How to Fix java.lang.reflect.InvocationTargetException Error in Java

1. the java.lang.reflect.InvocationTargetException Error in Java
2. Causes of the java.lang.reflect.InvocationTargetException Error
3. Fix the java.lang.reflect.InvocationTargetException Error in Java
4. Conclusion

In this article, we will learn about java.lang.reflect.InvocationTargetException in Java.

the java.lang.reflect.InvocationTargetException Error in Java

The java.lang.reflect.InvocationTargetException is a very common exception whenever a developer is working with Java Reflection API. A checked exception holds an exception thrown by the invoked method or a constructor.

As of release JDK 1.4, this exception has been retrofitted to conform to the general-purpose exception chaining mechanism. In short whenever a developer tries to invoke a class using the Method.invoke() we get InvocationTargetException and it is wrapped around by java.lang.reflect.InvocationTargetException.

Causes of the java.lang.reflect.InvocationTargetException Error

The InvocationTargetException mainly occurs when a developer is working with the reflection layer and trying to invoke a constructor or a method that throws an underlying exception itself. So the Java reflection API wraps the exception thrown by the method with the InvocationTargetException.

Let’s have a code example to understand it better.

Example code:

import java.lang.reflect.*;

public class Test {
  public int divideByZero() {
    return 89 / 0;
  }

  public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException {
    Test obj = new Test();
    Method method = Test.class.getMethod("divideByZero");
    try {
      method.invoke(obj);
    } catch (InvocationTargetException e) {
      e.printStackTrace();
    }
  }
}

Output:

java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at Test.main(Test.java:13)
Caused by: java.lang.ArithmeticException: / by zero
    at Test.divideByZero(Test.java:6)
    ... 5 more

Fix the java.lang.reflect.InvocationTargetException Error in Java

Based on the above, we understood that the underlying exception is the reason for the java.lang.reflect.InvocationTargetException error. We can get more information about the underlying exception using the getCause () method of the Throwable class.

Hence, solving the InvocationTargetException involves finding and resolving the underlying exception.

Example code:

import java.lang.reflect.*;

public class Test {
  public int divideByZero() {
    return 89 / 0;
  }

  public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException {
    Test obj = new Test();
    Method method = Test.class.getMethod("divideByZero");
    try {
      method.invoke(obj);
    } catch (InvocationTargetException e) {
      System.out.println(e.getCause());
    }
  }
}

Output:

java.lang.ArithmeticException: / by zero

In the above output, the actual underlying exception is ArithmeticException, occurring because we are dividing by zero.

Once we fix the underlying exception, the InvocationTargetException is also resolved. The following is the full working code with no exceptions; We just removed the divide by zero part.

Complete Source Code:

import java.lang.reflect.*;

public class Test {
  public int divideByZero() {
    return 89 / 9;
  }

  public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException {
    Test obj = new Test();
    Method method = Test.class.getMethod("divideByZero");
    try {
      method.invoke(obj);
    } catch (InvocationTargetException e) {
      e.printStackTrace();
    }
  }
}

Conclusion

In this article, we learned how underlying exceptions are wrapped when we are working reflection layer in Java. We understood how to get the underlying exception when working with java.lang.reflect.InvocationTargetException and how to resolve it.