B4J Question [jReflection] Method not found

MathiasM · Jun 17, 2021

Hello

I try to run a method which retrieves a string on an object using the jReflection library.
Here is a testcase:

I have an class named "MyObject"

B4X:

Sub Class_Globals
    Private mName As String
End Sub

Public Sub Initialize(Name As String)
    mName = Name
End Sub

Public Sub getName As String
    Return mName
End Sub

So I try to run getName so I receive the name of the instance. I now have this code:

B4X:

Dim mo As MyObject
mo.Initialize("Testname")

Dim reflect As Reflector
reflect.Target = mo
Log(reflect.RunMethod("_getname"))
'Log(reflect.RunMethod("getname"))
'Log(reflect.RunMethod("getName"))

I always run into an error stating that _getname doesn't exist. "getname" and "getName" also won't work.
While in the java files, "_getname" really exists:

Java:

public String  _getname(b4j.example.myobject __ref) throws Exception{
__ref = this;
RDebugUtils.currentModule="myobject";
if (Debug.shouldDelegate(ba, "getname", false))
     {return ((String) Debug.delegate(ba, "getname", null));}
RDebugUtils.currentLine=720896;
 //BA.debugLineNum = 720896;BA.debugLine="Public Sub getName As String";
RDebugUtils.currentLine=720897;
 //BA.debugLineNum = 720897;BA.debugLine="Return mName";
if (true) return __ref._mname /*String*/ ;
RDebugUtils.currentLine=720898;
 //BA.debugLineNum = 720898;BA.debugLine="End Sub";
return "";
}

What am I missing here?

Thanks a bunch!

Star-Dust · Jun 17, 2021

Please note that if you fill in with obfuscation the variables may change no and if you don't put a low line in the name. (my_name)
In any case use JavaObject, because reflect would use them if the variable was private not public

MathiasM · Jun 17, 2021

Thanks @Star-Dust for your reply. I tried using the JavaObject Library, yet a comparable error appears:

B4X:

Dim mo As MyObject
mo.Initialize("Testname")

Dim jo As JavaObject = mo
'Log(jo.RunMethod("_getname", Null))
'Log(jo.RunMethod("getname", Null))
'Log(jo.RunMethod("getName", Null))

The 3 different methods throw the same error:

java.lang.RuntimeException: Method: getName not found in: b4j.example.myobject

Star-Dust · Jun 17, 2021

B4X:

Sub Class_Globals
    Private mName As String
End Sub

Public Sub Initialize(Name As String)
    mName = Name
End Sub

Public Sub getMy_Name As String 'modify this
    Return mName
End Sub

Star-Dust · Jun 17, 2021

While in the java files, "_getname" really exists:

it exists compiled in debug mode, but if you compile in obfuscated it does not exist

klaus · Jun 17, 2021

If I understand well, you have written the class in B4J?
Then why do you want to use Reflection or JavaObject?
Just use:

B4X:

Log(mo.Name)

This routine:

B4X:

Public Sub getName As String
    Return mName
End Sub

Means that Name is a readable property, because of 'get' at the beginning.
A routine beginning with 'set' means a writable property.

agraham · Jun 17, 2021

MathiasM said:
always run into an error stating that _getname doesn't exist. "getname" and "getName" also won't work.

You are calling _getname with no parameters whereas your Java fragment shows that it takes one parameter. The error message is correct in this case. Because Java can overload method names as long as the method signatures differ it is correctly telling you that a method _getname with no parameters does not exist. You would need to call it with the instance of MyObject as a parameter.

MathiasM · Jun 17, 2021

agraham said:
You are calling _getname with no parameters whereas your Java fragment shows that it takes one parameter. The error message is correct in this case. Because Java can overload method names as long as the method signatures differ it is correctly telling you that a method _getname with no parameters does not exist. You would need to call it with the instance of MyObject as a parameter.

Spot on, this was the problem. I was confused with overloading and the fact that the 'method didn't exist' without parameters indeed. Thanks a lot!

Star-Dust said:

B4X:

Sub Class_Globals
    Private mName As String
End Sub

Public Sub Initialize(Name As String)
    mName = Name
End Sub

Public Sub getMy_Name As String 'modify this
    Return mName
End Sub

Thanks again for your reply. I changed the code as you said but the problem persisted. See @agraham

klaus said:
If I understand well, you have written the class in B4J?
Then why do you want to use Reflection or JavaObject?
Just use:

B4X:

Log(mo.Name)

Thanks for your reply @klaus , This example was very simplified. In my 'real' application the property names were loaded from a JSON file, not typed in code.

Thank you everybody for thinking with me and the very fast response times! Saved my day!

B4J Question [jReflection] Method not found

MathiasM

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