Struct TransformMiddleware 

pub struct TransformMiddleware {
    pub mapping: HashMap<String, MappingRule>,
    pub schema: Option<Value>,
    pub schema_file: Option<String>,
    pub coerce: bool,
    pub apply_defaults: bool,
    pub on_error: TransformErrorPolicy,
}

JSON transform middleware configuration.

Reshapes JSON payloads declaratively, in two stages over a single parse: field mapping (rename/move/nest), then schema (type coercion, defaults, validation). Either stage may be omitted; with neither configured the message passes through untouched and is never parsed.

On an output endpoint a rejected message becomes a non-retryable failure, so a dlq middleware listed after this one captures it (publisher middlewares are wrapped in list order, so the last entry is the outermost layer). On an input endpoint a rejected message is dropped from the batch and acknowledged, which is how invalid input is kept out of the route.

Fields

mapping: HashMap<String, MappingRule>

Output field name -> source path (e.g. firstName: "$.first_name"). Dots nest the output.

schema: Option<Value>

Inline JSON Schema subset (type, properties, required, default, items, nullable, enum).

schema_file: Option<String>

Path to a JSON Schema file. Read once at startup; never re-read per message.

coerce: bool

Coerce safely convertible types (e.g. "42" -> 42) instead of rejecting. Defaults to true.

apply_defaults: bool

Insert default values from the schema for missing fields. Defaults to true.

on_error: TransformErrorPolicy

What to do with a message that fails to transform. Defaults to reject.

Trait Implementations

impl Clone for TransformMiddleware

fn clone(&self) -> TransformMiddleware

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TransformMiddleware

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for TransformMiddleware

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for TransformMiddleware

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for TransformMiddleware

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.