Class JsonBuffer

java.lang.Object

io.jstach.rainbowgum.json.JsonBuffer

All Implemented Interfaces:

LogEncoder.Buffer, AutoCloseable

public final class JsonBuffer
extends Object
implements LogEncoder.Buffer

A buffer designed for encoding JSON efficiently.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	JsonBuffer.ExtendedFieldPrefix	Extended fields are just fields that have some special prefix for things like GELF and ECS.
static enum	JsonBuffer.JSONToken	JSON tokens.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_INITIAL_JSON_CAPACITY	Default initial capacity of the raw JSON byte buffer, matching what this class has always used - big enough that most events never need to grow it.
static final int	DEFAULT_INITIAL_MESSAGE_CAPACITY	Default initial capacity of getFormattedMessageBuilder().
static final int	EXTENDED_F	A flag to indicate this field is extended which means it will be prefixed with JsonBuffer.ExtendedFieldPrefix.

Constructor Summary

Constructors

Constructor	Description
JsonBuffer(boolean prettyPrint, JsonBuffer.ExtendedFieldPrefix extendedFieldPrefix, int maxBufferSize)	Create a JSON buffer.

Method Summary

Modifier and Type	Method	Description
void	clear()	Prepare the buffer for reuse.
void	drain(LogOutput output, LogEvent event)	The appender will call this usually within a lock to transfer content from the buffer to the output.
StringBuilder	getFormattedMessageBuilder()	Reusable String buffer for formatted messages.
boolean	isOversized()	Whether this buffer has grown large enough (its capacity, not how much of that capacity the last event actually used) that its backing storage is worth shrinking back down rather than kept at its grown size indefinitely - reused buffers only grow on their own, they never shrink back down without deliberate help.
final void	write(JsonBuffer.JSONToken token)	Writes a JSON token.
final int	write(String k, @Nullable String v, int index)	Writes a string field.
final int	write(String k, @Nullable String v, int index, int flag)	Writes a string field.
final void	writeArrayElementObjectEnd()	Ends an array element object previously started with writeArrayElementObjectStart(int).
final int	writeArrayElementObjectStart(int index)	Starts an anonymous JSON object as an array element (no field name), e.g. the { in [{...},{...}].
final void	writeArrayEnd()	Ends a nested JSON array previously started with writeArrayStart(String, int, int).
final int	writeArrayStart(String k, int index, int flag)	Starts a nested JSON array as a field value, e.g.
final int	writeDouble(String k, double v, int index, int flag)	Writes a double field.
final int	writeInt(String k, int v, int index, int flag)	Writes a string field.
final void	writeLineFeed()	Efficiently writes a line feed.
final int	writeLong(String k, long v, int index, int flag)	Writes a long field.
final void	writeObjectEnd()	Ends a nested JSON object previously started with writeObjectStart(String, int, int).
final int	writeObjectStart(String k, int index, int flag)	Starts a nested JSON object as a field value, e.g.

Methods inherited from class Object

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

Methods inherited from interface LogEncoder.Buffer

close

Modifier and Type	Method	Description
default void	close()	Convenience that will call clear.

Field Details

DEFAULT_INITIAL_JSON_CAPACITY

public static final int DEFAULT_INITIAL_JSON_CAPACITY

Default initial capacity of the raw JSON byte buffer, matching what this class has always used - big enough that most events never need to grow it.

See Also:

• Constant Field Values

DEFAULT_INITIAL_MESSAGE_CAPACITY

public static final int DEFAULT_INITIAL_MESSAGE_CAPACITY

Default initial capacity of getFormattedMessageBuilder(). Bigger than StringBuilder's own default of 16 since most log messages exceed that immediately, but still small relative to DEFAULT_INITIAL_JSON_CAPACITY since this buffer is just the formatted message, not the whole encoded event.

See Also:

• Constant Field Values

EXTENDED_F

public static final int EXTENDED_F

A flag to indicate this field is extended which means it will be prefixed with JsonBuffer.ExtendedFieldPrefix.

See Also:

• Constant Field Values

Constructor Details

JsonBuffer

public JsonBuffer(boolean prettyPrint,
 JsonBuffer.ExtendedFieldPrefix extendedFieldPrefix,
 int maxBufferSize)

Create a JSON buffer.

Parameters:

prettyPrint - whether or not to pretty print the JSON.

extendedFieldPrefix - prefix for extended fields.

maxBufferSize - a negative value disables isOversized() entirely. Applied, for simplicity, as a single combined threshold across both the raw JSON byte buffer and getFormattedMessageBuilder() rather than tracked separately per buffer.

Method Details

drain

public void drain(LogOutput output,
 LogEvent event)

Description copied from interface: LogEncoder.Buffer

The appender will call this usually within a lock to transfer content from the buffer to the output.

Specified by:

drain in interface LogEncoder.Buffer

Parameters:

output - output to receive content.

event - log event.

clear

public void clear()

Description copied from interface: LogEncoder.Buffer

Prepare the buffer for reuse.

An appender may not call clear before being passed to the encoder so the encoder should do its own clearing.

Built-in implementations also shrink their own backing storage back down here if LogEncoder.Buffer.isOversized() - see that method - so a single unusually large event does not permanently bloat a buffer that gets reused for many more events after it.

Specified by:

clear in interface LogEncoder.Buffer

isOversized

public boolean isOversized()

Description copied from interface: LogEncoder.Buffer

Whether this buffer has grown large enough (its capacity, not how much of that capacity the last event actually used) that its backing storage is worth shrinking back down rather than kept at its grown size indefinitely - reused buffers only grow on their own, they never shrink back down without deliberate help. This is a soft ceiling checked between events, not a hard cap enforced during one: nothing here stops a single event from growing the buffer past whatever threshold it was configured with while that event is being encoded. Built-in implementations consult this themselves inside LogEncoder.Buffer.clear() to decide whether to shrink their own backing storage in place (e.g. StringBuilder.trimToSize(), or reallocating a smaller ByteBuffer) - most callers do not need to call this directly; it remains here mainly for tests/observability and for a custom LogEncoder.Buffer implementation that wants the same self-shrinking behavior.

What "large enough" means, and whether it means anything at all, is entirely up to the buffer/encoder - the same way charset is an encoder concern rather than something an appender configures (see LogEncoder.builder(LogFormatter)). The default implementation returns false - a buffer implementation that does not override this, or an encoder that never configured a threshold, never shrinks.

Specified by:

isOversized in interface LogEncoder.Buffer

Returns:

true if this buffer's backing storage has grown past whatever threshold it was configured with.

getFormattedMessageBuilder

public StringBuilder getFormattedMessageBuilder()

Reusable String buffer for formatted messages.

Returns:

buffer.

write

public final void write(JsonBuffer.JSONToken token)

Writes a JSON token.

Parameters:

token - token not null.

writeLineFeed

public final void writeLineFeed()

Efficiently writes a line feed.

write

public final int write(String k,
 @Nullable String v,
 int index)

Writes a string field.

Parameters:

k - field name

v - value

index - the current index for comma determination

Returns:

index + 1

write

public final int write(String k,
 @Nullable String v,
 int index,
 int flag)

Writes a string field.

Parameters:

k - field name

v - value

index - the current index for comma determination

flag - see EXTENDED_F

Returns:

index + 1

writeDouble

public final int writeDouble(String k,
 double v,
 int index,
 int flag)

Writes a double field.

Parameters:

k - field name

v - value

index - the current index for comma determination

flag - see EXTENDED_F

Returns:

index + 1

writeInt

public final int writeInt(String k,
 int v,
 int index,
 int flag)

Writes a string field.

Parameters:

k - field name

v - value

index - the current index for comma determination

flag - see EXTENDED_F

Returns:

index + 1

writeLong

public final int writeLong(String k,
 long v,
 int index,
 int flag)

Writes a long field.

Parameters:

k - field name

v - value

index - the current index for comma determination

flag - see EXTENDED_F

Returns:

index + 1

writeObjectStart

public final int writeObjectStart(String k,
 int index,
 int flag)

Starts a nested JSON object as a field value, e.g. "key":{. Fields written after this and before the matching writeObjectEnd() should use the returned index (a fresh comma-counter local to the nested object) rather than the outer index.

Parameters:

k - field name

index - the current index (of the enclosing object) for comma determination

flag - see EXTENDED_F

Returns:

0, the starting index for fields inside the nested object

writeObjectEnd

public final void writeObjectEnd()

Ends a nested JSON object previously started with writeObjectStart(String, int, int).

writeArrayStart

public final int writeArrayStart(String k,
 int index,
 int flag)

Starts a nested JSON array as a field value, e.g. "key":[. Elements written after this and before the matching writeArrayEnd() should use writeArrayElementObjectStart(int) (with a fresh, local index) rather than the outer index.

Parameters:

k - field name

index - the current index (of the enclosing object) for comma determination

flag - see EXTENDED_F

Returns:

0, the starting index for elements inside the nested array

writeArrayEnd

public final void writeArrayEnd()

Ends a nested JSON array previously started with writeArrayStart(String, int, int).

writeArrayElementObjectStart

public final int writeArrayElementObjectStart(int index)

Starts an anonymous JSON object as an array element (no field name), e.g. the { in [{...},{...}].

Parameters:

index - the current index (within the array) for comma determination

Returns:

0, the starting index for fields inside the element object

writeArrayElementObjectEnd

public final void writeArrayElementObjectEnd()

Ends an array element object previously started with writeArrayElementObjectStart(int).