Anuken/Mindustry · error · SerializationException

Content JSON must be an object, not a single value.

Error message

Content JSON must be an object, not a single value.

What it means

In parse(), the raw JSON is parsed and the result must be an arc JsonValue (i.e. a JSON object at top level). If the file is a bare scalar or array at the root, fromJson yields a non-JsonValue and the parser rejects it, because every content type parser expects an object to map onto fields.

Source

Thrown at core/src/mindustry/mod/ContentParser.java:1035

     * @param name the name of the file without its extension
     * @param json the json to parse
     * @param type the type of content this is
     * @param file file that this content is being parsed from
     * @return the content that was parsed
     */
    public Content parse(LoadedMod mod, String name, String json, Fi file, ContentType type) throws Exception{
        checkInit();

        //remove extra # characters to make it valid json... apparently some people have *unquoted* # characters in their json
        if(file.extension().equals("json")){
            json = json.replace("#", "\\#");
        }

        currentFile = file;
        currentMod = mod;

        var rawValue = parser.fromJson(null, Jval.read(json).toString(Jformat.plain));
        if(!(rawValue instanceof JsonValue value)) throw new SerializationException("Content JSON must be an object, not a single value.");

        if(!parsers.containsKey(type)){
            throw new SerializationException("No parsers for content type '" + type + "'");
        }

        boolean located = allowPatching && locate(type, name) != null;
        Content c = parsers.get(type).parse(mod.name, name, value);
        c.minfo.sourceFile = file;
        toBeParsed.add(c);

        if(!located){
            c.minfo.mod = mod;
        }

        currentMod = null;
        currentFile = null;
        return c;
    }

View on GitHub (pinned to f695ad7e60)

Solutions

1. Make the file's top-level JSON an object enclosed in { }.
2. Each content file should define exactly one content entry as an object.

Example fix

// before
[ { "name":"a" }, { "name":"b" } ]
// after
{ "name": "a" }  // one file per entry

Object raw = parser.fromJson(null, Jval.read(json).toString(Jformat.plain));
if(!(raw instanceof JsonValue)) throw new IllegalStateException("Content file root must be a JSON object");

boolean isJsonObject(Object raw){ return raw instanceof JsonValue && ((JsonValue)raw).isObject(); }

When it happens

Trigger: A content file whose root JSON node is a number, string, boolean, or array rather than an object.

Common situations: Authoring a content file as a single quoted string or array; a malformed/truncated file; accidentally saving a list of items instead of one item definition.

Related errors

• Unknown consumption type: '${child.name}' for block '${block
• Blocks cannot be larger than ${maxBlockSize}
• Unit '${name}' has an incorrect type. Types must be strings.
• Missing a valid 'block' in 'requirements'
• SectorPresets must have a sector number.

AI-assisted analysis of Anuken/Mindustry@f695ad7e60 (2026-08-14). Data as JSON: /api/errors/058229795b0e21a5. Report an issue: GitHub.