I'm trying to use MaxMind's GeoIP2 database, I've added the jar to my Java build path and configured it with Javadoc and source but when I run the program I get a NoClassDefFound error, which according to this stack overflow answer is because I need to add the dependencies, but I have no clue how to add them in eclipse, I tried extracting the jar files and adding them to the build path but that didn't work, how do I do this in eclipse?
Thanks for any help.
In eclipse you have to create a new maven java project. If you dont know maven you can get informations here:
apache maven startsite
how to install maven
Afer that you are able to configure your dependencies in your pom.xml file. Which is the configuration file for maven.
You can find some dependencies for your usage here:
maxmind documentation
The include of the dependency would look like this:
<dependency>
<groupId>com.maxmind.geoip2</groupId>
<artifactId>geoip2</artifactId>
<version>v2.3.0</version>
</dependency>
But first, you should look at maven installation and using. It will make your life easier by handling all the necessary dependencies you will need in this project and in all of your other projects in future.
You don't need to use Maven
For Eclipse, you may use Rightclick on Project > Properties > Java Build Path > Add External JARs. Select the JAR file you downloaded.
3 Questions:
Below are two maven dependencies for JUnit. I have been scouring the interwebs for hours and cannot seem to determine if the second one is Javadoc + code or only Javadoc. Do I need one or both? Further, what is the most effecient way to include Javadocs in a project for development yet not in the production build? (I would prefer not to manually download javadocs for every dependency on every machine.)
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
</dependency>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<classifier>javadoc</classifier>
</dependency>
EDIT: Questions:
What is the difference between these dependencies?
Do I need both of
them to be able to use the dependency & have Javadoc on hand?
What is best practice for including Javadocs for development?
Generally Javadocs are not primarily used as dependency. Because these are neither required at compile nor runtime. It’s just to help the developer while developing or debugging.
Assuming using the java IDE Eclipse we can use the java docs as referenced. Following are the approaches we can associate the javadocs/sources with the respective jars.
1. If it’s non-maven project :
Download the javadocs jar or zipped file, whatever available and placed it in some directory.
Right click on the application project in the IDE Eclipse, click Properties and choose Java Build Path then select tab Libraries under the Java Build Path. Now expand the jar you want to link with java docs/source. Select the Javadoc location link and click on Edit button, a new window appears where we need to choose the javadocs jar path. Click OK and we have linked the javadoc/source with the respective jars.
2. If it’s a maven project
If we are using the Maven project then go to jar files under the Maven dependency under the project in Project Explorer view as shown below. Now right click on the jar file you want to add the Javadoc/source, choose Maven then click on Javadoc or Source you want to link with the project. Now IDE will automatically download the required javadoc/source and will link it with the respective jar in the project.
You can verify this by right click on the project in the IDE and click on Java Build Path and select the Libraries tab under the Java Build Path and then expand the desired jar, here when you click the Edit button you will see the linked path of the Javadoc/Source with the respective jar as shown below in the image.
3. If it’s Maven project and we are setting the default behaviour:
Eclipse will aquatically download the javadoc/source along with the main required jar at the starting.
By default setting instruction to Maven to download the Javadoc/sources for all the jars linked in the project.
Click Windows – preferences – select Maven and click the checkbox Download Artifact Javadoc as shown below
Now click on apply and save it and now when you create new Maven project , by default the Javadocs will get downloaded and linked with all the dependent jars in the project.
You can verify by right click on the project and Properties and under Java Build path can see the javadocs are linked with all the jars as shown below.
If your project is Maven project then It’s always best to use 2nd approach because by using this approach the IDE and Maven, takes care of downloading the correct version of the Javadoc/source and linked it with the relative jar as well.
Approach 3rd is bit costly because the javadoc/sources will be downloaded forall the dependent jars, may be you are not interested for javadocs/sources for all the dependent jars.
Generally speaking, your IDE will handle the resolution of javadoc for you in a maven project. This is assuming your IDE understands maven - e.g. netbeans, intellij or eclipse w/ m2e.
The second artifact is only the javadocs. The first artifact is the code. There's almost never a good reason to include the javadoc artifact as a dependency.
I stumbled upon this problem when I created a maven project in eclipse and neither javadoc nor source of my dependencies where attached to my project, and I wondered which dependency to add.
What helped me was adding
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-source-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
</plugin>
</plugins>
</build>
to my pom.xml. That way, you only have to use the first dependency, and maven/eclipse take care of downloading the second (which is, as pointed out in the other answer, only the javadoc).
I've been trying to add a custom .jar (ftp://ftp.ncbi.nlm.nih.gov/pub/eutils/soap/v2.0/java/axis2_1.5.2_jdk_6.0.12/eutils_axis2.jar) to a project that doesn't have a central corporate maven repository and that instead will have the custom JARs checked into SCM in the project directory tree. I was following this post to make it happen: Maven: add a dependency to a jar by relative path (awesome post btw).
What I did was:
Add local repository to pom.xml
install the file into the local repository
Add dependency to pom.xml
Based on what I see in m2eclipse, the library has been successfully recognized by Maven and added to the dependency list (or it'd be called ? : ? or something similar)
The problem is that Eclipse still doesn't see the referenced lib, so this still fails:
import gov.nih.nlm.ncbi.www.soap.eutils.*;
Pardon my maven newbiness, but what are changes / next steps I need to make to get to:
Have Eclipse see the library so that autocomplete works (and the import can be resolved)
Be able to compile the project
Be able to execute the jar produced by mvn package?
Thanks!
If you see the JAR under "Maven Dependencies" in your project, Eclipse should be able to see and use it. If it's not there, then m2eclipse wasn't able to resolve the dependency properly.
If it is missing, m2eclipse was unable to download the dependency from your local repository for some reason. Check the Maven 2 Console for errors and the Problem View.
Lastly, the JAR itself might be corrupt. Maven doesn't check for that, it simply adds the file to the classpath. If Eclipse can't open the JAR, you can also get the errors you mentioned.
Does anyone have any idea if you can find source JARs on Maven repositories?
Maven Micro-Tip: Get sources and Javadocs
When you're using Maven in an IDE you often find the need for your IDE to resolve source code and Javadocs for your library dependencies. There's an easy way to accomplish that goal.
mvn dependency:sources
mvn dependency:resolve -Dclassifier=javadoc
The first command will attempt to download source code for each of the dependencies in your pom file.
The second command will attempt to download the Javadocs.
Maven is at the mercy of the library packagers here. So some of them won't have source code packaged and many of them won't have Javadocs.
In case you have a lot of dependencies it might also be a good idea to use
inclusions/exclusions to get specific artifacts, the following command
will for example only download the sources for the dependency with
a specific artifactId:
mvn dependency:sources -DincludeArtifactIds=guava
Source: http://tedwise.com/2010/01/27/maven-micro-tip-get-sources-and-javadocs/
Documentation: https://maven.apache.org/plugins/maven-dependency-plugin/sources-mojo.html
Configuring and running the maven-eclipse plugin, (for example from the command line mvn eclipse:eclipse )
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-eclipse-plugin</artifactId>
<configuration>
<downloadSources>true</downloadSources>
<downloadJavadocs>true</downloadJavadocs>
</configuration>
</plugin>
</plugins>
</build>
If a project creates a jar of the project sources and deploys it to a maven repository, then you'll find it :)
Just FYI, sources artifacts are generally created by the maven-source-plugin. This plugin can bundle the main or test sources of a project into a jar archive and, as explained in Configuring Source Plugin:
(...) The generated jar file will be named by the value of the finalName plus "-sources" if it is the main sources. Otherwise, it would be finalName plus "-test-sources" if it is the test sources.
The additional text was given to describe an artifact ("-sources" or "-test-sources" here) is called a classifier.
To declare a dependency on an artifact that uses a classifier, simply add the <classifier> element. For example:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate</artifactId>
<version>3.2.7.ga</version>
<classifier>sources</classifier>
</dependency>
Note that you generally don't do this, most IDEs provide support to download sources (and/or JavaDoc) from the main artifact without declaring explicitly a dependency on them.
Finally, also note that some repository search engines allow searching for artifacts using the classifier (at least Nexus does with the advanced search). See this search for example.
The maven idea plugin for IntelliJ Idea allows you to specify whether or not sources and java doc should be resolved and downloaded
mvn idea:idea -DdownloadSources=true -DdownloadJavadocs=true
To download any artifact use
mvn dependency:get -Dartifact=groupId:artifactId:version:packaging:classifier
For Groovy sources this would be
mvn dependency:get -Dartifact=org.codehaus.groovy:groovy-all:2.4.6:jar:sources
For Groovy's javadoc you would use
mvn dependency:get -Dartifact=org.codehaus.groovy:groovy-all:2.4.6:jar:javadoc
This puts the given artifact into your local Maven repository, i.e. usually $HOME/.m2/repository.
dependency:sources just downloads the project dependencies' sources, not the plugins sources nor the sources of dependencies defined inside plugins.
To download some specific source or javadoc we need to include the GroupIds - Its a comma separated value as shown below
mvn dependency:sources -DincludeGroupIds=com.jcraft,org.testng -Dclassifier=sources
Note that the classifier are not comma separated, to download the javadoc we need to run the above command one more time with the classifier as javadoc
mvn dependency:sources -DincludeGroupIds=com.jcraft,org.testng -Dclassifier=javadoc
you can find info in this related question: Get source jar files attached to Eclipse for Maven-managed dependencies
if you use the eclipse maven plugin then use 'mvn eclipse:eclipse -DdownloadSources=true'
if you're using eclipse you could also open Preferences > Maven and select Download Artifact Sources, this would let the pom.xml intact and keep your sources or java docs (if selected) just for development right at your machine location ~/.m2
In Eclipse
Right click on the pom.xml
Select Run As -> Maven generate-sources
it will generate the source by default in .m2 folder
Pre-Requisite:
Maven should be configured with Eclipse.
In eclipse - click on the project then:
.
You can, if they are uploaded. Generally they are called "frameworkname-version-source(s)"
NetBeans, Context-Click
In NetBeans 8 with a Maven-driven project, merely context-click on the jar file list item of the dependency in which you are interested. Choose Download Sources. Wait a moment and NetBeans will automatically download and install the source code, if available.
Similarly you can choose Download Javadoc to get the doc locally installed. Then you can context-click some code in the editor and choose to see the JavaDoc.
Based on watching the Maven console in Eclipse (Kepler), sources will be automatically downloaded for a Maven dependency if you attempt to open a class from said Maven dependency in the editor for which you do not have the sources downloaded already. This is handy when you don't want to grab source for all of your dependencies, but you don't know which ones you want ahead of time (and you're using Eclipse).
I ended up using #GabrielRamierez's approach, but will employ #PascalThivent's approach going forward.
If you know the groupId and aritifactId,you can generate download url like this.
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
http://central.maven.org/maven2/ch/qos/logback/logback-classic/
and you will get a page like this, chose the version you need,just enjoy it!
I have also used the eclipse plugin to get the project into the eclipse workspace.
Since I've worked on a different project I saw that it is possible to work with eclipse but without the maven-eclipse-plugin. That makes it easier to use with different environments and enables the easy use of maven over eclipse. And that without changing the pom.xml-file.
So, I recommend the approach of Gabriel Ramirez.
Maven repositories do provide simple way to download sources jar.
I will explain it using a demonstration for "spring-boot-actuator-autoconfigure".
Go to maven repository -
https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-actuator-autoconfigure
The page lists various versions. Click-on to desired one, let's say, 2.1.6.RELEASE - https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-actuator-autoconfigure/2.1.6.RELEASE
The page have link "View All" next to "Files". Click it -
https://repo1.maven.org/maven2/org/springframework/boot/spring-boot-actuator-autoconfigure/2.1.6.RELEASE/
The page lists various files including the one for sources -
https://repo1.maven.org/maven2/org/springframework/boot/spring-boot-actuator-autoconfigure/2.1.6.RELEASE/spring-boot-actuator-autoconfigure-2.1.6.RELEASE-sources.jar
Otherwise, you can always "git clone" the repo from github, if its there and get the specific code.
As explained by others, you can use "mvn dependency:sources" command the get and generate sources jar for the dependency you are using.
Note: Some dependencies will not have sources.jar, as those contains no source code but a pom file. e.g. spring-boot-starter-actuator.
As in this case:
Starter POMs are a set of convenient dependency descriptors that you can include in your application. You get a one-stop-shop for all the Spring and related technology that you need, without having to hunt through sample code and copy paste loads of dependency descriptors.
Reference: Intro to Spring Boot Starters
In IntelliJ IDEA you can download artifact sources automatically while importing by switching on Automatically download Sources option:
Settings → Build, Execution, Deployment → Build Tools → Maven → Importing
If you want find the source jar file for any of the artifact manually, go to maven repository location for the particular artifact and in Files click on 'view All'. You can find source jar file.
For debugging you can also use a "Java Decompiler" such as: JAD and decompile source on the fly (although the generated source is never the same as the original). Then install JAD as a plugin in Eclipse or your favorite IDE.
If you're using Eclipse, I would recommend downloading both the source and the Javadocs of third-party libraries.
Right click on project and download both as per the screenshot below.
Downloading Javadocs means that typically you can get contextual help for methods from third-party libraries, with useful description of parameters, etc. This is essential if you don't know the library well. In some cases I have found that Javadocs are available when the source isn't.
I use Eclipse, Maven, and Java in my development. I use Maven to download dependencies (jar files and javadoc when available) and Maven's eclipse plug-in to generate the .project and .classpath files for Eclipse. When the dependency downloaded does not have attached javadoc I manually add a link for the javadoc in the .classpath file so that I can see the javadoc for the dependency in Eclipse. Then when I run Maven's eclipse plugin to regenerate the .classpath file it of course wipes out that change.
Is there a way to configure Maven's eclipse plug-in to automatically add classpath attributes for javadoc when running Maven's eclipse plug-in?
I'm only interested in answers where the javadoc and/or sources are not provided for the dependency in the maven repository, which is the case most often for me. Using downloadSources and/or downloadJavadocs properties won't help this problem.
From the Maven Eclipse Plugin FAQ
The following example shows how to do
this in the command-line:
mvn eclipse:eclipse -DdownloadSources=true -DdownloadJavadocs=true
or in your pom.xml:
<project>
[...]
<build>
[...]
<plugins>
[...]
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-eclipse-plugin</artifactId>
<configuration>
<downloadSources>true</downloadSources>
<downloadJavadocs>true</downloadJavadocs>
</configuration>
</plugin>
[...]
</plugins>
[...]
</build>
[...]
</project>
I'm running STS 2.8.1 which is basically eclipse + spring tools; In an existing maven project, I right clicked on the project -> maven -> Download Sources and Download JavaDocs
As mentioned in How to download sources and javadoc artifacts with Maven Eclipse plugin from other repository?, you can do this:
In Eclipse go to Windows-> Preferences-> Maven. Check the box that says "Download Artifact Javadoc." That has worked well for me.
You might consider just avoiding this problem completely by installing the javadoc jar into your local repository manually using the install-file goal and passing in the -Dclassifier=javadoc option. Once you do that the .classpath that mvn generates should be correct.
If you use a remote repo as a proxy to central you could also deploy the javadocs to that repo and then everyone else who uses that proxy will now get the javadocs automatically as well.
Generally Javadocs are not primarily used as dependency . Because these are neither required at compile nor runtime. It’s just to help the developer while developing or debugging.
Assuming using the java IDE Eclipse we can use the java docs as referenced. Following are the approaches we can associate the javadocs/sources with the respective jars.
1. If it’s non-maven project :
Download the javadocs jar or zipped file, whatever available and placed it in some directory.
Right click on the application project in the IDE Eclipse, click Properties and choose Java Build Path then select tab Libraries under the Java Build Path. Now expand the jar you want to link with java docs/source. Select the Javadoc location link and click on Edit button, a new window appears where we need to choose the javadocs jar path. Click OK and we have linked the javadoc/source with the respective jars.
2. If it’s a maven project
If we are using the Maven project then go to jar files under the Maven dependency under the project in Project Explorer view as shown below. Now right click on the jar file you want to add the Javadoc/source, choose Maven then click on Javadoc or Source you want to link with the project. Now IDE will automatically download the required javadoc/source and will link it with the respective jar in the project.
You can verify this by right click on the project in the IDE and click on Java Build Path and select the Libraries tab under the Java Build Path and then expand the desired jar, here when you click the Edit button you will see the linked path of the Javadoc/Source with the respective jar as shown below in the image.
3. If it’s Maven project and we are setting the default behavior:
Eclipse will aquatically download the javadoc/source along with the main required jar at the starting.
By default setting instruction to Maven to download the Javadoc/sources for all the jars linked in the project.
Click Windows – preferences – select Maven and click the checkbox Download Artifact Javadoc as shown below
Now click on apply and save it and now when you create new Maven project , by default the Javadocs will get downloaded and linked with all the dependent jars in the project.
You can verify by right click on the project and Properties and under Java Build path can see the javadocs are linked with all the jars as shown below.
If your project is Maven project then It’s always best to use 2nd approach because by using this approach the IDE and Maven, takes care of downloading the correct version of the Javadoc/source and linked it with the relative jar as well.
Approach 3rd is bit costly because the javadoc/sources will be downloaded for-all the dependent jars, may be you are not interested for javadocs/sources for all the dependent jars.
Would having the sources for the dependency help? You can tell the eclipse plugin to download those (and refer to them in the .classpath) with -DdownloadSources=true