Quoting, Sun's Official Java Tutorial
Class names, 'HelloWorldApp', are only
accepted if annotation processing is
explicitly requested
What does it mean? And how to apply it?
"Annotation Processing" is a hook into the compile process of the java compiler, to analyse the source code for user defined annotations and handle then (by producing compiler errors, compiler warning, emitting source code, byte code ...).
API reference: javax.annotation.processing (Java Platform SE 6).
From the very next line of the page that you refer to:
Class names, 'HelloWorldApp', are only accepted if annotation processing is explicitly requested
If you receive this error, you forgot to include the .java suffix when compiling the program. Remember, the command is javac HelloWorldApp.java not javac HelloWorldApp.
That is, the string that you are referring to is a possible error that you might get when trying to compile the examples. The very next line in the document, tells you how to resolve the issue.
If you want to know more about annotations, what they are, and how to use them, then I would suggest to go through the Annotations tutorial.
This error is due to incorrect use of java compilation command i.e javac with file name w/o java extension (.java)
Use proper compilation command
javac HelloWorldApp.java
Command used foe execution
java HelloWorldApp
Related
Sonarqube Version -7.9.5
SonarQube Scanner - sonar-scanner-msbuild-5.0.4.24009-net46
Source code contains - C#, angular.js, html5, javascript.
Hi,
I executed the following commands and after executing the 3rd command I am getting execution failure error.
The command I executed in the CMD prompt are browsing to the path where solution is present are,
SonarScanner.MSBuild.exe begin /k:"Demo" /d:sonar.host.url="http://localhost:9000" /d:sonar.login="TokenID_ABC"
MsBuild.exe /t:Rebuild
SonarScanner.MSBuild.exe end /d:sonar.login="TokenID_ABC"
ERROR: Error during SonarScanner execution
org.sonar.java.AnalysisException: Please provide compiled classes of your project with sonar.java.binaries property
I found one similar kind of issue reported where it is said that due to .java file present in the code the issue occurs, in our code as well .java files are present, not sure the use of them. How can I exclude those .java files while SonarQube analysis is performed and in which file do I need to add exclusion code?
Also, if there is some another solution to resolve this issue, then please let me know as I have very limited knowledge of Sonar.
Link of similar issue -
https://community.sonarsource.com/t/error-while-running-sonar-scanner-please-provide-compiled-classes-of-your-project-with-sonar-java-binaries-property/30027/2
You can exclude arbitrary files by going to your project settings in SonarQube -> Analysis Scope -> Source File Exclusions. Use regex to match your java files, i.e. *.java.
Motivation:
In our code we have a few places where some methods are run by their name. There are some big if-else-if blocks with each function name and call of the corresponding method (I use the term function to describe just names, for example function X01 might correspond to method SomeClass.functionX01). I've been looking into ways to improve that
Goal:
Write just methods that are annotated with some custom annotation, removing the need to update or even include if-else-if blocks in order to run specific function. Have access to any generated code if any code is generated.
What I did:
I've created first prove of concept using runtime annotations and it proved successful, but slower then if-else-if. Next attempt was with source annotation
I've followed this link for an example, however it did not seam to run in IntelliJ. What I wanted is to have - in this case PersonBuilder class generated, instead there was none. In some cases an error was raised Error:java: Bad service configuration file, or exception thrown while constructing Processor object: javax.annotation.processing.Processor: Provider BuilderProcessor not found
After some Googling and failing to find anything I've turned to book (Core Java, Volume II - Advanced Features - 9th Edition, Polish translation) and there was reccomended to run the following commands:
javac [AbstractProcessor implementation]
javac -processor [Compiled Processor] [other source files to compile]
This worked, however is unsatisfactory as it needs to happen inside IDE (NetBeans and IntelliJ to be specific) automatically during build. Code does not need to be generated on the fly, but programmer must have access to it after build (as in - be able to call methods of generated classes)
Question:
How to have and use generated code used in NetBeans and IntelliJ without the need of using external tools? Is it possible, or using reflection, runtime annotations or external tools is the only way?
Additional info (just in case):
Language level: Java 1.8
JVM versions: 12 and 13
IDEs: NetBeans and IntelliJ
I have a project that uses Java annotations to generate code. Since there is also Scala code in this project, I want to run my build in 3 phases:
Annotation processing (Java code generation)
Scala compilation
Java compilation
I'm trying to accomplish step 1 at the moment using javac's proc:only flag. I'm calling javac like this: javac -processor org.my.processor -processorpath /path/to/processor.jar /path/to/annotated/file.java
The code I want generated does in fact get generated and written to disk, but javac still insists on (seemingly) compiling my source files - the javac call fails with a bunch of symbol not found errors.
Does anyone know a) why the javac call is failing with "sumbol not found" despite the proc:only flag, and b) if there is another way I should be doing this?
I'm trying to look under the hood about java compilation. So I put my IDE away and started using MS-DOS command-line...
I created a simple project, as described in the tree below :
SampleApp
|____**src**
|_____pack
|______Sample.java
|____**classes**
This is the Sample.java source code :
public class Sample
{
private String s = new String("Hello, world");
public Sample(){
System.out.println(s);
}
}
I just want to compile this class, so I used the javac command :
prompt\SampleApp\src>javac -d ..\classes -sourcepath . pack\Sample.java
All works fine, but i didn't expect that because I deleted my CLASSPATH environment variable before compiling my Sample.java file. So I was expecting a compiler error due to the fact that the compiler would not be able to find the java.lang.String class file.
I read this article http://www.ibm.com/developerworks/java/library/j-classpath-windows/ which helped me understand many things. The article author says that the default classpath is the current working directory. But I don't understand why my source code compile without error. Could someone explain this to me?
So I was expecting a compiling error due to the fact that the compiler would not be able to find the java.lang.String class file.
The short answer is that the compiler knows where to find all of the standard Java SE library classes without you telling it.
The longer answer is that String class is being found on the bootclasspath. This is implicitly set by the javac command to refer to the relevant JARs in the JDK installation. The javac command searches the bootclasspath before it looks for stuff on the regular classpath.
The classpath variable doesn't do what you think. To cite the oracle documentation:
The CLASSPATH variable is one way to tell applications, including the
JDK tools, where to look for user classes. (Classes that are part of
the JRE, JDK platform, and extensions should be defined through other
means, such as the bootstrap class path or the extensions directory.)
Source: http://docs.oracle.com/javase/tutorial/essential/environment/paths.html
Basically since java.lang.* is part of the platform and delivered with the JDK/JRE, the compiler doesn't have to be told by you where to look for them.
I'm currently using Apache Tomcat 5.5.16 to serve a Lucene-based search API.
Lately I've been having some NullPointerExceptions inside my servlet class. The class is called com.my_company.search.servlet.SearchServlet.
With certain types of input I can routinely create a NullPointerException, but I'm having trouble figuring out where exactly it is.
The StackTrace indicates that the bug is occuring here:
com.my_company.search.servlet.SearchServlet.doGet(Unknown Source)
The source and .class files for this class is all in:
$TOMCAT_HOME/webapps/my_servlet/WEB-INF/classes/com/my_company/search/servlet/
My question is, how can I get Tomcat to provide me with more descriptive error locations?
Tomcat cannot provide you more detailed information unless the classes in question were compiled with debugging information. Without this debugging information, the JVM cannot determine what line of code the error occurred on.
Edit: You can ask the compiler to include this information by specifying the -g option when running javac on the command line. You can also specify this option using the debug parameter of the Javac Ant task.
you have to add debugging information to your classes. compile them with the option -g:
javac -g YourServlet.java
the location unknown source can occurs when the JIT compiler has optimized your class. At that point the source information is lost. to get the original location, restart the server and retry your test. Most of the time you will get the location in your source