java.lang.NoSuchFieldException in reflection?

Question

Long time lurker, first time poster here. I've tried searching but couldn't find anything to resolve my issue.

Basically, I'm writing an addon for a game mod to get a few more features to the closed-source mod. As it's closed, and the original developer is Japanese, I figured reflection is probably my best bet.

I'm able to get an array of all the fields in the class I need, but I'm not able to get the value of any field. I need to get the "currentThrottle" value, so I can do some stuff when the entity is moving (and only when it's moving)

Here's my current code. I can't figure out why it's not working, because as you can see I use an if statement to make sure the field DOES exist, and then it still tells me it can't find it.

Final note; I'm totally self-educated in Java, everything I know is from reading forums like this and just diving in and playing with it; that's the best way I learn. So, if there's any really bad practice here please do let me know :)

Class planeClass = Class.forName("mcheli.plane.MCP_EntityPlane");
Field[] fields = planeClass.getFields();

//Some other irrelevant code

            for (Field field2 : fields) {
                String name = field2.getName();
                if (name.contains("currentThrottle")) { 
                    System.out.println("name: " + name);
                    try {
                        field = baseClass.getClass().getField(name);
                        field.setAccessible(true);

                        Class<?> targetType = field.getType();
                        Object objValue = targetType.newInstance();

                        Object value = field.get(objValue);

                        System.out.println("Throttle: " + value);
                    } catch (NoSuchFieldException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (SecurityException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (InstantiationException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (IllegalAccessException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }

What is `baseClass`? And why aren't you just using `field2`? — Jon Skeet, May 14 '14 at 14:41

score 0 · Answer 1 · answered May 14 '14 at 14:49

0

The variable objValue should be replaced with the object instance you want to get the field from:

Object value = field.get(objValue);

Should be:

Object value = field.get(baseClass)

answered May 14 '14 at 14:49

Anthony_Michael

42
4

score 0 · Answer 2 · answered May 14 '14 at 15:05

Your code doesn't show what baseClass is. Are you working with the Class that you think you are using?

Why not just use (try/catch not shown):

Class planeClass = Class.forName("mcheli.plane.MCP_EntityPlane");
Object plane = planeClass.newInstance();
Field throttleField = planeClass.getField("currentThrottle");
Object thottleValue = throttleField.get(plane);

java.lang.NoSuchFieldException in reflection?

2 Answers2