Tipps und Tricks für Entwickler und IT-Interessierte
Add line to file src/main/resources/application.properties
server.port=9010
Get JSON Data from a remote Rest Server
final RestTemplate restTemplate = new RestTemplate();
final String response = restTemplate.getForObject("https://httpbin.org/ip", String.class);
System.out.println(response);Keycloak – Open Source Identity and Access Management for Modern Applications and Services
Using AdoptOpenJDK8
brew info adoptopenjdk8
By default, executing standalone.sh (for Linux) / standalone.bat (for Windows) makes the server available at following urls:
https://localhost:8443/auth/ http://localhost:8080/auth/
If we need to run multiple instance of server at different ports, run the following command:
For Linux:
standalone.sh -Djboss.socket.binding.port-offset=100
For Windows:
standalone.bat -Djboss.socket.binding.port-offset=100
The above commands will add the offset of 100 to the defaults ports available for Keycloak server.
For example, previously the ports where 8443 and 8000. Now the new ports become 8443 + 100 = 8543 and 8080 + 100 = 8180.
References:
https://www.keycloak.org/docs/3.2/getting_started/topics/secure-jboss-app/before.html
\standalone\log
$ brew install maven
Let’s look into some popular and must know maven commands. We will use a sample Maven project to showcase the command output.
This command cleans the maven project by deleting the target directory. The command output relevant messages are shown below.
$ mvn clean ... [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ maven-example-jar --- [INFO] Deleting /Users/pankaj/Desktop/maven-examples/maven-example-jar/target ...
This command compiles the java source classes of the maven project.
$ mvn compiler:compile ... [INFO] --- maven-compiler-plugin:3.8.1:compile (default-cli) @ maven-example-jar --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to /Users/pankaj/Desktop/maven-examples/maven-example-jar/target/classes ...
This command compiles the test classes of the maven project.
$ mvn compiler:testCompile ... [INFO] --- maven-compiler-plugin:3.8.1:testCompile (default-cli) @ maven-example-jar --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to /Users/pankaj/Desktop/maven-examples/maven-example-jar/target/test-classes ...
This command builds the maven project and packages them into a JAR, WAR, etc.
$ mvn package ... [INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ maven-example-jar --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to /Users/pankaj/Desktop/maven-examples/maven-example-jar/target/classes ... ------------------------------------------------------- T E S T S ------------------------------------------------------- Running com.journaldev.maven.classes.AppTest Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.005 sec Results : Tests run: 1, Failures: 0, Errors: 0, Skipped: 0 [INFO] [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ maven-example-jar --- [INFO] Building jar: .../maven-examples/maven-example-jar/target/maven-example-jar-0.0.1-SNAPSHOT.jar [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS ...
The output shows the location of the JAR file just before the “BUILD SUCCESS” message. Notice the package goal executes compile, testCompile, and test goals before packaging the build.
This command builds the maven project and installs the project files (JAR, WAR, pom.xml, etc) to the local repository.
$ mvn install ... [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-example-jar --- ... [INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ maven-example-jar --- ...
This command is used to deploy the artifact to the remote repository. The remote repository should be configured properly in the project pom.xml file distributionManagement tag. The server entries in the maven settings.xml file is used to provide authentication details.
This command validates the maven project that everything is correct and all the necessary information is available.
This command generates the dependency tree of the maven project.
$ mvn dependency:tree ... [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ Mockito-Examples --- [INFO] com.journaldev.mockito:Mockito-Examples:jar:1.0-SNAPSHOT [INFO] +- org.junit.platform:junit-platform-runner:jar:1.2.0:test [INFO] | +- org.apiguardian:apiguardian-api:jar:1.0.0:test [INFO] | +- org.junit.platform:junit-platform-launcher:jar:1.2.0:test ...
This command analyzes the maven project to identify the unused declared and used undeclared dependencies. It’s useful in reducing the build size by identifying the unused dependencies and then remove it from the pom.xml file.
$ mvn dependency:analyze ... [INFO] --- maven-dependency-plugin:2.8:analyze (default-cli) @ Mockito-Examples --- [WARNING] Used undeclared dependencies found: [WARNING] org.junit.jupiter:junit-jupiter-api:jar:5.2.0:test [WARNING] org.mockito:mockito-core:jar:2.19.0:test [WARNING] Unused declared dependencies found: [WARNING] org.junit.platform:junit-platform-runner:jar:1.2.0:test ...
Maven archetypes is a maven project templating toolkit. We can use this command to generate a skeleton maven project of different types, such as JAR, web application, maven site, etc.
Recommended Reading: Creating a Java Project using Maven Archetypes
This command generates a site for the project. You will notice a “site” directory in the target after executing this command. There will be multiple HTML files inside the site directory that provides information related to the project.
This command is used to run the test cases of the project using the maven-surefire-plugin.
$ mvn test ... [INFO] --- maven-surefire-plugin:2.22.0:test (default-test) @ Mockito-Examples --- [INFO] [INFO] ------------------------------------------------------- [INFO] T E S T S [INFO] ------------------------------------------------------- [INFO] Running TestSuite first-element second-element Employee setName Argument = Pankaj ... [INFO] Results: [INFO] [INFO] Tests run: 5, Failures: 0, Errors: 0, Skipped: 0 ...
It’s used to compile the source Java classes of the project.
$ mvn compile ... [INFO] --- maven-compiler-plugin:3.7.0:compile (default-compile) @ Mockito-Examples --- [INFO] Changes detected - recompiling the module! [WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent! [INFO] Compiling 10 source files to /Users/pankaj/Desktop/maven-examples/Mockito-Examples/target/classes ...
This command build the project, runs all the test cases and run any checks on the results of the integration tests to ensure quality criteria are met.
Maven provides a lot of command-line options to alter the maven build process. Let’s look at some of the important maven options.
This command prints the maven usage and all the available options for us to use.
This command is used to build a project from a different location. We are providing the pom.xml file location to build the project. It’s useful when you have to run a maven build from a script.
This command is used to run the maven build in the offline mode. It’s useful when we have all the required JARs download in the local repository and we don’t want Maven to look for any JARs in the remote repository.
Runs the maven build in the quiet mode, only the test cases results and errors are displayed.
$ mvn -q package ------------------------------------------------------- T E S T S ------------------------------------------------------- Running com.journaldev.maven.classes.AppTest Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.006 sec Results : Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
Prints the maven version and runs the build in the debug mode. It’s opposite of the quiet mode and you will see a lot of debug messages in the console.
mvn -X Debug Mode
Used to display the maven version information.
$ mvn -v Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f) Maven home: /Users/pankaj/Downloads/apache-maven-3.6.3 Java version: 13.0.1, vendor: Oracle Corporation, runtime: /Library/Java/JavaVirtualMachines/jdk-13.0.1.jdk/Contents/Home Default locale: en_IN, platform encoding: UTF-8 OS name: "mac os x", version: "10.15.1", arch: "x86_64", family: "mac"
This command prints the maven version and then continue with the build. It’s equivalent to the commands mvn -v;mvn package.
The skipTests system property is used to skip the unit test cases from the build cycle. We can also use -Dmaven.test.skip=true to skip the test cases execution.
This command tells maven to run parallel builds using the specified thread count. It’s useful in multiple module projects where modules can be built in parallel. It can reduce the build time of the project.
You’re missing the .mvn folder in your git repository. You should have a folder called .mvn which contains the following files
wrapper/maven-wrapper.jar, wrapper/maven-wrapper.propertiesjvm.config.Try doing git add -f .mvn from the command line then commit and push.
Here is how to create .mvn directory with needed jar inside.
mvn -N io.takari:maven:wrapper
We can also specify the version of Maven:
mvn -N io.takari:maven:wrapper -Dmaven=3.5.2
$ brew tap adoptopenjdk/openjdk
Java 8
# Install Java 8 $ brew cask install adoptopenjdk8 # Install Java 11 $ brew cask install adoptopenjdk11
# Install Gradle $ brew install gradle # Install Maven $ brew install maven
$ brew install jenv
Add java home folder to jenv
$ jenv add /Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home $ jenv add /Library/Java/JavaVirtualMachines/adoptopenjdk-11.jdk/Contents/Home
Spring makes programming Java quicker, easier, and safer for everybody. Spring’s focus on speed, simplicity, and productivity has made it the world’s most popular Java framework.
Spring recommend AdoptOpenJDK version 8 or version 11.
Eclipse IDE for Enterprise Java Developers
Create a starter app using spring.io from the commandline
$ curl https://start.spring.io/starter.zip -d language=java -d dependencies=web,mustache,jpa,h2,devtools -d packageName=com.example.blog -d name=Blog -o blog.zip
| Build App | ./mvnw clean package |
| Run App | ./mvnw spring-boot:run |
Add line to file src/main/resources/application.properties
server.port=9010