Encoder (Apache Avro Java 1.8.2 API)

java.lang.Object
- org.apache.avro.io.Encoder

All Implemented Interfaces:

Flushable

Direct Known Subclasses:

BinaryEncoder, ParsingEncoder
```
public abstract class Encoder
extends Object
implements Flushable
```
Low-level support for serializing Avro values.
This class has two types of methods. One type of methods support the writing of leaf values (for example, writeLong(long) and writeString(org.apache.avro.util.Utf8)). These methods have analogs in Decoder.
The other type of methods support the writing of maps and arrays. These methods are writeArrayStart(), startItem(), and writeArrayEnd() (and similar methods for maps). Some implementations of Encoder handle the buffering required to break large maps and arrays into blocks, which is necessary for applications that want to do streaming. (See writeArrayStart() for details on these methods.)
EncoderFactory contains Encoder construction and configuration facilities.

See Also:
EncoderFactory, Decoder

Constructor Summary

Constructors
Constructor and Description

Encoder()

Constructors
Constructor and Description
`Encoder()`

Method Summary

Methods
Modifier and Type	Method and Description
`abstract void`	`setItemCount(long itemCount)` Call this method before writing a batch of items in an array or a map.
`abstract void`	`startItem()` Start a new item of an array or map.
`abstract void`	`writeArrayEnd()` Call this method to finish writing an array.
`abstract void`	`writeArrayStart()` Call this method to start writing an array.
`abstract void`	`writeBoolean(boolean b)` Write a boolean value.
`void`	`writeBytes(byte[] bytes)` Writes a byte string.
`abstract void`	`writeBytes(byte[] bytes, int start, int len)` Write a byte string.
`abstract void`	`writeBytes(ByteBuffer bytes)` Write a byte string.
`abstract void`	`writeDouble(double d)` Write a double.
`abstract void`	`writeEnum(int e)` Writes an enumeration.
`void`	`writeFixed(byte[] bytes)` A shorthand for `writeFixed(bytes, 0, bytes.length)`
`abstract void`	`writeFixed(byte[] bytes, int start, int len)` Writes a fixed size binary object.
`void`	`writeFixed(ByteBuffer bytes)` Writes a fixed from a ByteBuffer.
`abstract void`	`writeFloat(float f)` Write a float.
`abstract void`	`writeIndex(int unionIndex)` Call this method to write the tag of a union.
`abstract void`	`writeInt(int n)` Writes a 32-bit integer.
`abstract void`	`writeLong(long n)` Write a 64-bit integer.
`abstract void`	`writeMapEnd()` Call this method to terminate the inner-most, currently-opened map.
`abstract void`	`writeMapStart()` Call this to start a new map.
`abstract void`	`writeNull()` "Writes" a null value.
`void`	`writeString(CharSequence charSequence)` Write a Unicode character string.
`void`	`writeString(String str)` Write a Unicode character string.
`abstract void`	`writeString(Utf8 utf8)` Write a Unicode character string.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.io.Flushable
flush

- Constructor Detail
  - Encoder
```
public Encoder()
```
- Method Detail
  - writeNull
```
public abstract void writeNull()
                        throws IOException
```
    "Writes" a null value. (Doesn't actually write anything, but advances the state of the parser if this class is stateful.)
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a null is not expected
    
    IOException
  - writeBoolean
```
public abstract void writeBoolean(boolean b)
                           throws IOException
```
    Write a boolean value.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a boolean is not expected
    
    IOException
  - writeInt
```
public abstract void writeInt(int n)
                       throws IOException
```
    Writes a 32-bit integer.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and an integer is not expected
    
    IOException
  - writeLong
```
public abstract void writeLong(long n)
                        throws IOException
```
    Write a 64-bit integer.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a long is not expected
    
    IOException
  - writeFloat
```
public abstract void writeFloat(float f)
                         throws IOException
```
    Write a float.
    
    Throws:
    
    IOException
    
    AvroTypeException - If this is a stateful writer and a float is not expected
  - writeDouble
```
public abstract void writeDouble(double d)
                          throws IOException
```
    Write a double.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a double is not expected
    
    IOException
  - writeString
```
public abstract void writeString(Utf8 utf8)
                          throws IOException
```
    Write a Unicode character string.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a char-string is not expected
    
    IOException
  - writeString
```
public void writeString(String str)
                 throws IOException
```
    Write a Unicode character string. The default implementation converts the String to a Utf8. Some Encoder implementations may want to do something different as a performance optimization.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a char-string is not expected
    
    IOException
  - writeString
```
public void writeString(CharSequence charSequence)
                 throws IOException
```
    Write a Unicode character string. If the CharSequence is an Utf8 it writes this directly, otherwise the CharSequence is converted to a String via toString() and written.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a char-string is not expected
    
    IOException
  - writeBytes
```
public abstract void writeBytes(ByteBuffer bytes)
                         throws IOException
```
    Write a byte string.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a byte-string is not expected
    
    IOException
  - writeBytes
```
public abstract void writeBytes(byte[] bytes,
              int start,
              int len)
                         throws IOException
```
    Write a byte string.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a byte-string is not expected
    
    IOException
  - writeBytes
```
public void writeBytes(byte[] bytes)
                throws IOException
```
    Writes a byte string. Equivalent to writeBytes(bytes, 0, bytes.length)
    
    Throws:
    
    IOException
    
    AvroTypeException - If this is a stateful writer and a byte-string is not expected
  - writeFixed
```
public abstract void writeFixed(byte[] bytes,
              int start,
              int len)
                         throws IOException
```
    Writes a fixed size binary object.
    
    Parameters:
    bytes - The contents to write
    start - The position within bytes where the contents start.
    len - The number of bytes to write.
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and a byte-string is not expected
    
    IOException
  - writeFixed
```
public void writeFixed(byte[] bytes)
                throws IOException
```
    A shorthand for writeFixed(bytes, 0, bytes.length)
    
    Parameters:
    bytes -
    
    Throws:
    
    IOException
  - writeFixed
```
public void writeFixed(ByteBuffer bytes)
                throws IOException
```
    Writes a fixed from a ByteBuffer.
    
    Throws:
    
    IOException
  - writeEnum
```
public abstract void writeEnum(int e)
                        throws IOException
```
    Writes an enumeration.
    
    Parameters:
    e -
    
    Throws:
    
    AvroTypeException - If this is a stateful writer and an enumeration is not expected or the e is out of range.
    
    IOException
  - writeArrayStart
```
public abstract void writeArrayStart()
                              throws IOException
```
    Call this method to start writing an array. When starting to serialize an array, call writeArrayStart(). Then, before writing any data for any item call setItemCount(long) followed by a sequence of startItem() and the item itself. The number of startItem() should match the number specified in setItemCount(long). When actually writing the data of the item, you can call any Encoder method (e.g., writeLong(long)). When all items of the array have been written, call writeArrayEnd(). As an example, let's say you want to write an array of records, the record consisting of an Long field and a Boolean field. Your code would look something like this:
```
  out.writeArrayStart();
  out.setItemCount(list.size());
  for (Record r : list) {
    out.startItem();
    out.writeLong(r.longField);
    out.writeBoolean(r.boolField);
  }
  out.writeArrayEnd();
  
```
    Throws:
    
    AvroTypeException - If this is a stateful writer and an array is not expected
    
    IOException
  - setItemCount
```
public abstract void setItemCount(long itemCount)
                           throws IOException
```
    Call this method before writing a batch of items in an array or a map. Then for each item, call startItem() followed by any of the other write methods of Encoder. The number of calls to startItem() must be equal to the count specified in setItemCount(long). Once a batch is completed you can start another batch with setItemCount(long).
    
    Parameters:
    itemCount - The number of startItem() calls to follow.
    
    Throws:
    
    IOException
  - startItem
```
public abstract void startItem()
                        throws IOException
```
    Start a new item of an array or map. See writeArrayStart() for usage information.
    
    Throws:
    
    AvroTypeException - If called outside of an array or map context
    
    IOException
  - writeArrayEnd
```
public abstract void writeArrayEnd()
                            throws IOException
```
    Call this method to finish writing an array. See writeArrayStart() for usage information.
    
    Throws:
    
    AvroTypeException - If items written does not match count provided to writeArrayStart()
    
    AvroTypeException - If not currently inside an array
    
    IOException
  - writeMapStart
```
public abstract void writeMapStart()
                            throws IOException
```
    Call this to start a new map. See writeArrayStart() for details on usage. As an example of usage, let's say you want to write a map of records, the record consisting of an Long field and a Boolean field. Your code would look something like this:
```
 out.writeMapStart();
 out.setItemCount(list.size());
 for (Map.Entry entry : map.entrySet()) {
   out.startItem();
   out.writeString(entry.getKey());
   out.writeLong(entry.getValue().longField);
   out.writeBoolean(entry.getValue().boolField);
 }
 out.writeMapEnd();
 
```
    Throws:
    
    AvroTypeException - If this is a stateful writer and a map is not expected
    
    IOException
  - writeMapEnd
```
public abstract void writeMapEnd()
                          throws IOException
```
    Call this method to terminate the inner-most, currently-opened map. See writeArrayStart() for more details.
    
    Throws:
    
    AvroTypeException - If items written does not match count provided to writeMapStart()
    
    AvroTypeException - If not currently inside a map
    
    IOException
  - writeIndex
```
public abstract void writeIndex(int unionIndex)
                         throws IOException
```
    Call this method to write the tag of a union. As an example of usage, let's say you want to write a union, whose second branch is a record consisting of an Long field and a Boolean field. Your code would look something like this:
```
 out.writeIndex(1);
 out.writeLong(record.longField);
 out.writeBoolean(record.boolField);
 
```
    Throws:
    
    AvroTypeException - If this is a stateful writer and a map is not expected
    
    IOException

Class Encoder

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.io.Flushable

Constructor Detail

Encoder

Method Detail

writeNull

writeBoolean

writeInt

writeLong

writeFloat

writeDouble

writeString

writeString

writeString

writeBytes

writeBytes

writeBytes

writeFixed

writeFixed

writeFixed

writeEnum

writeArrayStart

setItemCount

startItem

writeArrayEnd

writeMapStart

writeMapEnd

writeIndex