I'm a tech writer documenting an API written in Swagger YAML.
swagger2markup is distributed as a .jar file. The docs say to add the library to my project's classpath.
I find no classpath setting or .jar files in the Swagger projects, nor is there a classpath environment variable, though npm start works fine.
Turns out that for my environment I should have been using swagger2markup-api.
Related
I have a scala project built with dependancy on a locally built jar file (java code). Once I need to check in my scala code into a different environment for building and deployment, what's the best way to keep my jar file in the dependancy?
I know that if I use the sbt dependancy from online modules, I don't need to worry, it will download the version and build, but what if I want to use my own jar file for this purpose?
This is in OSX, and code will be checked into linux machines, I am using intellij and sbt to manage my scala project. I also used intellij to build my external java lib into jar file and added dependancy of this specific path.
I hope there should be some generic solution, but I am new in JAVA and SBT
I got it figured out. Add the jar files under the lib directory right under the project will solve the problem. SBT will pick it up automatically and you can certainly check in the jar files like source code.
Just recently started using Eclipse and ran into an issue with exporting the plugin I'm working on. I tried to search but so far no luck - but if the answer is already here I'd be grateful if someone can point me to it.
I'm writing a n OSGi/Equinox plugin with Eclipse. The plugin is for a 3rd party system, which allows extensions: basically all jars placed in the application's plugin folder are automatically loaded into the application at startup. I have managed to put together my plugin, it's loading fine and it works.
The issue is that I rely on another plugin which is placed beside mine in the plugins folder. For obvious reasons I do not want to package that plugin into my plugin jar file. I have tried to add the dependency as an external archive, but this breaks the export: when I try to export my plugin project ant complains about missing dependencies and types. (If I actually include the other jar file in my plugin everything works, but obviously this is less then ideal.)
So: how do I set up my plugin project dependency, that it's a) an external dependency and b) doesn't need to be specified with a path or a variable - i.e. how do I tell my exporter to "don't worry, it will be there right beside you"?
Edit: Apparently there's an important detail I didn't mention. The external jar file I depend on is not an OSGi plugin, just a regular jar file with some classes in it. To the 3rd party system it seems all the same (all are under the plugins folder, all are loaded into the application), but for Eclipse the distinction seems important.
If you reference the other plug-in as a dependency in your plug-in's MANIFEST.MF the export should work without errors. The plug-in should be listed in the Require-Bundle list in the MANIFEST.MF.
You can do this in the MANIFEST.MF editor by adding to the 'Required Plug-ins' list on the 'Dependencies' tab of the editor.
Note: When referencing other plug-ins you must always use this method. Do not try adding the plug-in jar to the Java build path or anything like that.
If the jar you want to use is not an Eclipse plug-in you must should include it as part of the plug-in and list the jar in the Bundle-Classpath in the MANIFEST.MF. If you cannot do this you can reference an external jar in the Bundle-Classpath using something like:
Bundle-Classpath: .,external:$LIB_LOCATION$/lib.jar
. is the normal entry in for the plug-in code. external:$LIB_LOCATION$/lib.jar looks for lib.jar in a location defined by the environment variable LIB_LOCATION. This method can be difficult to get right.
In the end the solution to my specific problem was to add the external jar file as an Extra Classpath Entry on the build properties tab (this translated to a "jars.extra.classpath = .jar" entry in the build.properties file). I have also added the jar file to the project itself - after adding the extra class path entry that got changed into an external dependency automatically.
With these two changes I was able to successfully export my plugin, which didn't contain the external jar file, but was able to reference it when loaded into the 3rd party system.
I have a multi-project SBT build: some projects are dependent on each other, some are dependent on third-party JARs, and there's a "main" project which depends on everything .
When I sbt package it, I get one JAR in each target/ directory.
What I want to achieve is getting all relevant JARs (mine and external) is one directory. Very similar to the way you package a WAR with Maven.
(And to clarify - I'm not interested in an assembled "FAT JAR" that contains all the dependencies in a single file. Just one directory with all JARs in it)
Im not 100% sure about the suprobject dependencies but I think SBT native packager should help you do something like that, and will also provide a start-script for windows and unixes:
http://www.scala-sbt.org/sbt-native-packager/GettingStartedApplications/MyFirstProject.html
I would recommend sbt-pack for creating self-contained JARs:
https://github.com/xerial/sbt-pack
I use it and haven't seen a glitch so far.
It also generates both OS X/Linux as well as Windows .bat entry scripts for the main classes/objects you choose.
So I'm relatively new to Java EE and I am having a tough time understanding when, where and why Java deployment files are packaged with their dependencies.
Say I build my project into myapp.jar, and it depends on fizz.jar, buzz.jar and JODA (joda-time-2.0.jar).
I've heard that the default classloader doesn't package jars inside of other jars, so I have to assume that if I called a jar task from Ant, then the default classloader would get invoked and myapp.jar would be created without those 3 dependencies in it.
Is this because the mentality is to deploy main-less jars in containers or other systems that will provide its requirements at runtime? If not, then how does myapp.jar ever run correctly?
What about executable jars? To met, these must be different than main-less jars, because they are meant to be standalone units, right? That means they would need all of their dependencies packaged with them, right?
Last but not least, what about jars that depend on jars that depend on jars...etc. (i.e., dependencygraphs that are huge)?
I guess all of these questions can be summed up as follows:
Is the idea behind a non-executable jar that it will be ran in such a way that it will know what classpath(s) to look on for its dependencies at runtime? (And thus doesn't need to be packaged with its dependencies)?
Is the idea behind an executable jar that it is a standalone unit and should be pacakged with its dependencies?
If my assertion to Question #1 above is correct, how does such classpath configuration take place? Are these settings that are stored inside the jar (such as in the manifest)? Else, how would a JRE know where to search for a particular jars dependencies at runtime?
Answers to these questions will actually clarify quite a lot of hangups I have with Java fundamentals, and so any input/help here will be appreciated enormously! Thanks
Jars do not know about other jars (unless assisted by some tools like Maven). The inter dependency of the jars is purely resolved by the Classloaders. I strongly recommend to have some idea about classloaders.
To address your questions,
Is the idea behind a non-executable jar that it will be ran in such a way that it will know what classpath(s) to look on for its dependencies at runtime? (And thus doesn't need to be packaged with its dependencies)?
NO. As mentioned, it's the classloader which looks the classpath and the jars mentioned therein. The jars do not have any information about other jars.
Is the idea behind an executable jar that it is a standalone unit and should be packaged with its dependencies?
NO. A classloader loads the standalone executable jars at the start of execution. If it needs other dependency jars it'll look into the classpath for those jars.
If my assertion to Question #1 above is correct, how does such classpath configuration take place? Are these settings that are stored inside the jar (such as in the manifest)? Else, how would a JRE know where to search for a particular jars dependencies at runtime?
For standalone jar (executable jar), the classloader looks for the classpath variable OR classpath passed while invoking the application.
For other type of application (WAR, EAR), There are predefined places/folders where the dependencies should be placed in order to get picked up. This is standardized by specs.
In a nutshell, it's the classloader which is pulling all the threads. There is standard places where it looks for all the dependent jars. This link nicely describes how the classloaders in standalone application and in a deployed (in some container) works.
JAR files are a way to package togher complex java application. Jar application are easy to move between diffrent machines and operating system.
I think the right way to use Jars is not tu put everything (every dependencies) into a single jar.
For example if your application uses a jar libryra (for example jdbc) to access a database you should not put the jdbc jar into your jar.
You had better to build a jar file with only your .class file.
Of course your code needs the jdbc jar to work properly. Here comes to explain how the virtual machine searches for extarnal classes:
-it first searches in the directories that contain the classes that come standard with J2SE (the path depends on your installation)
-it searches in the directories specified by the classpath (a classpath is either an environment variable or an option of the java command)
for example:
java -jar -c /your/path/ yourApp.jar
will run your application and will search th classes your application refers to in the directory /your/path/ so if you have external jars you can put them in that directory.
For detailed documentation: http://download.oracle.com/javase/tutorial/deployment/jar/index.html
How should I add JAR libraries to a WAR project in Eclipse without facing java.lang.ClassNotFoundException or java.lang.NoClassDefFoundError?
The CLASSPATH environment variable does not seem to work. In some cases we add JAR files to the Build Path property of Eclipse project to make the code compile. We sometimes need to put JAR files inside /WEB-INF/lib folder of the Java EE web application to make the code to run on classes inside that JAR.
I do not exactly understand why CLASSPATH does not work and in which cases we should add JARs to Build Path and when exactly those JARs should be placed in /WEB-INF/lib.
The CLASSPATH environment variable is only used by the java.exe command and even then only when the command is invoked without any of the -cp, -classpath, -jar arguments. The CLASSPATH environment variable is ignored by IDEs like Eclipse, Netbeans and IDEA. See also java.lang.ClassNotFoundException in spite of using CLASSPATH environment variable.
The Build Path is only for libraries which are required to get the project's code to compile. Manually placing JAR in /WEB-INF/lib, or setting the Deployment Assembly, or letting an external build system like Maven place the <dependency> as JAR in /WEB-INF/lib of produced WAR during the build, is only for libraries which are required to get the code to deploy and run on the target environment too. Do note that you're not supposed to create subfolders in /WEB-INF/lib. The JARs have to be placed in the root.
Some libraries are already provided by the target JEE server or servletcontainer, such as JSP, Servlet, EL, etc. So you do not need put JARs of those libraries in /WEB-INF/lib. Moreover, it would only cause classloading trouble. It's sufficient to (indirectly) specify them in Build Path only. In Eclipse, you normally do that by setting the Targeted Runtime accordingly. It will automatically end up in Build Path. You do not need to manually add them to Build Path. See also How do I import the javax.servlet / jakarta.servlet API in my Eclipse project?
Other libraries, usually 3rd party ones like Apache Commons, JDBC drivers and JEE libraries which are not provided by the target servletcontainer (e.g. Tomcat doesn't support many JEE libraries out the box such as JSF, JSTL, CDI, JPA, EJB, etc), need to end up in /WEB-INF/lib. You can just copy and paste the physical JAR files in there. You do not necessarily need to specify it in Build Path. Only perhaps when you already have it as User Library, but you should then use Deployment assembly setting for this instead. See also ClassNotFoundException when using User Libraries in Eclipse build path.
In case you're using Maven, then you need to make absolutely sure that you mark libraries as <scope>provided</scope> if those are already provided by the target runtime, such as JEE, Servlet, EL, etc in case you deploy to WildFly, TomEE, etc. This way they won't end up in /WEB-INF/lib of produced WAR (and potentially cause conflicts with server-bundled libraries), but they will end up in Eclipse's Build Path (and get the project's code to compile). See also How to properly install and configure JSF libraries via Maven?
Those JARs in the build path are referenced for the build (compile) process only. If you export your Web Application they are not included in the final WAR (give it a try).
If you need the JARs at runtime you must place them in WEB-INF/lib or the server classpath. Placing your JARs in the server classpath does only make sense if several WARs share a common code base and have the need to access shared objects (e.g. a Singleton).
If you are using Maven:
Open the project properties, and under Deployment Assembly click Add...
Then select Java Build Path Entries and select Maven Dependencies
Resolved by setting permissions.
Had related issue using PySpark and Oracle jdbc. The error does not state that the file cannot be accessed, just that the class cannot be loaded.
So if anyone still struggles, check the permissions. Some might find it obvious tho'.
I want to give the answer for the folowing link question ClassNotFoundException oracle.jdbc.driver.OracleDriver only in servlet, using Eclipse
Ans: In Myeclipse go to Server-->left click on Myeclipse Tomcat7-->Configure Server Connector-->(Expand)Myeclipse Tomcat7--> Paths-->Prepend to classpath-->Add jar (add oracle14 jar)-->ok