Avoid redundant JSON to string conversion

When creating the param definition, the JSON payload was converted to string.
And then converted again when encoding the param.

In fact, MSSQL allows to send JSON as NVARCHAR(MAX) regardless of the size.
And then we can have a single conversion when encoding the param.

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

Author: tsegismont

vertx-mssql-client/src/main/java/io/vertx/mssqlclient/impl/codec/DataType.java

@@ -873,11 +873,6 @@ public void encodeParam(ByteBuf byteBuf, String name, boolean out, Object value)
         byteBuf.writeCharSequence(val, StandardCharsets.UTF_16LE);
       }
     }
-
-    private void writeCollation(ByteBuf byteBuf) {
-      byteBuf.writeInt(0x0904d000);
-      byteBuf.writeByte(0x34);
-    }
   },
   NCHAR(0xEF) {
     @Override
@@ -995,14 +990,19 @@ public Object decodeValue(ByteBuf byteBuf, TypeInfo typeInfo) {
 
     @Override
     public String paramDefinition(Object value) {
-      // SQL Server expects text for JSON params
-      return NVARCHAR.paramDefinition(value);
+      return "nvarchar(max)";
     }
 
     @Override
     public void encodeParam(ByteBuf byteBuf, String name, boolean out, Object value) {
-      // SQL Server expects text for JSON params
-      NVARCHAR.encodeParam(byteBuf, name, out, value);
+      writeParamDescription(byteBuf, name, out, NVARCHAR.id);
+      String val = value.toString();
+      byteBuf.writeShortLE(0xFFFF);
+      writeCollation(byteBuf);
+      byteBuf.writeLongLE(val.length() * 2L);
+      byteBuf.writeIntLE(val.length() * 2);
+      byteBuf.writeCharSequence(val, StandardCharsets.UTF_16LE);
+      byteBuf.writeIntLE(0);
     }
   },
 
@@ -1212,4 +1212,9 @@ private static int daysFromStartDate(LocalDate localDate) {
   private static long hundredsOfNanos(LocalTime localTime) {
     return localTime.toNanoOfDay() / 100;
   }
+
+  private static void writeCollation(ByteBuf byteBuf) {
+    byteBuf.writeInt(0x0904d000);
+    byteBuf.writeByte(0x34);
+  }
 }