Java

In a maven project there are lots of dependencies to handle – often one wants to know which version of a software comes from. The solution to this problem is the Maven Dependency Plugin which helps you to find used/unused/declared/undeclared dependencies in your project. In addition the plugin allows you to copy or unpack artifacts. Maven Goals dependency:copy – copies artifacts defined in the config to a specified location – details available here dependency:resolve – resolves all dependencies and shows the versions dependency:go-offline – resolves everything the project needs like dependencies, plugins and reports dependency:analyze - parses the dependencies and shows if they are used/declared/unused/undeclared .. dependency:analyze-dep-gmt - finds mismatches between resolved dependencies and those listed in the dependencyManagement section dependency:tree – shows a nice dependency tree for the maven project ...

Building a simple IMAP Client that displays the subject of the messages in the “inbox” Folder using Maven (I just like Maven). Project Setup / Maven Create a new Maven project mvn archetype:create -DgroupId=com.hascode.imap -DartifactId=imap-client Edit your pom.xml and add some dependencies <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>com.hascode.imap</groupId> <artifactId>imap-client</artifactId> <version>0.0.1-SNAPSHOT</version> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.8.1</version> </dependency> <dependency> <groupId>javax.mail</groupId> <artifactId>mail</artifactId> <version>1.4.2</version> </dependency> </dependencies> </project> Creating the E-Mail Client Create a package .. something like com.hascode.imap.client ;) Create a simple mail client using javax.mail in a class named ImapClient package com.hascode.imap.client; import javax.mail.Folder; import javax.mail.Message; import javax.mail.MessagingException; import javax.mail.Session; import javax.mail.Store; public class ImapClient { private Session session = null; private Store store = null; private String host = null; private String userName = null; private String password = null; public ImapClient(String host, String userName, String password){ this.host = host; this.userName = userName; this.password = password; } public boolean getMail() throws MessagingException { session = Session.getDefaultInstance(System.getProperties(),null); // session.setDebug(true); System.out.println("get store.."); store = session.getStore("imaps"); System.out.println("connect.."); store.connect(this.host, this.userName, this.password); System.out.println("get default folder .."); Folder folder = store.getDefaultFolder(); folder = folder.getFolder("inbox"); folder.open(Folder.READ_ONLY); System.out.println("reading messages.."); Message[] messages = folder.getMessages(); for(Message m:messages){ System.out.println(m.getSubject()); } return false; } } ...

This short tutorial shows how to set-up a developer instance of the popular Confluence Wiki from Atlassian in a few minutes. It’s a prerequisite for a few following tutorials regarding the Confluence API and plug-in development for this system. We want a quick install so we are going to run Confluence with the embedded servlet container and HSQL database. update Meanwhile it is way much easier to use Atlassian’s Plugin SDK using atlas-mvn run or atlas-mvn-run-standalone –product confluence –version x.x.x but if you need to setup an independant instance, this article still might be useful. ...

Helo – today I wanted to post a small tutorial for a small index and search operation using the Lucene indexer and Maven for the project setup. Setup Create an empty Maven sample project using the Eclipse Maven Plugin or use the following console command: mvn archetype:create -DgroupId=com.hascode.demo.search -DartifactId=lucene-sample Here is my pom.xml there are some dependencies for Lucene defined: <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>com.hascode.demo.search</groupId> <artifactId>lucene-sample</artifactId> <version>0.0.1-SNAPSHOT</version> <name>My Lucene Search Sample</name> <description>Lucene Search Sample</description> <dependencies> <dependency> <groupId>org.apache.lucene</groupId> <artifactId>lucene-core</artifactId> <version>2.4.1</version> </dependency> <dependency> <groupId>lucene</groupId> <artifactId>lucene</artifactId> <version>1.4.3</version> </dependency> </dependencies> </project> ...

Sometimes there is a dependency not available at a remote repository and one is too lazy to set up a local maven repository – that’s when one adds a directory in the project structure and wants maven to find dependencies there. Create a directory called “lib” in the project root Add the following markup to the pom.xml inside the <repositories>-Tag (create if it does not exist): <repository> <id>lib</id> <name>lib</name> <releases> <enabled>true</enabled> <checksumPolicy>ignore</checksumPolicy> </releases> <snapshots> <enabled>false</enabled> </snapshots> <url>file://${project.basedir}/lib</url> </repository> ...

Disable YUI compressor <plugin> <groupId>com.atlassian.maven.plugins</groupId> <artifactId>maven-jira-plugin</artifactId> <version>${amps.version}</version> <extensions>true</extensions> <configuration> <compressResources>false</compressResources> [..] </configuration> </plugin> Confluence – Get favourites by user Using the label manager. List getFavouriteSpaces(String username) Confluence – Determine the base URL Using the SettingsManager: String baseUrl = settingsManager.getGlobalSettings().getBaseUrl(); Confluence – Get the context path Using the BootstrapManager: String contextPath = bootstrapManager.getWebAppContextPath(); Confluence – Using Velocity Template for a Macro final VelocityContext contextMap = new VelocityContext(MacroUtils.defaultVelocityContext()); contextMap.put("key", obj); // references obj as variable named $key in the velocity template VelocityUtils.getRenderedTemplate("path/to/template.vm", contextMap); ...

Favorites Spare my time when using static imports .. Window > Preferences > Java > Editor > Content Assist > Favorites: com.google.common.collect.Lists com.jayway.restassured.matcher.RestAssuredMatchers com.jayway.restassured.RestAssured io.restassured.matcher.RestAssuredMatchers io.restassured.RestAssured org.hamcrest.MatcherAssert org.hamcrest.Matchers org.mockito.Mockito javaslang.API javaslang.Predicates Template to insert a static logger instance Go Windows > Preferences > Java > Editor > Templates > New … Enter logger as name and as template: ${:import(org.slf4j.Logger,org.slf4j.LoggerFactory)} private static final Logger LOG = LoggerFactory.getLogger(${enclosing_type}.class); Afterwards you’re able to type logger in your code and ctrl+space gives the option to insert the logger ...

Remote Debug a Pod’s Java Process Simple steps for remote debugging a Java process running on a k8 pod: Edit deployment and add the following parameters to the Java start line: -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=127.0.0.1:5005 Also add the following port mapping at the section container → ports in the deployment: - containerPort: 5005 protocol: TCP Safe, wait for the new pods and then add a port forward for port 5005 for this pod: kubectl port-forward podname 5005 ...

Start an Image with kcat / kafka-cat for Debugging kubectl -n NAMESPACE run "$(whoami)-debug" -it --rm \ --image=confluentinc/cp-kafkacat:6.1.9 \ --restart=Never \ -- bash Dockerfile for Kafka Analysis Container with different Tools With jq, kafka console tools, schema registry tools and kafkacat installed …​. Dockerfile FROM confluentinc/cp-kafka:6.2.1 as cp-kafka FROM confluentinc/cp-schema-registry:6.2.1 as cp-schema-registry FROM debian:10-slim ARG DEBIAN_FRONTEND=noninteractive # Install necessary tools RUN apt-get update && apt-get install -y \ curl \ jq \ yq \ && rm -rf /var/lib/apt/lists/* # Install kafkacat binary RUN apt-get update && apt-get install -y kafkacat && rm -rf /var/lib/apt/lists/* # Copy Kafka binaries COPY --from=cp-kafka /usr/bin/kafka-* /usr/bin/ COPY --from=cp-schema-registry /usr/bin/schema-registry* /usr/bin/ # Copy entrypoint script COPY entrypoint.sh /usr/bin/entrypoint.sh RUN chmod +x /usr/bin/entrypoint.sh ENTRYPOINT ["/usr/bin/entrypoint.sh"] ...

Checks / Exit Conditions Instead of writing something like if !condition throw …​ we may use require and check for quick exit conditions: val num = 1; require(num > 1){ // ... } val num = 1; require(num > 1){ // .. } Pluralize Strings Adding pluralization as extension function fun String.pluralize(count:Int):String { return if (count > 1){ this + 's' } else { this } } Use it like this ...