Specified by:

skipArray in class Decoder

Throws:

IOException

readMapStart

public long readMapStart()
                  throws IOException

Description copied from class: Decoder

Reads and returns the size of the next block of map-entries. Similar to Decoder.readArrayStart(). As an example, let's say you want to read a map of records, the record consisting of an Long field and a Boolean field. Your code would look something like this:

   Map m = new HashMap();
   Record reuse = new Record();
   for(long i = in.readMapStart(); i != 0; i = in.readMapNext()) {
     for (long j = 0; j < i; j++) {
       String key = in.readString();
       reuse.intField = in.readInt();
       reuse.boolField = in.readBoolean();
       m.put(key, reuse);
     }
   }
 

Specified by:

readMapStart in class Decoder

Throws:

IOException

mapNext

public long mapNext()
             throws IOException

Description copied from class: Decoder

Processes the next block of map entries and returns the count of them. Similar to Decoder.arrayNext(). See Decoder.readMapStart() for details.

Specified by:

mapNext in class Decoder

Throws:

IOException

skipMap

public long skipMap()
             throws IOException

Description copied from class: Decoder

Support for quickly skipping through a map similar to Decoder.skipArray(). As an example, let's say you want to skip a map of records, the record consisting of an Long field and a Boolean field. Your code would look something like this:

   for(long i = in.skipMap(); i != 0; i = in.skipMap()) {
     for (long j = 0; j < i; j++) {
       in.skipString();  // Discard key
       in.readInt(); // Discard int-field of value
       in.readBoolean(); // Discard boolean-field of value
     }
   }
 

Specified by:

skipMap in class Decoder

Throws:

IOException

readIndex

public int readIndex()
              throws IOException

Description copied from class: Decoder

Reads the tag of a union written by Encoder.writeIndex(int).

Specified by:

readIndex in class Decoder

Throws:

IOException

doAction

public Symbol doAction(Symbol input,
                       Symbol top)
                throws IOException

Description copied from interface: Parser.ActionHandler

Handle the action symbol top when the input is sought to be taken off the stack.

Specified by:

doAction in interface Parser.ActionHandler

Parameters:

input - The input symbol from the caller of advance

top - The symbol at the top the stack.

Returns:

null if advance() is to continue processing the stack. If not null the return value will be returned by advance().

Throws:

IOException

setItemCount

public void setItemCount(long itemCount)
                  throws IOException

Throws:

IOException