The dropwizard manual suggests to implement a javax.ws.rs.ext.ExceptionMapper in order to have more control of the generated responses for error cases. However, it does not tell me which maven dependency to use. The central maven repository yields dozens of result pages for this class. So which artifact should I choose?
The ExceptionMapper interface should already be pulled in when you reference dropwizard-core. You shouldn't need to add any other dependencies.
dropwizard-core depends on dropwizard-jersey which depends on jersey-server which depends on jersey-common which depends on javax.ws.rs-api which has the ExceptionMapper interface.
Related
I read the Akka v2.3.11 docs (Java, not Scala) and am still a bit confused about how configuration works. In section 2.9.2 ("Akka and JAR bundling") it states:
Akka’s configuration approach relies heavily on the notion of every module/jar having its own reference.conf file, all of these will be discovered by the configuration and loaded. Unfortunately this also means that if you put/merge multiple jars into the same jar, you need to merge all the reference.confs as well. Otherwise all defaults will be lost and Akka will not function.
Being brand new to Akka and actors, but having been a Java developer for 10+ years, I have never once before seen a reference.conf file in any JAR. So what is Akka talking about here? Are they insinuating that if my Akka project uses, say, Guice and Guava, that I need to define reference.conf files for each of these?!?
Also, can someone confirm my understanding of application.conf vs reference.conf? My understanding is that you are supposed to define a reference.conf that contains default Akka configs, and then also define an application.conf that overrides it? If that's true, why use reference.conf in the first place? Why not just use an application.conf? I'm so confused.
Akka uses typesafe config library, have a look at the documentation https://github.com/typesafehub/config/blob/master/README.md that explains the difference between reference.conf and application.conf.
Basically reference.conf comes with Akka libraries, user shouldn't touch it (but can use as a reference) unless merging multiple jars (not necessary akka jars) that use typesafe config library into one jar.
I've been using c3p0 with hibernate for a couple of years. When looking at exception stack traces, I see classes such as com.mchange.v2.c3p0.impl.NewProxyPreparedStatement in the stack. I went looking for the source code for these classes and came across the curous com.mchange.v2.c3p0.codegen package.
In particular, it looks like JdbcProxyGenerator is metaprogramming in Java. I'm having a hard time understanding the codegen mechanism and why it is used. The built jar contains these generated classes, so I'm assuming these classes are built during the build, perhaps as part of a two-phase build. The codegen package does not appear to be in the generated jar.
Any insight would be appreciated, just for my own curiosity. Thanks!
yes, you are absolutely right.
c3p0 uses code generation to generate non reflective proxy implementations of large JDBC interfaces, "java bean" classes with lots of properties, and some classes containing debug and logging flags (to set up conditional compilation within the build).
You can always see the generated classes by typing ant codegen in the source distribution, and then looking at the build/codebase directory. The latest binary distribution of c3p0 (0.9.2-pre2) includes the generated sources in a src.jar file, which you can also find as a maven artifact at http://repo1.maven.org/maven2/com/mchange/c3p0/0.9.2-pre2-RELEASE/c3p0-0.9.2-pre2-RELEASE-sources.jar
I hope this helps!
I'm following this guide http://javaeenotes.blogspot.com/2011/06/short-introduction-to-jmock.html
I've received the error
java.lang.SecurityException: class "org.hamcrest.TypeSafeMatcher"'s signer information does not match signer information of other classes in the same package.
In the guide the author says:
The solution is make sure the jMock libraries are included before the
standard jUnit libraries in the build path.
What makes up the "standard jmock libraries" and the "junit libraries"?
Junit only has one jar so that's easy, but jmock comes with over 10 different jars.
I've been using: j-unit4.10, jmock-2.5, hamrest-core and hamcrest-library
What are the hamcrest core and library classes for?
i'm a committer on both libraries. JMock depends on hamcrest to help it decide whether an call to an object is expected. I suggest just using the hamcrest-all jar. The split between hamcrest core and library was to separate the fundamental behaviour of matching and reporting differences from a convenient implementations of the most common cases.
Finally, if you're using hamcrest, I suggest you use the junit-dep jar to avoid clashes with some features of hamcrest that are included in the junit.jar
JUnit is used to do Unit test in order to test your methods. JMock is used to test your program inside a context, You will have to know what you are expecting to send to the context (ENV) and what will answer the context.
JMock use JUnit, that is why, in order to avoid dependency conflicts, you need to include it before JUnit.
The 10 libraries of JMock are kind of add-ons if you need to use JMock script or any other functionnality not available in the JMock core.
You don't need to know about Hamcrest-core library to use JMock. Just follows the guide on the web site (don't use version 1 of JMock) and Organize your libraries in the correct order (JUnit should be last in order to avoid your error)
mock frameworks licke jmock do some black magic behind the scenes
( including, but not limited to runtime byte code manipulation )
to provide mock methods classes and whatever. To be able to do this,
some tweaks in basic junit classes are necessary, and the only way to do this is to
register itself as java agent before JU classes are loaded.
Also, put your mock framework before junit in classpath
After installing jdk 7 and switching java platform for my project in ide i get this when im trying to build project.
warning: [options] bootstrap class path not set in conjunction with -source 1.6
An annotation processor threw an uncaught exception.
Consult the following stack trace for details.
java.lang.NoSuchMethodError: com.sun.tools.javac.util.Name$Table.instance(Lcom/sun/tools/javac/util/Context;)Lcom/sun/tools/javac/util/Name$Table;
at uk.org.retep.util.javac.JavacUtils.<init>(JavacUtils.java:128)
at uk.org.retep.util.annotation.AnnotationScannerProcessor.process(AnnotationScannerProcessor.java:76)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:793)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:722)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$1700(JavacProcessingEnvironment.java:97)
at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1029)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1163)
at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1106)
at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:824)
at com.sun.tools.javac.main.Main.compile(Main.java:419)
at com.sun.tools.javac.main.Main.compile(Main.java:333)
at com.sun.tools.javac.main.Main.compile(Main.java:324)
at com.sun.tools.javac.Main.compile(Main.java:76)
at com.sun.tools.javac.Main.main(Main.java:61)
I know that sun switched some apis or something, but ide doesnt tell me whats wrong exactly. Thanks in advance.
You should really share your code that's causing the exception, but the exception indicates that you're using an internal Java API (any class contained in the com.sun packages). You shouldn't be using those APIs directly, as they're considered private implementations and subject to change. As those APIs are private, it isn't as simple as looking for the Javadoc to see what methods are available, but suffice it to say that the method you're calling doesn't exist. You have a few options:
If you're calling this method directly, you need to refactor. You should look for ways to accomplish the same work using public APIs.
If this happens after calling a library method, you should file a bug with the library maintainer informing them about the error and the risks of using the com.sun APIs.
If this happens after calling a public Java API (anything in the java or javax packages) then You should file a bug report with Oracle. This one seems unlikely though.
Also, if you share your code, we may be able to better help you.
[edit]
Further, see this page for more information about why you shouldn't use classes in the com.sun packages.
I am curious about the usage of the feature known as open classes or monkey-patching in languages like e.g. Ruby, Python, Groovy etc. This feature allows you to make modifications (like adding or replacing methods) to existing classes or objects at runtime.
Does anyone know if major frameworks (such as Rails/Grails/Zope) make (extensive) use of this opportunity in order to provide services to the developer? If so, please provide examples.
Rails does this to a (IMHO) ridiculous extent.
.Net allows it via extension methods.
Linq, specifically, relies heavily on extension methods monkey-patched onto the IEnumerable interface.
An example of its use on the Java platform (since you mentioned Groovy) is load-time weaving with something like AspectJ and JVM instrumentation. In this particular case, however, you have the option of using compile-time weaving instead. Interestingly, one of my recent SO questions was related to problems with using this load-time weaving, with some recommending compile-time as the only reliable option.
An example of AspectJ using load-time (run-time) weaving to provide a helpful service to the developer can be Spring's #Configuration annotation which allows you to use Dependency Injection on object not instantiated by Spring's BeanFactory.
You specifically mentioned modifying the method (or how it works), and an example of that being used is an aspect which intercepts am http request before being sent to the handler (either some Controller method or doPost, etc) and checking to see if the user is authorized to access that resource. Your aspect could then decide to return – prematurely – a response with a redirect to login. While not modifying the contents of the method per se, you are still modifying the way the method works my changing the return value it would otherwise give.