On my java project, I have a bunch of strings externalized on a messages.properties file. On its respective Messages.java file I had the same number of public static String-typed attributes, so I could access those externalized texts.
Then, I implemented a method called getString, which receives the name of the constant as its argument and returns the wanted text. This way, there is no need to declare all the public static Strings-typed attributes inside the Messages.java file.
But after doing this my log became filled with "NLS unused message" messages.
Do you know if there's a way to prevent those warning messages to be logged?
Thanks in advance.
Your Messages class - it sounds like it extends org.eclipse.osgi.util.NLS.
If this is the case, it is designed to fill the requirements:
to provide compile time checking that a message exists.
to avoid the memory usage of a map containing both keys and values (this would be the case in a resource bundle approach).
good i18n support.
i.e. NLS populates the value of the Message.staticVariable with the value of the staticVariable found in messages.properties.
The warning logging provides information about a mismatch between the Messages.java and the messages.properties file.
Your getString() method sounds like it does not use any of the advantages of NLS, so as others have suggested, you may be better off using a ResourceBundle.
Messages sounds like a class you wrote, because I don't see it in my JDK 6 javadocs.
It sounds like you've tried to reinvent java.util.ResourceBundle. I'd recommend using that instead and ditching your class. It'll have the added advantage of handling I18N properly.
I don't see any value in hard-coding the public static message keys in the class. It's just another thing you'll have to maintain. If I understand what you're doing properly, I'd throw away your Messages and use ResourceBundle instead.
duffymo, as jamesh said, Messages is a class I wrote, and it extends org.eclipse.osgi.util.NLS. It has a private static attribute, and its type is... ResourceBundle!
jamesh, thanks for detailing the way NLS works.
Based on your answers I removed my Messages class from my project and added a ResourceBundle-typed attribute on the classes that need to use the externalized strings. Plus, I did it in a way that the lines accessing the externalized strings did not need to be changed.
The number of files on our project has been reduced, the code was kept as clean as before and there are no more log warnings.
Thank you, guys. You rock.
Related
I joined a new project which uses lombok #Slf4j for logging but has the following configuration:
lombok.log.fieldIsStatic=false
This prevents me from using Lombok's logger in static methods. I didn't get an explanation on why it is configured like this, but I am not allowed to change it. Obviously I can do it the old fashion way for static methods, e.g.
private static final Logger LOG = LoggerFactory.getLogger(MyClass.class);
but I love the annotated approach. So my question is whether it is possible to have it both ways, i.e. use Lombok's logging approach for both static and non-static methods without changing the lombok.log.fieldIsStatic property value.
Thank you for your attention.
From the docs
Configuration files are hierarchical: Any configuration setting
applies to all source files in that directory, and all source files in
subdirectories, but configuration settings closer to the source file
take precedence.
So you could create a second Lombok config file which is exclusive to one module, or maybe even just one package, which overrides the property at the root level to reset it back to static.
Otherwise, no.
I didn't get an explanation on why it is configured like this, but I
am not allowed to change it
This sounds like a cultural issue. I am all for following an established precedent, but only if someone can and will justify why it was chosen.
I am currently taking a project management class and the professor gave this assignment to compare two .java files methods and fields in all cases programmatically. I don't think it's actually possible to do but maybe I am wrong!
The assignment spec is as following (its extremely ambiguous I know)
In this assignment, you are required to write a comparison tool for two
versions of a Java source file.
Your program takes as input two .java files representing those two versions
and reports the following atomic changes:
1. AM: Add a new method
2. DM: Delete a method
3. CM: Change the body of a method (note: you need to handle the case where a method is
relocated within the body of its class)
4. AF: Add a field
5. DF: Delete a field
6. CFI: Change the definition of an instance field initializer (including (i) adding an initialization to a
field, (ii) deleting an initialization of a field, (iii) making changes to the initialized value of a field,
and (iv) making changes to a field modifier, e.g., private to public)
So that's what I am working with and my approach was to use reflection as it allows you to do everything but detect differences in the method body.
I had considered the idea that you could create a parser but that seemed ridiculous, especially for a 3 credit undergrad class in project management. Tools like BeyondCompare don't list what methods or fields changed, just lines that are different so don't meet the requirements.
I turned in this assignment and pretty much the entire class failed it with the reason as "our code would not work for java files with external dependencies that are not given or with java files in different projects" - which is completely correct but also I'm thinking, impossible to do.
I am trying to nail down a concrete answer as to why this is not actually possible to do or learn something new about why this is possible so any insight would be great.
What you got wrong here is that you have started to examine the .class files (using reflection). Some of the information listed above is not even available at that stage (generics, in-lined functions). What you need to do is parsing the .java files as text. That is the only way to actually solve the problem. A very high-level solution could be writing a program that:
reads the files
constructs a specific object for each .java file containing all the informations that needs to be compared (name of the functions, name of the instance variables, etc)
compares the constructed objects (example: addedFunctions = functionsFromA.removeAll(functionsFromB)) to provide the requested results
Note: if this is an assignment, you should not be using solutions provided by anybody else, you need to do it on your own. Likely you will not get a single point if you use a library written by somebody else.
hello guys i'm not sure if the title is descriptive enough.what i mean is creating an enum
like so
public enum Test{
ONE, TWO ,THREE
}
this looks like hard coded.if for some reason i need to add the FOUR some certain business rules evolution reasons.should i code it and deploy it again?
isn't a way to let it pick the elements from a file , spring config for example or property file?
THanks for reading.
If the enum value doesn't explicitly exist in code, how could you ever use it? Test.Four would not compile. Any code which could somehow reference Test.Four would be invalid and would crash, until the point in time when the file is read and the new values are added.
You can, of course, use arrays or collections of values and manipulate those at runtime - load them from a file or from the database or whatever - but not enums.
I asked a similar question here. The content may be of interest.
The concensus seemed to be that Java's enum type is static by design. If you need something that can be altered at runtime, you should ideally use a different data structure.
The less preferred ideas were along the lines of extending Enum, etc.
You may store in a database table.
I'm building a very simple Java parser, to look for some specific usage models. This is in no way lex/yacc or any other form of interpreter/compiler for puposes of running the code.
When I encounter a word or a set of two words separated by a dot ("word.word"), I would like to know if that's a standard Java class (and method), e.g. "Integer", or some user defined name. I'm not interested in whether the proper classes were included/imported in the code (i.e. if the code compiles well), and the extreme cases of user defined classes that override the names of standard Java classes also does not interest me. In other words: I'm okay with false negative, I'm only interesting in being "mostly" right.
If there a place wher I could find a simple list of all the names of all Java standard classes and methods, in the form easily saved into a text file or database? (J2SE is okay, but J2EE is better). I'm familiar with http://java.sun.com/j2se/ etc, but it seems I need a terrible amount of manual work to extract all the names from there. Also, the most recent JDK is not neccesary, I can live with 1.4 or 1.5.
Clarification: I'm not working in Java but in Python, so I can't use Java-specific commands in my parsing mechanism.
Thanks
What's wrong with the javadoc? The index lists all classes, methods, and static variables. You can probably grep for parenthesis.
To get all classes and methods you can look at the index on
http://java.sun.com/javase/6/docs/api/index-files/index-1.html
This will be 10's of thousands classes and method which can be overwhelming.
I suggest instead you use auto-complete in your IDE. This will show you all the matching classes/methods appropriate based on context.
e.g. say you have a variable
long time = System.
This will show you all the methods in System which return a long value, such as
long time = System.nanoTime();
Even if you know a lot of the method/classes, this can save you a lot of typing.
If you just want to create a list of all classes in Java and their methods (so that you can populate a database or an XML file), you may want to write an Eclipse-plugin that looks at the entire JavaCore model, and scans all of its classes (e.g., by searching all subtypes of Object). Then enumerate all the methods. You can do that technically to any library by including it in your context.
IBM had a tool for creating XML from JavaDocs, if I am not mistaken:
http://www.ibm.com/developerworks/xml/library/x-tipjdoc/index.html
There's also an option to either parse classlist file from jre/lib folder or open the jsse.jar file, list all classes there and make a list of them in dot-separated form by yourself.
When I encounter a word or a set of two words separated by a dot ("word.word"), I would like to know if that's a standard Java class (and method), e.g. "Integer", or some user defined name.
If thats what you're after, you could do without a (limited) list of Java Classes by using some simple reflection:
http://java.sun.com/developer/technicalArticles/ALT/Reflection/
try {
Class.forName("word.word");
System.out.println("This is a valid class!");
} catch (ClassNotFoundException e) {
System.out.println("This is not a valid class.");
}
Something like this should be enough for your purposes, with he added benefit of not being limited to a subset of classes, and extensible by any libraries on the classpath.
What is the purpose of annotations in Java? I have this fuzzy idea of them as somewhere in between a comment and actual code. Do they affect the program at run time?
What are their typical usages?
Are they unique to Java? Is there a C++ equivalent?
Annotations are primarily used by code that is inspecting other code. They are often used for modifying (i.e. decorating or wrapping) existing classes at run-time to change their behavior. Frameworks such as JUnit and Hibernate use annotations to minimize the amount of code you need to write yourself to use the frameworks.
Oracle has a good explanation of the concept and its meaning in Java on their site.
Also, are they unique to Java, is there a C++ equivalent?
No, but VB and C# have attributes which are the same thing.
Their use is quite diverse. One typical Java example, #Override has no effect on the code but it can be used by the compiler to generate a warning (or error) if the decorated method doesn't actually override another method. Similarly, methods can be marked obsolete.
Then there's reflection. When you reflect a type of a class in your code, you can access the attributes and act according to the information found there. I don't know any examples in Java but in .NET this is used by the compiler to generate (de)serialization information for classes, determine the memory layout of structures and declare function imports from legacy libraries (among others). They also control how the IDE form designer works.
/EDIT: Attributes on classes are comparable to tag interfaces (like Serializable in Java). However, the .NET coding guidelines say not to use tag interfaces. Also, they only work on class level, not on method level.
Anders gives a good summary, and here's an example of a JUnit annotation
#Test(expected=IOException.class)
public void flatfileMissing() throws IOException {
readFlatFile("testfiles"+separator+"flatfile_doesnotexist.dat");
}
Here the #Test annotation is telling JUnit that the flatfileMissing method is a test that should be executed and that the expected result is a thrown IOException. Thus, when you run your tests, this method will be called and the test will pass or fail based on whether an IOException is thrown.
Java also has the Annotation Processing Tool (apt) where not only you create annotations, but decide also how do these annotations work on the source code.
Here is an introduction.
To see some cool stuff you can do with Annotations, check out my JavaBean annotations and annotation processor.
They're great for generating code, adding extra validations during your build, and I've also been using them for an error message framework (not yet published -- need to clear with the bosses...).
The first thing a newcomer to annotations will ask about annotations is: "What is an annotation?" It turns out that there is no answer to this question, in the sense that there is no common behavior which is present in all of the various kinds of java annotations. There is, in other words, nothing that binds them together into an abstract conceptual group other than the fact that they all start with an "#" symbol.
For example, there is the #Override annotation, which tells the compiler to check that this member function overrides one in the parent class. There is the #Target annotation, which is used to specify what kinds of objects a user defined annotation (a third type of construct with nothing in common with other kinds of annotation) can be attached to. These have nothing to do with one another except for starting with an # symbol.
Basically, what appears to have happened is that some committee responsible for maintaining the java language definition is gatekeeping the addition of new keywords to the java language, and therefore other developers are doing an end run around that by calling new keywords "annotations". And that's why it is hard to understand, in general what an annotation is: because there is no common feature linking all annotations that could be used to put them in a conceptual group. In other words, annotations as a concept do not exist.
Therefore I would recommend studying the behavior of every different kind of annotation individually, and do not expect understanding one kind of annotation to tell you anything about the others.
Many of the other answers to this question assume the user is asking about user defined annotations specifically, which are one kind of annotation that defines a set of integers or strings or other data, static to the class or method or variable they are attached to, that can be queried at compile time or run time. Sadly, there is no marker that distinguishes this kind of annotation from other kinds like #interface that do different things.
By literal definition an annotation adds notes to an element. Likewise, Java annotations are tags that we insert into source code for providing more information about the code. Java annotations associate information with the annotated program element. Beside Java annotations Java programs have copious amounts of informal documentation that typically is contained within comments in the source code file. But, Java annotations are different from comments they annotate the program elements directly using annotation types to describe the form of the annotations. Java Annotations present the information in a standard and structured way so that it could be used amenably by processing tools.
When do you use Java's #Override annotation and why?
The link refers to a question on when one should use the override annotation(#override)..
This might help understand the concept of annotation better.Check out.
Annotations when it comes to EJB is known as choosing Implicit middle-ware approach over an explicit middle-ware approach , when you use annotation you're customizing what you exactly need from the API
for example you need to call transaction method for a bank transfer :
without using annotation :
the code will be
transfer(Account account1, Account account2, long amount)
{
// 1: Call middleware API to perform a security check
// 2: Call middleware API to start a transaction
// 3: Call middleware API to load rows from the database
// 4: Subtract the balance from one account, add to the other
// 5: Call middleware API to store rows in the database
// 6: Call middleware API to end the transaction
}
while using Annotation your code contains no cumbersome API calls to use the middle-
ware services. The code is clean and focused on business logic
transfer(Account account1, Account account2, long amount)
{
// 1: Subtract the balance from one account, add to the other
}