Object.requireNonNull skip nullable String

Question

My desktop client communicates with the server through Hessian.

Clients call search API method to find member by passed string teamId.

public Member findMemberByTeamId(FeedProvider provider, String teamId)
{
    Objects.requireNonNull(provider, "Provider can't be a null");
    Objects.requireNonNull(teamId, "Team id can't be a null");

    long starttime = System.currentTimeMillis();

    logger.debug("Started searching member: provider={}, teamId={}", provider, teamId);

    return dao.findMemberByTeamId(provider, teamdId);
}

But I got exception:

[WEB-68] [Service] ERROR Error occurred while downloading member: provider = Hedgehog, teamId = null org.springframework.dao.DataIntegrityViolationException: PreparedStatementCallback; SQL [SELECT * FROM TEAM WHERE ID = ?]; ORA-01722: invalid number ; nested exception is java.sql.SQLSyntaxErrorException:

Inside the logs I found following line:
[WEB-34] [Service] DEBUG Started searching member: provider=Hedgehog, teamId=null

If I connect to my server directly and call search API method with teamId = null, I get the NPE:

Exception in thread "main" java.lang.NullPointerException: Team id can't be a null
    at java.util.Objects.requireNonNull(Objects.java:228)

So, you pass null to a method that explicitly checks that its parameters are non null, and throws an NPE if one is null. Is that right? Why are you surprised to get an NPE? — JB Nizet, Aug 18 '16 at 14:44
@JBNizet, that's not the point. 4ex0V ask why this it the behavior because, in the log, the teamId=null but it seems not because no NPE is throw. If 4ex0V pass a null value to the method, the NPE is launched. — Ogma, Aug 18 '16 at 14:45
@4ex0V, could you debug and check if during the communication, the teamId is set to blank ? (put a debug point juste before your `Objects.requireNonNull` — Ogma, Aug 18 '16 at 14:46
Ah, so the question is "why does the log shows a null teamId although teamId is not null, since when I pass null, an NPE is thrown instead of the log to happen?", right? If so, check how the teamId is logged. That's probably where the problem is. — JB Nizet, Aug 18 '16 at 14:48
TeamId is logged by logback: logger.debug("Started searching member: provider={}, teamId={}", provider, teamId); — 4ex0V, Aug 18 '16 at 14:57
I can say that it is not a logging problem. Because then this id pass to DAO layer and there I get ORA-01722: invalid number `2016-08-18 14:44:11,272 +0000 [WEB-68] [Service] ERROR Error occurred while downloading member: provider = Hedgehog, teamId = null org.springframework.dao.DataIntegrityViolationException: PreparedStatementCallback; SQL [SELECT * FROM TEAM WHERE ID = ?]; ORA-01722: invalid number ; nested exception is java.sql.SQLSyntaxErrorException:` — 4ex0V, Aug 18 '16 at 15:10
It would help if you clarified your question, and posted all the relevant code. In the question itself. We already kind of guess what the problem is, and since we can't see any code, we're also forced to guess where the problem comes from. — JB Nizet, Aug 18 '16 at 15:37
The most likely cause is that the method is being called with teamId = "null" instead of teamId = null. — Klitos Kyriacou, Aug 18 '16 at 16:26
What is the detail on the nested SQLSyntaxErrorException referred to above? — Klitos Kyriacou, Aug 19 '16 at 08:48
@KlitosKyriacou, you were right. I received from client string = "null". Please write down the answer and I will mark it as solution. — 4ex0V, Aug 19 '16 at 09:15

score 0 · Accepted Answer · answered Aug 19 '16 at 12:35

Problems like this one are quite often caused by a misinterpretation of what you see reported:

[WEB-34] [Service] DEBUG Started searching member: provider=Hedgehog, teamId=null

This means that teamId either really is null, or is the String object containing the word "null". Unfortunately, there is nothing visible in the output to make the distinction. But the fact that you are already checking for null in your code, and not catching it, would mean that either there's a problem with your code or the variable is set to the string "null". As it turned out, it was indeed the string "null". (Other possibilities might have been that the code you see in your IDE was not the code you actually ran, which can sometimes happen due to e.g. configuration issues.)

But why on earth would your method be passed a String object containing "null"? A common cause is that the caller is converting from an Integer (for example, it might be an integer column from a JDBC connection where nulls are allowed in that column). It then gets the Integer object and converts it using String.valueOf(Object) before passing it to your method. If the Integer object contained an actual int, that would result in the string representation of that int. If it contained null, it would result in the string "null".

So a possible fix is to look at the caller of findMemberByTeamId and catch nulls before they get converted to String.

Object.requireNonNull skip nullable String

1 Answers1