Java 反射：使用树形图中的参数创建实例，如 python

Question

I am a python dev, now i want to create a Java instance using params from a treemap just like create a python instance which params from a dict...i try to do it through java reflection. but i can't find the solution.

anybody can give me a hand? THX

Answer 1

Not sure I am following, but from what I understand - you are trying to create properties of the object on the fly.

Well, that cannot be done in java, partially because the language is statically typed [unlike python].

In java, all fields of the object must be created at compile time . Reflection can help you to manipulate objects, but not to change their structure completely.

A workaround could be to use a Map<String,Object> , and hold the properites there. You will not need reflection for using this solution [which is a good thing, since reflection is both unsafe and tends to slow-down overall performance of the program].

Answer 2

Is this what you are looking for. Create a map to keep your classes.

private static Map<String, Class<? extends MySuperClass>> classesMap = new HashMap<String, Class<? extends MySuperClass>>();

Put class objects in map

static {
      classesMap.put("PERSON_CLASS", Person.class); 
      classesMap.put("ADDRESS_CLASS", Address.class);
}

Then a getInstance method that returns the instance of given class.

private static MySuperClass getInstance(String classNameConstant) throws Exception{
     Class<? extends MySuperClass> myClass = classesMap.get(classNameConstant);
     if(myClass!=null){
        return myClass.newInstance();
     }
     return null;
}

Hope this helps. Note: I don't know python.