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.
Related
I created a plain old JAR with some fancy test classes I want to use to make testing more easy and fun.
Everybody knows Eclipse plug-ins aren't for unit testing and Tycho doesn't allow it, but we already managed a setup where we can test plug-ins using Surefire exactly the same way we test pure Maven projects. Using <pomDependencies>consider</pomDependencies> in the config of the target-platform-configuration allows for adding plain old Maven dependencies, so the Tycho build already works with the new fancy test classes.
Not Eclipse though. Plug-ins are missing the library "Maven Depdencies", and even adding it via the "Java Build Path" in the settings does nothing. I can add the project with the test classes there, but that would mean checking it from SVN and adding it to every workspace (I have 100, and I can't rule out that other people are working here, too).
On the other hand I can't just add it to the Manifest.MF because that would mean the test library would be shipped to our customers (which fancy or not is a bad idea). And I don't know how Tycho feels about optional dependencies, it's probably not a fan (and I feel like this would be bad style).
So how can I trick a plug-in in Eclipse into accepting a dependency that is not in the final plug-in?
I am new to J2EE. I would like to create a Spring+Primefaces+Hibernate project.
I googled for it.
But I found all projects examples show in internet contains maven. My questions are
Is it possible to create a spring+primefaces+hibernate project in eclipse without Maven? If no, what is need of maven?
How to add the jar file of primefaces and spring and hibernate in eclipse?
Will the spring controller xml file (spring context or dispatcher servlet) be created automatically or manually?I mean Spring MVC.
Will the hibernate file (mapping file) also be created automatically or manually?
If possible, can anyone guide me to tutorial (preferably video) to implement the same?
I am using tomcat 7 and Eclipse - kepler.
Any help is appreciated.
If this is downvoted , do specify the reason also.
Although it's not a 'must' to use Maven or any other build tool, you should strongly consider using one.Eclipse Kepler has by default maven support but feel free to use other build tools(Gradle, Ant) or none(see 2.).Maven and the other build tools remove the headache of scaffolding, searching for dependencies(external jars like spring-mvc, hibernate, some db drivers), even deploying applications in a server.
If you chose not to use a build tool you have to manually get your project dependencies and enter them
into your project's buildpath(Right Click -> Build Path then enter their location).As you have noticed this step can be really really time consuming...
No, you have to manually create the configuration unless you use another project that already has what you need, again this might get easier with a build tool(maven archetypes for example)
The same as 3.
You won't have a hard time finding resources about these technologies, they are being used practically everywhere, and I think the Spring team has some videos in their YouTube channel.
Hope that helps a little!
1:* The fundamental difference between Maven and Ant is that Maven's design regards all projects as having a certain structure and a set of supported task work-flows (e.g., getting resources from source control, compiling the project, unit testing, etc.). While most software projects in effect support these operations and actually do have a well-defined structure, Maven requires that this structure and the operation implementation details be defined in the POM file. Thus, Maven relies on a convention on how to define projects and on the list of work-flows that are generally supported in all projects.
This design constraint resembles the way that an IDE handles a project, and it provides many benefits, such as a succinct project definition, and the possibility of automatic integration of a Maven project with other development tools such as IDEs, build servers, etc.
But one drawback to this approach is that Maven requires a user to first understand what a project is from the Maven point of view, and how Maven works with projects, because what happens when one executes a phase in Maven is not immediately obvious just from examining the Maven project file. In many cases, this required structure is also a significant hurdle in migrating a mature project to Maven, because it is usually hard to adapt from other approaches.
In Ant, projects do not really exist from the tool's technical perspective. Ant works with XML build scripts defined in one or more files. It processes targets from these files and each target executes tasks. Each task performs a technical operation such as running a compiler or copying files around. Targets are executed primarily in the order given by their defined dependency on other targets. Thus, Ant is a tool that chains together targets and executes them based on inter-dependencies and other Boolean conditions.
The benefits provided by Ant are also numerous. It has an XML language optimized for clearer definition of what each task does and on what it depends. Also, all the information about what will be executed by an Ant target can be found in the Ant script.
A developer not familiar with Ant would normally be able to determine what a simple Ant script does just by examining the script. This is not usually true for Maven.
However, even an experienced developer who is new to a project using Ant cannot infer what the higher level structure of an Ant script is and what it does without examining the script in detail. Depending on the script's complexity, this can quickly become a daunting challenge. With Maven, a developer who previously worked with other Maven projects can quickly examine the structure of a never-before-seen Maven project and execute the standard Maven work-flows against it while already knowing what to expect as an outcome.
It is possible to use Ant scripts that are defined and behave in a uniform manner for all projects in a working group or an organization. However, when the number and complexity of projects rises, it is also very easy to stray from the initially desired uniformity. With Maven this is less of a problem because the tool always imposes a certain way of doing thi
2:* You have to download all required jars file for hibernate/spring/primefaces from internet and place them in your project build path or in lib folder.
3:* Spring configuration files need to be created by you so that you can get the concept.
4:* Hibernate mapping files can be created by using reverse Engineering techniques for hibernate from where you can generates hbm files or you can use annotations if you dont want xml.
I suggest you to first create a sample java project in eclipse then download all required jars and place them in lib folder. Then configure hibernate in projects and spring integration.
I use Java/Eclipse for development and I've never really used any conventional build tools like ant or maven. I generally just rely on building projects through eclipse and I rarely use commandline. I don't really want to spend time getting to know ant/maven, but I'd like to know whether eclipse can really substitute all functionality of ant/maven through its .classpath file any other settings.
(Please don't suggest me some tutorial that makes it really easy to learn ant).
Eclipse knows how to build a project based on the .project and .classpath files.
build.xml is the default filename of build rules used by Ant, so that when you run ant without parameters, it will use this file to figure out what to do.
pom.xml is the default filename to describe a Maven project, so that when you run mvn compile, it will use this file to figure out how to build the project.
Eclipse can import a project based on an Ant build file or a POM file, and create the appropriate .project and .classpath files.
Eclipse, Ant, Maven are all different tools that cannot replace each other. They have some overlapping functions, but also some unique functions.
Being able to build a project using the command line is a very useful skill, and part of being a good programmer. In the Programmer Competency Matrix, being able to build your software using the command line is considered Level 1 (out of Level 0, 1, 2, 3), if you cannot do this, that's not so good.
http://www.indiangeek.net/programmer-competency-matrix/
I strongly recommend to learn Maven.
If your applications have little existence outside of Eclipse then maybe you should keep using Eclipse in that way. But Eclipse is a developer tool (developer as in the person who writes the code). Any other than the most trivial projects have to deal with roles other than developers. and applications go through an entire life cycle. In fact, different axes of life cycles exist, whether it being from a project management perspective, from the perspective of deliverables traversing a number of phases such as coding, compiling, assembling dependencies, packaging, deployment, or from other perspectives.
When you look at those deliverables traversing phases, a lot of these steps can be done (manually) from within Eclipse. So, again, if that works for you, praise. However, it misses automation and for some steps (phases) Eclipse just ain't the right tool. For example: Continuous Integration is not something Eclipse is built for. A CI server may want to checkout your sources and build stuff from scratch. It needs to find dependencies and such, may do so on basis of Eclipse's .classpath file, but that introduces a dependency on Eclipse. Now, I've seen large companies do it exactly that way, but it's a bit clunky because that's again not what Eclipse was meant for.
Instead there's tools that are great at dealing with the entire* life cycle.
*Note that "entire" is a very subjective matter. From a developer's perspective the life cycle may be nicely split up in phases, but other people in your larger organization may find that their duties are underrepresented in any given breakdown of life cycle phases.
Maven or Gradle are such tools. Look at them as an assembly line with a number of stations. The developer is at one of the stations, using Eclipse, but underneath the assembly line keeps rolling. CI is another station, using Bamboo, Hudson, Jenkins or similar, but underneath still the assembly line at work. Within Eclipse the m2e plugin is the connector between Eclipse and the assembly line Maven.
A different approach to the matter is to use scripts, either to replace the manual steps that you're doing in Eclipse, to hook them together, or to complement them. There is clearly many languages that can be used, but within the build tooling domain Ant is wildly popular because its functionality aligns well with exactly this purpose.
If you're a professional software factory (which might already be the case for a single developer project) you need an assembly line. Maven or Gradle give you one out of the box. If you want to swim upstream you build your own, using Ant or other stuff. And if you really have no requirements in this area to speak of, keep doing things manually in Eclipse.
Even though being defined in XML, Ant comes naturally to us as developers, since it has much of traditional sequential programming languages. Maven and Gradle have a different approach, and have thus a steeper learning curve. But it is definitely worth it. If you do it their way things become a breeze and you don't have to code every other thing you want to add to your assembly line. This hand-crafted scripts always start small, but they never stay that way, do they? :)
In addition to all this, I'd like to mention that Maven is also really good at resolving dependencies. That's what it's most known for, but that's not what this question was about, and it is in fact only such a small part of what it can do for you.
In Dependencies tab, I have a choice between plug-ins and packages.
What's the difference between them? For org.eclipse.compare, I have it in imported package and also in plug-ins.
I find the jar file in plugins directory, but I don't know where the package file of org.eclipse.compare is located.
In the export menu, it seems like that there seems to be only exporting to jar, not exporting a plugin or packages. How can I export packages?
ADDED
Based on this post - How to import a package from Eclipse? and shiplu's answer. This is what I came to understand. Please correct me if I'm wrong.
In eclipse, when I use come external class, I can use Quick-Assistant or Organize imports (Ctrl-Shift-O) to resolve the reference. Eclipse adds the package that contains the class in Imported Packages for the project that I'm working on. A package can contain multiple classes (types). Eclipse understands what plugin contains the package, and resolve the reference issues.
A plug-in (jar file) can contain multiple packages. By specifying a required plug-ins in the dependencies tab, we can reference all the packages (and classes in the packages) for all the java projects in the eclipse IDE.
And from my experience, I had to add all the dependencies in order to make headless RCP standalone (http://prosseek.blogspot.com/2012/12/headless-rcp-standalone.html).
An Eclipse plug-in is basically an OSGi bundle with additional plugin.xml file which Eclipse IDE understands and interprets.
So the answer to your question lies in the OSGi specification and the OSGi programming model, since, very simply put, Eclipse is an Application running on implementation of OSGi called Equinox.
OSGi is all about having modular applications and so it defines several levels of modularity.
One such level is a bundle-level (module-level) modularity and more fine grained level is the package level modularity.
So you can have your OSGi application (a set of bundles; eclipse is just that) which consists of db-bundle (which provides data store services), app-domain-bundle (which provides your application domain services) and remote-bundle (which exposes to the web your application via REST for example).
And then you say remote-bundle depends on domain-bundle which depends on db-bundle.
Which is all good, but cripples the inherent modularity OSGi provides, because you are basically restricting your application to specific implementations of db-bundle and remote-bundle i.e. to specific implementations of the services they provide.
Instead, you can establish the above dependencies not between bundles but between packages i.e. establish a service-level dependencies.
Then you say domain-bundle requires dbstore.service package to run, it doesn't care which bundle provides it it just needs an instance of this service to be able to work. So you can have multiple bundles providing implementations of the dbstore.service, and the domain-bundle can pick and choose at runtime what service to use.
It is really hard to explain OSGi concepts in just a several sentences, I'd really suggest you dig around the web on this and maybe even have a look at the OSGi specification.
Another way to explain it is to say that bundle/plug-in is a jar file with specific structure and metadata descriptors (MANIFEST.MF and plugin.xml), which describe its contents in Java language concepts - which java packages and services this specific jar contains and will expose to the OSGi runtime so that they can be consumed by other bundles. I.e. the bundle is the physical deployable entity while the descriptors are metadata about what actually is being deployed.
EDIT:
Package or Service-level dependencies also have some drawbacks, as Lii points out in the comments below, the main one being that it adds complexity and dynamics to the dependency model. Have a look at her or his comment below - it is worth reading!
You use Imported Packages when you want to use a specific package but do not care which plugin provides it. OSGI will choose one for you.
Eclipse plugins is something like extension to the IDE itself. But imported packages are actually packages that you'll use in your current project.
One is for development IDE another is for the project you are coding.
I have inherited a big project with several subprojects.
all of them use several jar files, all of them located under each project's lib directory. I want to take all the projects and migrate them to maven, but dependencies are a problem (too many of them), some of them are commonly used libraries (apache projects, xerces, jms, etc) and others are not.
is there a way to autogenerate maven dependencies for those jars that can be found on public maven repositories. for example, see that my project use the spice-jndikit-1.2.jar file and automatically get the appropiate depedency with group, artifact and (if possible) version?
thank you
I wrote a groovy script to generate a starting set of Apache ivy files.
https://github.com/myspotontheweb/ant2ivy
In my case, I wanted to "Maven-ize" my ANT builds without switching completely away from ANT.
It is feasible to extend this code to generate a Maven POM, if people were interested in this feature.
You can convert a project to Maven using the m2e plugin, but this erases your jar references, and should not be used.
I doubt that such a thing exists since typical jars (unless themselves built with Maven) don't have the necessary information to correlate the groupId, artifactId and version back to a repository to get the proper path.
You might be able to write something that parses the file name for the name and version, but you still have the package-based path to figure out.
If you're building using Ant, you might also consider using Apache Ivy, and its file-system based resolution (very fast and easy to configure), to get you started, and slowly role over to the Maven repos for the artifacts, this way you're not spending a lot of time up-front finding Maven dependencies.