fix null json bug

Author: vincentlauvlwj

ktorm-jackson/src/main/kotlin/org/ktorm/jackson/JsonSqlType.kt

@@ -78,12 +78,24 @@ public inline fun <reified C : Any> BaseTable<*>.json(
 public class JsonSqlType<T : Any>(
     public val objectMapper: ObjectMapper,
     public val javaType: JavaType
-) : SqlType<T>(Types.VARCHAR, "json") {
+) : SqlType<T>(Types.OTHER, "json") {
 
     private val hasPostgresqlDriver by lazy {
         runCatching { Class.forName("org.postgresql.Driver") }.isSuccess
     }
 
+    override fun setParameter(ps: PreparedStatement, index: Int, parameter: T?) {
+        if (parameter != null) {
+            doSetParameter(ps, index, parameter)
+        } else {
+            if (hasPostgresqlDriver && ps is PGStatement) {
+                ps.setNull(index, Types.OTHER)
+            } else {
+                ps.setNull(index, Types.VARCHAR)
+            }
+        }
+    }
+
     override fun doSetParameter(ps: PreparedStatement, index: Int, parameter: T) {
         if (hasPostgresqlDriver && ps is PGStatement) {
             val obj = PGobject()

ktorm-support-mysql/src/test/kotlin/org/ktorm/support/mysql/MySqlTest.kt

@@ -392,6 +392,11 @@ class MySqlTest : BaseTest() {
             set(it.arr, listOf(1, 2, 3))
         }
 
+        database.insert(t) {
+            set(it.obj, null)
+            set(it.arr, null)
+        }
+
         database
             .from(t)
             .select(t.obj, t.arr)

ktorm-support-postgresql/src/test/kotlin/org/ktorm/support/postgresql/PostgreSqlTest.kt

@@ -815,6 +815,11 @@ class PostgreSqlTest : BaseTest() {
             set(it.arr, listOf(1, 2, 3))
         }
 
+        database.insert(t) {
+            set(it.obj, null)
+            set(it.arr, null)
+        }
+
         database
             .from(t)
             .select(t.obj, t.arr)