inject JSON $schema definition to the final document

src/main/java/com/siemens/sbom/standardbom/StandardBomParser.java

@@ -184,11 +184,35 @@ public String stringify(@Nonnull final StandardBom pBom)
         json = unescapeComponentFields(json);
         json = unescapeExtRefPurls(json);
         json = removeEmptyServicesMetadata(json);
+        json = injectSchemaSpec(json);
         return json.concat(System.lineSeparator());
     }
 
 
 
+    @Nonnull
+    private String injectSchemaSpec(@Nonnull final String pJson)
+    {
+        String schemaAttribute = "  \"$schema\": \"http://cyclonedx.org/schema/bom-1.6.schema.json\","
+            .concat(System.lineSeparator());
+
+        // Check if $schema attribute already exists
+        if (pJson.contains("\"$schema\"")) {
+            return pJson;
+        }
+
+        // Find the position right after the opening curly brace
+        final String insertMarker = '{' + System.lineSeparator();
+        int insertPosition = pJson.indexOf(insertMarker) + insertMarker.length();
+
+        // Insert the $schema attribute at the found position
+        StringBuilder sb = new StringBuilder(pJson);
+        sb.insert(insertPosition, schemaAttribute);
+        return sb.toString();
+    }
+
+
+
     private void escapeExtRefPurls(@Nonnull final StandardBom pBom)
     {
         if (pBom.getCycloneDxBom().getExternalReferences() != null) {

src/test/resources/com/siemens/sbom/standardbom/full-valid-1.4.cdx.json

@@ -1,4 +1,5 @@
 {
+  "$schema": "http://cyclonedx.org/schema/bom-1.4.schema.json",
   "bomFormat" : "CycloneDX",
   "specVersion" : "1.4",
   "version" : 1,

src/test/resources/com/siemens/sbom/standardbom/full-valid.cdx.json

@@ -1,4 +1,5 @@
 {
+  "$schema": "http://cyclonedx.org/schema/bom-1.6.schema.json",
   "bomFormat" : "CycloneDX",
   "specVersion" : "1.6",
   "version" : 1,