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.

#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: 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.