dotsid - Developer IT

Catching OutOfMemoryError

- by dotsid

Documentation for java.lang.Error says: An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch But as java.lang.Error is subclass of java.lang.Throwable I can catch this type of throwable. I understand why this is not good idea to catch this sort of exceptions. As far as I understand, if we decide to caught it, the catch handler should not allocate any memory by itself. Otherwise OutOfMemoryError will be thrown again. So, my question is: is there any real word scenarios when catching java.lang.OutOfMemoryError may be a good idea? if we catching java.lang.OutOfMemoryError how can we sure that catch handler doesn't allocate any memory by itself (any tools or best practicies)? Thanks a lot.

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Catching java.lang.OutOfMemoryError

- by dotsid

Documentation for java.lang.Error says: An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch But as java.lang.Error is subclass of java.lang.Throwable I can catch this type of throwable. I understand why this is not good idea to catch this sort of exceptions. As far as I understand, if we decide to caught it, the catch handler should not allocate any memory by itself. Otherwise OutOfMemoryError will be thrown again. So, my question is: is there any real word scenarios when catching java.lang.OutOfMemoryError may be a good idea? if we catching java.lang.OutOfMemoryError how can we sure that catch handler doesn't allocate any memory by itself (any tools or best practicies)? Thanks a lot.

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Throughput measurements

- by dotsid

I wrote simple load testing tool for testing performance of Java modules. One problem I faced is algorithm of throughput measurements. Tests are executed in several thread (client configure how much times test should be repeated), and execution time is logged. So, when tests are finished we have following history: 4 test executions 2 threads 36ms overall time - idle * test execution 5ms 9ms 4ms 13ms T1 |-*****-*********-****-*************-| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-----| <-----------------36ms---------------> For the moment I calculate throughput (per second) in a following way: 1000 / overallTime * threadCount. But there is problem. What if one thread will complete it's own tests more quickly (for whatever reason): 3ms 3ms 3ms 3ms T1 |-***-***-***-***----------------| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-| <--------------32ms--------------> In this case actual throughput is much better because of measured throughput is bounded by the most slow thread. So, my question is how should I measure throughput of code execution in multithreaded environment.

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Two pass JSP page rendering

- by dotsid

Suppose an example. I have following interface: public interface DataSource<T> { Future<T> fetch(); } This datasource can do asynchronous data fetching. And we have following tag for using datasource in JSP: <html> <d:fetch from="${orderDS}" var="orders"> <c:foreach in="${orders}" var="order"> <div class="order"> <c:out value="${order.title}" /> </div> </c:foreach> </d:fetch> </html> So, what I want? I want JSP rendering engine to call my custom tag (FetchTag in this example) twice. On first call FetchTag will do DataSource.fetch() call and save Future locally as a object field. On second call FetchTag do Future.get() call and will be blocked until data becomes available. Is there any way to do such a thing?

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Spring+JSP url building best practices

- by dotsid

I wonder if there are any good practices for addressing Spring controllers in JSP. Suppose I have controller: @Controller class FooController { // Don't bother about semantic of this query right now @RequestMapping("/search/{applicationId}") public String handleSearch(@PathVariable String applicationId) { [...] } } Of course in JSP I can write: <c:url value="/search/${application.id}" /> But it's very hard to change url then. If you familiar with Rails/Grails then you now how this problem resolved: redirect_to(:controller => 'foo', :action = 'search') But in Spring there is so much UrlMappers. Each UrlMapper have own semantic and binding scheme. Rails alike scheme simply doesn't work (unless you implement it yourself). And my question is: are there any more convenient ways to address controller from JSP in Spring?

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Getting source code information from groovy stack trace

- by dotsid

When exception generated I want to show some additional information (source code) for particular exception. But grails have very hairy exceptions (it's all about groovy dynamic nature). It's my problem where to get and how to display source code. All I need is file/line information. So... Is there any possibility to get file and line where exception were generated in grails/groovy?

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