Class HandlerWithoutInvocation

java.lang.Object

dev.langchain4j.internal.HandlerWithoutInvocation

All Implemented Interfaces:

StreamingChatResponseHandler

public final class HandlerWithoutInvocation
extends Object
implements StreamingChatResponseHandler

Wraps the handler an AI Service passes to its streaming chat model, so that the handler runs without the current invocation, also when the model calls it on the thread of the call, during the call. The handler calls code of the caller (for example the handlers of a TokenStream), which is not part of the work of the invocation.

Method Summary

Modifier and Type	Method	Description
void	onCompleteResponse(ChatResponse completeResponse)	Invoked when the model has finished streaming a response.
void	onCompleteToolCall(CompleteToolCall completeToolCall)	Invoked when the model has finished streaming a single tool call.
void	onError(Throwable error)	This method is invoked when an error occurs during streaming.
void	onPartialResponse(PartialResponse partialResponse, PartialResponseContext context)	Invoked each time the model generates a partial textual response, usually a single token.
void	onPartialResponse(String partialResponse)	Invoked each time the model generates a partial textual response, usually a single token.
void	onPartialThinking(PartialThinking partialThinking)	Invoked each time the model generates a partial thinking/reasoning text, usually a single token.
void	onPartialThinking(PartialThinking partialThinking, PartialThinkingContext context)	Invoked each time the model generates a partial thinking/reasoning text, usually a single token.
void	onPartialToolCall(PartialToolCall partialToolCall)	This callback is invoked each time the model generates a partial tool call, which contains a single token of the tool's arguments.
void	onPartialToolCall(PartialToolCall partialToolCall, PartialToolCallContext context)	This callback is invoked each time the model generates a partial tool call, which contains a single token of the tool's arguments.
void	onUnmappedRawEvent(Object rawEvent)	Invoked when a provider emits a raw streaming event that is not already exposed through one of the typed callbacks (such as StreamingChatResponseHandler.onPartialResponse(PartialResponse, PartialResponseContext), StreamingChatResponseHandler.onPartialThinking(PartialThinking, PartialThinkingContext), StreamingChatResponseHandler.onPartialToolCall(PartialToolCall, PartialToolCallContext) or StreamingChatResponseHandler.onCompleteToolCall(CompleteToolCall)).
static StreamingChatResponseHandler	wrap(StreamingChatResponseHandler handler)

Methods inherited from class Object

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

Method Details

wrap

public static StreamingChatResponseHandler wrap(StreamingChatResponseHandler handler)

onPartialResponse

public void onPartialResponse(String partialResponse)

Description copied from interface: StreamingChatResponseHandler

Invoked each time the model generates a partial textual response, usually a single token.

Please note that some LLM providers do not stream individual tokens, but send responses in batches. In such cases, this callback may receive multiple tokens at once.

Either this or the StreamingChatResponseHandler.onPartialResponse(PartialResponse, PartialResponseContext) method should be implemented if you want to consume tokens as soon as they become available.

This method does not provide a StreamingHandle, so the streaming cannot be cancelled from it. Implement StreamingChatResponseHandler.onPartialResponse(PartialResponse, PartialResponseContext) instead if you need to cancel.

Specified by:

onPartialResponse in interface StreamingChatResponseHandler

Parameters:

partialResponse - A partial textual response, usually a single token.

See Also:

• StreamingChatResponseHandler.onPartialResponse(PartialResponse, PartialResponseContext)

onPartialResponse

public void onPartialResponse(PartialResponse partialResponse,
 PartialResponseContext context)

Description copied from interface: StreamingChatResponseHandler

Invoked each time the model generates a partial textual response, usually a single token.

Please note that some LLM providers do not stream individual tokens, but send responses in batches. In such cases, this callback may receive multiple tokens at once.

Either this or the StreamingChatResponseHandler.onPartialResponse(String) method should be implemented if you want to consume tokens as soon as they become available.

Specified by:

onPartialResponse in interface StreamingChatResponseHandler

Parameters:

partialResponse - A partial textual response, usually a single token.

context - A partial response context. Contains a StreamingHandle that can be used to cancel streaming.

See Also:

• StreamingChatResponseHandler.onPartialResponse(String)

onPartialThinking

public void onPartialThinking(PartialThinking partialThinking)

Description copied from interface: StreamingChatResponseHandler

Invoked each time the model generates a partial thinking/reasoning text, usually a single token.

Please note that some LLM providers do not stream individual tokens, but send thinking tokens in batches. In such cases, this callback may receive multiple tokens at once.

Either this or the StreamingChatResponseHandler.onPartialThinking(PartialThinking, PartialThinkingContext) method should be implemented if you want to consume thinking tokens as soon as they become available.

This method does not provide a StreamingHandle, so the streaming cannot be cancelled from it. Implement StreamingChatResponseHandler.onPartialThinking(PartialThinking, PartialThinkingContext) instead if you need to cancel.

Specified by:

onPartialThinking in interface StreamingChatResponseHandler

Parameters:

partialThinking - A partial thinking text, usually a single token.

See Also:

• StreamingChatResponseHandler.onPartialThinking(PartialThinking, PartialThinkingContext)

onPartialThinking

public void onPartialThinking(PartialThinking partialThinking,
 PartialThinkingContext context)

Description copied from interface: StreamingChatResponseHandler

Invoked each time the model generates a partial thinking/reasoning text, usually a single token.

Please note that some LLM providers do not stream individual tokens, but send thinking tokens in batches. In such cases, this callback may receive multiple tokens at once.

Either this or the StreamingChatResponseHandler.onPartialThinking(PartialThinking) method should be implemented if you want to consume thinking tokens as soon as they become available.

Specified by:

onPartialThinking in interface StreamingChatResponseHandler

Parameters:

partialThinking - A partial thinking text, usually a single token.

context - A partial thinking context. Contains a StreamingHandle that can be used to cancel streaming.

See Also:

• StreamingChatResponseHandler.onPartialThinking(PartialThinking)

onPartialToolCall

public void onPartialToolCall(PartialToolCall partialToolCall)

Description copied from interface: StreamingChatResponseHandler

This callback is invoked each time the model generates a partial tool call, which contains a single token of the tool's arguments. It is typically invoked multiple times for a single tool call until StreamingChatResponseHandler.onCompleteToolCall(CompleteToolCall) is eventually invoked, indicating that the streaming for that tool call is finished.

Here's an example of what streaming a single tool call might look like:

1. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "{\"")
2. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "city")
3. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = ""\":\"")
4. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "Mun")
5. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "ich")
6. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "\"}")
7. onCompleteToolCall(index = 0, id = "call_abc", name = "get_weather", arguments = "{\"city\":\"Munich\"}")

If the model decides to call multiple tools, the index will increment, allowing you to correlate.

Please note that not all LLM providers stream tool calls token by token. Some providers (e.g., Bedrock, Google, Mistral, Ollama) return only complete tool calls. In those cases, this callback won't be invoked - only StreamingChatResponseHandler.onCompleteToolCall(CompleteToolCall) will be called.

Either this or the StreamingChatResponseHandler.onPartialToolCall(PartialToolCall, PartialToolCallContext) method should be implemented if you want to consume partial tool calls as soon as they become available.

This method does not provide a StreamingHandle, so the streaming cannot be cancelled from it. Implement StreamingChatResponseHandler.onPartialToolCall(PartialToolCall, PartialToolCallContext) instead if you need to cancel.

Specified by:

onPartialToolCall in interface StreamingChatResponseHandler

Parameters:

partialToolCall - A partial tool call that contains the index, tool ID, tool name and partial arguments.

See Also:

• StreamingChatResponseHandler.onPartialToolCall(PartialToolCall, PartialToolCallContext)

onPartialToolCall

public void onPartialToolCall(PartialToolCall partialToolCall,
 PartialToolCallContext context)

Description copied from interface: StreamingChatResponseHandler

This callback is invoked each time the model generates a partial tool call, which contains a single token of the tool's arguments. It is typically invoked multiple times for a single tool call until StreamingChatResponseHandler.onCompleteToolCall(CompleteToolCall) is eventually invoked, indicating that the streaming for that tool call is finished.

Here's an example of what streaming a single tool call might look like:

1. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "{\"")
2. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "city")
3. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = ""\":\"")
4. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "Mun")
5. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "ich")
6. onPartialToolCall(index = 0, id = "call_abc", name = "get_weather", partialArguments = "\"}")
7. onCompleteToolCall(index = 0, id = "call_abc", name = "get_weather", arguments = "{\"city\":\"Munich\"}")

If the model decides to call multiple tools, the index will increment, allowing you to correlate.

Please note that not all LLM providers stream tool calls token by token. Some providers (e.g., Bedrock, Google, Mistral, Ollama) return only complete tool calls. In those cases, this callback won't be invoked - only StreamingChatResponseHandler.onCompleteToolCall(CompleteToolCall) will be called.

Either this or the StreamingChatResponseHandler.onPartialToolCall(PartialToolCall) method should be implemented if you want to consume partial tool calls as soon as they become available.

Specified by:

onPartialToolCall in interface StreamingChatResponseHandler

Parameters:

partialToolCall - A partial tool call that contains the index, tool ID, tool name and partial arguments.

context - A partial tool call context. Contains a StreamingHandle that can be used to cancel streaming.

See Also:

• StreamingChatResponseHandler.onPartialToolCall(PartialToolCall)

onCompleteToolCall

public void onCompleteToolCall(CompleteToolCall completeToolCall)

Description copied from interface: StreamingChatResponseHandler

Invoked when the model has finished streaming a single tool call.

Specified by:

onCompleteToolCall in interface StreamingChatResponseHandler

Parameters:

completeToolCall - A complete tool call that contains the index, tool ID, tool name, and fully assembled arguments.

onUnmappedRawEvent

public void onUnmappedRawEvent(Object rawEvent)

Description copied from interface: StreamingChatResponseHandler

Invoked when a provider emits a raw streaming event that is not already exposed through one of the typed callbacks (such as StreamingChatResponseHandler.onPartialResponse(PartialResponse, PartialResponseContext), StreamingChatResponseHandler.onPartialThinking(PartialThinking, PartialThinkingContext), StreamingChatResponseHandler.onPartialToolCall(PartialToolCall, PartialToolCallContext) or StreamingChatResponseHandler.onCompleteToolCall(CompleteToolCall)).

This acts as an escape hatch for provider-specific events that langchain4j does not model, such as server-tool lifecycle events (e.g., OpenAI's web_search_call.in_progress). Events that are already delivered as partial responses, thinking or tool calls are not repeated here.

The event type depends on the provider implementation. Implementations using the dev.langchain4j.http.client.HttpClient abstraction (e.g., OpenAI, Anthropic, Google AI Gemini) typically expose ServerSentEvent; other implementations can expose provider-specific event objects (e.g., the OpenAI official Responses model exposes the SDK's ResponseStreamEvent).

Specified by:

onUnmappedRawEvent in interface StreamingChatResponseHandler

Parameters:

rawEvent - A raw provider streaming event.

onCompleteResponse

public void onCompleteResponse(ChatResponse completeResponse)

Description copied from interface: StreamingChatResponseHandler

Invoked when the model has finished streaming a response.

Specified by:

onCompleteResponse in interface StreamingChatResponseHandler

Parameters:

completeResponse - The complete response generated by the model, containing all assembled partial text and tool calls.

onError

public void onError(Throwable error)

Description copied from interface: StreamingChatResponseHandler

This method is invoked when an error occurs during streaming.

Specified by:

onError in interface StreamingChatResponseHandler

Parameters:

error - The error that occurred