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This article will explain in detail how to use maven to compile Java projects. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

Need

Time: 15-minute text editor or IDE JDK 6 or later

Create a project

The main purpose of this example is to show Maven, so the project of Java strives for simplicity.

Create project structure selection

Select a project directory and use the following statement on the * nix system

Mkdir-p src/main/java/hello

Use commands under window

Mkdir src\ main\ java\ hello

Create the following structure:

└── src └── main └── java └── hello

Create the Java files HelloWorld.java and Greeter.java in the src/main/java/hello directory

Src/main/java/hello/HelloWorld.java

Package hello;public class HelloWorld {public static void main (String [] args) {Greeter greeter = new Greeter (); System.out.println (greeter.sayHello ());}}

Src/main/java/hello/Greeter.java

Package hello;public class Greeter {public String sayHello () {return "Hello world!";}}

Now that the project is complete, you can compile with Maven. For the installation of Maven, please refer to Apache Maven 3.1.0 for installation, deployment, and use

Define simple Maven compilation

First, create a Maven project definition file pom.xml in the root directory of the project, which mainly describes the name, version, and dependent library of the project

Pom.xml

4.0.0org.springframeworkgs-mavenjar0.1.0org.apache.maven.pluginsmaven-shade-plugin2.1packageshadehello.HelloWorld

Apart from the optional elements, the other elements are the most basic elements that make up the pom.xml file. It includes the configuration of the following items:

POM module version (usually 4.0.0). The organization number to which the project belongs, usually using the name of the domain project (for example, the name of JAR or WAR). The version number compiled by the project is packaged with jar or war.

Compile Java code

Run the following statement to compile

Mvn compile

The compiled .class file will appear in the target/classes directory. The figure below is as follows

Run the project:

Mvn exec:java-Dexec.mainClass= "hello.HelloWorld"

The output is as follows:

If you don't want to run the .class file directly, you can package it:

Mvn package

When the packaging is complete, a JAR file with a name of and is generated in the target directory. For example, in this example, gs-maven-0.1.0.jar will be generated based on pom.xml

If you want to install the JAR file of your project to the local Maven repository, you should call the following statement:

Mvn installmvn install

At this point, your project code will be compiled, tested, packaged, and copied to the local dependent library for other project references.

In the above example, the demo1 in the source code address https://github.com/waylau/maven-demo

When it comes to project dependencies, let's declare dependencies

Declare dependence

The above example is relatively simple and does not use other libraries. But a real project may reference (depend on) many other libraries.

The following example relies on the library of Joda Time.

Modify src/main/java/hello/HelloWorld.java

Package hello;import org.joda.time.LocalTime;public class HelloWorld {public static void main (String [] args) {LocalTime currentTime = new LocalTime (); System.out.println ("The current local time is:" + currentTime); Greeter greeter = new Greeter (); System.out.println (greeter.sayHello ());}}

Running mvn compile now will result in an error because no dependency is declared. Insert under the node as follows:

Joda-timejoda-time2.2

This paragraph declares the dependency of the project. Each dependent node consists of three child nodes:

The name of the organization to which the dependent library belongs: dependent library name: dependent library version

In POM 4, it was also introduced in, which mainly manages dependent deployments. Currently, five values are available:

Compile, the default, applies to all phases and will be released with the project. Provided, similar to compile, expects JDK, container, or consumer to provide this dependency. Such as servlet.jar. Runtime, used only at run time, such as the JDBC driver, is suitable for the run and test phases. Test, used only during testing, is used to compile and run test code. Will not be released with the project. System, similar to provided, needs to explicitly provide a jar,Maven that contains dependencies and does not look for it in Repository.

Now if you run mvn compile or mvn package,Maven, you will automatically download the related dependencies.

Complete pom.xml

4.0.0org.springframeworkgs-mavenjar0.1.0joda-timejoda-time2.2org.apache.maven.pluginsmaven-shade-plugin2.1packageshadehello.HelloWorld

Run the project:

Mvn exec:java-Dexec.mainClass= "hello.HelloWorld"

This is the end of this article on "how to compile a Java project with maven". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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