In Eclipse Java EE perspective, how does one add a thridparty Jar to a Utility Project?
To elaborate: In a "normal" Java (Not Java EE) project, there's Referenced Libraries where you can put jars. In a Dynamic Web Project, there's Web App Libraries. In a Utility Project, there's only EAR Libraries, which don't appear relevant (well, there are Referenced Libraries that show up in the Package Explorer in Java perspective, but not in the Project Explorer in the Java EE perspective). I went ahead and added a /lib directory under my Utility Project root, and put a jar there (I forgot if I did that in the Java Package perspective, or just in the file system). I added it to Java Build Path, and everything compiles, including the Dynamic Web projects that reference the Utility Project. But when I deploy to Tomcat, I get ClassNotFoundException for the classes in the thirdparty jar.
How do I add the thirdparty jar to the Utility Project in a way that will make it get deployed as part of the web application?
I answered something similar before.
Eclipse and How it Handles JARS -- Odd Case
In essence, there's a difference between build-time and run-time JAR dependencies. For inclusion in EAR / WAR files, you have to use the "Deployment Assembly" panels.
I am not sure to understand exactly your question, but you can simply right-click on your project, in Properties you select Java Build path > Libraries, and then add your JAR in the list of third parties libraries. This will add your jar in the classpath project.
Another way is to use the (ugly) solution of creating a lib directory, put all your third parties libraries in it, and add this directory in the classpath of your project (like for the previous solution, as you can add a whole directory in Eclipse project).
The last solution is to give the responsibility of the dependencies management to a real build system, such as Maven, Ant+Ivy, Gradle...
Related
I try to find the way to organize a GAE with several projects within Eclipse using the Google plugin for GAE:
The Web App project (a WebApp project) containing the GAE web application.
A Java project with data access
A Java project with utility classes
My problem here is how to link things together. I want to add the two Java projects in both build and execution paths. Since a Web App project follows the JavaEE structure, only what is specified in the WEB-INF/lib directory is taken into account.
I would like to find out how to simulate a Jar file in this directory based on a Java project present in the Eclipse workspace based on what the Google Eclipse plugin for GAE provides.
I saw something that seems to be related in the WebApp project properties Google > Web Application, section "Suppress warnings about these build path entries being outside of WEB-INF/lib".
For the GAE web application to run then you'll need the classes or a jar from the projects you want to include in the WEB-INF/classes or WEB-INF/lib folders respectively.
One way would be to build your data and utility projects and put the resulting jars in the WEB-INF/lib folder. You can then then reference those jars as libraries from your web app and all should be fine. Of course that's a bit tiresome to do manually, so you should probably check out some dependency management tools. From personal experience Ivy and IvyDE were easy to get into and should cover your needs although Maven and others have their strengths.
Another way that is a easier (but less structured) is to used linked source folders in your build path (to the source folders for your data and utility projects). In such way Eclipse will build those sub projects to WEB-INF/classes and build and execution should work similarly.
So I'm fairly new to Java and especially Eclipse, so please excuse my ignorance. I took a project from a server and copied it locally to my machine. When I opened the workspace, I had many errors due to it not being able to find the jars. This makes sense because I don't have the same dir structure as the server I copied from. So if I copy the same external jar's to my machine and get it to compile into a jar and copy it back to the server, will it work? Or will it fail because now the external jar's are in a different place than it is expecting?
Also, down the road should I put the external jars into regular jars to avoid this problem?
You should be OK. Java is using what is called classpath to locate dependencies. The classpath may be different on the development machines, but as long as all the dependencies are on the classpath in the production everything should work.
To avoid issues with the synchronisation of directory structures the most common way is to use Maven - it will manage all the dependencies for you (but you have to manage the pom.xml - the Maven's project descriptor). A little clumsier way is to have the dependencies in the project, however you may end up with many projects having to include same jars, and then there will be version conflicts and so on.
For small projects you can manage dependencies yourself, however larger projects will need a more thought through strategy (like Maven).
In regard to the executable jars, make sure the Class-Path entry in <jarfile>:\META-INF\MANIFEST.MF is correct, e.g. where it references other jars, those jars are going to be there in the production. For example, assume we have ourjar.jar and assume this is a snippet from its MANIFEST.MF:
Class-Path: lib/myteamjar.jar
It will then be expected that a following directory structure is in place:
lib/myteamjar.jar
ourjar.jar
No, the location of the external jars does not mater. What you want to do is put the external jars on your classpath. How you do it depends on how you are running your java code. If you are running it from the CLI using the java command, it takes the classpath as an argument. If you want your code to build/run in Eclipse, you need to right click on your project, select "Build Path" > "Configure Build Path..." Use the "Add JARs..." button to add jars that are part of a project you have open and "Add External JARs..." to add jars that reside outside of the project. See specific documentation for your tool for more details about classpaths.
I would not recommend Maven to somebody who is fairly new to Java and Eclipse. I would forget about Eclipse, too.
You have a packaging and CLASSPATH issue. Focus on that.
What kind of project are you talking about? The answer you get will depend on what type of app you're creating. Is it an executable JAR? Then the right way to do it is to package everything into a ZIP file that's laid out exactly as the CLASSPATH in the JAR manifest expects.
If it's a web app, the right thing is a WAR file, with all the JARs your app needs in the WEB-INF/lib directory.
If you package things properly, you should end up with a single package that has everything laid out the right way. You should be able to deploy it to the server and make it all work.
I have two projects in eclipse, a library project producing a Jar file and a web project dependant on that Jar. How do I get the web project to export the first projects jar in its war automatically. I know this must have been answered before, but I really cant find it.
Thanks,
The mechanism to determine what goes in the war is not the build path as for "normal" applications, but the "Deployment assembly".
Right-click on the root node of the dynamic web project, and select Properties, and select Deployment assembly. Here you can add projects (which are jarred up and added to WEB-INF/lib) and individual jars in the project.
EDIT 2015-08-20: A few years later, Maven has become the standard way to build Java-based software primarily due to the script based approach to dependency management. This includes how to build WAR-files, and the three major IDE's (IntelliJ, Netbeans and Eclipse) fully support this allowing you to switch between IDE's while developing. In Eclipse the problem asked here will not apply, as this is fully controlled by the Maven plugin.
Summary
Classes from 3rd party jar files are accessible when added to build path while running a standalone JUnit test, but "ClassNotFoundException" when accessed through plain old java objects from within a dynamic web project.
IDE used: Eclipse
Web Server: Apache 7
Details
My project required a lot of 3rd party jars, namely sqlite, eclipse jdt & jsoup. I had created this project as a standalone project and all the classes from the jars were accessible fine.
But now I have copied the entire "src" folder into a "dynamic web project". I have created a folder "jars" which contains all these 3rd party jars and ensure that all of these are added to the build path by following these steps:
Project properties --> Java Build Path --> Libraries --> Add jars --> Select all the jar files from jars folder.
These jars are accessible fine when I run a standalone JUnit test inside the web project. Note that this junit test does not require a server by any means.
But when I try to "Run on Server.." , I keep on getting ClassNotFoundException like these for all the 3rd party classes:
java.lang.ClassNotFoundException: org.sqlite.JDBC
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1672)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1517)
I'm sure this has got to do something with my lack of knowledge of how applications are deployed on the web.
The runtime classpath can be different from the build classpath. Create an explicit launch configuration. The default will start with the build classpath but you may have to manually tweak it to include those 3rd party jars.
I've run into this problem before with Eclipse and the Web Server Tools project. Check your .settings files and other files for configuring the plugins that you're using with your project. You may have to remove some filters in the Eclipse view. WST constructs its build path differently, so it may not be using the jars that you've included in your project.
I figured it out. I just had to put all the jars in the WEB-INF/lib directory. I assumed that Eclipse would do all the required settings for me when I asked it to use the mentioned jars. But I guess there are somethings that are not automated very well.
When I was doing JSP/Servlet programming, whenever I dropped 3rd party libraries into the WEB-INF/lib folder, they were automatically included in the project classpath. In GWT, this is not the case. Anyone know why? I loved how easy this was in JSP and I'd like these jars to be included automatically the same way.
If you are using the Google Plugin for Eclipse then my understanding is that a Google Web Application Project is just not the same animal than a Dynamic Web Project and thus behave differently. So if your project depends on libraries not provided by the GWT and App Engine SDKs, you'll need to put them in war/WEB-INF/lib and to add them explicitly to your Java build path.
In Eclipse Galileo, right click the web project and select build path then select the Java EE Module Dependencies and add the jars.
There is a plug-in technique that may help you if you want a directory where new jars are automatically updated in your build path, see this other post:
Eclipse buildpath automatically taking all JARs of a internal directory
The reason it works like this for your JSP's is because that is how the Dynamic Web Project was made to behave.
"If you remove a library path entry but not the JAR file, the library entry will be re-added to the path automatically." from http://help.eclipse.org/help33/index.jsp?topic=/org.eclipse.wst.webtools.doc.user/topics/ccwebprj.html
You could adopt Maven and use the Maven Eclipse Plugin; this plugin would update your classpath whenever you add a dependency. There may be a similar plugin for Ivy.