I'm a Java and Maven newbie and I have a question about the default manifest file.
As far as I understand, a manifest is created when a Java application is built using maven and it is added to the generated jar file.
I've also seen lots of references to a manifest.mf file, which can be found in a directory called meta-inf. But I can't find it anywhere.
I have successfully built my Java application using mvn package. I can see the jar file but I can't find the manifest file anywhere. Is it automatically deleted when the build completes?
The MANIFEST.MF file is inside the jar in the META-INF directory. You can see the content of your jar with jar tf your_jar_file.jar
You can also unzip the content of your jar with jar -xf your_jar_file.jar.
Related
So what im trying to do is to build a JAR artifact which should include the necessary libraries as well as directories which are outside of the JAR file and can be looked at in the explorer.
I have already tried to add directories to the artifacts but these get put into the JAR file in a folder which i cant access later when converting it to a exe using launch4j.
Is there an option in Intellij to exclude directories from building into a JAR?
Edit: I want the output directory like this
Directory Structure
When I create an executable .jar file using IntelliJ, the .jar file always ignores it's own class-path in the manifest.mf file.
Thanks to this question: Executable JAR ignores its own Class-Path attribute I have been able to find that the cause of the problem is that during the creation of the .jar file, a META-INF/LIST.MF file is created. If I delete that file, everything works fine. However, unlike the question linked, my pom.xml file does not contain the command to create this file.
How do I turn this off in IntelliJ?
Try, when creating an artifact in IntelliJ,project structure -> Artifacts -> new from maven with dependencies, in the path for Directory for the META-INF/MANIFEST.MF, always change the path to the sibling resources directory, it should not be set tojava` directory.
The structure of my first app is simple:
libs
opencsv-3.8.jar
yamlbeans-1.0.jar
out
artifacts
...
production
...
src
META-INF
MANIFEST.MF
pl.krzysiu
App.java
CsvReplacer.java
Everything is fine during the compile and running the program. After building artifact jar file in the default out\artifacts directory, I get
java.lang.NoClassDefFoundError: net/sourceforge/yamlbeans/YamlException
when I try to run it by java -jar CsvReplacer.jar command
The libraries are included inside the jar file (they are there after unpacking it) - they are added to Libraries section in Project Structure (separately - one file per one lib), the whole libs dir is included in the Dependencies tab of Modules section (with export checkbox checked) and the libs dir is added in Output Layout of Artifacts section similarily.
The manifest file contains:
Manifest-Version: 1.0
Class-Path: libs\yamlbeans-1.0.jar libs\opencsv-3.8.jar
Main-Class: pl.krzysiu.App
Why the libs aren't visible for the App? If I copy this dir manually to the CsvReplacer.jar file's location - everything works fine.
The structure inside CsvReplacer.jar file looks like:
libs
opencsv-3.8.jar
yamlbeans-1.0.jar
META-INF
MANIFEST.MF
pl
krzysiu
App.java
CsvReplacer.java
IDE: Intellij IDEA 2016.3
The standard Java classloaders cannot find a JAR file embedded inside another JAR file.
You have two choices when making an executable JAR with dependencies.
Create a so-called uberJAR file by merging the contents of the dependent JARs into your main JAR.
References:
IntelliJ IDEA export Runnable program as Uber Jar
https://blog.jetbrains.com/idea/2010/08/quickly-create-jar-artifact/
Give your JAR a "Class-Path" manifest attribute to tell it where the (external!) dependent JARs are located.
You can't give a -cp and a -jar option together. But another alternative would be to get rid of the -jar option and use a -cp argument to specify the classpath.
Alternatively, you could implement a custom classloader that can load from a jar inside a jar, or use something like one-jar or Spring Boot.
I have seen this question asked a lot, but I still can't figure out a solution to it. Well a solution that works for me. I have a project that is using Apache POI, and I made sure to include all the external JARs. The project compiles and runs fine in eclipse but when I run the jar with "java -jar Test.jar" I get this error:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/poi/ss/usermodel/Sheet
I'm not sure if this is useful information, but I created a lib folder for my project and put the poi library in there. This means that the dependcies are in the JAR file when I create it, I figured I should mention this because I saw a few solutions about just having your external jars right next to your executable jar. I also tried setting my classpath to the directory of the project.
What do I seem to be doing wrong?
The Apache POI JAR file is not on your runtime classpath. Rebuild Test.jar with the following manifest entry in the MANIFEST.MF file
Class-Path: poi-3.9-20121203.jar
When the java -jar [filename].jar command fails, it's almost always because of one of two things:
Your MANIFEST.MF is messed up and doesn't list dependencies properly. Make sure all jar dependencies in your manifest file point to jars, relative to your jar's parent directory.
You are missing .class files, either in your specific jar or in one you depend on. Ensure your jar contains org/apache/poi/ss/usermodel/Sheet.class or that your manifest hierarchy points to a jar that contains that class.
You will need to provide classpath in Jar file's manifest file. See this official doc
An Example
We want to load classes in MyUtils.jar into the class path for use in MyJar.jar. These two JAR files are in the same directory.
We first create a text file named Manifest.txt with the following contents:
Class-Path: MyUtils.jar
First check if your target jar (Test.jar) is a fat jar containing all the required dependencies.
$ jar tf Test.jar
You should see your lib/ folder there containing all the required dependencies (including Apache POI). If that's the case do what others suggested, add Apache POI to your MANIFEST.MF.
About having your jar dependencies in a separate folder, as you suggested, that's also possible. Imagine your dependencies where stored in a lib/ folder outside your Test.jar. You could run your code with this command:
$ java -cp ".:lib/*" org.Test.Main
It simply adds all the .jars within lib/ folder to your classpath. In this case you also need to specify the name of the main class (full name).
I also got this problem and tried to google it..
i have found out that i have to read the error log
I cant save my file to .xls so
in my case after reading the error i found that a jar file is missing
i just added the jar file poi-3.7-20101029 located in the ext folder of my ireport
ex.YourIReportFolder/ireport/modules/ext-poi.x.x-xxxx
hope this helps :)
I am using Java Simple Plugin Framework. I export a jar that has my plugin implementation. The implementation depends on a library, which I have as a jar. That jar gets exported within the lib directory of my jar, and added to the classpath of my jar.
But when I load my jar with JSPF, it fails with "NoClassDefFound" because it can't find the jar in the lib director of my jar.
My apologies if my approach off base; I just need to know how this is supposed to be done. How should I bundle my plugin implementation as a jar if it depends on another jar?
I used JSPF and achieved this requirement the following way:
place the library jar file in a folder called lib outside the plugin jar file. (So that
the lib folder and the plugin jar file is in the same folder). Then I added lib/"name_of_libjar" to the classpath entry in the manifest.mf file of the plugin jar file (Which should be inside the plugin jar files META-INF folder), and it worked fine for me.