TYPO3 Exception 1278450972

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#1278450972: Class ... does not exist. Reflection failed. TYPO3 9.5

We had a whitespace at the beginning of the filename of the file containing the class.

When switching over from working with TYPO3 v10+ back to TYPO3 v9.5, remember that you have to specify the fully qualified name for parameters, as opposed to TYPO3 v10+ where you can import the class name.

#1278450972: Class ... does not exist. Reflection failed. After updating to TYPO3 11

We missed the required update in the registration of plugins and modules to use the full class name.

See Breaking: #92609 - Use controller classes when registering plugins/modules.

#1278450972: Class ... does not exist. Reflection failed. in TYPO3 11

Running composer update fixes the problem in a Composer based installation of TYPO3.

#1278450972: The classname "..." was not found and thus can not be reflected.

This (extbase) error can occur if you have annotated a (controller action) method using @param but have not given it a type hint. If the annotation is wrong this error will occur.

Example:

/**
 * A test action
 *
 * @param \MyVendor\MyExtension\Domain\Motel\InvalidName $myVariable
 */
public function testAction($myVariable) {

As you see the @param annotation is wrong. Because you usually have not any Domain\Motel namespace and there is no type hint for $myVariable in the function header.

So either correct the annotation, clear all caches:

/**
 * A test action
 *
 * @param \MyVendor\MyExtension\Domain\Model\ValidName $myVariable
 */
public function testAction($myVariable) {

Or try to add a type hint:

/**
 * A test action
 *
 * @param \MyVendor\MyExtension\Domain\Model\ValidName $myVariable
 */
public function testAction(\MyVendor\MyExtension\Domain\Model\ValidName $myVariable) {

I had a Composer based Installation. And i have to add my ext. to the psr4 autoload in copmposer.json:

"autoload": {
     "psr-4": {
             "MyVendor\\MyExtension\\":"web/typo3conf/ext/MyExtension/Classes"
     }
 },

#1278450972 TYPO3CMSExtbaseReflectionExceptionUnknownClassException

Class Boolean does not exist. Reflection failed.

at TYPO3\CMS\Extbase\Reflection\ReflectionService->buildClassSchema('Vendorname\\Extensionname\\Domain\\Model\\MyModel')

Got this error because in MyModel was a setter with a wrong typehint, in my case it was something like

public function setFreeShipping(\Boolean $freeShipping)

Solution was to change \Boolean to bool.