SFDC: Understanding With Sharing, Without Sharing & Unspecified Sharing Classes

Per my understanding of With Sharing, Without Sharing and non-sharing-specified Classes in Apex, I would like to jot down the following notes and leave certain blanks for not sure answers; I wanted to know if I were correct/not and clear/not with the following notes.

1) With Sharing keyword implies in another words, “with Security Settings enforced”. This again, pertains to only respecting OWDs and Sharing Rules [ What about Object Level Security/OLS and Field Level Security/FLS? ]

2) If a class is declared as “with sharing” then, the sharing settings apply to all code contained in the class, including initialization code, constructors and methods. However, Inner Classes DO NOT inherit sharing settings from the container class.

3) If a class is not declared either with sharing or without sharing, then by default, such a class is executed in system mode, i.e. without sharing mode; and current sharing rules remain in effect- which means that if any other class that has sharing enforced, calls such a non-specified-sharing class, then the called or non-specified-sharing class is executed in “with sharing” mode.

4) If class B extends class A, then all code in class B inherits the same sharing settings that class A has. However, class B’s inner classes do not inherit class B’s sharing settings.

5) If a with sharing class calls a without sharing class, then the called method(s) will be executed in the mode of the class in which they were defined, in this case, the called method(s) will execute in without sharing mode.

I have written a few example case scenarios, as below, that would summarize the understanding of the above concepts, I would like to learn if I am correct, also willing to know expert advice / suggestions w.r.t each of the below scenarios.

Say I have 3 classes:

  • public with sharing class A {}
  • public without sharing class B{}
  • public class C{} // Class C is a non-specified-sharing class.

Now, let’s consider the following case scenarios:

  1. class B extends A // class B’s code now executes in class A’s mode, i.e. in “with sharing” mode.

  2. class B calls class A // called code will now be executed in the mode of the class in which it was defined, in this case, in class A’s mode, i.e. in “with sharing” mode.

  3. class C calls class A // called method’s code in class A will execute in class A’s mode, i.e. in “with sharing” mode.

  4. class C extends class A // code in class C now executes in the parent class A’s mode, i.e. in “with sharing” mode.

  5. class A calls C // code in class C is executed in class C’s mode, i.e. in “without sharing” mode although it’s sharing settings are unspecified in the class’ declaration.

  6. class A extends C // class A’s code now executes in the parent class C’s mode, i.e. in “without sharing” mode.

I’m not quite sure of the case 6. Besides, I also wanted to know the use cases for which the with sharing and without sharing rules are applied and used. How are the sharing settings applicable in case of Visualforce Controller Classes and/or Controller Extensions.

Answer

Part 1

  1. Correct. You cannot “automatically” enforce field level security or profile permissions with “with sharing,” as this would make code much more difficult to debug because of failures. This is noted in Using the with sharing or without sharing Keywords, under the second note.

  2. Correct. This means that if do not specify “with sharing” or “without sharing” for the inner class, it behaves according to the calling class mode, or “without sharing” if called directly, except as noted in the first section of the link provided above.

  3. Partially correct. If you run a class that has no sharing in Execute Anonymous, or in Chatter, it is treated as “with sharing.” In all other cases, it is treated as “without sharing.” For most cases, this is not significant, but you should be aware of this feature.

  4. Correct. Extensions are basically a rewrite of the original class plus additional code, so they behave like the original class, including its sharing mode.

  5. Correct. Calling a function in a class will use the sharing mode of that class, unless it is undefined, in which case the mode stays the same.

Part 2

  1. Correct, as per 4 above.

  2. Correct, as per 5 above.

  3. Correct, as per 5 above.

  4. Correct, as per 4 above.

  5. Incorrect, as per 3 above. Because A has “with sharing”, C will have “with sharing” when called from A.

  6. Partially correct, or incorrect, depending on the exact definition of A. If A is “public with sharing class A extends C”, then it is “with sharing,” or if it is “public class A extends C”, then it falls under item 3 from part 1 (that is, “without sharing unless executed from executeAnonymous”).

With Sharing

This is when you’re trying to perform an update as the user. If user X cannot edit record Y, then an error will occur. If user X cannot see record Y, they cannot query that record. Use this mode when for pages that should respect sharing settings, or any other time you might want to enforce the rules.

For example, a page that edits opportunities should probably enforce sharing to make sure that users can’t modify other users’ sales data without the appropriate sharing in place. For Visualforce pages, this is true approximately 99% of the time. Some Visualforce pages might be able to circumvent sharing, for example, to show data that the user wouldn’t normally. A page that can tell users that a possible duplicate lead exists (without exposing who works the lead, or specific details) would not want to use “with sharing” in a private data model.

Without Sharing

This is when you’re trying to perform an update that should not fail ordinarily. For example, a logging system is designed to write certain non-fatal messages to a logging object. The user doesn’t have any right to edit the logging files normally (OWD is private, and the logging records are owned by a system administrator), but the logging files need to be queried and updated accordingly (to save space, etc). Using “with sharing” would make this code impossible, but by placing that code in a “without sharing” class, the code can make logs on behalf of the user even though that user has no access to the object normally. As another example, users can’t see others leads, but the system needs to flag potential duplicates and notify someone that there is a duplicate. “Without sharing” makes this code possible.

Attribution
Source : Link , Question Author : Swati , Answer Author : Matthew Souther

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