Package org.springframework.util

Class ClassUtils

java.lang.Object
org.springframework.util.ClassUtils
public abstract class ClassUtils extends Object
Miscellaneous java.lang.Class utility methods. Mainly for internal use within the framework.
Since:
1.1
Author:
Juergen Hoeller, Keith Donald, Rob Harrop, Sam Brannen
See Also:

  • Field Details

  • Constructor Details

    • ClassUtils

      public ClassUtils()

  • Method Details

    • getDefaultClassLoader

      @Nullable public static ClassLoader getDefaultClassLoader()
      Return the default ClassLoader to use: typically the thread context ClassLoader, if available; the ClassLoader that loaded the ClassUtils class will be used as fallback.

      Call this method if you intend to use the thread context ClassLoader in a scenario where you clearly prefer a non-null ClassLoader reference: for example, for class path resource loading (but not necessarily for Class.forName, which accepts a null ClassLoader reference as well).

      Returns:
      the default ClassLoader (only null if even the system ClassLoader isn't accessible)
      See Also:

    • overrideThreadContextClassLoader

      @Nullable public static ClassLoader overrideThreadContextClassLoader(@Nullable ClassLoader classLoaderToUse)
      Override the thread context ClassLoader with the environment's bean ClassLoader if necessary, i.e. if the bean ClassLoader is not equivalent to the thread context ClassLoader already.
      Parameters:
      classLoaderToUse - the actual ClassLoader to use for the thread context
      Returns:
      the original thread context ClassLoader, or null if not overridden

    • forName

      public static Class<?> forName(String name, @Nullable ClassLoader classLoader) throws ClassNotFoundException, LinkageError
      Replacement for Class.forName() that also returns Class instances for primitives (e.g. "int") and array class names (e.g. "String[]"). Furthermore, it is also capable of resolving nested class names in Java source style (e.g. "java.lang.Thread.State" instead of "java.lang.Thread$State").
      Parameters:
      name - the name of the Class
      classLoader - the class loader to use (may be null, which indicates the default class loader)
      Returns:
      a class instance for the supplied name
      Throws:
      ClassNotFoundException - if the class was not found
      LinkageError - if the class file could not be loaded
      See Also:

    • resolveClassName

      public static Class<?> resolveClassName(String className, @Nullable ClassLoader classLoader) throws IllegalArgumentException
      Resolve the given class name into a Class instance. Supports primitives (like "int") and array class names (like "String[]").

      This is effectively equivalent to the forName method with the same arguments, with the only difference being the exceptions thrown in case of class loading failure.

      Parameters:
      className - the name of the Class
      classLoader - the class loader to use (may be null, which indicates the default class loader)
      Returns:
      a class instance for the supplied name
      Throws:
      IllegalArgumentException - if the class name was not resolvable (that is, the class could not be found or the class file could not be loaded)
      IllegalStateException - if the corresponding class is resolvable but there was a readability mismatch in the inheritance hierarchy of the class (typically a missing dependency declaration in a Jigsaw module definition for a superclass or interface implemented by the class to be loaded here)
      See Also:

    • isPresent

      public static boolean isPresent(String className, @Nullable ClassLoader classLoader)
      Determine whether the Class identified by the supplied name is present and can be loaded. Will return false if either the class or one of its dependencies is not present or cannot be loaded.
      Parameters:
      className - the name of the class to check
      classLoader - the class loader to use (may be null which indicates the default class loader)
      Returns:
      whether the specified class is present (including all of its superclasses and interfaces)
      Throws:
      IllegalStateException - if the corresponding class is resolvable but there was a readability mismatch in the inheritance hierarchy of the class (typically a missing dependency declaration in a Jigsaw module definition for a superclass or interface implemented by the class to be checked here)

    • isVisible

      public static boolean isVisible(Class<?> clazz, @Nullable ClassLoader classLoader)
      Check whether the given class is visible in the given ClassLoader.
      Parameters:
      clazz - the class to check (typically an interface)
      classLoader - the ClassLoader to check against (may be null in which case this method will always return true)

    • isCacheSafe

      public static boolean isCacheSafe(Class<?> clazz, @Nullable ClassLoader classLoader)
      Check whether the given class is cache-safe in the given context, i.e. whether it is loaded by the given ClassLoader or a parent of it.
      Parameters:
      clazz - the class to analyze
      classLoader - the ClassLoader to potentially cache metadata in (may be null which indicates the system class loader)

    • resolvePrimitiveClassName

      @Nullable public static Class<?> resolvePrimitiveClassName(@Nullable String name)
      Resolve the given class name as primitive class, if appropriate, according to the JVM's naming rules for primitive classes.

      Also supports the JVM's internal class names for primitive arrays. Does not support the "[]" suffix notation for primitive arrays; this is only supported by forName(String, ClassLoader).

      Parameters:
      name - the name of the potentially primitive class
      Returns:
      the primitive class, or null if the name does not denote a primitive class or primitive array class

    • isPrimitiveWrapper

      public static boolean isPrimitiveWrapper(Class<?> clazz)
      Check if the given class represents a primitive wrapper, i.e. Boolean, Byte, Character, Short, Integer, Long, Float, Double, or Void.
      Parameters:
      clazz - the class to check
      Returns:
      whether the given class is a primitive wrapper class

    • isPrimitiveOrWrapper

      public static boolean isPrimitiveOrWrapper(Class<?> clazz)
      Check if the given class represents a primitive (i.e. boolean, byte, char, short, int, long, float, or double), void, or a wrapper for those types (i.e. Boolean, Byte, Character, Short, Integer, Long, Float, Double, or Void).
      Parameters:
      clazz - the class to check
      Returns:
      true if the given class represents a primitive, void, or a wrapper class

    • isPrimitiveArray

      public static boolean isPrimitiveArray(Class<?> clazz)
      Check if the given class represents an array of primitives, i.e. boolean, byte, char, short, int, long, float, or double.
      Parameters:
      clazz - the class to check
      Returns:
      whether the given class is a primitive array class

    • isPrimitiveWrapperArray

      public static boolean isPrimitiveWrapperArray(Class<?> clazz)
      Check if the given class represents an array of primitive wrappers, i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double.
      Parameters:
      clazz - the class to check
      Returns:
      whether the given class is a primitive wrapper array class

    • resolvePrimitiveIfNecessary

      public static Class<?> resolvePrimitiveIfNecessary(Class<?> clazz)
      Resolve the given class if it is a primitive class, returning the corresponding primitive wrapper type instead.
      Parameters:
      clazz - the class to check
      Returns:
      the original class, or a primitive wrapper for the original primitive type

    • isAssignable

      public static boolean isAssignable(Class<?> lhsType, Class<?> rhsType)
      Check if the right-hand side type may be assigned to the left-hand side type, assuming setting by reflection. Considers primitive wrapper classes as assignable to the corresponding primitive types.
      Parameters:
      lhsType - the target type
      rhsType - the value type that should be assigned to the target type
      Returns:
      if the target type is assignable from the value type
      See Also:

    • isAssignableValue

      public static boolean isAssignableValue(Class<?> type, @Nullable Object value)
      Determine if the given type is assignable from the given value, assuming setting by reflection. Considers primitive wrapper classes as assignable to the corresponding primitive types.
      Parameters:
      type - the target type
      value - the value that should be assigned to the type
      Returns:
      if the type is assignable from the value

    • convertResourcePathToClassName

      public static String convertResourcePathToClassName(String resourcePath)
      Convert a "/"-based resource path to a "."-based fully qualified class name.
      Parameters:
      resourcePath - the resource path pointing to a class
      Returns:
      the corresponding fully qualified class name

    • convertClassNameToResourcePath

      public static String convertClassNameToResourcePath(String className)
      Convert a "."-based fully qualified class name to a "/"-based resource path.
      Parameters:
      className - the fully qualified class name
      Returns:
      the corresponding resource path, pointing to the class

    • addResourcePathToPackagePath

      public static String addResourcePathToPackagePath(Class<?> clazz, String resourceName)
      Return a path suitable for use with ClassLoader.getResource (also suitable for use with Class.getResource by prepending a slash ('/') to the return value). Built by taking the package of the specified class file, converting all dots ('.') to slashes ('/'), adding a trailing slash if necessary, and concatenating the specified resource name to this.
      As such, this function may be used to build a path suitable for loading a resource file that is in the same package as a class file, although ClassPathResource is usually even more convenient.
      Parameters:
      clazz - the Class whose package will be used as the base
      resourceName - the resource name to append. A leading slash is optional.
      Returns:
      the built-up resource path
      See Also:

    • classPackageAsResourcePath

      public static String classPackageAsResourcePath(@Nullable Class<?> clazz)
      Given an input class object, return a string which consists of the class's package name as a pathname, i.e., all dots ('.') are replaced by slashes ('/'). Neither a leading nor trailing slash is added. The result could be concatenated with a slash and the name of a resource and fed directly to ClassLoader.getResource(). For it to be fed to Class.getResource instead, a leading slash would also have to be prepended to the returned value.
      Parameters:
      clazz - the input class. A null value or the default (empty) package will result in an empty string ("") being returned.
      Returns:
      a path which represents the package name
      See Also:

    • classNamesToString

      public static String classNamesToString(Class<?>... classes)
      Build a String that consists of the names of the classes/interfaces in the given array.

      Basically like AbstractCollection.toString(), but stripping the "class "/"interface " prefix before every class name.

      Parameters:
      classes - an array of Class objects
      Returns:
      a String of form "[com.foo.Bar, com.foo.Baz]"
      See Also:

    • classNamesToString

      public static String classNamesToString(@Nullable Collection<Class<?>> classes)
      Build a String that consists of the names of the classes/interfaces in the given collection.

      Basically like AbstractCollection.toString(), but stripping the "class "/"interface " prefix before every class name.

      Parameters:
      classes - a Collection of Class objects (may be null)
      Returns:
      a String of form "[com.foo.Bar, com.foo.Baz]"
      See Also:

    • toClassArray

      public static Class<?>[] toClassArray(@Nullable Collection<Class<?>> collection)
      Copy the given Collection into a Class array.

      The Collection must contain Class elements only.

      Parameters:
      collection - the Collection to copy
      Returns:
      the Class array
      Since:
      3.1
      See Also:

    • getAllInterfaces

      public static Class<?>[] getAllInterfaces(Object instance)
      Return all interfaces that the given instance implements as an array, including ones implemented by superclasses.
      Parameters:
      instance - the instance to analyze for interfaces
      Returns:
      all interfaces that the given instance implements as an array

    • getAllInterfacesForClass

      public static Class<?>[] getAllInterfacesForClass(Class<?> clazz)
      Return all interfaces that the given class implements as an array, including ones implemented by superclasses.

      If the class itself is an interface, it gets returned as sole interface.

      Parameters:
      clazz - the class to analyze for interfaces
      Returns:
      all interfaces that the given object implements as an array

    • getAllInterfacesForClass

      public static Class<?>[] getAllInterfacesForClass(Class<?> clazz, @Nullable ClassLoader classLoader)
      Return all interfaces that the given class implements as an array, including ones implemented by superclasses.

      If the class itself is an interface, it gets returned as sole interface.

      Parameters:
      clazz - the class to analyze for interfaces
      classLoader - the ClassLoader that the interfaces need to be visible in (may be null when accepting all declared interfaces)
      Returns:
      all interfaces that the given object implements as an array

    • getAllInterfacesAsSet

      public static Set<Class<?>> getAllInterfacesAsSet(Object instance)
      Return all interfaces that the given instance implements as a Set, including ones implemented by superclasses.
      Parameters:
      instance - the instance to analyze for interfaces
      Returns:
      all interfaces that the given instance implements as a Set

    • getAllInterfacesForClassAsSet

      public static Set<Class<?>> getAllInterfacesForClassAsSet(Class<?> clazz)
      Return all interfaces that the given class implements as a Set, including ones implemented by superclasses.

      If the class itself is an interface, it gets returned as sole interface.

      Parameters:
      clazz - the class to analyze for interfaces
      Returns:
      all interfaces that the given object implements as a Set

    • getAllInterfacesForClassAsSet

      public static Set<Class<?>> getAllInterfacesForClassAsSet(Class<?> clazz, @Nullable ClassLoader classLoader)
      Return all interfaces that the given class implements as a Set, including ones implemented by superclasses.

      If the class itself is an interface, it gets returned as sole interface.

      Parameters:
      clazz - the class to analyze for interfaces
      classLoader - the ClassLoader that the interfaces need to be visible in (may be null when accepting all declared interfaces)
      Returns:
      all interfaces that the given object implements as a Set

    • createCompositeInterface

      public static Class<?> createCompositeInterface(Class<?>[] interfaces, @Nullable ClassLoader classLoader)
      Create a composite interface Class for the given interfaces, implementing the given interfaces in one single Class.

      This implementation builds a JDK proxy class for the given interfaces.

      Parameters:
      interfaces - the interfaces to merge
      classLoader - the ClassLoader to create the composite Class in
      Returns:
      the merged interface as Class
      Throws:
      IllegalArgumentException - if the specified interfaces expose conflicting method signatures (or a similar constraint is violated)
      See Also:

    • determineCommonAncestor

      @Nullable public static Class<?> determineCommonAncestor(@Nullable Class<?> clazz1, @Nullable Class<?> clazz2)
      Determine the common ancestor of the given classes, if any.
      Parameters:
      clazz1 - the class to introspect
      clazz2 - the other class to introspect
      Returns:
      the common ancestor (i.e. common superclass, one interface extending the other), or null if none found. If any of the given classes is null, the other class will be returned.
      Since:
      3.2.6

    • isJavaLanguageInterface

      public static boolean isJavaLanguageInterface(Class<?> ifc)
      Determine whether the given interface is a common Java language interface: Serializable, Externalizable, Closeable, AutoCloseable, Cloneable, Comparable - all of which can be ignored when looking for 'primary' user-level interfaces. Common characteristics: no service-level operations, no bean property methods, no default methods.
      Parameters:
      ifc - the interface to check
      Since:
      5.0.3

    • isInnerClass

      public static boolean isInnerClass(Class<?> clazz)
      Determine if the supplied class is an inner class, i.e. a non-static member of an enclosing class.
      Returns:
      true if the supplied class is an inner class
      Since:
      5.0.5
      See Also:

    • isCglibProxy

      @Deprecated public static boolean isCglibProxy(Object object)
      Deprecated.
      as of 5.2, in favor of custom (possibly narrower) checks
      Check whether the given object is a CGLIB proxy.
      Parameters:
      object - the object to check
      See Also:

    • isCglibProxyClass

      @Deprecated public static boolean isCglibProxyClass(@Nullable Class<?> clazz)
      Deprecated.
      as of 5.2, in favor of custom (possibly narrower) checks
      Check whether the specified class is a CGLIB-generated class.
      Parameters:
      clazz - the class to check
      See Also:

    • isCglibProxyClassName

      @Deprecated public static boolean isCglibProxyClassName(@Nullable String className)
      Deprecated.
      as of 5.2, in favor of custom (possibly narrower) checks
      Check whether the specified class name is a CGLIB-generated class.
      Parameters:
      className - the class name to check

    • getUserClass

      public static Class<?> getUserClass(Object instance)
      Return the user-defined class for the given instance: usually simply the class of the given instance, but the original class in case of a CGLIB-generated subclass.
      Parameters:
      instance - the instance to check
      Returns:
      the user-defined class

    • getUserClass

      public static Class<?> getUserClass(Class<?> clazz)
      Return the user-defined class for the given class: usually simply the given class, but the original class in case of a CGLIB-generated subclass.
      Parameters:
      clazz - the class to check
      Returns:
      the user-defined class

    • getDescriptiveType

      @Nullable public static String getDescriptiveType(@Nullable Object value)
      Return a descriptive name for the given object's type: usually simply the class name, but component type class name + "[]" for arrays, and an appended list of implemented interfaces for JDK proxies.
      Parameters:
      value - the value to introspect
      Returns:
      the qualified name of the class

    • matchesTypeName

      public static boolean matchesTypeName(Class<?> clazz, @Nullable String typeName)
      Check whether the given class matches the user-specified type name.
      Parameters:
      clazz - the class to check
      typeName - the type name to match

    • getShortName

      public static String getShortName(String className)
      Get the class name without the qualified package name.
      Parameters:
      className - the className to get the short name for
      Returns:
      the class name of the class without the package name
      Throws:
      IllegalArgumentException - if the className is empty

    • getShortName

      public static String getShortName(Class<?> clazz)
      Get the class name without the qualified package name.
      Parameters:
      clazz - the class to get the short name for
      Returns:
      the class name of the class without the package name

    • getShortNameAsProperty

      public static String getShortNameAsProperty(Class<?> clazz)
      Return the short string name of a Java class in uncapitalized JavaBeans property format. Strips the outer class name in case of a nested class.
      Parameters:
      clazz - the class
      Returns:
      the short name rendered in a standard JavaBeans property format
      See Also:

    • getClassFileName

      public static String getClassFileName(Class<?> clazz)
      Determine the name of the class file, relative to the containing package: e.g. "String.class"
      Parameters:
      clazz - the class
      Returns:
      the file name of the ".class" file

    • getPackageName

      public static String getPackageName(Class<?> clazz)
      Determine the name of the package of the given class, e.g. "java.lang" for the java.lang.String class.
      Parameters:
      clazz - the class
      Returns:
      the package name, or the empty String if the class is defined in the default package

    • getPackageName

      public static String getPackageName(String fqClassName)
      Determine the name of the package of the given fully-qualified class name, e.g. "java.lang" for the java.lang.String class name.
      Parameters:
      fqClassName - the fully-qualified class name
      Returns:
      the package name, or the empty String if the class is defined in the default package

    • getQualifiedName

      public static String getQualifiedName(Class<?> clazz)
      Return the qualified name of the given class: usually simply the class name, but component type class name + "[]" for arrays.
      Parameters:
      clazz - the class
      Returns:
      the qualified name of the class

    • getQualifiedMethodName

      public static String getQualifiedMethodName(Method method)
      Return the qualified name of the given method, consisting of fully qualified interface/class name + "." + method name.
      Parameters:
      method - the method
      Returns:
      the qualified name of the method

    • getQualifiedMethodName

      public static String getQualifiedMethodName(Method method, @Nullable Class<?> clazz)
      Return the qualified name of the given method, consisting of fully qualified interface/class name + "." + method name.
      Parameters:
      method - the method
      clazz - the clazz that the method is being invoked on (may be null to indicate the method's declaring class)
      Returns:
      the qualified name of the method
      Since:
      4.3.4

    • hasConstructor

      public static boolean hasConstructor(Class<?> clazz, Class<?>... paramTypes)
      Determine whether the given class has a public constructor with the given signature.

      Essentially translates NoSuchMethodException to "false".

      Parameters:
      clazz - the clazz to analyze
      paramTypes - the parameter types of the method
      Returns:
      whether the class has a corresponding constructor
      See Also:

    • getConstructorIfAvailable

      @Nullable public static <T> Constructor<T> getConstructorIfAvailable(Class<T> clazz, Class<?>... paramTypes)
      Determine whether the given class has a public constructor with the given signature, and return it if available (else return null).

      Essentially translates NoSuchMethodException to null.

      Parameters:
      clazz - the clazz to analyze
      paramTypes - the parameter types of the method
      Returns:
      the constructor, or null if not found
      See Also:

    • hasMethod

      public static boolean hasMethod(Class<?> clazz, Method method)
      Determine whether the given class has a public method with the given signature.
      Parameters:
      clazz - the clazz to analyze
      method - the method to look for
      Returns:
      whether the class has a corresponding method
      Since:
      5.2.3

    • hasMethod

      public static boolean hasMethod(Class<?> clazz, String methodName, Class<?>... paramTypes)
      Determine whether the given class has a public method with the given signature.

      Essentially translates NoSuchMethodException to "false".

      Parameters:
      clazz - the clazz to analyze
      methodName - the name of the method
      paramTypes - the parameter types of the method
      Returns:
      whether the class has a corresponding method
      See Also:

    • getMethod

      public static Method getMethod(Class<?> clazz, String methodName, @Nullable Class<?>... paramTypes)
      Determine whether the given class has a public method with the given signature, and return it if available (else throws an IllegalStateException).

      In case of any signature specified, only returns the method if there is a unique candidate, i.e. a single public method with the specified name.

      Essentially translates NoSuchMethodException to IllegalStateException.

      Parameters:
      clazz - the clazz to analyze
      methodName - the name of the method
      paramTypes - the parameter types of the method (may be null to indicate any signature)
      Returns:
      the method (never null)
      Throws:
      IllegalStateException - if the method has not been found
      See Also:

    • getMethodIfAvailable

      @Nullable public static Method getMethodIfAvailable(Class<?> clazz, String methodName, @Nullable Class<?>... paramTypes)
      Determine whether the given class has a public method with the given signature, and return it if available (else return null).

      In case of any signature specified, only returns the method if there is a unique candidate, i.e. a single public method with the specified name.

      Essentially translates NoSuchMethodException to null.

      Parameters:
      clazz - the clazz to analyze
      methodName - the name of the method
      paramTypes - the parameter types of the method (may be null to indicate any signature)
      Returns:
      the method, or null if not found
      See Also:

    • getMethodCountForName

      public static int getMethodCountForName(Class<?> clazz, String methodName)
      Return the number of methods with a given name (with any argument types), for the given class and/or its superclasses. Includes non-public methods.
      Parameters:
      clazz - the clazz to check
      methodName - the name of the method
      Returns:
      the number of methods with the given name

    • hasAtLeastOneMethodWithName

      public static boolean hasAtLeastOneMethodWithName(Class<?> clazz, String methodName)
      Does the given class or one of its superclasses at least have one or more methods with the supplied name (with any argument types)? Includes non-public methods.
      Parameters:
      clazz - the clazz to check
      methodName - the name of the method
      Returns:
      whether there is at least one method with the given name

    • getMostSpecificMethod

      public static Method getMostSpecificMethod(Method method, @Nullable Class<?> targetClass)
      Given a method, which may come from an interface, and a target class used in the current reflective invocation, find the corresponding target method if there is one. E.g. the method may be IFoo.bar() and the target class may be DefaultFoo. In this case, the method may be DefaultFoo.bar(). This enables attributes on that method to be found.

      NOTE: In contrast to AopUtils.getMostSpecificMethod(java.lang.reflect.Method, java.lang.Class<?>), this method does not resolve Java 5 bridge methods automatically. Call BridgeMethodResolver.findBridgedMethod(java.lang.reflect.Method) if bridge method resolution is desirable (e.g. for obtaining metadata from the original method definition).

      NOTE: Since Spring 3.1.1, if Java security settings disallow reflective access (e.g. calls to Class#getDeclaredMethods etc, this implementation will fall back to returning the originally provided method.

      Parameters:
      method - the method to be invoked, which may come from an interface
      targetClass - the target class for the current invocation (may be null or may not even implement the method)
      Returns:
      the specific target method, or the original method if the targetClass does not implement it
      See Also:

    • getInterfaceMethodIfPossible

      @Deprecated public static Method getInterfaceMethodIfPossible(Method method)
      Deprecated.
      in favor of getInterfaceMethodIfPossible(Method, Class)
      Determine a corresponding interface method for the given method handle, if possible.

      This is particularly useful for arriving at a public exported type on Jigsaw which can be reflectively invoked without an illegal access warning.

      Parameters:
      method - the method to be invoked, potentially from an implementation class
      Returns:
      the corresponding interface method, or the original method if none found
      Since:
      5.1

    • getInterfaceMethodIfPossible

      public static Method getInterfaceMethodIfPossible(Method method, @Nullable Class<?> targetClass)
      Determine a corresponding interface method for the given method handle, if possible.

      This is particularly useful for arriving at a public exported type on Jigsaw which can be reflectively invoked without an illegal access warning.

      Parameters:
      method - the method to be invoked, potentially from an implementation class
      targetClass - the target class to check for declared interfaces
      Returns:
      the corresponding interface method, or the original method if none found
      Since:
      5.3.16
      See Also:

    • isUserLevelMethod

      public static boolean isUserLevelMethod(Method method)
      Determine whether the given method is declared by the user or at least pointing to a user-declared method.

      Checks Method.isSynthetic() (for implementation methods) as well as the GroovyObject interface (for interface methods; on an implementation class, implementations of the GroovyObject methods will be marked as synthetic anyway). Note that, despite being synthetic, bridge methods (Method.isBridge()) are considered as user-level methods since they are eventually pointing to a user-declared generic method.

      Parameters:
      method - the method to check
      Returns:
      true if the method can be considered as user-declared; false otherwise

    • getStaticMethod

      @Nullable public static Method getStaticMethod(Class<?> clazz, String methodName, Class<?>... args)
      Return a public static method of a class.
      Parameters:
      clazz - the class which defines the method
      methodName - the static method name
      args - the parameter types to the method
      Returns:
      the static method, or null if no static method was found
      Throws:
      IllegalArgumentException - if the method name is blank or the clazz is null