You would make that a module-level variable. For example, // In foo.js define(function () { var theFoo = {}; return { getTheFoo: function () { return theFoo; } }; }); // In bar.js define([“./foo”], function (foo) { var theFoo = foo.getTheFoo(); // save in convenience variable return { setBarOnFoo: function () { theFoo.bar = “hello”; … Read more
See the comments section for other questions about the same matter. Short answer for your question: no, it’s not ok to put these classes in a singleton. Neither DocumentBuilderFactory nor DocumentBuilder are guaranteed to be thread safe. If you have several threads parsing XML, make sure each thread has its own version of DoumentBuilder. You … Read more
First, you should generally use -fPIC flag when building shared libraries. Not using it “works” on 32-bit Linux, but would fail on 64-bit one with an error similar to: /usr/bin/ld: /tmp/ccUUrz9c.o: relocation R_X86_64_32 against `.rodata’ can not be used when making a shared object; recompile with -fPIC Second, your program will work as you expect … Read more
You could use reflection to reset your singleton object to prevent tests from affecting each other. @Before public void resetSingleton() throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException { Field instance = MySingleton.class.getDeclaredField(“instance”); instance.setAccessible(true); instance.set(null, null); } Ref: unit-testing-singletons
monostate and singleton are two faces of the same medal (global state): monostate forces a behaviour (only one value along all class instances) singleton forces a structural constraint (only one instance) singleton usage is not transparent i.e.: Singleton singleton = Singleton.getInstance(); monostate usage is transparent i.e.: MonoState m1 = new MonoState(); MonoState m2 = new … Read more
Yes, singletons are bad. They are bad because all they do for you is combine two properties, each of which is bad about 95% of the time. (Which would mean that on average, singletons are bad 99.75% of the time ;)) A singleton, as defined by the GoF, is a data structure which: Grants global … Read more
Have a look at the Google Testing blog: Using dependency injection to avoid singletons Singletons are Pathological Liars Root Cause of Singletons Where have all the Singletons Gone? Clean Code Talks – Global State and Singletons Dependency Injection. And also: Once Is Not Enough Performant Singletons Finally, Misko Hevery wrote a guide on his blog: … Read more
The main advantage of a singleton over a class consisting of statics is that you can later easily decide that you need in fact more than one instance, e.g. one per thread. However, in practice the main purpose of singletons is to make people feel less bad about having global variables. A practical example for … Read more
Spring’s default scope is singleton. It’s just that your idea of what it means to be a singleton doesn’t match how Spring defines singletons. If you tell Spring to make two separate beans with different ids and the same class, then you get two separate beans, each with singleton scope. All singleton scope means is … Read more
Typically singletons are used for global configuration. The simplest example would be LogManager – there’s a static LogManager.getLogManager() method, and a single global instance is used. In fact this isn’t a “true” singleton as you can derive your own class from LogManager and create extra instances that way – but it’s typically used as a … Read more