Cannot cast object 'class centaur.demo.Profile' with class 'java.lang.Class' to-CodePudding

Please help me to fix this issue. Thank you!

I am working on a Grails-5.2.4 project with Java 1.8. Class Loader is not working as expected.

I am getting class cast exception for the following piece of code.

def index() {
    Profile profile = getClass().classLoader.loadClass("centaur.demo.Profile") as Profile
}

Below is the exception details:

Caused by: org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object 'class centaur.demo.Profile' with class 'java.lang.Class' to class 'centaur.demo.Profile'
    at org.grails.web.converters.ConverterUtil.invokeOriginalAsTypeMethod(ConverterUtil.java:147)
    at org.grails.web.converters.ConvertersExtension.asType(ConvertersExtension.groovy:56)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at centaur.demo.IndexController.index(IndexController.groovy:10)
    ... 13 common frames omitted

Expected behavior:

The line below should return an object of class Profile.

getClass().classLoader.loadClass("centaur.demo.Profile")

This is working fine with Grails 3.3.9.

CodePudding user response：

As the name suggests ClassLoader#loadClass returns an instance of java.lang.Class. You have to instantiate the class to get an object of its referenced type using new Profile(...) or by calling Class#newInstance on the result of loadClass (provided your Profile class has an accessible default constructor)

CodePudding user response：

this line:

getClass().classLoader.loadClass("centaur.demo.Profile")

should return you a Class object.

check out the documentation: https://docs.oracle.com/javase/8/docs/api/java/lang/ClassLoader.html#loadClass-java.lang.String-

so, you could assign result to Class:

Class c = getClass().classLoader.loadClass("centaur.demo.Profile")

you could instantiate class:

def profile = getClass().classLoader.loadClass("centaur.demo.Profile").newInstance()

but the following code could fail:

centaur.demo.Profile profile = getClass().classLoader.loadClass("centaur.demo.Profile").newInstance()

when class loader used for declaration is different from the one returned by getClass().classLoader