Question
Given a Classpath Container I've written as a plugin/extension, how do I add it to the classpath, automatically?
Background
Ok so I'm an experienced Java Developer but extremely new to writing Eclipse Plugins. I've been googling, following tutorials and reading source code of other plugins for a couple days. I know exactly what I want to do but not exactly how to do it.
Right now, in Eclipse, when I click a resource and choose "Run as JUnit test" as in:
Behind the scenes, the m2eclipse plugin somehow generates a run configuration that contains the "Maven Dependencies" classpath container, like the following:
My best guess is that the "Maven Dependencies" classpath container is added through some extension point being used by the M2Eclipse plugin. Similarly, I want to add my classpath container, automatically, whenever a user runs a JUnit test--so it shows up under "User Entries." What extension point(s) can I use to make something like that happen? I've been looking at org.eclipse.jdt.core.classpathContainerInitializer but I'm not sure that's going to do what I need.
Ideal Result
Ideally, I'd like to write a plugin that takes every entry in the project's build path and adds it to the classpath of a run configuration (whenever a new launch configuration is created via: Run As > JUnit test). This should be the default behavior of Eclipse but it's not!
My next-best solution would be to simply add my custom classpath container to the run configuration's build path, automatically. At the end of the day, I just want one classpath for any java code our team runs/launches. This shouldn't be so hard!
Any advise on how to achieve any of this would be appreciated! Even basic pointers on where to look to understand how particular Extension Points are intended to be used (the basic JavaDocs APIs are terrible). Thanks,
gMale
Roostergx provides part of the answer (i.e., how to create the classpath container). The second part, as you admit, is how to add it automatically.
I would recommend using an extension point called org.eclipse.ui.startup. This allows you to contribute code that runs (pretty much) as early as possible when Eclipse starts up. On every startup, you can iterate through all projects and see if any existing projects require the classpath container that you created.
The article at http://www.ibm.com/developerworks/opensource/tutorials/os-eclipse-classpath/index.html provides an exellent description and source for a plugin that defines a project specific classpath container that includes all the jar files in a specified directory.
Related
I don't understand exactly what is the way of working with maven projects in Eclipse.
The problems I have are often with projects I download from github. If I set the project myself it usually work, so I think I'm doing something different from the majority of people.
I'll try to detail a specific case:
I clone a repo, let's say: https://github.com/spring-guides/tut-spring-boot-oauth2
In Eclipse I import "existing maven project"
The project has a "Maven nature" as indicated by M on the folder icon
I try to run java class with main from Eclipse. First strange thins is that the "Run As" menu doesn't have "Run as a Java application"
I have to configure the configuration manually. Now it runs, but strange things happens, like I can't edit the file as the "content assist" throw errors instead of giving the normal assists.
I notice that the project has no "source folder". So my first instinct is to add a Java nature or select src as source folder
So I add Java nature to the project. This is a disaster. It can compile anymore as it can find packages. All classes have errors. I try to play around setting source folders on /src or /src/main/java. Sometimes I fix the errors but I can't run (and now I have run as Java application) but when I run it can't load the class
So in the end, I'm a bit confused and I don't know if I explained clearly what I'm doing.
I think I would like to know in a simple way how people are doing it, rather than trying to correct my steps as I'm probably creating a mess myself.
Any help or suggestion welcome.
I'm using the last version of eclipse. I don't know which other tool's versions are relevant.
P.S. I also refresh,restart,clean rebuild the project often after touching things...but it doesn't get better
Maven is a build (management) tool. Simply spoken, its task is to create a JAR that can be used as a dependency/library by other projects or when running java -jar ....
Running a project's code isn't part of it (apart from unit and integration tests code and by using non-default plugins for special situations). Running code is part of Eclipse (or any other IDE) with its Run Configurations.
I am new to the scala eclipse environment and also new to typesafe/activator.
I need to modify some of the activator initialization code because of some very specific host-side dependencies.
I cannot see how to "import" the actual jar files into eclipse. I know exactly what I need to change and how (via manually opening the jar and looking at the code). But I want to maintain complete integrity with the change management (ivy and sbt) but I do understand how to do this.
Is there some basic way to pull in/open a source jar, modify it, and build/deploy it? I see lots of help on the export/build, but I need help with the open/import/modify portion of this task.
Thanks for your kind help.
Typically if you wanted to change how a project works you'd go back to the source repository (in Activator's case https://github.com/typesafehub/activator ) and modify from there and then rebuild. Source jars don't have the build configuration so they are not useful for creating new binaries. Usually source jars are used to show source in a debugger or to click on a type in the IDE and see the source code for that type.
example:
For logging, my code uses log4j. but other jars my code is dependent upon, uses slf4j instead. So both jars must be in the build path. Unfortunately, its possible for my code to directly use (depend on) slf4j now, either by context-assist, or some other developers changes. I would like any use of slf4j to show up as an error, but my application (and tests) will still need it in the classpath when running.
explanation:
I'd like to find out if this is possible in eclipse. This scenario happens often for me. I'll have a large project, that uses alot of 3rd party libraries. And of course those 3rd party jars have their own dependencies as well. So I have to include all dependencies in the classpath ("build path" in eclipse) for the application and its tests to compile and run (from within eclipse).
But I don't want my code to use all of those jars, just the few direct dependencies I've decided upon myself. So if my code accidentally uses a dependency of a dependency, I want it to show up as a compilation error. Ideally, as class not found, but any error would do.
I know I can manually configure the classpath when running outside of eclipse, and even within eclipse I can modify the classpath for a specific class I'm running (in the run configurations), but thats not manageable if you run alot of individual test cases, or have alot of main() classes.
It sounds like your project has enough dependency relationships that you might consider structuring it with OSGi bundles (plug-ins). Each bundle gets its own classloader and gets to specify what bundles (and optionally what version ranges, etc.) it depends on, what packages it exports, whether it re-exports stuff from its dependencies, etc.
Eclipse itself is structured out of Eclipse plug-ins and fragments, which are just OSGi bundles with an optional tiny bit of additional Eclipse wiring (plugin.xml, which is used to declare Eclipse "extension points" and "extensions") attached. Eclipse thus has fairly good tooling for creating and managing bundles built-in (via the Plug-in Development Environment). Much of what you find out there may lead you to conflate "OSGi bundle" with "plug-in that extends the Eclipse IDE", but the two concepts are quite separable.
The Eclipse tooling does distinguish rather clearly (and sometimes annoyingly, but in the "helpful medicine" way) between the bundles in your build environment vs. the bundles that a particular run configuration includes.
After a few years of living in OSGi land, the default Java "flat classpath" feels weird and even kind of broken to me, largely because (as you've experienced) it throws all JARs into one giant arena and hopes they can sort of work things out. The OSGi environment gives me a lot more control over dependency relationships, and as a "side effect" also naturally demands clarification of those relationships. Between these clear declarations and the tooling's enforcement of them, the project's structure is more obvious to everyone on the team.
if my code accidentally uses a dependency of a dependency, I want it to show up as a compilation error. Ideally, as class not found, but any error would do.
Put your code in one plug-in, your direct dependencies in other plug-ins, their dependencies in other plug-ins, etc. and declare each plug-in's dependencies. Eclipse will immediately do exactly what you want. You won't be offered dependencies' dependencies' contents in autocompletes; you'll get red squiggles and build errors; etc.
Why not use access rules to keep your code clean?
It looks like it would better be managed with maven, integrated in eclipse with m2eclipse.
That way, you can only execute part of the maven build lifecycle, and you can manage separate set of dependencies per build steps.
In my experience it helps to be more resrictive, I made the team filling out (paper) forms why this jar is needed and what license...
and they did rather type in a few lines of code instead of drag along 20 jars to open a file using only one line of code, or another fancy 'feature'.
Using maven could help for a while, but when you first spot jars having names like nightly-build or snapshot, you will know you're in jar-hell.
conclusion: Choose dependencies well
Would using the slf4j-over-log4j jar be useful? That allows using slf4j with actual logging going to log4j.
I would like to write a simple Ant task that would interact with an Eclipse workspace to get some information from it. I would like to be able to use the various Eclipse API's (for example, IWorkspace).
My question is what would be the simplest way to go about doing this.
I have excellent knowledge of the Eclipse platform as a user of it - but none with development for Eclipse. I understand that, in runtime, my Ant task will have to be invoked under the same JRE as the workspace - that's a restriction I'm willing to be bound to.
I started by creating a Java project to hold my Ant task. I believe that the only thing in my way now is how to define the JAR dependency on Eclipse's JARs. I obviously don't want to depend on one specific Eclipse JAR as these are versioned (for example, Eclipse's "Resources" plugin). Is it possible to have my Java project buildtime-depend on "whatever the current JAR is for the Resources plugin"?
I think this article quite much addresses your problem: http://www.ibm.com/developerworks/rational/library/09/eclipsecustomanttasks/
It is targeted to the IBM Rational Application Developer, but that one is based on Eclipse and AFAIS there is not overly much non-eclipse-specific happening here, at least not regarding the specifics about how to make the task available in Eclipse (writing the plugin definition etc).
So, you want an Ant task that runs within Eclipse. And as you say, it's clear that those tasks are using the Eclipse API. As of this moment, I don't really understand how they're doing it. I've looked at the source of a couple of them and I still have questions.
To find the locations of all the Ant tasks contributed by Eclipse, do a Plug-in Search for org.eclipse.ant.core.antTasks. When I do that, I see twenty or so extensions, many of which define multiple tasks.
If you get the source bundle for a plugin that contributes one of these tasks, you can look at the source for it. RefreshLocalTask is in org.eclipse.core.resources; unfortunately, when I import this bundle into my workspace as a source project, the source for the Ant tasks doesn't get linked correctly. There is a separate jar (inside the bundle) for them, and, while the source is in the bundle, it's not clear how the jar is compiled. The upshot is that I don't have the Ant task source compiling in my workspace.
You can also Google for the Ant task source; here's the 3.6.0 source for RefreshLocalTask.
Anyway, in the source you can see calls to org.eclipse.core.resources.ResourcePlugin that are illustrative of what you probably need.
Ah, I see in the extension point description - right-click on one of those search results and choose "Show Description", or go there from the Manifest editor - that there is a flag you can set, "eclipseRuntime"; the text implies that if it is set, Eclipse will launch the task in the same VM.
You should probably say more about what you want to do, because there are several routes you can take.
Eclipse provides some Ant tasks that you can use in your build scripts. Here are a few. There are more, so search for "ant tasks" in the Eclipse docs; they're scattered throughout different pages. Eclipse Preferences (Window..Preferences, then select Ant/Runtime, and look at the "Contributed Entries" in the Classpath tab) shows you a list of Ant tasks that Eclipse contributes to the runtime whenever Ant is invoked from Eclipse; you can invoke any of these tasks yourself as long as you include the right jar.
It's possible to start up Eclipse from within an Ant task, because it's possible to start Eclipse from Java. You need to include the right jars and make the right calls; you also need to configure Eclipse correctly. "org.eclipse.core.runtime.adaptor.EclipseStarter" should give you some detail.
Perhaps you can use one or more of the variables Eclipse defines for use when launching Ant (or any other program). Try creating an External Tool Configuration (at the bottom of the Run menu) - select an Ant Build and try customizing it with arguments (from the Main tab) or environment variables (from the Environment) tab. Both give you access to Eclipse variables. But of course these are just values you can pass into your Ant script, not handles to anything you can invoke a method on.
What you can't do: I'm pretty sure that when Eclipse launches Ant, it is always in a separate VM, with no way to call back into Eclipse.
So perhaps you should say more about what you want to do.
I'm going to try to give as much detail as possible here, pardon me if some is irrelevant.
I have two projects in eclipse. Project 1: com.myworkplace.parent, with code in the package of the same name. Project 2: com.myworkplace.child, with code in package of the same name (I moved my code to that package, from the default package, if that makes a difference). Both are located in my workspace folder and structured the way you'd expect them to be, as far as I can tell.
I've added child to the build path of parent in eclipse using Java Build Path -> Projects -> Add. Parent's .classpath file contains the entry:
<classpathentry combineaccessrules="false" kind="src" path="/com.myworkplace.child"/>
I add a reference to a com.myworkplace.child.Child class in parent, import it, compile it with no errors, run and get:
java.lang.NoClassDefFoundError: com/myworkplace/child/Child
What gives?
Edit: The parent application is an RCP app, maybe OSGI (I really don't know much about RCP and related stuff.) Some googling leads me to believe it might have something to do with this.
Since your application is an RCP app there is a difference between the eclipse classpath that is used while you are editing code and the OSGi classpath that is used at runtime. It sounds like you need to add the com.myworkplace.child plugin to the list of dependencies of the com.myworkplace.parent plugin.
Open either plugin.xml or META-INF/manifest.mf in the parent project. Eclipse should open the PDE plugin editor (a form based editor for the underlying config files). Click the Dependencies tab at the bottom and add your child plugin to the "Required Plug-ins" list on the left hand section of the form. Alternately you could add the com.myworkplace.child package to the "Imported Package" list on the right. The difference between the two is beyond the scope of this answer, but you can read about that in the eclipse docs now that you (hopefully) are moving in the right direction.
We found that even doing all the proper things in the eclipse rcp project, we were still getting such errors. The solution was to delete the application's workspace directory (by default it would store workspace settings under .eclipse, but we've tweaked our code to use another dir that is not shared with other eclipse stuff).
When we removed this dir after a rebuild, our app worked. Apparently it was storing the classpath somehow along with other settings, but we didn't investigate the exact details.
(NOTE: This applies only if you've called the IWorkbenchConfigurer.setSaveAndRestore method passing a boolean value of 'true' - which means that your application will save and restore various rcp settings after a shutdown of the application and subsequent relaunch.)
If your code is running in an application server, you need to configure the Classpath correctly for that application server.
To do that, find your Servers tab, double-click it, click Open Launch Configuration in the new tab that appears in the main editing area, click the Classpath tab and ensure the Classpath there is correct.