I am using STS 3.4 and working on a web application based on Grails framework.
When i try to use System.err.println in groovy classes it does not print anything on standard eclipse console(STS console).
Actually there are times when in print things but that is like 1 in 10, I couldn't understand this random behavior.
I am using some library that uses System.err.println for debugging purposes but i could not get any debugging info. All i need to know is where and how to get System.err.println output?
Please help me, Thanks in advance
If it is a random behaviour, it may be not-flush-ed buffered stream. Especially, that can happen when output comes from different thread.
As a solution, you can hook in into System.err dispatching (it's a stream, that you can set from outside), and overload functions, to get desired output anywhere you want. Or simply force flush it. But be careful, as it may lead to performance problems.
Consider using logging instead for more standard and configurable output. This should help you to set it up: http://groovy.codehaus.org/Logging
Lets say for example I write many times priavte instead private.
Is there a way to let Eclipse automatically fix my common typo?
Something like construct a map of my common typo to its desire fix,
and then just let Eclipse fix it without asking me about that.
Are there any other IDE\editors that have such support?
There is no builtin support for automatically changing strings. The closest to your request are the templates of the Java editor, but even those must explicitly be activated using CtrlSpace.
To get around your problem, I suggest simply not to write that much yourself. If you want to declare a private field, type just "pr" and hit CtrlSpace to invoke code completion. Eclipse can do code completion quite well, often even without any trigger characters (try it with an empty class file).
i have this Problem with my test ..the
driver.findElement(By.xpath("//html/body/div[2]/div/div/div[2]/div[2]/div/div[2]/div/div/div/div/div/div/div/ul/li[2]/a[2]/em/span/span/span")).click();
don't find the element.
the eclipse show this message of error
Cannot locate a node using
//html/body/div[2]/div/div/div[2]/div[2]/div/div[2]/div/div/div/div/div/div/div/ul/li[2]/a[2]/em/span/span/span
EDIT : Post edited to reflect answer to actual problem. Original answer follows.
Long XPath expressions are fragile, and tests are prone to fail when relying on them : a completely unrelated change somewhere else in the document can mess everything up, and even if you're aware of the problem, the tests' code is just harder to maintain.
In this particular case, since the site is generated by GWT, it's even worse - there is little control over the actual HTML changes. A good solution when using GWT is to use the ensureDebugId method (see link in comments).
Are you sure that this XPath expression is correct ? Does other tests work with this driver ?
I'd recommend avoiding the use of long XPath expressions like that - wouldn't it be safer in the long term to start the expression at an id-specified div somewhere in the page rather than at the root of the DOM ?
I'm not much of an Eclipse guru, so please forgive my clumsiness.
In Eclipse, when I call Assert.assertEquals(obj1,obj2) and that fails, how do I get the IDE to show me obj1 and obj2?
I'm using JExample, but I guess that shouldn't make a difference.
Edit: Here's what I see:
(source: yfrog.com)
.
Comparison with failure trace is not a easy task when your object is a little bit complex.
Comparison with debugger is useful if you have not redefined toString(). It remains still very tedious as solution because you should inspect with your eyes each objects from both sides.
Junit Eclipse plugin offers a option when there is a failure : "Compare actual With Expected TestResult". The view is close enough to classic content comparison tools :
Problem is that it is avaiable only when you writeassertEquals() with String objects (in the screenshot, we can see that the option in the corner is not proposed with no String class) :
You may use toString() on your object in assertion but it's not a good solution :
firstly, you correlate toString() with equals(Object)... modification of one must entail modification of the other.
secondly, the semantic is not any longer respected. toString() should return a useful method to debug the state of one object, not to identify an object in the Java semantic (equals(Object)).
According to me, I think that the JUnit Eclipse plugin misses a feature.
When comparison fails, even when we compare not String objects, it should offer a comparison of the two objects which rely on their toString() method.
It could offer a minimal visual way of comparing two unequals objects.
Of course, as equals(Object) is not necessarily correlated to toString(), highlighted differences should be studied with our eyes but it would be already a very good basis and anyway, it is much better than no comparison tool.
If the information in the JUnit view is not enough for you, you can always set a exception breakpoint on, for example, java.lang.AssertionError. When running the test, the debugger will stop immediately before the exception is actually being thrown.
Assert.assertEquals() will put the toString() representation of the expected and actual object in the message of the AssertionFailedError it throws, and eclipse will display that in the "failure trace" part of the JUnit view:
(source: ibm.com)
If you have complex objects you want to inspect, you'll have to use the debugger and put a breakpoint inside Assert.assertEquals()
What are you seeing?
When you do assertTrue() and it fails, you see a null.
But when you do assertEquals, it is supposed to show you what it expected and what it actually got.
If you are using JUnit, mke sure you are looking at the JUnit view and moving the mouse to the failed test.
FEST Assert will display comparison dialog in case of assertion failure even when objects you compare are not strings. I explained it in more detail on my blog.
If what you are comparing is a String then you can double click stack element and it will popup a dialog showing the diff in eclipse.
This only works with Strings though. For the general case the only way to see the real reason is to install a breakpoint and step into it.
Some of the developers on the project I work on have a habit of commenting their code to show which version of the product it was added for, e.g.
// added for superEnterpriseyWonder v2.5
string superMappingTag = MakeTag(extras);
if (superMappingTag.empty())
{
autoMapping = false;
}
// end added for superEnterpriseyWonder v2.5
Whenever I see this my blood pressure rises, and I have to spend 5 minutes browsing SO to cool off. It seems to me that they don't understand version control and if I were to use this practice too every other line in the source files would be a comment about when things were added. I'm considering removing all such comments from files that I work on, but am wondering is it just me being picky and is there actually some value to these comments?
If you're using Source Control then I would advocate adding a build label to Source Control after every build. That way you can search for all source modified for a specific build, with no nasty comments clogging your code.
This from Clean Code, a book by Bob Martin:
"The proper use of comments is to
compensate for our failure to express
ourself in code. Note that I used the
word failure. I meant it. Comments are
always failures."
I always think of that quote when I see a comment so I'm not suprised your blood boils.
No value whatsoever. If you have a blame tool in your version control this will achieve this, they just add noise.
Whats worse is they will attract further comments to your code to make it completely unreadable
// added for superEnterpriseyWonder v2.5
string superMappingTag = MakeTag(extras);
if (superMappingTag.empty())
{
// bug fix #12345674 shuld have been true
autoMapping = true;
// bug fix #12345674 should have been true
i++; // v2.6 now need to up the counter DO NOT DELETE
}
// end added for superEnterpriseyWonder v2.5
and then someone will delete the method but leave the code comment in
// added for superEnterpriseyWonder v2.5
// bug fix #12345674 should have been true
// v2.6 now need to up the counter DO NOT DELETE
// end added for superEnterpriseyWonder v2.5
Just say no to crappy comments
I'd say there's no value: This info can also be retrieved with your SCM's annotate/blame functionality. Also, anyone can add text between these comments, which make the comments dated (since you might add something for v2.6 while the comments say v2.5)
Another thing to note is that these comments are essentially hidden: You only see them when you are looking at the source code in question, so you can't use it to generate a changelog or something.
The comment as shown, is probably not to useful. However, there may be times that adding a feature may cause the addition of not so obvious code. In which case, a comment describing the change and/or why it the code is not obvious would be appropriate.
Not only is there no value here...there's negative value. Maintenance of comments is already sketchy in most places, this just adds another thing for people to screw with. These comments have no value to the reader and are therefore clogging their brain up with useless version information when they could have another line of code in their memory. It's also another line to have a merge conflict on (totally not joking here..I've seen merge conflicts on comments).
Could be useful in some cases (e.g. if this helps to understand why some function works differently in V3 than in V2) but in general, it's the job of the SCM to know what has been added when.
You are not picky IMHO. There are at least three good reasons not to add this type of comment in source code:
their place is actually in a Version Control System, where you can have a global view of everything that has changed to accommodate a new version of a library or a new feature. Provided it is done correctly and the logs are used.
if the source code is part of the deliverables to clients, maybe they don't need to know the history of what happened. Imagine you have done a modification for another client, and put that in comments!
too many comments are no better than too few.
The line is not clear though, what would be the difference between
// Compliance with specs abc (additional xyz feature)
...
... // some code
and:
// xyz feature:
...
... // some code
In general terms, I would not put anything that is related to the history in the source code, but stick to commenting what is done, how it is done, so that someone else can easily browse through the code and understand it.
My advice: have a methodology document written, or an informal discussion.
If seeing a superfluos comment makes your blood pressure rise, you need to take up drinking or something.
That said, I agree that such comments are mostly useless. If used consistently, the program would quickly become a maze of such comments. What if a line is changed once for version 2.5 and then a year later changed again for bug 3294? Do you put two "version" comments on the same line, or just keep the latest? If you only keep the latest, then you've lost the fact that this was originally added for 2.5. If you keep them both, what happens when there's a third change or a fourth? How do we know what the state was at each change? What happens when you add a block of code in version 2.5, and then for version 2.6 you add another block of code embedded within the 2.5 block? Etc etc. The program could easily end up having more version comments than lines of code.
If not done consistently, the comments would quickly become misleading. Someone could put a comment saying this block was added for 2.5, someone else could insert code inside that block for version 2.6 and not comment it, and now we have a comment that seems to say that the second block was added for 2.5.
And do we care that much? It's pretty rare that I care when a change was made. Oh, okay a couple of weeks ago I cared because I wanted to know who to blame for a major screw up.
As others have pointed out, version control systems do this for you on the rare occasions when you need it. I guess if you didn't have any sort of VCS, a case could be made for doing this. But you can get some very nice VCSs for free. If you need one, get one. Otherwise you're like the people who say that you should practice doing arithmetic in your head because otherwise what would you do if your calculator quit working. The assumption apparently being that at any moment, all the calculators in the world might simultaneously break.
You might say that it can help to be able to say, "Ohhhh, this was added to order entry to support the new salesman timecard function" or some such. But then the important this is not "This code was changed by Bob for version 3.2.4", but rather, "This code produces this data which isn't used here but is needed by another module over there".
I am a firm believer in writing comments that introduce sections of code and describe the general idea behind complex or otherwise non-obvious code. But that's an entirely different thing.
Consider that some may have to grab snapshots from the VCS. In that case, they don't have history to fall back on .. and such comments become useful.
I saw that a lot in code written by people that didn't use version control until recently. I guess they just took the habit and now it's hard to stop.
Another reason I found was that sometime it is important to know what piece of code is associated with what version. Of course you can always check the version log, but you don't always have time for that, and it's annoying. In some cases saying "code for v3.2" speaks more to other developers than "code to do x, y and z"... it all depends on the conventions established by the team.
Another answer is that in some projects I worked with some code was commented like that, but it was before the project actually started using version control. In that case it also made sense to keep it that way.
I find them useful, it saves chasing through the VCS to find out why a change was made to the code, or to find the BugId for a defect, given I remember what the code change was.
Although in theory the VCS contains the information, in practice it can get buried, particularly by integrations.
In other works which is easier:
// DEF43562 - changed default value
foobar = true
Or
blame(or equiv)
chase through
history to find the correct change.
Follow integration to source, and
repeat 1&2.
Find bug id attached
to original change, if you are
lucky.
Basically the comment is a short-cut around the VCS, and flaky VCS/BugTracking integration.
I find that the comments are also useful as a marker for: "This decision has been reviewed by customers/users/review committee, and this is the selected answer, be careful about changing the behaviour".