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Maven dependencies exclusions not working

I'm using enforcer plugin of Maven and I see a behavior that I dont quite understand and it's dangerous.
Let's say that I have a conflict since dependency A has bla.jar:1.0 and is in conflict with my dependnecy B which has bla.jar:2.0
Then to fix the conflict, I make an exclude of bla.jar:1.0 from A
<dependency>
<groupId>com.foo</groupId>
<artifactId>A</artifactId>
<version>a.version.bla</version>
<exclusions>
<exclusion>
<groupId>com.omg</groupId>
<artifactId>bla</artifactId>
</exclusion>
</exclusions>
</dependency>
expecting the application will get the bla.jar:2.0 fron classpath. But then I see when I run some unit test that the java proce3ss cannot find bla.jar ion the classpath at all and is giving me ClassNotFound in runtime.
Any idea what's wrong here?
I have in my pom defined from top to bottom B and then A

Please note that exclusions are not the best way to resolve dependency version conflicts.
The best approach is to use <dependencyManagement>. It allows you to set a version that replaces all transitive versions of that dependency.
In your case, I would first change the exclusion to <dependencyManagement>. Then I would proceed in the following way:
Check mvn dependency:list which version of the dependency is on the classpath. It should be the one specified in <dependencyManagement> unless there is no version of that dependency in your dependency tree. If you find more than one, then probably the groupId changed at some point. Then you need exclusions.
Check the scope of the dependency and verify that it is indeed compile.
Then open the dependency jar and see whether this jar really contains the class for which you get ClassNotFound. Often classes change from version to version.

Cannot instantiate the type ADBDataSource using axis2

After using Eclipse EE and Eclipse Axis2 Code Generator plugin, I got a two
operation generated java files with the same error:
Cannot instantiate the type ADBDataSource ConcatRequest.java
Cannot instantiate the type ADBDataSource ConcatResponse.java
Here is the problem:
org.apache.axiom.om.OMDataSource dataSource = new
org.apache.axis2.databinding.ADBDataSource(this,MY_QNAME);
This code appears in both ConcatRequest.java and ConcatResponse.java and
causes the error. I see that ADBDataSource is abstract and cannot be instantiated.
I'm totally new to Axis and I don't know how to solve this problem. Please help.

I had this problem due to a version mismatch of axis2-adb. Safest way to deal with this problem is to have a look at the lib folder of the eclipse plugin (eclipse/(dropins|plugins)/ ... .jar). Then look for the versions of the dependecies and include them (the ones you actually need) in your build path.

i faced the same issue while generating JAVA Stubs from WSDL. Following are the steps I used to solve the issues :
Follow the below link to generate Stubs : https://support.pcmiler.com/en/support/solutions/articles/19000053078-java-client-axis2-code-generator-for-eclipse.
Now there is a small tweak to this link. After doing point no 10 & 11 as mentioned in the above link , only use axis2-1.7.9 to generate your stubs and when they are generated used the jars mentioned in the \axis2-1.7.9\lib in your build path.
Hope this solves your issue.

Old topic, but I was working on a legacy project with several subprojects.
In one of those subprojects, I came across this same message.
It also was a version problem (Maven dependencies...).
Ctrl-Click (in Eclipse/IntelliJ) on "ADBDataSource". Which version is it? For me it was 1.5.6, but in my pom.xml there was only
<dependency>
<groupId>org.apache.axis2</groupId>
<artifactId>axis2</artifactId>
<version>1.7.4</version>
</dependency>
However, this subproject had a dependency on another subproject which WAS using 1.5.6 (I found it by searching in the whole project for "1.5.6" using the Notepad++ "Search / Find in Files" menu option).
Then in the dependency to that other project, I excluded 1.5.6 :
<dependency>
<groupId>com.group.id</groupId>
<artifactId>anotherproject</artifactId>
<version>version</version>
<exclusions>
<exclusion>
<groupId>org.apache.axis2</groupId>
<artifactId>axis2</artifactId>
</exclusion>
</exclusions>
</dependency>
After adding the exclusion, the project did use the 1.7.4 version.

Need to configure Maven project dependency tree, but *not for me*--it's only for those using my projects via Maven Central

I have a new library, called Codelet. It depends on two other libraries I've created, called Template Featherweight and XBN-Java. But the primary library--the one I'm trying to get other people to use!--is Codelet. The other two are secondary. Both are required, but they are only directly used when advanced features are needed.
I build all aspects of all three of these projects with Ant. I use Maven for one reason only: To sign the jars
codelet-0.1.0.jar
codelet-0.1.0-sources.jar
codelet-0.1.0-javadoc.jar
and push them to Maven Central. After shedding significant blood, sweat, tears, and soul in the past week, as evidenced by these four questions
How to use Maven to only sign three jars and push them to Maven Central?
Followup questions: Using Maven to only sign and deploy jars to Maven Central. Build and compilation is done entirely with Ant
Followup part 2 -- Using Maven to only sign and deploy jars to Maven Central. Build and compilation is done entirely with Ant
Why am I getting a "401 Unauthorized" error in Maven?
I have finally gotten the jars to upload to Maven Central via mvn deploy, at least once anyway, so that's big progress.
I'm realizing, however, that in order for other people to actually use Codelet, they need the entire dependency tree to be mapped out in Codelet's POM. I believe this is correct.
I am concerned that mapping this three-project dependency tree, in their three POMs, will essentially require that I duplicate much of my Ant build process in Maven. I am hoping with all hope that I don't need to do this, as Ant works well for me, and Maven and I do not get along.
Here are the dependency trees:
Dependencies for compilation of core library classes and example code, only
All items are listed by Maven groupId / artifactId / version.
XBN-Java 0.1.3 depends on
org.apache.commons / commons-collections4 / 4.0
org.apache.commons / commons-io / 2.4
org.apache.commons / commons-lang3 / 3.3.2
com.google.guava / guava / 16.0
Template Featherweight 0.1.0 depends on
com.github.aliteralmind / xbnjava / 0.1.3 (and its dependencies)
Codelet 0.1.0 depends on
com.github.aliteralmind / templatefeather / 0.1.0 (and its dependencies)
${java.home}/../lib/tools.jar (This is considered "provided", since it's part of the JDK and not on Maven Central)
Dependencies for compilation and execution of unit tests, only
These are in addition to those needed for core-compilation.
For all projects: junit / junit / 4.11 (and its dependency: hamcrest core)
For compilation of "Codelets" (which are used only by javadoc.exe), and execution of javadoc.exe
These are in addition to those needed for core-compilation.
For all projects: com.github.aliteralmind / codelet / 0.1.0 (and all its "core-compilation" dependencies)
(Some background: Codelet automates the insertion of example code into JavaDoc, using inline taglets like
{#.codelet.and.out com.github.mylibrary.examples.AGoodExample}
These optional "Codelet classes", called "customizers", are compiled before running javadoc.exe. They are used to customize how example code is displayed. Once compiled, Codelet is executed automatically, as are all inline taglets, via javadoc.exe.)
For core-compilation it's pretty much linear:
XBN-Java is the root
Template Feather depends on XBN-Java, and
Codelet depends on Template Feather
But for "javadoc", all three projects depend on Codelet. So even XBN-Java depends on Codelet...which depends on Template Feather...which depends on XBN-Java.
The POMs in all three projects are working, although this is only as far as it concerns signing and pushing the jars to Maven Central.
After reading Maven's dependency Mechanism documentation, it seems that all three projects could have the same flat dependency tree
<dependencies>
<dependency>
<groupId>com.github.aliteralmind</groupId>
<artifactId>templatefeather</artifactId>
<version>0.1.0</version>
</dependency>
<dependency>
<groupId>com.github.aliteralmind</groupId>
<artifactId>codelet</artifactId>
<version>0.1.0</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.0</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-io</artifactId>
<version>2.4</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.3.2</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>16.0</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
</dependencies>
But the right way is to have a parent project, which is inherited by the other two. It seems that XBN-Java should be the parent, but given the recursive nature of the dependencies, I'm not sure.
I am not getting the difference between dependencies and dependencyManagement (why some dependencies blocks can go right into the project proper, and others are sub-blocks in dependencyManagement...although it seems related to parent-child), and I also don't understand how "javadoc" fits into the "scope" attribute. While compile and test are explicitely listed, the word "doc" doesn't even exist on the page.
I would appreciate some advice. Thank you.

If your code needs something, but not for compile-time (just for run-time) then declare the dependency, but add a runtime scope.
Now if you want to provide a "starter parent" pom.xml, then release a "starter parent" pom.xml but don't use it in your actual build chain.

java.lang.NoSuchFieldError: org.apache.http.message.BasicLineFormatter.INSTANCE from Mashape Unirest in Java application

I have a Maven Java project that uses Mashape Unirest for sending HTTP requests to other URLs. I am currently writing an integration test (using TestNG) that sends a normal HTTP request using Unirest. When I run the integration test through Maven (via the Failsafe plugin), the request is sent out successfully. However, when I try to run the integration test via Eclipse, I keep on getting the following error:
FAILED: getCurrentTimeTest
java.lang.NoSuchFieldError: INSTANCE
at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.<init>(DefaultHttpRequestWriterFactory.java:52)
at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.<init>(DefaultHttpRequestWriterFactory.java:56)
at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.<clinit>(DefaultHttpRequestWriterFactory.java:46)
at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.<init>(ManagedHttpClientConnectionFactory.java:72)
at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.<init>(ManagedHttpClientConnectionFactory.java:84)
at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.<clinit>(ManagedHttpClientConnectionFactory.java:59)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$InternalConnectionFactory.<init>(PoolingHttpClientConnectionManager.java:487)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.<init>(PoolingHttpClientConnectionManager.java:147)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.<init>(PoolingHttpClientConnectionManager.java:136)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.<init>(PoolingHttpClientConnectionManager.java:112)
at org.apache.http.impl.client.HttpClientBuilder.build(HttpClientBuilder.java:726)
at com.mashape.unirest.http.options.Options.refresh(Options.java:41)
at com.mashape.unirest.http.options.Options.<clinit>(Options.java:27)
at com.mashape.unirest.http.HttpClientHelper.prepareRequest(HttpClientHelper.java:141)
at com.mashape.unirest.http.HttpClientHelper.requestAsync(HttpClientHelper.java:80)
at com.mashape.unirest.request.BaseRequest.asStringAsync(BaseRequest.java:56)
at ...
I am also able to reproduce this error using a basic Java application script.
I have made sure that the dependencies I am using in my pom.xml file are the latest and greatest, as seen below:
<dependency>
<groupId>com.mashape.unirest</groupId>
<artifactId>unirest-java</artifactId>
<version>1.3.5</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.3.2</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpasyncclient</artifactId>
<version>4.0</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpmime</artifactId>
<version>4.3.2</version>
</dependency>
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20140107</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcore</artifactId>
<version>4.3.2</version>
</dependency>
I have also checked out the source code of BasicLineFormatter.java, both from the source file downloaded to Eclipse and from Apache's Httpcore Github repo. In the Github repo, notice how the INSTANCE field is defined for the 4.3.x branch and the trunk branch, but not in older branches like 4.2.x. However, I am indeed using version 4.3.2 in my project, so I should be using a JAR file for Httpcore that has the latest version of BasicLineFormatter. I know that, based on the Maven Dependencies JAR files that are in my project, that I am indeed using the latest versions of these Apache dependencies, not the older versions specified as downstream dependencies of my project.
I have checked other various SOF and blog posts about this issue, such as Mashape Unirest Java : java.lang.NoClassDefFoundError and this blog post too, but they all seem to be talking about solving the NoSuchFieldError problem for Android. However, I'm dealing with a standalone Java application, not an Android application.
I am at a loss in determining how to troubleshoot this issue. Anyone have any idea what I need to do?
UPDATE
Instead of showing my test case, I will reduce the illustration of a reproduction of this problem to just a simple one-liner Java application, because the problem exists with any Java application or test case run through Eclipse, not just one particular test:
System.out.println(Unirest.get("http://www.google.com").asStringAsync().get().getBody());
Normally, this should print the HTML of the Google home page, but I instead get the NoSuchFieldError stack trace.
FIXED!
The problem was that the AWS SDK (it's on my classpath because I'm developing for Elastic Beanstalk) had a conflicting JAR file. Using Oleg's solution (thanks BTW), I printed the following output in a unit test:
jar:file:/some/path/aws-java-sdk/1.7.1/third-party/httpcomponents-client-4.2.3/httpcore-4.2.jar!/org/apache/http/message/BasicLineFormatter.class
I'll have to rearrange my classpath so that AWS SDK is no longer conflicting.

The only plausible explanation to this problem is there is an older version of HttpCore on the classpath (unless you also want to consider a possibility of green men from Mars messing with your computer remotely from a flying saucer).
You can add this snippet to your code to find out what jar the class gets picked up from. This might help find out why that jar is on your classpath in the first place.
ClassLoader classLoader = MyClass.class.getClassLoader();
URL resource = classLoader.getResource("org/apache/http/message/BasicLineFormatter.class");
System.out.println(resource);
This basically tells me that in my case the jar resides in the local maven repository and likely to have been added to the classpath by Maven
jar:file:/home/oleg/.m2/repository/org/apache/httpcomponents/httpcore/4.3.1/httpcore-4.3.1.jar!/org/apache/http/message/BasicLineFormatter.class

As already mentioned by previous comments, It's mainly because of the conflicting versions of httpcore jar, the static field INSTANCE is been added to BasicLineFormatter class in versions > 4.3.1, Though you might have added the latest version of the httpcore jar in your dependencies, but its highly possible that other (lower) version of jar is getting picked up.
So, first to confirm that, wrong jar is getting picked up, Use the following line of code -
ClassLoader classLoader = <Your Class>.class.getClassLoader();
URL resource = classLoader.getResource("org/apache/http/message/BasicLineFormatter.class");
System.out.println(resource);
If this prints, the lower version of the jar, then it's confirmed that it's picking the lower version of the httpcore jar (May be from other dependencies of your project),
Solution -
Add following maven/gradle dependencies at the top of dependency list (Or above the other project dependency which caused the conflict) -
<dependency>
<groupId>com.mashape.unirest</groupId>
<artifactId>unirest-java</artifactId>
<version>1.4.5</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcore</artifactId>
<version>4.4.1</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.4.1</version>
</dependency>

I faced the same exception using unirest:
java.lang.NoSuchFieldError: INSTANCE
at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.<init>(DefaultHttpRequestWriterFactory.java:52)
at com.mashape.unirest.http.options.Options.refresh(Options.java:55)
at com.mashape.unirest.http.options.Options.<clinit>(Options.java:36)
And found it was due to DefaultConnectionKeepAliveStrategy.INSTANCE; and the conflicting jar was apache-httpcomponents-httpclient.jar in my classpath. Adding this post to help anyone who faces similar exception

I got this Exception: Caused by: java.lang.NoSuchFieldError: INSTANCE
Solution:
This happens if you have two different version classes in your classpath…. […], So I first find that class (one version of class), click that class, select build path, then I click remove from build path.

if you are using aws sdk this error occurs because of dependency mismatch.
To avoid this error do the following:
1.Put the dependecies in the required order aws sdk and the end preferably
2.Add shade plugin to the project
This solved my problem

you can refer to my answer in
HTTPClient Example - Exception in thread "main" java.lang.NoSuchFieldError: INSTANCE
my case is i have httpclient-4.4.1.jar, and httpcore-4.4.1.jar in my class path, but JVM loaded BasicLineFormatter from httpcore-4.0.jar

Maven 2 - different dependency versions in test and compile

I have project that depends on commons-httpclient [2.0] (compile).
I would like to write some jbehave tests - jbehave-core 3.4.5 (test).
Both this dependencies depend on commons-lang but in different versions - 1.0.1 and 2.5.
When I execute mvn package I get [BUID FAILURE] in tests section.
There is an exception for my testcase in surefire-plugin output:
java.lang.NoSuchMethodError: org.apache.commons.lang.StringUtils.substringBeforeLast(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
As I looked in source code - in commons-lang 1.0.1 - indeed, there is no StringUtils.substringBeforeLast(...) method.
Why maven uses commons-lang from commons-httpclient (compile) and not from jbehave-core in testing?
I can't afford to exclude this conflicting dependency in commons-httpclient so it must stay in compile time.
So how can this be resolved - commons-lang 2.5 version in testing and 1.0.1 in compile time?

Maven 3:
Maven 3 will attempt to obtain the nearest dependency, effectively ensuring that only one of the compile or test scoped dependency is used for both the compile and test phases.
(Thanks Vineet Reynolds)
Maven 2 (OLD):
try to define 2 different <dependency> tags with different versions and scopes. Use tag <scope>test</scope> inside dependency for tests and <scope>compile</scope> for compilation.

In Maven 3, you can trick maven by adding a dot after groupId
<dependency>
<groupId>groupId.</groupId>
<artifactId>artifactId</artifactId>
<version>version1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>groupId</groupId>
<artifactId>artifactId</artifactId>
<version>version2</version>
<scope>compile</scope>
</dependency>
The sequence matters here. need to have test first and then compile.

<dependency>
<groupId>groupId.</groupId>
<artifactId>artifactId</artifactId>
<version>version1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>groupId</groupId>
<artifactId>artifactId</artifactId>
<version>version2</version>
<scope>compile</scope>
</dependency>
Adding a dot doesnt work in pom.xml as . is converted to slash which in return generated incorrect URL.
Is thr any other way to do this

It's a really bad idea to have two different versions for compile and test dependency:
Your non-test code might rely on behavior of the newer JAR and fail when using classes of the older JAR.
When you use the older JAR in your tests, the non-test code would fail with the old JAR.
Otherwise you could have used the older JAR anywhere, with the same version...
If you get both JAR versions into your classpath, you cannot know which one gets picked up when running your tests. That's also a bad idea.
Hence you should get non-test and test to the same JAR version dependency.