json-path/JsonPath · error · UnsupportedOperationException

JsonObject is immutable in JSON-P

Error message

JsonObject is immutable in JSON-P

What it means

JSON-P JsonObject is immutable, so JakartaJsonProvider.setProperty throws UnsupportedOperationException when the target is a plain JsonObject that is neither a JsonObjectBuilder nor (in mutableJson mode) a JsonObjectProxy. Setting properties on such objects is impossible without converting to a builder.

Solutions

1. Enable mutableJson on the provider so documents are parsed into mutable proxies.
2. Convert with Json.createObjectBuilder(jsonObject), mutate the builder, then build().
3. Use a provider based on plain Maps (Jackson/Gson/JacksonJsonNodeJsonProvider) when mutation is required.

Example fix

// before
jsonPath.put(document, "newKey", value); // throws on immutable JsonObject
// after
JsonObjectBuilder b = Json.createObjectBuilder((JsonObject) document);
b.add("newKey", value);
document = b.build();

// Java
static boolean isObjectMutable(Object o, boolean mutableJson) {
    return o instanceof JsonObjectBuilder || (mutableJson && o instanceof JsonObjectProxy);
}

try { provider.setProperty(obj, key, value); } catch (UnsupportedOperationException e) { obj = Json.createObjectBuilder((JsonObject) obj).add(key.toString(), value).build(); }

When it happens

Trigger: JsonPath.put/set operations targeting an object member where the node is a JsonObject, mutableJson is false, and it is not a JsonObjectProxy.

Common situations: Attempting to add or overwrite fields in a JSON-P parsed document with the default (immutable) provider configuration.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• JsonArray is immutable in JSON-P
• Json object is expected
• JSON-P adapter does not support getLocation()
• Add can not be performed to multiple properties
• an array or object instance is expected

AI-assisted analysis of json-path/JsonPath@62a4c9f0f6 (2026-09-11). Data as JSON: /api/errors/ddfaae8ec68ca4d7. Report an issue: GitHub.

Appendix: source

Thrown at json-path/src/main/java/com/jayway/jsonpath/spi/json/JakartaJsonProvider.java:193

            JsonValue o = ((JsonObject) obj).get(key);
            if (o == null) {
                return UNDEFINED;
            } else {
                return unwrap(o);
            }
        } else {
            throw new UnsupportedOperationException();
        }
    }

    @Override
    public void setProperty(Object obj, Object key, Object value) {
        if (obj instanceof JsonObjectBuilder) {
            ((JsonObjectBuilder) obj).add(key.toString(), wrap(value));
        } else if (mutableJson && obj instanceof JsonObjectProxy) {
    		((JsonObjectProxy) obj).put(key.toString(), wrap(value));
    	} else if (obj instanceof JsonObject) {
    		throw new UnsupportedOperationException("JsonObject is immutable in JSON-P");
    	} else if (obj instanceof JsonArrayBuilder) {
    		if (key == null) {
    			((JsonArrayBuilder) obj).add(wrap(value));
    		} else {
				((JsonArrayBuilder) obj).set(toArrayIndex(key), wrap(value));
    		}
        } else if (mutableJson && obj instanceof JsonArrayProxy) {
        	if (key == null) {
    			((JsonArrayProxy) obj).add(wrap(value));
        	} else {
        		((JsonArrayProxy) obj).set(toArrayIndex(key), wrap(value));
    		}
    	} else if (obj instanceof JsonArray) {
    		throw new UnsupportedOperationException("JsonArray is immutable in JSON-P");
        } else if (obj instanceof List) {
        	@SuppressWarnings("unchecked")
        	List<JsonValue> array = (List<JsonValue>) obj;
        	if (key == null) {

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