Improve company productivity with a Business Account.Sign Up

x
?
Solved

Private class members in reflected class

Posted on 2012-04-12
3
Medium Priority
?
300 Views
Last Modified: 2012-04-16
Here:
http://docs.oracle.com/javase/tutorial/reflect/index.html
is a discussion of reflection. One part says:
Exposure of Internals
    Since reflection allows code to perform operations that would be illegal in non-reflective code, such as accessing private fields and methods, the use of reflection can result in unexpected side-effects, which may render code dysfunctional and may destroy portability. Reflective code breaks abstractions and therefore may change behavior with upgrades of the platform.

How and why does this happen? Why do class members lose their access modifier definition?
0
Comment
Question by:allelopath
  • 2
3 Comments
 
LVL 19

Accepted Solution

by:
ramazanyich earned 1400 total points
ID: 37841541
IT is due to setAccessible API which is available in reflection APi.
lets say you have class:
public class PrivateObject {

  private String privateString = null;

  public PrivateObject(String privateString) {
    this.privateString = privateString;
  }
}

by usin reflection API you can get privateString value

Field privateStringField = PrivateObject.class.
            getDeclaredField("privateString");

privateStringField.setAccessible(true);

String fieldValue = (String) privateStringField.get(privateObject);
System.out.println("fieldValue = " + fieldValue);
0
 
LVL 19

Expert Comment

by:ramazanyich
ID: 37841543
same setAccesible API is applicable for Method
0
 
LVL 12

Assisted Solution

by:Sharon Seth
Sharon Seth earned 600 total points
ID: 37841972
Reflective code breaks abstractions

Say the following is a property in your class and you have a setter for this property:

private List  items;

public void setItems(Map items)
{
   this.items = items;
}      

Here you have declared an abstraction over the underlying collection for items . The actual collection used can be any of the List implementations

When you go for reflection and try to access the setter on items , but items was assigned  an ArrayList , then the reflection mechanism would throw  NoSuchMethodException , clearly breaking the abstraction you had defined .
0

Featured Post

Get your problem seen by more experts

Be seen. Boost your question’s priority for more expert views and faster solutions

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Are you developing a Java application and want to create Excel Spreadsheets? You have come to the right place, this article will describe how you can create Excel Spreadsheets from a Java Application. For the purposes of this article, I will be u…
Introduction This article is the last of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article covers our test design approach and then goes through a simple test case example, how …
Viewers learn about the scanner class in this video and are introduced to receiving user input for their programs. Additionally, objects, conditional statements, and loops are used to help reinforce the concepts. Introduce Scanner class: Importing…
Viewers will learn one way to get user input in Java. Introduce the Scanner object: Declare the variable that stores the user input: An example prompting the user for input: Methods you need to invoke in order to properly get  user input:

588 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question