Class MethodInvoker

Direct Known Subclasses:

public class MethodInvoker extends Object
Helper class that allows for specifying a method to invoke in a declarative fashion, be it static or non-static.

Usage: Specify "targetClass"/"targetMethod" or "targetObject"/"targetMethod", optionally specify arguments, prepare the invoker. Afterwards, you may invoke the method any number of times, obtaining the invocation result.

Colin Sampaleanu, Juergen Hoeller
See Also:
  • Field Details

  • Constructor Details

    • MethodInvoker

      public MethodInvoker()
  • Method Details

    • setTargetClass

      public void setTargetClass(@Nullable Class<?> targetClass)
      Set the target class on which to call the target method. Only necessary when the target method is static; else, a target object needs to be specified anyway.
      See Also:
    • getTargetClass

      @Nullable public Class<?> getTargetClass()
      Return the target class on which to call the target method.
    • setTargetObject

      public void setTargetObject(@Nullable Object targetObject)
      Set the target object on which to call the target method. Only necessary when the target method is not static; else, a target class is sufficient.
      See Also:
    • getTargetObject

      @Nullable public Object getTargetObject()
      Return the target object on which to call the target method.
    • setTargetMethod

      public void setTargetMethod(@Nullable String targetMethod)
      Set the name of the method to be invoked. Refers to either a static method or a non-static method, depending on a target object being set.
      See Also:
    • getTargetMethod

      @Nullable public String getTargetMethod()
      Return the name of the method to be invoked.
    • setStaticMethod

      public void setStaticMethod(String staticMethod)
      Set a fully qualified static method name to invoke, e.g. "example.MyExampleClass.myExampleMethod". Convenient alternative to specifying targetClass and targetMethod.
      See Also:
    • setArguments

      public void setArguments(Object... arguments)
      Set arguments for the method invocation. If this property is not set, or the Object array is of length 0, a method with no arguments is assumed.
    • getArguments

      public Object[] getArguments()
      Return the arguments for the method invocation.
    • prepare

      public void prepare() throws ClassNotFoundException, NoSuchMethodException
      Prepare the specified method. The method can be invoked any number of times afterwards.
      See Also:
    • resolveClassName

      protected Class<?> resolveClassName(String className) throws ClassNotFoundException
      Resolve the given class name into a Class.

      The default implementations uses ClassUtils.forName, using the thread context class loader.

      className - the class name to resolve
      the resolved Class
      ClassNotFoundException - if the class name was invalid
    • findMatchingMethod

      @Nullable protected Method findMatchingMethod()
      Find a matching method with the specified name for the specified arguments.
      a matching method, or null if none
      See Also:
    • getPreparedMethod

      public Method getPreparedMethod() throws IllegalStateException
      Return the prepared Method object that will be invoked.

      Can for example be used to determine the return type.

      the prepared Method object (never null)
      IllegalStateException - if the invoker hasn't been prepared yet
      See Also:
    • isPrepared

      public boolean isPrepared()
      Return whether this invoker has been prepared already, i.e. whether it allows access to getPreparedMethod() already.
    • invoke

      Invoke the specified method.

      The invoker needs to have been prepared before.

      the object (possibly null) returned by the method invocation, or null if the method has a void return type
      InvocationTargetException - if the target method threw an exception
      IllegalAccessException - if the target method couldn't be accessed
      See Also:
    • getTypeDifferenceWeight

      public static int getTypeDifferenceWeight(Class<?>[] paramTypes, Object[] args)
      Algorithm that judges the match between the declared parameter types of a candidate method and a specific list of arguments that this method is supposed to be invoked with.

      Determines a weight that represents the class hierarchy difference between types and arguments. A direct match, i.e. type Integer → arg of class Integer, does not increase the result - all direct matches means weight 0. A match between type Object and arg of class Integer would increase the weight by 2, due to the superclass 2 steps up in the hierarchy (i.e. Object) being the last one that still matches the required type Object. Type Number and class Integer would increase the weight by 1 accordingly, due to the superclass 1 step up the hierarchy (i.e. Number) still matching the required type Number. Therefore, with an arg of type Integer, a constructor (Integer) would be preferred to a constructor (Number) which would in turn be preferred to a constructor (Object). All argument weights get accumulated.

      Note: This is the algorithm used by MethodInvoker itself and also the algorithm used for constructor and factory method selection in Spring's bean container (in case of lenient constructor resolution which is the default for regular bean definitions).

      paramTypes - the parameter types to match
      args - the arguments to match
      the accumulated weight for all arguments