How to configure a proxy in Maven settings?

When we work behind a proxy server we need to configure Maven to be able to connect to the internet. To enable proxy we can configure Maven settings.xml file, either in ${M2_HOME}/conf/settings.xml or ${user.home}/.m2/settings.xml file.

<?xml version="1.0" encoding="UTF-8"?>
<settings>
    .
    .
    <proxies>
        <proxy>
            <id>my-proxy</id>
            <active>true</active>
            <protocol>http</protocol>
            <host>proxy.example.org</host>
            <port>8080</port>
            <username>username</username>
            <password>password</password>
            <nonProxyHosts>*.example.org|*.example.com</nonProxyHosts>
        </proxy>
    </proxies>
    .
    .
</settings>

The <proxy> element in the configuration below contains the information about the proxy server. These include information about the host, port, username and password. Set these elements to match your proxy server configuration.

How do I specify the Java compiler version in a pom.xml file?

When you need to compile a project for a specific Java version you can configure maven compiler plugin to set the source and the target version. The following pom.xml file configuration show you how to do it.

<project>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.2</version>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>    

Invalid value for the source and the target version in our project will make our project compilation process failed. For example when we try to use the diamond operator (<>) which available in Java 7, while the maven compiler plugin is set to version 1.5, can produce compiler error like this:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project servlet-example: Compilation failure
[ERROR] /Users/wsaryada/Studio/kodejava.org/webapp-example/servlet-example/src/main/java/org/kodejava/example/servlet/SessionCounter.java:[10,51] diamond operator is not supported in -source 1.5
[ERROR] (use -source 7 or higher to enable diamond operator)

How do I install Gradle in Mac OS X?

Gradle

In this post we will learn how to install Gradle in OS X. The following steps will guide our installation process to make Gradle available in our OS X machine. But before we start let’s take a look at the definition from wikipedia about Gradle.

Gradle is an open source build automation system that builds upon the concepts of Apache Ant and Apache Maven and introduces a Groovy-based domain-specific language (DSL) instead of the XML form used by Apache Maven of declaring the project configuration.

From: Wikipedia

Gradle Installation Steps:

1. Download Gradle

To download visit Gradle Releases Page. Download the complete distribution which includes binaries, sources and offline documentation. For example you can download the latest release of Gradle, as of this update the version is gradle-4.0.2-all.zip.

2. Upacking Gradle and Configure Environment Variables

  • Open Terminal.app.
  • Create a new directory sudo mkdir /usr/local/gradle.
  • Extract the downloaded Gradle distribution archive by executing sudo unzip gradle-4.0.2-all.zip -d /usr/local/gradle.
  • Edit .bash_profile in your home directory to add GRADLE_HOME variable with the following line export GRADLE_HOME=/usr/local/gradle/gradle-4.0.2
  • Also update the PATH variable to include $GRADLE_HOME/bin. If you don’t already have the PATH variable add the following line export PATH=$GRADLE_HOME/bin:$PATH
  • Run source ~/.bash_profile to executes the update version of .bash_profile. Or you can open a new Terminal.app to make this changes active.

3. Running the Installation

To test Gradle installation open the Terminal.app and execute gradle -v command. If your installation was correct you will see something like the following output:

$ gradle -v

------------------------------------------------------------
Gradle 4.0.2
------------------------------------------------------------

Build time:   2017-07-26 15:04:56 UTC
Revision:     108c593aa7b43852f39045337ee84ee1d87c87fd

Groovy:       2.4.11
Ant:          Apache Ant(TM) version 1.9.6 compiled on June 29 2015
JVM:          1.8.0_121 (Oracle Corporation 25.121-b13)
OS:           Mac OS X 10.12.6 x86_64