Use a single ObjectMapper instance because it is thread-safe

gitlfs-client/src/main/java/ru/bozaro/gitlfs/client/Client.java

@@ -60,7 +60,7 @@ public Client(@NotNull AuthProvider authProvider, @NotNull final HttpClient http
 
   public Client(@NotNull AuthProvider authProvider, @NotNull HttpExecutor http) {
     this.authProvider = authProvider;
-    this.mapper = JsonHelper.createMapper();
+    this.mapper = JsonHelper.mapper;
     this.http = http;
   }
 

gitlfs-client/src/main/java/ru/bozaro/gitlfs/client/auth/ExternalAuthProvider.java

@@ -81,7 +81,7 @@ protected Link getAuthUncached(@NotNull Operation operation) throws IOException,
     if (exitValue != 0) {
       throw new IOException("Command returned with non-zero exit code " + exitValue + ": " + Arrays.toString(builder.command().toArray()));
     }
-    return JsonHelper.createMapper().readValue(stdoutData.toByteArray(), Link.class);
+    return JsonHelper.mapper.readValue(stdoutData.toByteArray(), Link.class);
   }
 
   @NotNull

gitlfs-client/src/test/java/ru/bozaro/gitlfs/client/ClientBatchTest.java

@@ -5,8 +5,8 @@
 import org.testng.Assert;
 import org.testng.annotations.Test;
 import ru.bozaro.gitlfs.common.JsonHelper;
-import ru.bozaro.gitlfs.common.data.*;
 import ru.bozaro.gitlfs.common.data.Error;
+import ru.bozaro.gitlfs.common.data.*;
 
 import java.io.IOException;
 import java.net.URI;
@@ -44,7 +44,7 @@ private void batchUpload(@NotNull String path) throws IOException {
             new Meta("1cbec737f863e4922cee63cc2ebbfaafcd1cff8b790d8cfd2e6a5d550b648afa", 3)
         )
     ));
-    Assert.assertEquals(JsonHelper.toString(result), JsonHelper.toString(new BatchRes(
+    Assert.assertEquals(JsonHelper.mapper.writeValueAsString(result), JsonHelper.mapper.writeValueAsString(new BatchRes(
         Arrays.asList(
             new BatchItem(
                 new Meta("b810bbe954d51e380f395de0c301a0a42d16f115453f2feb4188ca9f7189074e", 28),
@@ -104,7 +104,7 @@ private void batchDownload(@NotNull String path) throws IOException {
             new Meta("1cbec737f863e4922cee63cc2ebbfaafcd1cff8b790d8cfd2e6a5d550b648afa", 3)
         )
     ));
-    Assert.assertEquals(JsonHelper.toString(result), JsonHelper.toString(new BatchRes(
+    Assert.assertEquals(JsonHelper.mapper.writeValueAsString(result), JsonHelper.mapper.writeValueAsString(new BatchRes(
         Arrays.asList(
             new BatchItem(
                 new Meta("b810bbe954d51e380f395de0c301a0a42d16f115453f2feb4188ca9f7189074e", 28),

gitlfs-common/src/main/java/ru/bozaro/gitlfs/common/JsonHelper.java

@@ -1,7 +1,6 @@
 package ru.bozaro.gitlfs.common;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
-import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.util.DefaultIndenter;
 import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -17,15 +16,11 @@
  * @author Artem V. Navrotskiy
  */
 public final class JsonHelper {
-  private JsonHelper() {
-  }
 
-  /**
-   * Creating mapper for serialize/deserialize data to JSON.
-   */
   @NotNull
-  public static ObjectMapper createMapper() {
-    final ObjectMapper mapper = new ObjectMapper();
+  public static final ObjectMapper mapper = new ObjectMapper();
+
+  static {
     mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
     mapper.enable(SerializationFeature.INDENT_OUTPUT);
     mapper.setDateFormat(new StdDateFormat());
@@ -36,17 +31,8 @@ public static ObjectMapper createMapper() {
             .withObjectIndenter(new DefaultIndenter("  ", "\n")));
 
     mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
-    return mapper;
   }
 
-  /**
-   * Convert object to string.
-   *
-   * @param data Object.
-   * @return JSON data.
-   */
-  @NotNull
-  public static String toString(@NotNull Object data) throws JsonProcessingException {
-    return createMapper().writeValueAsString(data);
+  private JsonHelper() {
   }
 }

gitlfs-server/src/main/java/ru/bozaro/gitlfs/server/PointerServlet.java

@@ -5,8 +5,8 @@
 import org.jetbrains.annotations.Nullable;
 import ru.bozaro.gitlfs.common.Constants;
 import ru.bozaro.gitlfs.common.JsonHelper;
-import ru.bozaro.gitlfs.common.data.*;
 import ru.bozaro.gitlfs.common.data.Error;
+import ru.bozaro.gitlfs.common.data.*;
 import ru.bozaro.gitlfs.server.internal.ObjectResponse;
 import ru.bozaro.gitlfs.server.internal.ResponseWriter;
 
@@ -60,7 +60,7 @@ public PointerServlet(@NotNull ContentManager manager, @NotNull String contentLo
 
   public PointerServlet(@NotNull PointerManager manager) {
     this.manager = manager;
-    this.mapper = JsonHelper.createMapper();
+    this.mapper = JsonHelper.mapper;
     this.accessCheckerVisitor = new AccessCheckerVisitor(manager);
   }
 
@@ -135,7 +135,7 @@ protected void doPost(@NotNull HttpServletRequest req, @NotNull HttpServletRespo
     } catch (ServerError e) {
       resp.setStatus(e.getStatusCode());
       resp.setContentType(Constants.MIME_LFS_JSON);
-      JsonHelper.createMapper().writeValue(resp.getOutputStream(), new Error(e.getStatusCode(), e.getMessage()));
+      JsonHelper.mapper.writeValue(resp.getOutputStream(), new Error(e.getStatusCode(), e.getMessage()));
       return;
     }
     super.doPost(req, resp);

gitlfs-server/src/main/java/ru/bozaro/gitlfs/server/internal/ObjectResponse.java

@@ -27,6 +27,6 @@ public ObjectResponse(int status, @NotNull Object value) {
   public void write(@NotNull HttpServletResponse response) throws IOException {
     response.setStatus(status);
     response.setContentType(MIME_LFS_JSON);
-    JsonHelper.createMapper().writeValue(response.getOutputStream(), value);
+    JsonHelper.mapper.writeValue(response.getOutputStream(), value);
   }
 }