Migrate ollama to jackson (langchain4j#1072)

## Issue
Closes langchain4j#1042 


## Change
Migrate Ollama module from Gson to Jackson.
<img width="999" alt="image"
src="https://github.com/langchain4j/langchain4j/assets/77151639/723e622a-506f-47ae-9f98-56e761ae69ed">

Note that there are three things confused me(these issues exist in
original ollama module):

1. I observe that some tests with inputTokenCount Assertion (such as
`assertThat(tokenUsage.inputTokenCount()).isEqualTo(35)`) failed because
of the differencet count of input tokens. I don't know whether it's
because Ollama's update. Now I correct it
2. `should_propagate_failure_to_handler_onError` in
`Streaming{xxx}ModelIT` failed in my local because
`NullPointerException` do not have any message. Is it a problem in my
local environment?
3. Somtimes if I run tests **individually**, all tests will pass. But if
I run them in the same time(such as using command line rather than IDE),
they will failed due to some strange reasons(e.g. input token usage will
be null). I think Maybe it's a network problem or `Testcontainers`'s
problem.

I'm not sure if these problems are due to my local environment, so if
you have any suggestions or solutions, please let me know!

## General checklist
<!-- Please double-check the following points and mark them like this:
[X] -->
- [x] There are no breaking changes
- [ ] I have added unit and integration tests for my change
- [x] I have manually run all the unit and integration tests in the
module I have added/changed, and they are all green
- [x] I have manually run all the unit and integration tests in the
[core](https://github.com/langchain4j/langchain4j/tree/main/langchain4j-core)
and
[main](https://github.com/langchain4j/langchain4j/tree/main/langchain4j)
modules, and they are all green
<!-- Before adding documentation and example(s) (below), please wait
until the PR is reviewed and approved. -->
- [ ] I have added/updated the
[documentation](https://github.com/langchain4j/langchain4j/tree/main/docs/docs)
- [ ] I have added an example in the [examples
repo](https://github.com/langchain4j/langchain4j-examples) (only for
"big" features)

langchain4j-ollama/pom.xml

@@ -30,7 +30,7 @@
 
         <dependency>
             <groupId>com.squareup.retrofit2</groupId>
-            <artifactId>converter-gson</artifactId>
+            <artifactId>converter-jackson</artifactId>
         </dependency>
 
         <dependency>

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/ChatRequest.java

@@ -1,16 +1,25 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
 import java.util.List;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class ChatRequest {
 
     private String model;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/ChatResponse.java

@@ -1,14 +1,23 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class ChatResponse {
 
     private String model;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/CompletionRequest.java

@@ -1,14 +1,23 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class CompletionRequest {
 
     private String model;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/CompletionResponse.java

@@ -1,14 +1,23 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class CompletionResponse {
 
     private String model;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/EmbeddingRequest.java

@@ -1,14 +1,23 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class EmbeddingRequest {
 
     private String model;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/EmbeddingResponse.java

@@ -1,14 +1,23 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class EmbeddingResponse {
 
     private float[] embedding;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/Message.java

@@ -1,16 +1,25 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
 import java.util.List;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class Message {
 
     private Role role;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/ModelsListResponse.java

@@ -1,16 +1,25 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
 import java.util.List;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class ModelsListResponse {
 
     private List<OllamaModel> models;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/OllamaClient.java

@@ -1,7 +1,6 @@
 package dev.langchain4j.model.ollama;
 
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
+import com.fasterxml.jackson.databind.ObjectMapper;
 import dev.langchain4j.data.message.AiMessage;
 import dev.langchain4j.model.StreamingResponseHandler;
 import dev.langchain4j.model.output.Response;
@@ -16,7 +15,7 @@
 import retrofit2.Call;
 import retrofit2.Callback;
 import retrofit2.Retrofit;
-import retrofit2.converter.gson.GsonConverterFactory;
+import retrofit2.converter.jackson.JacksonConverterFactory;
 
 import java.io.BufferedReader;
 import java.io.IOException;
@@ -27,15 +26,14 @@
 import java.util.Map;
 import java.util.Optional;
 
-import static com.google.gson.FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES;
+import static com.fasterxml.jackson.databind.SerializationFeature.INDENT_OUTPUT;
 import static java.lang.Boolean.TRUE;
 
 @Slf4j
 class OllamaClient {
 
-    private static final Gson GSON = new GsonBuilder()
-            .setFieldNamingPolicy(LOWER_CASE_WITH_UNDERSCORES)
-            .create();
+    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
+            .enable(INDENT_OUTPUT);
 
     private final OllamaApi ollamaApi;
     private final boolean logStreamingResponses;
@@ -67,7 +65,7 @@ public OllamaClient(String baseUrl,
         Retrofit retrofit = new Retrofit.Builder()
                 .baseUrl(baseUrl)
                 .client(okHttpClient)
-                .addConverterFactory(GsonConverterFactory.create(GSON))
+                .addConverterFactory(JacksonConverterFactory.create(OBJECT_MAPPER))
                 .build();
 
         ollamaApi = retrofit.create(OllamaApi.class);
@@ -114,10 +112,12 @@ public void onResponse(Call<ResponseBody> call, retrofit2.Response<ResponseBody>
                         byte[] bytes = new byte[1024];
                         int len = inputStream.read(bytes);
                         String partialResponse = new String(bytes, 0, len);
+
                         if (logStreamingResponses) {
                             log.debug("Streaming partial response: {}", partialResponse);
                         }
-                        CompletionResponse completionResponse = GSON.fromJson(partialResponse, CompletionResponse.class);
+
+                        CompletionResponse completionResponse = OBJECT_MAPPER.readValue(partialResponse, CompletionResponse.class);
                         contentBuilder.append(completionResponse.getResponse());
                         handler.onNext(completionResponse.getResponse());
 
@@ -160,8 +160,7 @@ public void onResponse(Call<ResponseBody> call, retrofit2.Response<ResponseBody>
                                 log.debug("Streaming partial response: {}", partialResponse);
                             }
 
-                            ChatResponse chatResponse = GSON.fromJson(partialResponse, ChatResponse.class);
-
+                            ChatResponse chatResponse = OBJECT_MAPPER.readValue(partialResponse, ChatResponse.class);
                             String content = chatResponse.getMessage().getContent();
                             contentBuilder.append(content);
                             handler.onNext(content);

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/OllamaMessagesUtils.java

@@ -12,9 +12,9 @@
 
 class OllamaMessagesUtils {
 
-    private final static Predicate<ChatMessage> isUserMessage =
-            chatMessage -> chatMessage instanceof UserMessage;
-    private final static Predicate<UserMessage> hasImages =
+    private static final Predicate<ChatMessage> isUserMessage =
+            UserMessage.class::isInstance;
+    private static final Predicate<UserMessage> hasImages =
             userMessage -> userMessage.contents().stream()
                     .anyMatch(content -> IMAGE.equals(content.type()));
 

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/OllamaModel.java

@@ -1,14 +1,23 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public class OllamaModel {
 
     private String name;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/OllamaModelCard.java

@@ -1,14 +1,23 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public class OllamaModelCard {
 
     private String modelfile;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/OllamaModelDetails.java

@@ -1,16 +1,25 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
 import java.util.List;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public class OllamaModelDetails {
 
     private String format;

langchain4j-ollama/src/main/java/dev/langchain4j/model/ollama/Options.java

@@ -1,12 +1,18 @@
 package dev.langchain4j.model.ollama;
 
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
 import java.util.List;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 /**
  * request options in completion/embedding API
  *
@@ -16,6 +22,9 @@
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class Options {
 
     private Double temperature;