SUBMARINE-1349. Fix the syntax error reported in sonarcloud and add init value for apiversion in XGboostjobList.java

### What is this PR for?

1. Fix the syntax error reported in sonarcloud
2. Add init value for apiversion in XGboostjobList.java
3. change the following class to a singleton, [ModelVersionService.java](https://github.com/apache/submarine/pull/1020/files#diff-0b498de1dff04b42428e969cc3e0fb1376b75b9f33db4ae8d9740c7e1a2e43be), [RegisteredModelService.java](https://github.com/apache/submarine/pull/1020/files#diff-5894fdc7eea50e5065c43846308e16847562089db57b207ea23ceef86c639668),[RegisteredModelTagService.java](https://github.com/apache/submarine/pull/1020/files#diff-56494d2d82488701eb8e3738e8ff3835a27e7f5add8c9d3421ee35e4e2b09661), and the managers used thems.

### What type of PR is it?
Bug Fix

### Todos
* [ ] - Task

### What is the Jira issue?
[SUBMARINE-1349](https://issues.apache.org/jira/browse/SUBMARINE-1349)
### How should this be tested?
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* Strongly recommended: add automated unit tests for any new or changed behavior
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### Screenshots (if appropriate)

### Questions:
* Do the license files need updating? No
* Are there breaking changes for older versions? No
* Does this need new documentation? No

Author: HH <hhcs9527@gmail.com>

Signed-off-by: cdmikechen <cdmikechen@apache.org>

Closes #1020 from hhcs9527/SUBMARINE-1349 and squashes the following commits:

fad6b5a [HH] SUBMARINE-1349. export localhost for CI .
f73915e [HH] SUBMARINE-1349. Change the minio client initialization to local host when clientTest.
725b978 [HH] SUBMARINE-1349. Remove indentdent.
f0263c8 [HH] SUBMARINE-1349. Add BeforeClass to change submarine endpoint before testing.
64f9b4f [HH] SUBMARINE-1349. Change the enum class for singleton and add unit-test to cover it.
bf4918a [HH] SUBMARINE-1349. Fix check error by re-uesing get Instance, since the usage of conf may be used in both staitc and non-static.
fc16e0d [HH] SUBMARINE-1349. Fix check error by remove the static when declaring SubmarineConfiguration conf.
2d29e99 [HH] SUBMARINE-1349. Fix check error.
cc4365b [HH] SUBMARINE-1349. Fix check error.
c513613 [HH] SUBMARINE-1349. Fix check error.
b1ccac1 [HH] SUBMARINE-1349. Fix check error.
3893d01 [HH] SUBMARINE-1349. Change the Client to be singleton with enum class.
0e95639 [HH] SUBMARINE-1349. Fix for the style check.
eaccfbc [HH] SUBMARINE-1349. Fix for the style check.
8ab7029 [HH] SUBMARINE-1349. Fix for the style check.
6b3b311 [HH] SUBMARINE-1349. Fix the syntax error reported in sonarcloud, add init value for kind in XGboostjobList.java and make some class to be singleton.
5f756bc [HH] SUBMARINE-1349. Fix the syntax error reported in sonarcloud and add init value for apiversion in XGboostjobList.java

Author: hhcs9527

.github/workflows/master.yml

@@ -436,6 +436,7 @@ jobs:
           TEST_MODULES: "-pl :submarine-server-core"
         run: |
           echo ">>> mvn $TEST_FLAG $TEST_MODULES -B"
+          export SUBMARINE_S3_ENDPOINT=http://localhost:9000
           mvn $TEST_FLAG $TEST_MODULES -B
       - name: Build submarine-serve
         env:

submarine-server/server-core/src/main/java/org/apache/submarine/server/manager/ModelManager.java

@@ -56,13 +56,13 @@ private ModelManager(Submitter submitter, ModelVersionService modelVersionServic
    *
    * @return object
    */
+  private static class ModelManagerHolder {
+    private static ModelManager manager = new ModelManager(SubmitterManager.loadSubmitter(),
+                                                            ModelVersionService.getInstance());
+  }
+
   public static ModelManager getInstance() {
-    if (manager == null) {
-      synchronized (ModelManager.class) {
-        manager = new ModelManager(SubmitterManager.loadSubmitter(), new ModelVersionService());
-      }
-    }
-    return manager;
+    return ModelManager.ModelManagerHolder.manager;
   }
 
   /**
@@ -141,7 +141,7 @@ private void setServeInfo(ServeSpec spec, ModelVersionEntity modelVersion){
   }
 
   private void transferDescription(ServeSpec spec) {
-    Client s3Client = new Client();
+    Client s3Client = Client.getInstance();
     String modelUniquePath = String.format("%s-%d-%s",
         spec.getModelName(), spec.getModelVersion(), spec.getModelId());
     String res  = new String(s3Client.downloadArtifact(String.format("registry/%s/%s/%d/description.json",

submarine-server/server-core/src/main/java/org/apache/submarine/server/manager/ModelVersionManager.java

@@ -50,16 +50,14 @@ public class ModelVersionManager {
    *
    * @return object
    */
+  private static class ModelVersionManagerHolder {
+    private static ModelVersionManager manager = new ModelVersionManager(ModelVersionService.getInstance(),
+                                                                        new ModelVersionTagService(),
+                                                                        Client.getInstance());
+  }
+
   public static ModelVersionManager getInstance() {
-    if (manager == null) {
-      synchronized (ModelVersionManager.class) {
-        if (manager == null) {
-          manager = new ModelVersionManager(new ModelVersionService(), new ModelVersionTagService(),
-            new Client());
-        }
-      }
-    }
-    return manager;
+    return ModelVersionManager.ModelVersionManagerHolder.manager;
   }
 
   @VisibleForTesting

submarine-server/server-core/src/main/java/org/apache/submarine/server/manager/RegisteredModelManager.java

@@ -37,7 +37,6 @@
  * Registered model manager.
  */
 public class RegisteredModelManager {
-  private static RegisteredModelManager manager;
   /* Registered model service */
   private final RegisteredModelService registeredModelService;
 
@@ -54,16 +53,17 @@ public class RegisteredModelManager {
    *
    * @return object
    */
+
+  private static class RegisteredModelManagerHolder {
+    private static RegisteredModelManager manager = new RegisteredModelManager(
+                                                          RegisteredModelService.getInstance(),
+                                                          ModelVersionService.getInstance(),
+                                                          RegisteredModelTagService.getInstance(),
+                                                          Client.getInstance());
+  }
+
   public static RegisteredModelManager getInstance() {
-    if (manager == null) {
-      synchronized (RegisteredModelManager.class) {
-        if (manager == null) {
-          manager = new RegisteredModelManager(new RegisteredModelService(), new ModelVersionService(),
-              new RegisteredModelTagService(), new Client());
-        }
-      }
-    }
-    return manager;
+    return RegisteredModelManager.RegisteredModelManagerHolder.manager;
   }
 
   @VisibleForTesting

submarine-server/server-core/src/main/java/org/apache/submarine/server/rest/ExperimentRestApi.java

@@ -58,7 +58,7 @@
 @Produces({MediaType.APPLICATION_JSON + "; " + RestConstants.CHARSET_UTF8})
 public class ExperimentRestApi {
   private ExperimentManager experimentManager = ExperimentManager.getInstance();
-  private final Client minioClient = new Client();
+  private final Client minioClient = Client.getInstance();
 
   @VisibleForTesting
   public void setExperimentManager(ExperimentManager experimentManager) {

submarine-server/server-core/src/main/java/org/apache/submarine/server/s3/Client.java

@@ -45,30 +45,26 @@
 /**
  * S3(Minio) default client
  */
-public class Client {
-
-  /* minio client */
-  public MinioClient minioClient;
+public enum Client {
+  INSTANCE(SubmarineConfiguration.getInstance().getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_ENDPOINT));
 
   /* submarine config */
-  private static final SubmarineConfiguration conf = SubmarineConfiguration.getInstance();
-
-  public Client() {
-    minioClient = MinioClient.builder()
-        .endpoint(conf.getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_ENDPOINT))
-        .credentials(
-            conf.getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_ACCESS_KEY_ID),
-            conf.getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_SECRET_ACCESS_KEY)
-        ).build();
+  private final SubmarineConfiguration conf = SubmarineConfiguration.getInstance();
+
+  /* minio client */
+  private final MinioClient minioClient;
+
+  Client(String endpoint) {
+    this.minioClient =  MinioClient.builder()
+                        .endpoint(endpoint)
+                        .credentials(
+                          conf.getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_ACCESS_KEY_ID),
+                          conf.getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_SECRET_ACCESS_KEY)
+                        ).build();
   }
 
-  public Client(String endpoint) {
-    minioClient = MinioClient.builder()
-        .endpoint(endpoint)
-        .credentials(
-            conf.getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_ACCESS_KEY_ID),
-            conf.getString(SubmarineConfVars.ConfVars.SUBMARINE_S3_SECRET_ACCESS_KEY)
-        ).build();
+  public static Client getInstance() {
+    return INSTANCE;
   }
 
   /**

submarine-server/server-core/src/test/java/org/apache/submarine/server/rest/ModelVersionRestApiTest.java

@@ -55,9 +55,9 @@ public class ModelVersionRestApiTest {
   private final String modelVersionModelType = "experiment_123";
   private final String modelVersionTag = "testTag";
 
-  private final RegisteredModelService registeredModelService = new RegisteredModelService();
+  private final RegisteredModelService registeredModelService = RegisteredModelService.getInstance();
 
-  private final ModelVersionService modelVersionService = new ModelVersionService();
+  private final ModelVersionService modelVersionService = ModelVersionService.getInstance();
 
   private static final GsonBuilder gsonBuilder = new GsonBuilder()
       .registerTypeAdapter(ExperimentId.class, new ExperimentIdSerializer())

submarine-server/server-core/src/test/java/org/apache/submarine/server/rest/RegisteredModelRestApiTest.java

@@ -39,7 +39,7 @@
 import org.apache.submarine.server.utils.gson.ExperimentIdSerializer;
 
 public class RegisteredModelRestApiTest {
-  private final RegisteredModelService registeredModelService = new RegisteredModelService();
+  private final RegisteredModelService registeredModelService = RegisteredModelService.getInstance();
   private final String registeredModelName = "testRegisteredModel";
   private final String newRegisteredModelName = "newTestRegisteredModel";
   private final String registeredModelDescription = "test registered model description";

submarine-server/server-core/src/test/java/org/apache/submarine/server/s3/ClientTest.java

@@ -19,22 +19,33 @@
 
 package org.apache.submarine.server.s3;
 
+import org.apache.submarine.commons.utils.SubmarineConfVars;
+import org.apache.submarine.commons.utils.SubmarineConfiguration;
+
+import org.junit.BeforeClass;
 import org.junit.After;
-import org.junit.Assert;
 import org.junit.Test;
+import org.junit.Assert;
 
 import java.util.List;
 
 
 public class ClientTest {
-  private final Client client = new Client("http://localhost:9000");
+  private static Client client;
   private final String testExperimentId = "experiment-sample";
 
   @After
   public void cleanAll() {
     client.deleteAllArtifacts();
   }
 
+  @BeforeClass
+  public static void init() {
+    SubmarineConfiguration conf = SubmarineConfiguration.getInstance();
+    conf.setString(SubmarineConfVars.ConfVars.SUBMARINE_S3_ENDPOINT, "http://localhost:9000");
+    client = Client.getInstance();
+  }
+
   @Test
   public void testLogArtifactAndDownloadArtifact() {
     String path = "sample_folder/sample_file";
@@ -79,4 +90,10 @@ public void testCopyObject() {
     response = client.downloadArtifact(copyPath);
     Assert.assertArrayEquals(content, response);
   }
+
+  @Test
+  public void testSingleton() {
+    Client testClient = Client.getInstance();
+    Assert.assertEquals(testClient, client);
+  }
 }

submarine-server/server-database/src/main/java/org/apache/submarine/server/database/model/service/ModelVersionService.java

@@ -30,6 +30,13 @@
 import java.util.List;
 
 public class ModelVersionService {
+  private static class ModelVersionServiceHolder {
+    private static ModelVersionService service = new ModelVersionService();
+  }
+
+  public static ModelVersionService getInstance() {
+    return ModelVersionService.ModelVersionServiceHolder.service;
+  }
 
   private static final Logger LOG = LoggerFactory.getLogger(ModelVersionService.class);
 

submarine-server/server-database/src/main/java/org/apache/submarine/server/database/model/service/RegisteredModelService.java

@@ -31,6 +31,14 @@
 
 public class RegisteredModelService {
 
+  private static class RegisteredModelServiceHolder {
+    private static RegisteredModelService service = new RegisteredModelService();
+  }
+
+  public static RegisteredModelService getInstance() {
+    return RegisteredModelService.RegisteredModelServiceHolder.service;
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(RegisteredModelService.class);
 
   public List<RegisteredModelEntity> selectAll() throws SubmarineRuntimeException {

submarine-server/server-database/src/main/java/org/apache/submarine/server/database/model/service/RegisteredModelTagService.java

@@ -28,6 +28,13 @@
 import org.slf4j.LoggerFactory;
 
 public class RegisteredModelTagService {
+  private static class RegisteredModelTagServiceHolder {
+    private static RegisteredModelTagService service = new RegisteredModelTagService();
+  }
+
+  public static RegisteredModelTagService getInstance() {
+    return RegisteredModelTagService.RegisteredModelTagServiceHolder.service;
+  }
 
   private static final Logger LOG = LoggerFactory.getLogger(RegisteredModelTagService.class);
 

submarine-server/server-database/src/test/java/org/apache/submarine/server/database/model/ModelVersionTagTest.java

@@ -33,8 +33,8 @@
 
 public class ModelVersionTagTest {
   private static final Logger LOG = LoggerFactory.getLogger(ModelVersionTagTest.class);
-  RegisteredModelService registeredModelService = new RegisteredModelService();
-  ModelVersionService modelVersionService = new ModelVersionService();
+  RegisteredModelService registeredModelService = RegisteredModelService.getInstance();
+  ModelVersionService modelVersionService = ModelVersionService.getInstance();
   ModelVersionTagService modelVersionTagService = new ModelVersionTagService();
 
 

submarine-server/server-database/src/test/java/org/apache/submarine/server/database/model/ModelVersionTest.java

@@ -31,8 +31,8 @@
 import org.apache.submarine.server.database.model.service.RegisteredModelService;
 
 public class ModelVersionTest {
-  RegisteredModelService registeredModelService = new RegisteredModelService();
-  ModelVersionService modelVersionService = new ModelVersionService();
+  RegisteredModelService registeredModelService = RegisteredModelService.getInstance();
+  ModelVersionService modelVersionService = ModelVersionService.getInstance();
 
   @After
   public void cleanAll() {

submarine-server/server-database/src/test/java/org/apache/submarine/server/database/model/RegisteredModelServiceTest.java

@@ -29,7 +29,7 @@
 import java.util.List;
 
 public class RegisteredModelServiceTest {
-  RegisteredModelService registeredModelService = new RegisteredModelService();
+  RegisteredModelService registeredModelService = RegisteredModelService.getInstance();
 
   @After
   public void cleanAll() {

submarine-server/server-database/src/test/java/org/apache/submarine/server/database/model/RegisteredModelTagServiceTest.java

@@ -31,8 +31,8 @@
 
 public class RegisteredModelTagServiceTest {
   private static final Logger LOG = LoggerFactory.getLogger(RegisteredModelTagServiceTest.class);
-  RegisteredModelService registeredModelService = new RegisteredModelService();
-  RegisteredModelTagService registeredModelTagService = new RegisteredModelTagService();
+  RegisteredModelService registeredModelService = RegisteredModelService.getInstance();
+  RegisteredModelTagService registeredModelTagService = RegisteredModelTagService.getInstance();
 
   @After
   public void cleanAll() {

submarine-server/server-submitter/submitter-k8s/src/main/java/org/apache/submarine/server/submitter/k8s/model/xgboostjob/XGBoostJobList.java

@@ -27,10 +27,10 @@
 
 public class XGBoostJobList implements KubernetesListObject {
   @SerializedName("apiVersion")
-  private String apiVersion;
+  private String apiVersion = XGBoostJob.CRD_XGBOOST_API_VERSION_V1;
 
   @SerializedName("kind")
-  private String kind;
+  private String kind = XGBoostJob.CRD_XGBOOST_KIND_V1 + "List";
 
   @SerializedName("metadata")
   private V1ListMeta metadata;
@@ -55,6 +55,6 @@ public String getApiVersion() {
 
   @Override
   public String getKind() {
-    return XGBoostJob.CRD_XGBOOST_KIND_V1 + "List";
+    return kind;
   }
 }