com.google.protobuf

Class SingleFieldBuilder<MType extends GeneratedMessage,BType extends GeneratedMessage.Builder,IType extends MessageOrBuilder>

java.lang.Object

com.google.protobuf.SingleFieldBuilder<MType,BType,IType>

Type Parameters:

MType - the type of message for the field

BType - the type of builder for the field

IType - the common interface for the message and the builder

public class SingleFieldBuilder<MType extends GeneratedMessage,BType extends GeneratedMessage.Builder,IType extends MessageOrBuilder>
extends java.lang.Object

SingleFieldBuilder implements a structure that a protocol message uses to hold a single field of another protocol message. It supports the classical use case of setting an immutable Message as the value of the field and is highly optimized around this.
It also supports the additional use case of setting a Message.Builder as the field and deferring conversion of that Builder to an immutable Message. In this way, it's possible to maintain a tree of Builder's that acts as a fully read/write data structure.
Logically, one can think of a tree of builders as converting the entire tree to messages when build is called on the root or when any method is called that desires a Message instead of a Builder. In terms of the implementation, the SingleFieldBuilder and RepeatedFieldBuilder classes cache messages that were created so that messages only need to be created when some change occured in its builder or a builder for one of its descendants.

Author:

jonp@google.com (Jon Perlow)

Constructor Summary

Constructors

Constructor and Description
SingleFieldBuilder(MType message, com.google.protobuf.GeneratedMessage.BuilderParent parent, boolean isClean)

Method Summary

Methods

Modifier and Type	Method and Description
MType	build() Builds the message and returns it.
SingleFieldBuilder<MType,BType,IType>	clear() Clears the value of the field.
void	dispose()
BType	getBuilder() Gets a builder for the field.
MType	getMessage() Get the message for the field.
IType	getMessageOrBuilder() Gets the base class interface for the field.
void	markDirty() A builder becomes dirty whenever a field is modified -- including fields in nested builders -- and becomes clean when build() is called.
SingleFieldBuilder<MType,BType,IType>	mergeFrom(MType value) Merges the field from another field.
SingleFieldBuilder<MType,BType,IType>	setMessage(MType message) Sets a message for the field replacing any existing value.

Methods inherited from class java.lang.Object

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

Constructor Detail

SingleFieldBuilder

public SingleFieldBuilder(MType message,
                  com.google.protobuf.GeneratedMessage.BuilderParent parent,
                  boolean isClean)

Method Detail

dispose

public void dispose()

getMessage

public MType getMessage()

Get the message for the field. If the message is currently stored as a Builder, it is converted to a Message by calling Message.Builder.buildPartial() on it. If no message has been set, returns the default instance of the message.

Returns:

the message for the field

build

public MType build()

Builds the message and returns it.

Returns:

the message

getBuilder

public BType getBuilder()

Gets a builder for the field. If no builder has been created yet, a builder is created on demand by calling Message.toBuilder().

Returns:

The builder for the field

getMessageOrBuilder

public IType getMessageOrBuilder()

Gets the base class interface for the field. This may either be a builder or a message. It will return whatever is more efficient.

Returns:

the message or builder for the field as the base class interface

setMessage

public SingleFieldBuilder<MType,BType,IType> setMessage(MType message)

Sets a message for the field replacing any existing value.

Parameters:

message - the message to set

Returns:

the builder

mergeFrom

public SingleFieldBuilder<MType,BType,IType> mergeFrom(MType value)

Merges the field from another field.

Parameters:

value - the value to merge from

Returns:

the builder

clear

public SingleFieldBuilder<MType,BType,IType> clear()

Clears the value of the field.

Returns:

the builder

markDirty

public void markDirty()

A builder becomes dirty whenever a field is modified -- including fields in nested builders -- and becomes clean when build() is called. Thus, when a builder becomes dirty, all its parents become dirty as well, and when it becomes clean, all its children become clean. The dirtiness state is used to invalidate certain cached values.
To this end, a builder calls markAsDirty() on its parent whenever it transitions from clean to dirty. The parent must propagate this call to its own parent, unless it was already dirty, in which case the grandparent must necessarily already be dirty as well. The parent can only transition back to "clean" after calling build() on all children.