JSON parsing utils Encoding utils ID generation utils Error utils Condition validation utils Null behavior utils Pattern matching utils Object validation utils CloudWatch logging utils Return value behavior utils Resolver authorization

Utility helpers in $util

Note

We now primarily support the APPSYNC_JS runtime and its documentation. Please consider using the APPSYNC_JS runtime and its guides here.

The $util variable contains general utility methods to help you work with data. Unless otherwise specified, all utilities use the UTF-8 character set.

JSON parsing utils

$util.parseJson(String) : Object: Takes "stringified" JSON and returns an object representation of the result.
$util.toJson(Object) : String: Takes an object and returns a "stringified" JSON representation of that object.

Encoding utils

$util.urlEncode(String) : String: Returns the input string as an application/x-www-form-urlencoded encoded string.
$util.urlDecode(String) : String: Decodes an application/x-www-form-urlencoded encoded string back to its non-encoded form.
$util.base64Encode( byte[] ) : String: Encodes the input into a base64-encoded string.
$util.base64Decode(String) : byte[]: Decodes the data from a base64-encoded string.

ID generation utils

$util.autoId() : String: Returns a 128-bit randomly generated UUID.
$util.autoUlid() : String: Returns a 128-bit randomly generated ULID (Universally Unique Lexicographically Sortable Identifier).
$util.autoKsuid() : String: Returns a 128-bit randomly generated KSUID (K-Sortable Unique Identifier) base62 encoded as a String with a length of 27.

Error utils

$util.error(String): Throws a custom error. Use this in request or response mapping templates to detect an error with the request or with the invocation result.
$util.error(String, String): Throws a custom error. Use this in request or response mapping templates to detect an error with the request or with the invocation result. You can also specify an errorType.
$util.error(String, String, Object): Throws a custom error. Use this in request or response mapping templates to detect an error with the request or with the invocation result. You can also specify an errorType and a data field. The data value will be added to the corresponding error block inside errors in the GraphQL response.

Note
data will be filtered based on the query selection set.
$util.error(String, String, Object, Object): Throws a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType field, a data field, and an errorInfo field can be specified. The data value will be added to the corresponding error block inside errors in the GraphQL response.

Note
data will be filtered based on the query selection set. The errorInfo value will be added to the corresponding error block inside errors in the GraphQL response.
errorInfo will NOT be filtered based on the query selection set.
$util.appendError(String): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Unlike $util.error(String), the template evaluation will not be interrupted, so that data can be returned to the caller.
$util.appendError(String, String): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType can be specified. Unlike $util.error(String, String), the template evaluation will not be interrupted, so that data can be returned to the caller.
$util.appendError(String, String, Object): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType and a data field can be specified. Unlike $util.error(String, String, Object), the template evaluation will not be interrupted, so that data can be returned to the caller. The data value will be added to the corresponding error block inside errors in the GraphQL response.

Note
data will be filtered based on the query selection set.
$util.appendError(String, String, Object, Object): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType field, a data field, and an errorInfo field can be specified. Unlike $util.error(String, String, Object, Object), the template evaluation will not be interrupted, so that data can be returned to the caller. The data value will be added to the corresponding error block inside errors in the GraphQL response.

Note
data will be filtered based on the query selection set. The errorInfo value will be added to the corresponding error block inside errors in the GraphQL response.
errorInfo will NOT be filtered based on the query selection set.

Condition validation utils

$util.validate(Boolean, String) : void: If the condition is false, throw a CustomTemplateException with the specified message.
$util.validate(Boolean, String, String) : void: If the condition is false, throw a CustomTemplateException with the specified message and error type.
$util.validate(Boolean, String, String, Object) : void: If the condition is false, throw a CustomTemplateException with the specified message and error type, as well as data to return in the response.

Null behavior utils

$util.isNull(Object) : Boolean: Returns true if the supplied object is null.
$util.isNullOrEmpty(String) : Boolean: Returns true if the supplied data is null or an empty string. Otherwise, returns false.
$util.isNullOrBlank(String) : Boolean: Returns true if the supplied data is null or a blank string. Otherwise, returns false.
$util.defaultIfNull(Object, Object) : Object: Returns the first Object if it is not null. Otherwise, returns second object as a "default Object".
$util.defaultIfNullOrEmpty(String, String) : String: Returns the first String if it is not null or empty. Otherwise, returns second String as a "default String".
$util.defaultIfNullOrBlank(String, String) : String: Returns the first String if it is not null or blank. Otherwise, returns second String as a "default String".

Pattern matching utils

$util.typeOf(Object) : String: Returns a String describing the type of the Object. Supported type identifications are: "Null", "Number", "String", "Map", "List", "Boolean". If a type cannot be identified, the return type is "Object".
$util.matches(String, String) : Boolean: Returns true if the specified pattern in the first argument matches the supplied data in the second argument. The pattern must be a regular expression such as $util.matches("a*b", "aaaaab"). The functionality is based on Pattern, which you can reference for further documentation.
$util.authType() : String: Returns a String describing the multi-auth type being used by a request, returning back either "IAM Authorization", "User Pool Authorization", "Open ID Connect Authorization", or "API Key Authorization".

Object validation utils

$util.isString(Object) : Boolean: Returns true if the Object is a String.
$util.isNumber(Object) : Boolean: Returns true if the Object is a Number.
$util.isBoolean(Object) : Boolean: Returns true if the Object is a Boolean.
$util.isList(Object) : Boolean: Returns true if the Object is a List.
$util.isMap(Object) : Boolean: Returns true if the Object is a Map.

CloudWatch logging utils

$util.log.info(Object) : Void: Logs the String representation of the provided Object to the requested log stream when request-level and field-level CloudWatch logging is enabled with log level ALL on an API.
$util.log.info(String, Object...) : Void: Logs the String representation of the provided Objects to the requested log stream when request-level and field-level CloudWatch logging is enabled with log level ALL on an API. This utility will replace all variables indicated by "{}" in the first input format String with the String representation of the provided Objects in order.
$util.log.error(Object) : Void: Logs the String representation of the provided Object to the requested log stream when field-level CloudWatch logging is enabled with log level ERROR or log level ALL on an API.
$util.log.error(String, Object...) : Void: Logs the String representation of the provided Objects to the requested log stream when field-level CloudWatch logging is enabled with log level ERROR or log level ALL on an API. This utility will replace all variables indicated by "{}" in the first input format String with the String representation of the provided Objects in order.

Return value behavior utils

$util.qr() and $util.quiet()

Runs a VTL statement while suppressing the returned value. This is useful for running methods without using temporary placeholders, such as adding items to a map. For example:


#set ($myMap = {})
#set($discard = $myMap.put("id", "first value"))

Becomes:


#set ($myMap = {})
$util.qr($myMap.put("id", "first value"))

$util.escapeJavaScript(String) : String: Returns the input string as a JavaScript escaped string.
$util.urlEncode(String) : String: Returns the input string as an application/x-www-form-urlencoded encoded string.
$util.urlDecode(String) : String: Decodes an application/x-www-form-urlencoded encoded string back to its non-encoded form.
$util.base64Encode( byte[] ) : String: Encodes the input into a base64-encoded string.
$util.base64Decode(String) : byte[]: Decodes the data from a base64-encoded string.
$util.parseJson(String) : Object: Takes "stringified" JSON and returns an object representation of the result.
$util.toJson(Object) : String: Takes an object and returns a "stringified" JSON representation of that object.
$util.autoId() : String: Returns a 128-bit randomly generated UUID.
$util.autoUlid() : String: Returns a 128-bit randomly generated ULID (Universally Unique Lexicographically Sortable Identifier).
$util.autoKsuid() : String: Returns a 128-bit randomly generated KSUID (K-Sortable Unique Identifier) base62 encoded as a String with a length of 27.
$util.unauthorized(): Throws Unauthorized for the field being resolved. Use this in request or response mapping templates to determine whether to allow the caller to resolve the field.
$util.error(String): Throws a custom error. Use this in request or response mapping templates to detect an error with the request or with the invocation result.
$util.error(String, String): Throws a custom error. Use this in request or response mapping templates to detect an error with the request or with the invocation result. You can also specify an errorType.
$util.error(String, String, Object): Throws a custom error. Use this in request or response mapping templates to detect an error with the request or with the invocation result. You can also specify an errorType and a data field. The data value will be added to the corresponding error block inside errors in the GraphQL response. Note: data will be filtered based on the query selection set.
$util.error(String, String, Object, Object): Throws a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType field, a data field, and a errorInfo field can be specified. The data value will be added to the corresponding error block inside errors in the GraphQL response. Note: data will be filtered based on the query selection set. The errorInfo value will be added to the corresponding error block inside errors in the GraphQL response. Note: errorInfo will NOT be filtered based on the query selection set.
$util.appendError(String): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Unlike $util.error(String), the template evaluation will not be interrupted, so that data can be returned to the caller.
$util.appendError(String, String): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType can be specified. Unlike $util.error(String, String), the template evaluation will not be interrupted, so that data can be returned to the caller.
$util.appendError(String, String, Object): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType and a data field can be specified. Unlike $util.error(String, String, Object), the template evaluation will not be interrupted, so that data can be returned to the caller. The data value will be added to the corresponding error block inside errors in the GraphQL response. Note: data will be filtered based on the query selection set.
$util.appendError(String, String, Object, Object): Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType field, a data field, and a errorInfo field can be specified. Unlike $util.error(String, String, Object, Object), the template evaluation will not be interrupted, so that data can be returned to the caller. The data value will be added to the corresponding error block inside errors in the GraphQL response. Note: data will be filtered based on the query selection set. The errorInfo value will be added to the corresponding error block inside errors in the GraphQL response. Note: errorInfo will NOT be filtered based on the query selection set.
$util.validate(Boolean, String) : void: If the condition is false, throw a CustomTemplateException with the specified message.
$util.validate(Boolean, String, String) : void: If the condition is false, throw a CustomTemplateException with the specified message and error type.
$util.validate(Boolean, String, String, Object) : void: If the condition is false, throw a CustomTemplateException with the specified message and error type, as well as data to return in the response.
$util.isNull(Object) : Boolean: Returns true if the supplied object is null.
$util.isNullOrEmpty(String) : Boolean: Returns true if the supplied data is null or an empty string. Otherwise, returns false.
$util.isNullOrBlank(String) : Boolean: Returns true if the supplied data is null or a blank string. Otherwise, returns false.
$util.defaultIfNull(Object, Object) : Object: Returns the first Object if it is not null. Otherwise, returns second object as a "default Object".
$util.defaultIfNullOrEmpty(String, String) : String: Returns the first String if it is not null or empty. Otherwise, returns second String as a "default String".
$util.defaultIfNullOrBlank(String, String) : String: Returns the first String if it is not null or blank. Otherwise, returns second String as a "default String".
$util.isString(Object) : Boolean: Returns true if Object is a String.
$util.isNumber(Object) : Boolean: Returns true if Object is a Number.
$util.isBoolean(Object) : Boolean: Returns true if Object is a Boolean.
$util.isList(Object) : Boolean: Returns true if Object is a List.
$util.isMap(Object) : Boolean: Returns true if Object is a Map.
$util.typeOf(Object) : String: Returns a String describing the type of the Object. Supported type identifications are: "Null", "Number", "String", "Map", "List", "Boolean". If a type cannot be identified, the return type is "Object".
$util.matches(String, String) : Boolean: Returns true if the specified pattern in the first argument matches the supplied data in the second argument. The pattern must be a regular expression such as $util.matches("a*b", "aaaaab"). The functionality is based on Pattern, which you can reference for further documentation.
$util.authType() : String: Returns a String describing the multi-auth type being used by a request, returning back either "IAM Authorization", "User Pool Authorization", "Open ID Connect Authorization", or "API Key Authorization".
$util.log.info(Object) : Void: Logs the String representation of the provided Object to the requested log stream when request-level and field-level CloudWatch logging is enabled with log level ALL on an API.
$util.log.info(String, Object...) : Void: Logs the String representation of the provided Objects to the requested log stream when request-level and field-level CloudWatch logging is enabled with log level ALL on an API. This utility will replace all variables indicated by "{}" in the first input format String with the String representation of the provided Objects in order.
$util.log.error(Object) : Void: Logs the String representation of the provided Object to the requested log stream when field-level CloudWatch logging is enabled with log level ERROR or log level ALL on an API.
$util.log.error(String, Object...) : Void: Logs the String representation of the provided Objects to the requested log stream when field-level CloudWatch logging is enabled with log level ERROR or log level ALL on an API. This utility will replace all variables indicated by "{}" in the first input format String with the String representation of the provided Objects in order.

$util.escapeJavaScript(String) : String: Returns the input string as a JavaScript escaped string.

Resolver authorization

$util.unauthorized(): Throws Unauthorized for the field being resolved. Use this in request or response mapping templates to determine whether to allow the caller to resolve the field.

Warning Javascript is disabled or is unavailable in your browser.

To use the Amazon Web Services Documentation, Javascript must be enabled. Please refer to your browser's Help pages for instructions.

Document Conventions

Resolver mapping template utility reference

AWS AppSync directives