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fix: Resolve IllegalArgumentException for text MIME types in LangChain4j adapter #1185

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fix: Resolve IllegalArgumentException for text MIME types in LangChain4j adapter #1185

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24 changes: 19 additions & 5 deletions contrib/langchain4j/src/main/java/com/google/adk/models/langchain4j/LangChain4j.java
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,7 @@
import dev.langchain4j.model.output.TokenUsage;
import io.reactivex.rxjava3.core.BackpressureStrategy;
import io.reactivex.rxjava3.core.Flowable;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Base64;
import java.util.HashMap;
Expand Down Expand Up @@ -388,13 +389,12 @@ private List<ChatMessage> toUserOrToolResultMessage(Content content) {
.mimeType(mimeType)
.build());
} else if (mimeType.startsWith("text/")
|| "application/json".equals(mimeType)
|| mimeType.endsWith("+json")
|| mimeType.endsWith("+xml")) {
|| mimeType.startsWith("application/json")
|| mimeType.contains("+json")
|| mimeType.contains("+xml")) {
// TODO are there missing text based mime types?
// TODO should we assume UTF_8?
lc4jContents.add(
TextContent.from(new String(bytes, java.nio.charset.StandardCharsets.UTF_8)));
lc4jContent = TextContent.from(new String(bytes, extractCharset(mimeType)));
}

if (lc4jContent != null) {
Expand All @@ -420,6 +420,20 @@ private List<ChatMessage> toUserOrToolResultMessage(Content content) {
}
}

private Charset extractCharset(String mimeType) {
String charSetString = "charset=";
if (mimeType == null || !mimeType.toLowerCase().contains(charSetString)) {
return java.nio.charset.StandardCharsets.UTF_8;
}
try {
String[] parts = mimeType.toLowerCase().split(charSetString);
String charsetName = parts[1].split(";")[0].trim().replace("\"", "").replace("'", "");
return java.nio.charset.Charset.forName(charsetName);
} catch (IllegalArgumentException e) {
return java.nio.charset.StandardCharsets.UTF_8;
}
}

private AiMessage toAiMessage(Content content) {
List<String> texts = new ArrayList<>();
List<ToolExecutionRequest> toolExecutionRequests = new ArrayList<>();
Expand Down
152 changes: 152 additions & 0 deletions contrib/langchain4j/src/test/java/com/google/adk/models/langchain4j/LangChain4jTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -993,4 +993,156 @@ void testGenerateContentWithNullAiMessageText() {
assertThat(response.content()).isPresent();
assertThat(response.content().get().parts().orElse(List.of())).isEmpty();
}

@Test
@DisplayName("Should parse text/plain inlineData as TextContent without exception")
void testGenerateContentWithTextPlainInlineData() {
final String textPayload = "Hello, plain text.";
final Blob textBlob =
Blob.builder()
.mimeType("text/plain")
.data(textPayload.getBytes(java.nio.charset.StandardCharsets.UTF_8))
.build();
final Part textPart = Part.builder().inlineData(textBlob).build();

final LlmRequest llmRequest =
LlmRequest.builder().contents(List.of(Content.fromParts(textPart))).build();

final ChatResponse chatResponse = mock(ChatResponse.class);
final AiMessage aiMessage = AiMessage.from("Acknowledged.");
when(chatResponse.aiMessage()).thenReturn(aiMessage);
when(chatModel.chat(any(ChatRequest.class))).thenReturn(chatResponse);

langChain4j.generateContent(llmRequest, false).blockingFirst();

final ArgumentCaptor<ChatRequest> requestCaptor = ArgumentCaptor.forClass(ChatRequest.class);
verify(chatModel).chat(requestCaptor.capture());
final ChatRequest capturedRequest = requestCaptor.getValue();

assertThat(capturedRequest.messages()).hasSize(1);
assertThat(capturedRequest.messages().get(0)).isInstanceOf(UserMessage.class);
final UserMessage userMessage = (UserMessage) capturedRequest.messages().get(0);

assertThat(userMessage.contents()).hasSize(1);
assertThat(userMessage.contents().get(0))
.isInstanceOf(dev.langchain4j.data.message.TextContent.class);

final dev.langchain4j.data.message.TextContent textContent =
(dev.langchain4j.data.message.TextContent) userMessage.contents().get(0);
assertThat(textContent.text()).isEqualTo(textPayload);
}

@Test
@DisplayName("Should parse application/json inlineData as TextContent without exception")
void testGenerateContentWithApplicationJsonInlineData() {
final String jsonPayload = "{\"key\":\"value\"}";
final Blob jsonBlob =
Blob.builder()
.mimeType("application/json")
.data(jsonPayload.getBytes(java.nio.charset.StandardCharsets.UTF_8))
.build();
final Part jsonPart = Part.builder().inlineData(jsonBlob).build();

final LlmRequest llmRequest =
LlmRequest.builder().contents(List.of(Content.fromParts(jsonPart))).build();

final ChatResponse chatResponse = mock(ChatResponse.class);
final AiMessage aiMessage = AiMessage.from("Parsed JSON.");
when(chatResponse.aiMessage()).thenReturn(aiMessage);
when(chatModel.chat(any(ChatRequest.class))).thenReturn(chatResponse);

langChain4j.generateContent(llmRequest, false).blockingFirst();

final ArgumentCaptor<ChatRequest> requestCaptor = ArgumentCaptor.forClass(ChatRequest.class);
verify(chatModel).chat(requestCaptor.capture());
final ChatRequest capturedRequest = requestCaptor.getValue();

final UserMessage userMessage = (UserMessage) capturedRequest.messages().get(0);
final dev.langchain4j.data.message.TextContent textContent =
(dev.langchain4j.data.message.TextContent) userMessage.contents().get(0);
assertThat(textContent.text()).isEqualTo(jsonPayload);
}

@Test
@DisplayName(
"Should throw IllegalArgumentException for genuinely unsupported inlineData mime types")
void testGenerateContentWithUnsupportedMimeType() {
final Blob unsupportedBlob =
Blob.builder().mimeType("application/x-yaml").data(new byte[] {1, 2, 3, 4}).build();
final Part unsupportedPart = Part.builder().inlineData(unsupportedBlob).build();

final LlmRequest llmRequest =
LlmRequest.builder().contents(List.of(Content.fromParts(unsupportedPart))).build();

assertThatThrownBy(() -> langChain4j.generateContent(llmRequest, false).blockingFirst())
.isInstanceOf(IllegalArgumentException.class)
.hasMessageContaining("Unknown or unhandled mime type: application/x-yaml");
}

@Test
@DisplayName("Should extract and apply explicit charset from mimeType (e.g., UTF-16)")
void testGenerateContentWithExplicitCharset() {
final String textPayload = "Hello, this is strictly UTF-16 encoded text.";

final byte[] utf16Bytes = textPayload.getBytes(java.nio.charset.StandardCharsets.UTF_16);

final Blob textBlob =
Blob.builder().mimeType("text/plain; charset=utf-16").data(utf16Bytes).build();
final Part textPart = Part.builder().inlineData(textBlob).build();

final LlmRequest llmRequest =
LlmRequest.builder().contents(List.of(Content.fromParts(textPart))).build();

final ChatResponse chatResponse = mock(ChatResponse.class);
final AiMessage aiMessage = AiMessage.from("Acknowledged.");
when(chatResponse.aiMessage()).thenReturn(aiMessage);
when(chatModel.chat(any(ChatRequest.class))).thenReturn(chatResponse);

langChain4j.generateContent(llmRequest, false).blockingFirst();

final ArgumentCaptor<ChatRequest> requestCaptor = ArgumentCaptor.forClass(ChatRequest.class);
verify(chatModel).chat(requestCaptor.capture());
final ChatRequest capturedRequest = requestCaptor.getValue();

final UserMessage userMessage = (UserMessage) capturedRequest.messages().get(0);
final dev.langchain4j.data.message.TextContent textContent =
(dev.langchain4j.data.message.TextContent) userMessage.contents().get(0);

assertThat(textContent.text()).isEqualTo(textPayload);
}

@Test
@DisplayName("Should safely fallback to UTF-8 if provided charset is malformed or unsupported")
void testGenerateContentWithMalformedCharsetFallback() {
final String textPayload = "{\"status\": \"fallback to UTF-8 successful\"}";

final byte[] utf8Bytes = textPayload.getBytes(java.nio.charset.StandardCharsets.UTF_8);

final Blob jsonBlob =
Blob.builder()
.mimeType("application/json; charset=not-a-real-charset-12345")
.data(utf8Bytes)
.build();
final Part jsonPart = Part.builder().inlineData(jsonBlob).build();

final LlmRequest llmRequest =
LlmRequest.builder().contents(List.of(Content.fromParts(jsonPart))).build();

final ChatResponse chatResponse = mock(ChatResponse.class);
final AiMessage aiMessage = AiMessage.from("Fallback verified.");
when(chatResponse.aiMessage()).thenReturn(aiMessage);
when(chatModel.chat(any(ChatRequest.class))).thenReturn(chatResponse);

langChain4j.generateContent(llmRequest, false).blockingFirst();

final ArgumentCaptor<ChatRequest> requestCaptor = ArgumentCaptor.forClass(ChatRequest.class);
verify(chatModel).chat(requestCaptor.capture());
final ChatRequest capturedRequest = requestCaptor.getValue();

final UserMessage userMessage = (UserMessage) capturedRequest.messages().get(0);
final dev.langchain4j.data.message.TextContent textContent =
(dev.langchain4j.data.message.TextContent) userMessage.contents().get(0);

assertThat(textContent.text()).isEqualTo(textPayload);
}
}