Fix suggestion classes for Term, Phrase, and Completion.

CHANGELOG.md

@@ -23,6 +23,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ### Fixed
 - Fix version and build ([#254](https://github.com/opensearch-project/opensearch-java/pull/254))
+- Fixed Suggesters for Completion, Term, and Phrase and refactored the Suggestion class ([#477](https://github.com/opensearch-project/opensearch-java/pull/477))
 
 ### Security
 

USER_GUIDE.md

@@ -11,6 +11,11 @@
   - [Search for the documents](#search-for-the-documents)
     - [Get raw JSON results](#get-raw-json-results)
   - [Search documents using a match query](#search-documents-using-a-match-query)
+  - [Search documents using suggesters](#search-documents-using-suggesters)
+    - [App Data class](#app-data-class)
+    - [Using completion suggester](#using-completion-suggester)
+    - [Using term suggester](#using-term-suggester)
+    - [Using phrase suggester](#using-phrase-suggester)
   - [Bulk requests](#bulk-requests)
   - [Aggregations](#aggregations)
   - [Delete the document](#delete-the-document)
@@ -169,6 +174,243 @@ for (int i = 0; i < searchResponse.hits().hits().size(); i++) {
 }
 ```
 
+## Search documents using suggesters
+
+### App Data class
+
+```java
+public static class AppData {
+
+    private int intValue;
+    private String msg;
+
+    public int getIntValue() {
+        return intValue;
+    }
+
+    public void setIntValue(int intValue) {
+        this.intValue = intValue;
+    }
+
+    public String getMsg() {
+        return msg;
+    }
+
+    public void setMsg(String msg) {
+        this.msg = msg;
+    }
+}
+```
+
+### Using completion suggester
+
+```java
+String index = "completion-suggester";
+
+Property intValueProp = new Property.Builder()
+                .long_(v -> v)
+                .build();
+Property msgCompletionProp = new Property.Builder()
+                .completion(c -> c)
+                .build();
+client.indices().create(c -> c
+                .index(index)
+                .mappings(m -> m
+                                .properties("intValue", intValueProp)
+                                .properties("msg", msgCompletionProp)));
+
+AppData appData = new AppData();
+appData.setIntValue(1337);
+appData.setMsg("foo");
+
+client.index(b -> b
+                .index(index)
+                .id("1")
+                .document(appData)
+                .refresh(Refresh.True));
+
+appData.setIntValue(1338);
+appData.setMsg("foobar");
+
+client.index(b -> b
+                .index(index)
+                .id("2")
+                .document(appData)
+                .refresh(Refresh.True));
+
+String suggesterName = "msgSuggester";
+
+CompletionSuggester completionSuggester = FieldSuggesterBuilders.completion()
+                .field("msg")
+                .size(1)
+                .build();
+FieldSuggester fieldSuggester = new FieldSuggester.Builder().prefix("foo")
+                .completion(completionSuggester)
+                .build();
+Suggester suggester = new Suggester.Builder()
+                .suggesters(Collections.singletonMap(suggesterName, fieldSuggester))
+                .build();
+SearchRequest searchRequest = new SearchRequest.Builder()
+                .index(index)
+                .suggest(suggester)
+                .build();
+
+SearchResponse<AppData> response = client.search(searchRequest, AppData.class);
+```
+
+### Using term suggester
+
+```java
+ String index = "term-suggester";
+
+// term suggester does not require a special mapping
+client.indices().create(c -> c
+                .index(index));
+
+AppData appData = new AppData();
+appData.setIntValue(1337);
+appData.setMsg("foo");
+
+client.index(b -> b
+                .index(index)
+                .id("1")
+                .document(appData)
+                .refresh(Refresh.True));
+
+appData.setIntValue(1338);
+appData.setMsg("foobar");
+
+client.index(b -> b
+                .index(index)
+                .id("2")
+                .document(appData)
+                .refresh(Refresh.True));
+
+String suggesterName = "msgSuggester";
+
+TermSuggester termSuggester = FieldSuggesterBuilders.term()
+                .field("msg")
+                .size(1)
+                .build();
+FieldSuggester fieldSuggester = new FieldSuggester.Builder().text("fool")
+                .term(termSuggester)
+                .build();
+Suggester suggester = new Suggester.Builder()
+                .suggesters(Collections.singletonMap(suggesterName, fieldSuggester))
+                .build();
+SearchRequest searchRequest = new SearchRequest.Builder()
+                .index(index)
+                .suggest(suggester)
+                .build();
+
+SearchResponse<AppData> response = client.search(searchRequest, AppData.class);
+```
+
+### Using phrase suggester
+
+```java
+String index = "phrase-suggester";
+
+String settingsJson = 
+"""
+  {
+    "index": {
+      "analysis": {
+        "analyzer": {
+          "trigram": {
+            "type": "custom",
+            "tokenizer": "standard",
+            "filter": [
+              "lowercase",
+              "shingle"
+            ]
+          }
+        },
+        "filter": {
+          "shingle": {
+            "type": "shingle",
+            "min_shingle_size": 2,
+            "max_shingle_size": 3
+          }
+        }
+      }
+    }
+  }
+""";
+
+String mappingJson =
+"""
+{
+  "properties": {
+    "msg": {
+      "type": "text",
+      "fields": {
+        "trigram": {
+          "type": "text",
+          "analyzer": "trigram"
+        }
+      }
+    }
+  }
+}
+""";
+
+
+    ObjectMapper mapper = new JsonMapper();
+JsonpMapper jsonpMapper = new JacksonJsonpMapper(mapper);
+IndexSettings settings;
+try (JsonParser settingsParser = new JacksonJsonpParser(mapper.createParser(settingsJson))) {
+settings = IndexSettings._DESERIALIZER.deserialize(settingsParser, jsonpMapper);
+}
+
+TypeMapping mapping;
+try (JsonParser mappingParser = new JacksonJsonpParser(mapper.createParser(mappingJson))) {
+mapping = TypeMapping._DESERIALIZER.deserialize(mappingParser, jsonpMapper);
+}
+
+client.indices().create(c -> c
+                .index(index)
+                .settings(settings)
+                .mappings(mapping));
+
+AppData appData = new AppData();
+appData.setIntValue(1337);
+appData.setMsg("Design Patterns");
+
+client.index(b -> b
+                .index(index)
+                .id("1")
+                .document(appData)
+                .refresh(Refresh.True));
+
+appData.setIntValue(1338);
+appData.setMsg("Software Architecture Patterns Explained");
+
+client.index(b -> b
+                .index(index)
+                .id("2")
+                .document(appData)
+                .refresh(Refresh.True));
+
+String suggesterName = "msgSuggester";
+
+PhraseSuggester phraseSuggester = FieldSuggesterBuilders.phrase()
+                .field("msg.trigram")
+                .build();
+FieldSuggester fieldSuggester = new FieldSuggester.Builder().text("design paterns")
+                .phrase(phraseSuggester)
+                .build();
+Suggester suggester = new Suggester.Builder()
+                .suggesters(Collections.singletonMap(suggesterName, fieldSuggester))
+                .build();
+SearchRequest searchRequest = new SearchRequest.Builder()
+                .index(index)
+                .suggest(suggester)
+                .build();
+
+SearchResponse<AppData> response = client.search(searchRequest, AppData.class);
+```
+
 ## Bulk requests
 
 ```java

java-client/build.gradle.kts

@@ -71,6 +71,10 @@ java {
     }
 }
 
+java.sourceSets["test"].java {
+    srcDir("src/test/resources")
+}
+
 tasks.withType<ProcessResources> {
     expand(
         "version" to version,