Develop Reference

How to override default version of library included by artifact in maven?

I have a spring batch dependency in my pom.xml declared as below:
<dependency>
<groupId>org.springframework.batch</groupId>
<artifactId>spring-batch-core</artifactId>
<version>3.0.9.RELEASE</version>
</dependency>
There is one artifact xstream that is included by above with version 1.4.7 and it needs to be updated to 1.4.11.
It can be added as follow:
<groupId>com.thoughtworks.xstream</groupId>
<artifactId>xstream</artifactId>
<version>1.4.11</version>
</dependency>
What is the correct way for this?I am thinking of following approach:
Both above pieces of code will be there but do I need to use < exclusions > to specifically exclude xstream artifact old version from spring-batch-core or does maven takes care of this automatically?

Better way will be using <dependencyManagement/> tag. Dependency management will make sure the version will be maintained even if some other transitive dependency brings higher version of the dependency.
Usage:
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.thoughtworks.xstream</groupId>
<artifactId>xstream</artifactId>
<version>1.4.11</version>
</dependency>
</dependencies>
</dependencyManagement>
Note: dependencyManagement tag is used for defining the version and scope (if not in the default scope which is compile) of a dependency it does not add the dependencies in it to you project, you must define separate <dependencies/> section in your pom.xml for adding dependencies to your project.
In your case it will be like.
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
...
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.thoughtworks.xstream</groupId>
<artifactId>xstream</artifactId>
<version>1.4.11</version>
</dependency>
</dependencies>
...
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.batch</groupId>
<artifactId>spring-batch-core</artifactId>
<version>3.0.9.RELEASE</version>
</dependency>
...
</dependencies>
...
</project>
In this case spring-batch-core is added as a direct dependency and if it has xstream as dependecny you project will use 1.4.11 version even spring-batch-core has a different version of xstream as dependency.
Ref: Dependency Management

NIFI: No controller service types found that are applicable for this property

I am developing a Milo OPCUA Processor and Service for Apache NiFi.
The Processor and Service compile fine, and I am able to start NiFi with them. However, when trying to configure the service for the processor that I just added, it just says "No controller service types found that are applicable for this property.".
Here are my POMs:
Processor JAR
<parent>
<groupId>com.tcon</groupId>
<artifactId>pubsub</artifactId>
<version>0.1</version>
</parent>
<artifactId>nifi-pubsub-processors</artifactId>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.apache.nifi</groupId>
<artifactId>nifi-api</artifactId>
</dependency>
<dependency>
<groupId>org.apache.nifi</groupId>
<artifactId>nifi-utils</artifactId>
</dependency>
<dependency>
<groupId>org.apache.nifi</groupId>
<artifactId>nifi-mock</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>tcon</groupId>
<artifactId>nifi-miloservice-api</artifactId>
<version>0.1</version>
</dependency>
</dependencies>
Processor NAR
<parent>
<groupId>com.tcon</groupId>
<artifactId>pubsub</artifactId>
<version>0.1</version>
</parent>
<artifactId>nifi-pubsub-nar</artifactId>
<version>0.1</version>
<packaging>nar</packaging>
<properties>
<maven.javadoc.skip>true</maven.javadoc.skip>
<source.skip>true</source.skip>
</properties>
<dependencies>
<dependency>
<groupId>com.tcon</groupId>
<artifactId>nifi-pubsub-processors</artifactId>
<version>0.1</version>
</dependency>
<dependency>
<groupId>org.apache.nifi</groupId>
<artifactId>nifi-standard-services-api-nar</artifactId>
<version>1.2.0</version>
<type>nar</type>
</dependency>
</dependencies>
The service POMs shouldn't matter, afaik. They haven't been modified, save for a few Milo dependencies.
As you can see, the processor JAR POM has the custom service API dependency from my custom service and the processor NAR POM has the standard API dependency from nifi.
The docs say that that is all I need to do to "link" my processor to my service.
What am I missing?

You also need to register your controller service with the ServiceLoader by including a file in the src/main/resources folder of your processor JAR project. You'll need a META-INF/services folder under your resources folder, with a file called org.apache.nifi.controller.ControllerService with a line containing the fully qualified name of the class implementing the ControllerService interface.

Spring Boot REST on Google App Engine throws 502

I have been struggling with this for about a week and nothing I have seen on SO has worked for me. I have a REST API built on Spring Boot that I am trying to deploy to the Google App Engine. Running locally is fine and when I run it on the GAE emulator it works fine as well; however, once I deploy using mvn appengine:deploy I get a successful build but when trying the endpoints I only get a 502. I'm not sure where the logs are so this is really kicking my butt.
My pom.xml:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany.admin</groupId>
<artifactId>admin-api</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<!-- Exclude this for deployment only -->
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- other project dependencies -->
<dependency>
<groupId>com.google.firebase</groupId>
<artifactId>firebase-admin</artifactId>
<version>5.3.0</version>
</dependency>
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.10.2</version>
</dependency>
<!-- end other project specific dependencies -->
<!-- Dependencies provided during deployment -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jul-to-slf4j</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<scope>provided</scope>
</dependency>
<!-- End dependencies for deployment -->
<!-- Dependencies for local -->
<!-- <dependency> -->
<!-- <groupId>org.springframework.boot</groupId> -->
<!-- <artifactId>spring-boot-starter-tomcat</artifactId> -->
<!-- <scope>provided</scope> -->
<!-- </dependency> -->
<!-- End dependencies for local -->
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>com.google.cloud.tools</groupId>
<artifactId>appengine-maven-plugin</artifactId>
<version>1.3.1</version>
<configuration>
<project>project-id-from-GAE-here</project
</configuration>
</plugin>
</plugins>
</build>
</project>
My application class is a simple annotated #SpringBootApplication class. I have 2 controllers with annotation of #RestController and simple #RequestMapping methods. One of the REST controllers is for the /_ah/health endpoint that returns 200 since one post mentioned constant restarts being triggered by the lack of a healthcheck endpoint.
I have a simple application.yml for my value injections and created an app.yaml file placed in src/main/appengine
runtime: java
env: flexible
threadsafe: true
manual_scaling:
instances: 1
handlers:
- url: /.*
script: this field is required, but ignored
runtime_config:
jdk: openjdk8
I am at a complete loss on this. It is my first GAE deployment with hopefully more to go. (I also am not using Docker yet since I am on a Windows 10 machine that breaks when I load Docker on it.)
UPDATE
I did notice that I had forgotten to put my project id under the maven plugin. Once I did that I got errors about not finding the app.yaml. I realized that since I am using a flexible environment, I did not need the appengine-web.xml and I had my file misnamed as app.yml rather than app.yaml. I updated my question with this and I am still getting a 502 after a successful deployment.

I realized my trial period with GAE included tech support so I contacted them. The asked for my pom and app.yaml. Their response was to add the following to my app.yaml "Since Java is known for consuming high memory usage, there is an overhead process consumed more than the approximate 0.4GB value"
resources:
cpu: 2
memory_gb: 2.3
disk_size_gb: 10
volumes:
- name: ramdisk1
volume_type: tmpfs
size_gb: 0.5
They also provided this link for reference: https://cloud.google.com/appengine/docs/flexible/java/configuring-your-app-with-app-yaml#resource-settings
Once I did this, my application started working just fine.
EDIT
If you have a simple application, set cpu:1 since you get billed on CPU hours and your daily quota is 28 and with 2 CPUs you end up with 48 CPU hours. I burned through the free $300 credit in 1 month because their tutorials setup a RDB ($80) that doesn't get used and doesn't show to kill the project. Also make sure when deploying something new you delete the old versions or you will be charged for every version that is up.

Missing artifact net.sf.jung:jung2:jar:2.0

jung2 is in maven repository, here and here.
But my Eclipse does not finding it out:
Code is here:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>tests.jung</groupId>
<artifactId>TryJung</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>net.sf.jung</groupId>
<artifactId>jung2</artifactId>
<version>2.0</version>
</dependency>
</dependencies>
</project>
UPDATE
Sorry can't accept answers about dependency type, because it is not complete. The code for jung dependency was taken from Maven repository directly:
So, I need an explanation, why doesn't code, taken from repository site, work actually.
What is happening here, who is "guilty"?

As already said, you are addressing a pom file. Which is, in a sense, correct, but if you want to compile you will need to add the actual jars in the dependencies section, such as:
<dependencies>
<dependency>
<groupId>net.sf.jung</groupId>
<artifactId>jung2</artifactId>
<version>${jung.version}</version>
<type>pom</type>
</dependency>
<dependency>
<groupId>net.sf.jung</groupId>
<artifactId>jung-api</artifactId>
<version>${jung.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>net.sf.jung</groupId>
<artifactId>jung-visualization</artifactId>
<version>${jung.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>net.sf.jung</groupId>
<artifactId>jung-graph-impl</artifactId>
<version>${jung.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>net.sf.jung</groupId>
<artifactId>jung-algorithms</artifactId>
<version>${jung.version}</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>net.sf.jung</groupId>
<artifactId>jung-io</artifactId>
<version>${jung.version}</version>
<scope>compile</scope>
</dependency>
</dependencies>
Do not forget to define the version property also in the properties section:
<properties>
<jung.version>2.0.1</jung.version>
</properties>
Hope this helps.

The problem is simply the artifact you are adressing is a pom file and not a jar file. That's the reason for the message.

just stumbled into the same problem pit. apparently these are pom files purely for building/documenting (all) sub-projects (or submodules in maven speak) of a project (in this case jung2)
they can't be used as a dependency in a useful way
actually you can depend on them with <type>pom</type> but will just include the dependencies of that pom but not it's modules.
see here for a more complete explanation:
How to use POMs as a dependency in Maven?

JSP class undefined type after project conversion to maven

Im trying to compile this project h__p://ross-warren.co.uk/my-twitter-clone-using-jsp-and-cassandra/
I have downloaded it, and spend almost one day searching for all dependency jar files and still I was not able to run that project. When I did some search I have discover maven. So I've downloaded it, in eclipse I click convert to maven or something, I've added some dependecy records to pom.xml and I still Im not able to run the project. There are some errors in jsp files. These errors werent there befoe.
for example in file LogChech.jsp
<jsp:useBean id="User"
class="uk.co.ross_warren.litter.stores.UserStore"
scope="session"
></jsp:useBean>
I have error Undefined type: UserStore.
I dont know where is the problem but I think there is somethign wrong with packages, becase before project conversion I had all java files in packages (at least eclipse showed package icon) and now there is only normal folder icons and folder tree structure with all java files however the first line in java files is package something which is fine I think.
thank you for your help
EDIT
this is my pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>Cinnamon</groupId>
<artifactId>Cinnamon</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.6.4</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.6.4</version>
</dependency>
<dependency>
<groupId>me.prettyprint</groupId>
<artifactId>hector-core</artifactId>
<version>1.0-4</version>
</dependency>
</dependencies>
<packaging>war</packaging>
</project>
This is the first image how it looked like before maven conversion
http://oi39.tinypic.com/2q84o5z.
And this is how it looks like now
http://oi44.tinypic.com/14nmgyf.
ok stack overflow says I cant submit images, so please take that url and add jpg extension to see image

The standard maven directory layout expects java sources to be in src/main/java and web resources in src/main/webapp. So your java sources directly in src weren't even compiled. These directories can be configured in the build section of your pom.xml. To set the directory for web resources you also have to configure the maven-war-plugin.
Edit: It seems you were also missing some dependencies, the pom below compiles without errors on the command line. I'm not an eclipse user myself but this should work in eclipse too.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>Cinnamon</groupId>
<artifactId>Cinnamon</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<build>
<directory>build</directory>
<sourceDirectory>src</sourceDirectory>
<outputDirectory>build/classes</outputDirectory>
<!-- not used in your project -->
<testSourceDirectory>srcTest</testSourceDirectory>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.1</version>
<configuration>
<warSourceDirectory>WebContent</warSourceDirectory>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.0.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.6.4</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.6.4</version>
</dependency>
<dependency>
<groupId>me.prettyprint</groupId>
<artifactId>hector-core</artifactId>
<version>1.0-4</version>
</dependency>
<dependency>
<groupId>org.expressme</groupId>
<artifactId>JOpenId</artifactId>
<version>1.08</version>
</dependency>
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20090211</version>
</dependency>
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.6.2</version>
</dependency>
</dependencies>
</project>