If I have a constructor object Constructor<?> productConstructor
, how can I call the run()
method that exists in that class?
For example, let’s say I have the class:
JavaScript
x
public class product1{
public product1(Instances instance){
// constructor
}
public void run(){
// do something
}
}
I can run the constructor for my class like this:
JavaScript
Constructor<?> productConstructor;
productConstructor = getProductConstructor(instance.getProductName());
// pass instance into constructor to run the tests
// example of what is happening here -> new product1(instance)
productConstructor.newInstance(new Object[] { instance });
JavaScript
public Constructor<?> getProductConstructor(String productName) {
try {
logger.info("Looking for Product Class: {}", productName);
String fullQualifiedClassPath = "com.products." + productName;
Class<?> clazz = Class.forName(fullQualifiedClassPath);
return clazz.getConstructor(Instances.class);
} catch (Exception e) {
logger.error("Product: {} does not exist", productName);
}
return null;
}
If I keep the code as is, then I have to place the run()
method inside of the constructor to run it, but I would like the run()
method outside of the constructor. How can I call my run method using the Constructor class for my class?
For example, something like this is what I had in mind but doesn’t work:
JavaScript
Constructor<?> productConstructor;
productConstructor = getProductConstructor(instance.getProductName());
productConstructor.newInstance(new Object[] { instance }).run(); // added .run() to the end but this doesn't work.
This doesn’t work because run
is undefined. This is because I cannot call a method this way on a class that is not known until runtime. This is where my problem lies.
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Answer
I was able to do it like this:
JavaScript
Constructor<?> productConstructor;
Class<?> productClass;
productConstructor = getProductConstructor(instance.getProductName());
productClass = getProductClass(instance.getProductName());
productClass.getMethod("run").invoke(productConstructor.newInstance(new Object[] { instance }));
public Constructor<?> getProductConstructor(String productName) {
try {
String fullQualifiedClassPath = "com.products." + productName;
logger.info("Looking for Product Constructor: {}", fullQualifiedClassPath);
Class<?> clazz = Class.forName(fullQualifiedClassPath);
return clazz.getConstructor(Instances.class);
} catch (Exception e) {
logger.error("Product: {} does not exist", productName);
}
return null;
}
public Class<?> getProductClass(String productName) {
try {
String fullQualifiedClassPath = "com.products." + productName;
logger.info("Looking for Product Class: {}", fullQualifiedClassPath);
return Class.forName(fullQualifiedClassPath);
} catch (Exception e) {
logger.error("Product: {} does not exist", productName);
}
return null;
}