Migrate Vearch from Gson to Jackson (#1706)

## Issue
Closes #1680 

## Change
Migrate Vearch from Gson to Jackson

## 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)
- [ ] I have added/updated [Spring Boot
starter(s)](https://github.com/langchain4j/langchain4j-spring) (if
applicable)

langchain4j-vearch/pom.xml

@@ -30,7 +30,7 @@
 
         <dependency>
             <groupId>com.squareup.retrofit2</groupId>
-            <artifactId>converter-gson</artifactId>
+            <artifactId>converter-jackson</artifactId>
         </dependency>
 
         <!-- DEPENDENCY CONFLICT RESOLUTION FOR OKHTTP (START) -->

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/BulkRequest.java

@@ -1,5 +1,9 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
@@ -7,10 +11,23 @@ import lombok.Setter;
 import java.util.List;
 import java.util.Map;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class BulkRequest {
 
     private List<Map<String, Object>> documents;
+
+    BulkRequest() {
+
+    }
+
+    BulkRequest(List<Map<String, Object>> documents) {
+        this.documents = documents;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/BulkResponse.java

@@ -1,17 +1,34 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import com.google.gson.annotations.SerializedName;
-import lombok.Builder;
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
-@Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class BulkResponse {
 
     private Integer status;
     private String error;
-    @SerializedName("_id")
+    @JsonProperty("_id")
     private String id;
+
+    BulkResponse() {
+
+    }
+
+    BulkResponse(Integer status, String error, String id) {
+        this.status = status;
+        this.error = error;
+        this.id = id;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/CreateDatabaseRequest.java

@@ -1,13 +1,30 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class CreateDatabaseRequest {
 
     private String name;
+
+    CreateDatabaseRequest() {
+
+    }
+
+    CreateDatabaseRequest(String name) {
+        this.name = name;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/CreateDatabaseResponse.java

@@ -1,14 +1,30 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import lombok.Builder;
+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.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
-@Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class CreateDatabaseResponse {
 
     private Long id;
     private String name;
+
+    CreateDatabaseResponse() {
+
+    }
+
+    CreateDatabaseResponse(Long id, String name) {
+        this.id = id;
+        this.name = name;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/CreateSpaceRequest.java

@@ -1,8 +1,9 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import dev.langchain4j.store.embedding.vearch.ModelParam;
-import dev.langchain4j.store.embedding.vearch.SpaceEngine;
-import dev.langchain4j.store.embedding.vearch.SpacePropertyParam;
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
@@ -10,9 +11,14 @@ import lombok.Setter;
 import java.util.List;
 import java.util.Map;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class CreateSpaceRequest {
 
     private String name;
@@ -21,4 +27,17 @@ class CreateSpaceRequest {
     private SpaceEngine engine;
     private Map<String, SpacePropertyParam> properties;
     private List<ModelParam> models;
+
+    CreateSpaceRequest() {
+
+    }
+
+    CreateSpaceRequest(String name, Integer partitionNum, Integer replicaNum, SpaceEngine engine, Map<String, SpacePropertyParam> properties, List<ModelParam> models) {
+        this.name = name;
+        this.partitionNum = partitionNum;
+        this.replicaNum = replicaNum;
+        this.engine = engine;
+        this.properties = properties;
+        this.models = models;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/CreateSpaceResponse.java

@@ -1,14 +1,30 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import lombok.Builder;
+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.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
-@Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class CreateSpaceResponse {
 
     private Integer id;
     private String name;
+
+    CreateSpaceResponse() {
+
+    }
+
+    CreateSpaceResponse(Integer id, String name) {
+        this.id = id;
+        this.name = name;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/ListDatabaseResponse.java

@@ -1,14 +1,30 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import lombok.Builder;
+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.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
-@Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class ListDatabaseResponse {
 
     private Integer id;
     private String name;
+
+    ListDatabaseResponse() {
+
+    }
+
+    ListDatabaseResponse(Integer id, String name) {
+        this.id = id;
+        this.name = name;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/ListSpaceResponse.java

@@ -1,14 +1,30 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import lombok.Builder;
+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.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
-@Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public class ListSpaceResponse {
 
     private Integer id;
     private String name;
+
+    ListSpaceResponse() {
+
+    }
+
+    ListSpaceResponse(Integer id, String name) {
+        this.id = id;
+        this.name = name;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/MetricType.java

@@ -1,6 +1,6 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import com.google.gson.annotations.SerializedName;
+import com.fasterxml.jackson.annotation.JsonProperty;
 
 /**
  * if metric type is not set when searching, it will use the parameter specified when building the space
@@ -12,6 +12,6 @@ public enum MetricType {
     /**
      * Inner Product
      */
-    @SerializedName("InnerProduct")
+    @JsonProperty("InnerProduct")
     INNER_PRODUCT
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/ModelParam.java

@@ -1,17 +1,36 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
 
 import java.util.List;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public class ModelParam {
 
     private String modelId;
     private List<String> fields;
     private String out;
+
+    ModelParam() {
+
+    }
+
+    ModelParam(String modelId, List<String> fields, String out) {
+        this.modelId = modelId;
+        this.fields = fields;
+        this.out = out;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/ResponseWrapper.java

@@ -1,15 +1,34 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class ResponseWrapper<T> {
 
     private Integer code;
     private String msg;
     private T data;
+
+    ResponseWrapper() {
+
+    }
+
+    ResponseWrapper(Integer code, String msg, T data) {
+        this.code = code;
+        this.msg = msg;
+        this.data = data;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/RetrievalParam.java

@@ -1,20 +1,35 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import com.google.gson.annotations.SerializedName;
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 /**
  * As a constraint of all engine type only
  *
  * @see RetrievalType
  */
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public abstract class RetrievalParam {
 
+    protected RetrievalParam() {
+
+    }
+
     @Getter
     @Setter
     @Builder
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class IVFPQParam extends RetrievalParam {
 
         @Builder.Default
@@ -31,11 +46,23 @@ public abstract class RetrievalParam {
          * <p>default 64, must be a multiple of 4</p>
          */
         private Integer nsubvector;
+
+        public IVFPQParam() {
+        }
+
+        public IVFPQParam(MetricType metricType, Integer ncentroids, Integer nsubvector) {
+            this.metricType = metricType;
+            this.ncentroids = ncentroids;
+            this.nsubvector = nsubvector;
+        }
     }
 
     @Getter
     @Setter
     @Builder
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class HNSWParam extends RetrievalParam {
 
         @Builder.Default
@@ -52,13 +79,24 @@ public abstract class RetrievalParam {
          * <p>default 40</p>
          * <p>The higher the value, the better the construction effect, and the longer it takes</p>
          */
-        @SerializedName("efConstruction")
         private Integer efConstruction;
+
+        public HNSWParam() {
+        }
+
+        public HNSWParam(MetricType metricType, Integer nlinks, Integer efConstruction) {
+            this.metricType = metricType;
+            this.nlinks = nlinks;
+            this.efConstruction = efConstruction;
+        }
     }
 
     @Getter
     @Setter
     @Builder
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class GPUParam extends RetrievalParam {
 
         @Builder.Default
@@ -75,11 +113,23 @@ public abstract class RetrievalParam {
          * <p>default 64</p>
          */
         private Integer nsubvector;
+
+        public GPUParam() {
+        }
+
+        public GPUParam(MetricType metricType, Integer ncentroids, Integer nsubvector) {
+            this.metricType = metricType;
+            this.ncentroids = ncentroids;
+            this.nsubvector = nsubvector;
+        }
     }
 
     @Getter
     @Setter
     @Builder
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class IVFFLATParam extends RetrievalParam {
 
         @Builder.Default
@@ -90,6 +140,14 @@ public abstract class RetrievalParam {
          * <p>default 2048</p>
          */
         private Integer ncentroids;
+
+        public IVFFLATParam() {
+        }
+
+        public IVFFLATParam(MetricType metricType, Integer ncentroids) {
+            this.metricType = metricType;
+            this.ncentroids = ncentroids;
+        }
     }
 
     @Getter
@@ -103,6 +161,14 @@ public abstract class RetrievalParam {
          * <p>default 256</p>
          */
         private Integer ncentroids;
+
+        public BINARYIVFParam() {
+
+        }
+
+        public BINARYIVFParam(Integer ncentroids) {
+            this.ncentroids = ncentroids;
+        }
     }
 
     @Getter
@@ -112,5 +178,12 @@ public abstract class RetrievalParam {
 
         @Builder.Default
         private MetricType metricType = MetricType.INNER_PRODUCT;
+
+        public FLAT() {
+        }
+
+        public FLAT(MetricType metricType) {
+            this.metricType = metricType;
+        }
     }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/RetrievalType.java

@@ -1,7 +1,15 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import lombok.Getter;
+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 static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public enum RetrievalType {
 
     IVFPQ(RetrievalParam.IVFPQParam.class),
@@ -11,10 +19,13 @@ public enum RetrievalType {
     BINARYIVF(RetrievalParam.BINARYIVFParam.class),
     FLAT(RetrievalParam.FLAT.class);
 
-    @Getter
-    private Class<? extends RetrievalParam> paramClass;
+    private final Class<? extends RetrievalParam> paramClass;
 
     RetrievalType(Class<? extends RetrievalParam> paramClass) {
         this.paramClass = paramClass;
     }
+
+    public Class<? extends RetrievalParam> getParamClass() {
+        return paramClass;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/SearchRequest.java

@@ -1,35 +1,78 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
 
 import java.util.List;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class SearchRequest {
 
     private QueryParam query;
     private Integer size;
     private List<String> fields;
 
-    @Getter
-    @Setter
-    @Builder
-    public static class QueryParam {
+    SearchRequest() {
 
-        private List<VectorParam> sum;
+    }
+
+    SearchRequest(QueryParam query, Integer size, List<String> fields) {
+        this.query = query;
+        this.size = size;
+        this.fields = fields;
     }
 
     @Getter
     @Setter
     @Builder
-    public static class VectorParam {
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
+    static class QueryParam {
+
+        private List<VectorParam> sum;
+
+        QueryParam() {
+
+        }
+
+        QueryParam(List<VectorParam> sum) {
+            this.sum = sum;
+        }
+    }
+
+    @Getter
+    @Setter
+    @Builder
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
+    static class VectorParam {
 
         private String field;
         private List<Float> feature;
         private Double minScore;
+
+        VectorParam() {
+
+        }
+
+        VectorParam(String field, List<Float> feature, Double minScore) {
+            this.field = field;
+            this.feature = feature;
+            this.minScore = minScore;
+        }
     }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/SearchResponse.java

@@ -1,48 +1,90 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import com.google.gson.annotations.SerializedName;
-import lombok.Builder;
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import lombok.Getter;
 import lombok.Setter;
 
 import java.util.List;
 import java.util.Map;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
-@Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 class SearchResponse {
 
     private Integer took;
-    @SerializedName("timed_out")
+    @JsonProperty("timed_out")
     private Boolean timeout;
     /**
      * not support shards yet
      */
-    @SerializedName("_shards")
+    @JsonProperty("_shards")
     private Object shards;
     private Hit hits;
 
+    SearchResponse() {
+
+    }
+
+    SearchResponse(Integer took, Boolean timeout, Hit hits, Object shards) {
+        this.took = took;
+        this.timeout = timeout;
+        this.hits = hits;
+        this.shards = shards;
+    }
+
     @Getter
     @Setter
-    @Builder
-    public static class Hit {
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
+    static class Hit {
 
         private Integer total;
         private Double maxScore;
         private List<SearchedDocument> hits;
+
+        Hit() {
+
+        }
+
+        Hit(Integer total, Double maxScore, List<SearchedDocument> hits) {
+            this.total = total;
+            this.maxScore = maxScore;
+            this.hits = hits;
+        }
     }
 
     @Getter
     @Setter
-    @Builder
-    public static class SearchedDocument {
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
+    static class SearchedDocument {
 
-        @SerializedName("_id")
+        @JsonProperty("_id")
         private String id;
-        @SerializedName("_score")
+        @JsonProperty("_score")
         private Double score;
-        @SerializedName("_source")
+        @JsonProperty("_source")
         private Map<String, Object> source;
+
+        SearchedDocument() {
+
+        }
+
+        SearchedDocument(String id, Double score, Map<String, Object> source) {
+            this.id = id;
+            this.score = score;
+            this.source = source;
+        }
     }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/SpaceEngine.java

@@ -1,10 +1,19 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public class SpaceEngine {
 
     private String name;
@@ -23,6 +32,10 @@ public class SpaceEngine {
         setRetrievalParam(retrievalParam);
     }
 
+    public static Builder builder() {
+        return new Builder();
+    }
+
     public void setRetrievalParam(RetrievalParam retrievalParam) {
         // do some constraint check
         Class<? extends RetrievalParam> clazz = retrievalType.getParamClass();
@@ -34,10 +47,6 @@ public class SpaceEngine {
         this.retrievalParam = retrievalParam;
     }
 
-    public static Builder builder() {
-        return new Builder();
-    }
-
     public static class Builder {
 
         private String name;

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/SpacePropertyParam.java

@@ -1,14 +1,25 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 /**
  * As a constraint type of all Space property only
  *
  * @see CreateSpaceRequest
  */
+@Getter
+@Setter
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public abstract class SpacePropertyParam {
 
     protected SpacePropertyType type;
@@ -19,6 +30,9 @@ public abstract class SpacePropertyParam {
 
     @Getter
     @Setter
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class StringParam extends SpacePropertyParam {
 
         /**
@@ -44,6 +58,9 @@ public abstract class SpacePropertyParam {
 
     @Getter
     @Setter
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class IntegerParam extends SpacePropertyParam {
 
         /**
@@ -66,6 +83,9 @@ public abstract class SpacePropertyParam {
 
     @Getter
     @Setter
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class FloatParam extends SpacePropertyParam {
 
         /**
@@ -88,6 +108,9 @@ public abstract class SpacePropertyParam {
 
     @Getter
     @Setter
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class VectorParam extends SpacePropertyParam {
 
         private Boolean index;

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/SpacePropertyType.java

@@ -1,26 +1,28 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import com.google.gson.annotations.SerializedName;
-import lombok.Getter;
+import com.fasterxml.jackson.annotation.JsonProperty;
 
 public enum SpacePropertyType {
 
     /**
      * keyword is equivalent to string
      */
-    @SerializedName("string")
+    @JsonProperty("string")
     STRING(SpacePropertyParam.StringParam.class),
-    @SerializedName("integer")
+    @JsonProperty("integer")
     INTEGER(SpacePropertyParam.IntegerParam.class),
-    @SerializedName("float")
+    @JsonProperty("float")
     FLOAT(SpacePropertyParam.FloatParam.class),
-    @SerializedName("vector")
+    @JsonProperty("vector")
     VECTOR(SpacePropertyParam.VectorParam.class);
 
-    @Getter
     private final Class<? extends SpacePropertyParam> paramClass;
 
     SpacePropertyType(Class<? extends SpacePropertyParam> paramClass) {
         this.paramClass = paramClass;
     }
+
+    public Class<? extends SpacePropertyParam> getParamClass() {
+        return paramClass;
+    }
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/SpaceStoreParam.java

@@ -1,12 +1,21 @@
 package dev.langchain4j.store.embedding.vearch;
 
+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.Builder;
 import lombok.Getter;
 import lombok.Setter;
 
+import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
+
 @Getter
 @Setter
 @Builder
+@JsonIgnoreProperties(ignoreUnknown = true)
+@JsonInclude(NON_NULL)
+@JsonNaming(SnakeCaseStrategy.class)
 public class SpaceStoreParam {
 
     /**
@@ -18,6 +27,9 @@ public class SpaceStoreParam {
     @Getter
     @Setter
     @Builder
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(NON_NULL)
+    @JsonNaming(SnakeCaseStrategy.class)
     public static class CompressRate {
 
         private Integer rate;

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/SpaceStoreType.java

@@ -1,14 +1,13 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import com.google.gson.annotations.SerializedName;
-import lombok.Getter;
+import com.fasterxml.jackson.annotation.JsonProperty;
 
 public enum SpaceStoreType {
 
-    @SerializedName("MemoryOnly")
+    @JsonProperty("MemoryOnly")
     MEMORY_ONLY,
-    @SerializedName("Mmap")
+    @JsonProperty("Mmap")
     M_MAP,
-    @SerializedName("RocksDB")
+    @JsonProperty("RocksDB")
     ROCKS_DB
 }

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/VearchApi.java

@@ -6,7 +6,7 @@ import retrofit2.http.*;
 
 import java.util.List;
 
-public interface VearchApi {
+interface VearchApi {
 
     int OK = 200;
 

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/VearchClient.java

@@ -1,7 +1,6 @@
 package dev.langchain4j.store.embedding.vearch;
 
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
+import com.fasterxml.jackson.databind.ObjectMapper;
 import dev.langchain4j.internal.Utils;
 import lombok.Builder;
 import okhttp3.MediaType;
@@ -9,7 +8,7 @@ import okhttp3.OkHttpClient;
 import okhttp3.RequestBody;
 import retrofit2.Response;
 import retrofit2.Retrofit;
-import retrofit2.converter.gson.GsonConverterFactory;
+import retrofit2.converter.jackson.JacksonConverterFactory;
 
 import java.io.IOException;
 import java.time.Duration;
@@ -17,14 +16,12 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import static com.google.gson.FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES;
+import static com.fasterxml.jackson.databind.SerializationFeature.INDENT_OUTPUT;
 import static dev.langchain4j.store.embedding.vearch.VearchApi.OK;
 
 class VearchClient {
 
-    private static final Gson GSON = new GsonBuilder()
-            .setFieldNamingPolicy(LOWER_CASE_WITH_UNDERSCORES)
-            .create();
+    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
 
     private final VearchApi vearchApi;
 
@@ -40,7 +37,7 @@ class VearchClient {
         Retrofit retrofit = new Retrofit.Builder()
                 .baseUrl(Utils.ensureTrailingForwardSlash(baseUrl))
                 .client(okHttpClient)
-                .addConverterFactory(GsonConverterFactory.create(GSON))
+                .addConverterFactory(JacksonConverterFactory.create(OBJECT_MAPPER))
                 .build();
 
         vearchApi = retrofit.create(VearchApi.class);
@@ -133,7 +130,7 @@ class VearchClient {
                         fieldsExceptId.put(fieldName, value);
                     }
                 }
-                bodyString.append(GSON.toJson(fieldsExceptId)).append("\n");
+                bodyString.append(OBJECT_MAPPER.writeValueAsString(fieldsExceptId)).append("\n");
             }
             RequestBody body = RequestBody.create(bodyString.toString(), MediaType.parse("application/json; charset=utf-8"));
             Response<List<BulkResponse>> response = vearchApi.bulk(dbName, spaceName, body).execute();

langchain4j-vearch/src/main/java/dev/langchain4j/store/embedding/vearch/VearchEmbeddingStore.java

@@ -56,44 +56,6 @@ public class VearchEmbeddingStore implements EmbeddingStore<TextSegment> {
         return new Builder();
     }
 
-    public static class Builder {
-
-        private VearchConfig vearchConfig;
-        private String baseUrl;
-        private Duration timeout;
-        private Boolean normalizeEmbeddings;
-
-        public Builder vearchConfig(VearchConfig vearchConfig) {
-            this.vearchConfig = vearchConfig;
-            return this;
-        }
-
-        public Builder baseUrl(String baseUrl) {
-            this.baseUrl = baseUrl;
-            return this;
-        }
-
-        public Builder timeout(Duration timeout) {
-            this.timeout = timeout;
-            return this;
-        }
-
-        /**
-         * Set whether to normalize embedding when add to embedding store
-         *
-         * @param normalizeEmbeddings whether to normalize embedding when add to embedding store
-         * @return builder
-         */
-        public Builder normalizeEmbeddings(Boolean normalizeEmbeddings) {
-            this.normalizeEmbeddings = normalizeEmbeddings;
-            return this;
-        }
-
-        public VearchEmbeddingStore build() {
-            return new VearchEmbeddingStore(baseUrl, timeout, vearchConfig, normalizeEmbeddings);
-        }
-    }
-
     @Override
     public String add(Embedding embedding) {
         String id = randomUUID();
@@ -284,4 +246,42 @@ public class VearchEmbeddingStore implements EmbeddingStore<TextSegment> {
                 throw new RuntimeException("Unsupported SpacePropertyParam type " + param.type);
         }
     }
+
+    public static class Builder {
+
+        private VearchConfig vearchConfig;
+        private String baseUrl;
+        private Duration timeout;
+        private Boolean normalizeEmbeddings;
+
+        public Builder vearchConfig(VearchConfig vearchConfig) {
+            this.vearchConfig = vearchConfig;
+            return this;
+        }
+
+        public Builder baseUrl(String baseUrl) {
+            this.baseUrl = baseUrl;
+            return this;
+        }
+
+        public Builder timeout(Duration timeout) {
+            this.timeout = timeout;
+            return this;
+        }
+
+        /**
+         * Set whether to normalize embedding when add to embedding store
+         *
+         * @param normalizeEmbeddings whether to normalize embedding when add to embedding store
+         * @return builder
+         */
+        public Builder normalizeEmbeddings(Boolean normalizeEmbeddings) {
+            this.normalizeEmbeddings = normalizeEmbeddings;
+            return this;
+        }
+
+        public VearchEmbeddingStore build() {
+            return new VearchEmbeddingStore(baseUrl, timeout, vearchConfig, normalizeEmbeddings);
+        }
+    }
 }

langchain4j-vearch/src/test/java/dev/langchain4j/store/embedding/vearch/DeleteSpaceLastOrderer.java

@@ -1,32 +0,0 @@
-package dev.langchain4j.store.embedding.vearch;
-
-import org.junit.jupiter.api.MethodOrderer;
-import org.junit.jupiter.api.MethodOrdererContext;
-
-import java.util.ArrayList;
-import java.util.List;
-
-public class DeleteSpaceLastOrderer implements MethodOrderer {
-    @Override
-    public void orderMethods(MethodOrdererContext methodOrdererContext) {
-        // should equal to VearchEmbeddingStoreIT#should_delete_space test name
-        String deleteSpaceTestName = "should_delete_space";
-        List<String> methodNames = new ArrayList<>();
-        methodOrdererContext.getMethodDescriptors().forEach(methodDescriptor -> methodNames.add(methodDescriptor.getMethod().getName()));
-        methodNames.sort((methodName1, methodName2) -> {
-            //
-            if (methodName1.equals(deleteSpaceTestName)) {
-                return 1;
-            } else if (methodName2.equals(deleteSpaceTestName)) {
-                return -1;
-            } else {
-                return 0;
-            }
-        });
-        methodOrdererContext.getMethodDescriptors().sort((md1, md2) -> {
-            int index1 = methodNames.indexOf(md1.getMethod().getName());
-            int index2 = methodNames.indexOf(md2.getMethod().getName());
-            return Integer.compare(index1, index2);
-        });
-    }
-}

langchain4j-vearch/src/test/java/dev/langchain4j/store/embedding/vearch/VearchEmbeddingStoreIT.java

@@ -3,10 +3,12 @@ package dev.langchain4j.store.embedding.vearch;
 import dev.langchain4j.data.document.Metadata;
 import dev.langchain4j.data.embedding.Embedding;
 import dev.langchain4j.data.segment.TextSegment;
-import dev.langchain4j.model.embedding.onnx.allminilml6v2q.AllMiniLmL6V2QuantizedEmbeddingModel;
 import dev.langchain4j.model.embedding.EmbeddingModel;
+import dev.langchain4j.model.embedding.onnx.allminilml6v2q.AllMiniLmL6V2QuantizedEmbeddingModel;
 import dev.langchain4j.store.embedding.*;
-import org.junit.jupiter.api.*;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInfo;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.wait.strategy.Wait;
 import org.testcontainers.junit.jupiter.Container;