JSON simple implementation for MSSQL (#1057)

- Use JSON_VALUE
  - Use NVARCHAR type

Signed-off-by: Thibault Meyer <meyer.thibault@gmail.com>

src/main/java/io/ebeaninternal/server/core/InternalConfiguration.java

@@ -248,19 +248,20 @@ public class InternalConfiguration {
    * Return the JSON expression handler for the given database platform.
    */
   private DbExpressionHandler getDbExpressionHandler(DatabasePlatform databasePlatform) {
-
-    Platform platform = databasePlatform.getPlatform();
-    if (platform == Platform.POSTGRES) {
-      return new PostgresJsonExpression();
+    final Platform platform = databasePlatform.getPlatform();
+    switch (platform) {
+      case POSTGRES:
+        return new PostgresJsonExpression();
+      case ORACLE:
+        return new OracleDbExpression();
+      case SQLSERVER:
+        return new SqlServerJsonExpression();
+      default:
+        return new NotSupportedDbExpression();
     }
-    if (platform == Platform.ORACLE) {
-      return new OracleDbExpression();
-    }
-    return new NotSupportedDbExpression();
   }
 
   public JsonContext createJsonContext(SpiEbeanServer server) {
-
     return new DJsonContext(server, jsonFactory, typeManager);
   }
 

src/main/java/io/ebeaninternal/server/core/SqlServerJsonExpression.java

@@ -0,0 +1,28 @@
+package io.ebeaninternal.server.core;
+
+import io.ebeaninternal.api.SpiExpressionRequest;
+import io.ebeaninternal.server.expression.Op;
+
+/**
+ * Microsoft SQL Server JSON. ARRAY expressions not supported.
+ */
+public class SqlServerJsonExpression implements DbExpressionHandler {
+
+  @Override
+  public void json(final SpiExpressionRequest request, final String propName,
+                   final String path, final Op operator, final Object value) {
+    request.append("json_value(").append(propName).append(", '$.").append(path).append("')");
+    request.append(operator.bind());
+  }
+
+  @Override
+  public void arrayContains(final SpiExpressionRequest request, final String propName,
+                            final boolean contains, final Object... values) {
+    throw new RuntimeException("ARRAY expressions not supported on Microsoft SQL Server");
+  }
+
+  @Override
+  public void arrayIsEmpty(final SpiExpressionRequest request, final String propName, final boolean empty) {
+    throw new RuntimeException("ARRAY expressions not supported on Microsoft SQL Server");
+  }
+}