Maven

#Tip of the Day:

Most of us are familiar with Maven. Many projects are built with maven now. I use maven from learning Spring boot. It is good to know original maven without Spring or IDE tools.

Package structure

src
    -main
        -java
            -package
    -test
        -java
            -package
        resources

pom.xml

GroupId is the package name of the project.

ArtifactId is the module name.

mvn commands

• mvn -v: check the version of maven.

• mvn compile: compile this project.

• mvn test: run the tests.

This will create a target folder in the project.

• mvn target: Package the whole project into a jar file within target folder.

• mvn clean: delete target folder

• mvn install: install jar file into local repository, then we can use dependency.

    <groupId>imooc</groupId>
    <artifactId>flashsale</artifactId>
    <version>0.0.1-SNAPSHOT</version>

After installation, this three lines can be added into another project as a dependency.

When we compile a project and import some libraries, maven will firstly search the dependencies in its pom.xml. If maven cannot find it, it will search online to download it.

Maven’s local repository

C:\Users***.m2\repository

We could change this in setting file.

<localRepository>/path/to/local/repo</localRepository>

Maven plugins

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-source-plugin</artifactId>
            <version>2.4</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>jar-no-fork</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

maven tags

<groupId>company site + project name</groupId>
<artifactId>project name + module name</artifactId>
<version>
snapshot; 
alpha: internal test version; 
beta: public test version 
release: stable version
GA: formally published version
</version>
<packaging>default jar</packaging>
<name>project name</name>
<url>project url</url>

<scope>test: only work in test files</scope>
<exclusions>
    <exclusion></exclusion>
</exclusions>

<dependencyManagement>
    <dependencies>
        <dependency></dependency>    
    </dependencies>
</dependencyManagement>

<build>
    <plugins>
        <plugin>
                
        </plugin>
    </plugins>
</build>

scope

• compile: default
• provided: compile and test, e.g., servlet API
• runtime: runtime and test, e.g., JDBC driver
• test: test, e.g., jUnit
• system: depend on current machine, for example, we used JAVA_HOME in the project.
• import:

dependency passing

Suppose that project A depends on project B, and B depends on C. When we compile project A, maven will import both B and C. Now, if we do not want A depend on C, we could use

Aggregation and Inheritance

If we want to put multiple modules in one project, do the following.

<packaging>pom</packaging>
<modules>
    <module>module1</module>
    <module>module2</module>
    <module>module3</module>
</modules>

If we want to inherit a dependency, use a tag.

In the parent module,

<properties>
    <junit.version></junit.version>
</properties>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
        </dependency>    
    </dependencies>
</dependencyManagement>