Coder (Apache Beam 2.49.0)

java.lang.Object
- org.apache.beam.sdk.coders.Coder<T>

Type Parameters:

T - the type of values being encoded and decoded

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

CustomCoder, StructuredCoder, ZstdCoder
```
public abstract class Coder<T>
extends java.lang.Object
implements java.io.Serializable
```
A Coder<T> defines how to encode and decode values of type T into byte streams.
Coder instances are serialized during job creation and deserialized before use. This will generally be performed by serializing the object via Java Serialization.
Coder classes for compound types are often composed from coder classes for types contains therein. The composition of Coder instances into a coder for the compound class is the subject of the CoderProvider type, which enables automatic generic composition of Coder classes within the CoderRegistry. See CoderProvider and CoderRegistry for more information about how coders are inferred.
All methods of a Coder are required to be thread safe.

See Also:

Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`Coder.Context` Deprecated. To implement a coder, do not use any `Coder.Context`. Just implement only those abstract methods which do not accept a `Coder.Context` and leave the default implementations for methods accepting a `Coder.Context`.
`static class`	`Coder.NonDeterministicException` Exception thrown by `verifyDeterministic()` if the encoding is not deterministic, including details of why the encoding is not deterministic.

Constructor Summary

Constructors
Constructor and Description

Coder()

Constructors
Constructor and Description
`Coder()`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`boolean`	`consistentWithEquals()` Returns `true` if this `Coder` is injective with respect to `Object.equals(java.lang.Object)`.
`abstract T`	`decode(java.io.InputStream inStream)` Decodes a value of type `T` from the given input stream in the given context.
`T`	`decode(java.io.InputStream inStream, Coder.Context context)` Deprecated. only implement and call `decode(InputStream)`
`abstract void`	`encode(T value, java.io.OutputStream outStream)` Encodes the given value of type `T` onto the given output stream.
`void`	`encode(T value, java.io.OutputStream outStream, Coder.Context context)` Deprecated. only implement and call `encode(Object value, OutputStream)`
`abstract java.util.List<? extends Coder<?>>`	`getCoderArguments()` If this is a `Coder` for a parameterized type, returns the list of `Coder`s being used for each of the parameters in the same order they appear within the parameterized type's type signature.
`protected long`	`getEncodedElementByteSize(T value)` Returns the size in bytes of the encoded value using this coder.
`TypeDescriptor<T>`	`getEncodedTypeDescriptor()` Returns the `TypeDescriptor` for the type encoded.
`boolean`	`isRegisterByteSizeObserverCheap(T value)` Returns whether `registerByteSizeObserver(T, org.apache.beam.sdk.util.common.ElementByteSizeObserver)` cheap enough to call for every element, that is, if this `Coder` can calculate the byte size of the element to be coded in roughly constant time (or lazily).
`void`	`registerByteSizeObserver(T value, org.apache.beam.sdk.util.common.ElementByteSizeObserver observer)` Notifies the `ElementByteSizeObserver` about the byte size of the encoded value using this `Coder`.
`java.lang.Object`	`structuralValue(T value)` Returns an object with an `Object.equals()` method that represents structural equality on the argument.
`abstract void`	`verifyDeterministic()` Throw `Coder.NonDeterministicException` if the coding is not deterministic.
`static void`	`verifyDeterministic(Coder<?> target, java.lang.String message, Coder<?>... coders)` Verifies all of the provided coders are deterministic.
`static void`	`verifyDeterministic(Coder<?> target, java.lang.String message, java.lang.Iterable<Coder<?>> coders)` Verifies all of the provided coders are deterministic.

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

- Constructor Detail
  - Coder
```
public Coder()
```
- Method Detail
  - encode
```
public abstract void encode(T value,
                            java.io.OutputStream outStream)
                     throws CoderException,
                            java.io.IOException
```
    Encodes the given value of type T onto the given output stream.
    
    Throws:
    
    java.io.IOException - if writing to the OutputStream fails for some reason
    
    CoderException - if the value could not be encoded for some reason
  - encode
```
@Deprecated
public void encode(T value,
                               java.io.OutputStream outStream,
                               Coder.Context context)
                        throws CoderException,
                               java.io.IOException
```
    Deprecated. only implement and call encode(Object value, OutputStream)
    
    Encodes the given value of type T onto the given output stream in the given context.
    
    Throws:
    
    java.io.IOException - if writing to the OutputStream fails for some reason
    
    CoderException - if the value could not be encoded for some reason
  - decode
```
public abstract T decode(java.io.InputStream inStream)
                  throws CoderException,
                         java.io.IOException
```
    Decodes a value of type T from the given input stream in the given context. Returns the decoded value.
    
    Throws:
    
    java.io.IOException - if reading from the InputStream fails for some reason
    
    CoderException - if the value could not be decoded for some reason
  - decode
```
@Deprecated
public T decode(java.io.InputStream inStream,
                            Coder.Context context)
                     throws CoderException,
                            java.io.IOException
```
    Deprecated. only implement and call decode(InputStream)
    
    Decodes a value of type T from the given input stream in the given context. Returns the decoded value.
    
    Throws:
    
    java.io.IOException - if reading from the InputStream fails for some reason
    
    CoderException - if the value could not be decoded for some reason
  - getCoderArguments
```
public abstract java.util.List<? extends Coder<?>> getCoderArguments()
```
    If this is a Coder for a parameterized type, returns the list of Coders being used for each of the parameters in the same order they appear within the parameterized type's type signature. If this cannot be done, or this Coder does not encode/decode a parameterized type, returns the empty list.
  - verifyDeterministic
```
public abstract void verifyDeterministic()
                                  throws Coder.NonDeterministicException
```
    Throw Coder.NonDeterministicException if the coding is not deterministic.
    In order for a Coder to be considered deterministic, the following must be true:
    - two values that compare as equal (via Object.equals() or Comparable.compareTo(), if supported) have the same encoding.
    - the Coder always produces a canonical encoding, which is the same for an instance of an object even if produced on different computers at different times.
    Throws:
    
    Coder.NonDeterministicException - if this coder is not deterministic.
  - verifyDeterministic
```
public static void verifyDeterministic(Coder<?> target,
                                       java.lang.String message,
                                       java.lang.Iterable<Coder<?>> coders)
                                throws Coder.NonDeterministicException
```
    Verifies all of the provided coders are deterministic. If any are not, throws a Coder.NonDeterministicException for the target Coder.
    
    Throws:
    
    Coder.NonDeterministicException
  - verifyDeterministic
```
public static void verifyDeterministic(Coder<?> target,
                                       java.lang.String message,
                                       Coder<?>... coders)
                                throws Coder.NonDeterministicException
```
    Verifies all of the provided coders are deterministic. If any are not, throws a Coder.NonDeterministicException for the target Coder.
    
    Throws:
    
    Coder.NonDeterministicException
  - consistentWithEquals
```
public boolean consistentWithEquals()
```
    Returns true if this Coder is injective with respect to Object.equals(java.lang.Object).
    Whenever the encoded bytes of two values are equal, then the original values are equal according to Objects.equals(). Note that this is well-defined for null.
    This condition is most notably false for arrays. More generally, this condition is false whenever equals() compares object identity, rather than performing a semantic/structural comparison.
    By default, returns false.
  - structuralValue
```
public java.lang.Object structuralValue(T value)
```
    Returns an object with an Object.equals() method that represents structural equality on the argument.
    For any two values x and y of type T, if their encoded bytes are the same, then it must be the case that structuralValue(x).equals(structuralValue(y)).
    Most notably:
    - The structural value for an array coder should perform a structural comparison of the contents of the arrays, rather than the default behavior of comparing according to object identity.
    - The structural value for a coder accepting null should be a proper object with an equals() method, even if the input value is null.
    See also consistentWithEquals().
    By default, if this coder is consistentWithEquals(), and the value is not null, returns the provided object. Otherwise, encodes the value into a byte[], and returns an object that performs array equality on the encoded bytes.
  - isRegisterByteSizeObserverCheap
```
public boolean isRegisterByteSizeObserverCheap(T value)
```
    Returns whether registerByteSizeObserver(T, org.apache.beam.sdk.util.common.ElementByteSizeObserver) cheap enough to call for every element, that is, if this Coder can calculate the byte size of the element to be coded in roughly constant time (or lazily).
    Not intended to be called by user code, but instead by PipelineRunner implementations.
    By default, returns false. The default registerByteSizeObserver(T, org.apache.beam.sdk.util.common.ElementByteSizeObserver) implementation invokes getEncodedElementByteSize(T) which requires re-encoding an element unless it is overridden. This is considered expensive.
  - registerByteSizeObserver
```
public void registerByteSizeObserver(T value,
                                     org.apache.beam.sdk.util.common.ElementByteSizeObserver observer)
                              throws java.lang.Exception
```
    Notifies the ElementByteSizeObserver about the byte size of the encoded value using this Coder.
    Not intended to be called by user code, but instead by PipelineRunner implementations.
    By default, this notifies observer about the byte size of the encoded value using this coder as returned by getEncodedElementByteSize(T).
    
    Throws:
    
    java.lang.Exception
  - getEncodedElementByteSize
```
protected long getEncodedElementByteSize(T value)
                                  throws java.lang.Exception
```
    Returns the size in bytes of the encoded value using this coder.
    
    Throws:
    
    java.lang.Exception
  - getEncodedTypeDescriptor
```
public TypeDescriptor<T> getEncodedTypeDescriptor()
```
    Returns the TypeDescriptor for the type encoded.

Class Coder<T>

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Coder

Method Detail

encode

encode

decode

decode

getCoderArguments

verifyDeterministic

verifyDeterministic

verifyDeterministic

consistentWithEquals

structuralValue

isRegisterByteSizeObserverCheap

registerByteSizeObserver

getEncodedElementByteSize

getEncodedTypeDescriptor