Maven - Zero to One [3.8.7]

4.1 Build Concepts and Processes

4.2 Command-based Project Build

4.3 Relationship between Build Plugins, Commands, and Lifecycle Commands

• The clean cycle: It mainly deals with the compiled files of the project and includes the command: clean.

• Default cycle: defines all the steps that need to be performed for a real build, it is the core part of the lifecycle Contains commands: compile → test → package → install → deploy

4.4 Dependency scopes

4.5 Solving Maven Project Dependency Download Failure Errors (Highlights)

1. When downloading dependencies, there is a network failure or the repository server is down, resulting in a failure to connect to the Maven repository, and thus the dependencies cannot be downloaded.

2. The version number of the dependency or the version number in the configuration file is wrong, or the dependency is not defined correctly, resulting in the dependency downloaded by Maven is not consistent with what is actually needed, and thus causing an error.

3. The local Maven repository cache is polluted or corrupted, preventing Maven from properly utilizing existing dependencies.

1. Check network connectivity and Maven repository server status.

2. Ensure that the version number of the dependency matches the version number of the project, and check that the dependency is correctly listed in the POM file.

3. Make sure that the local Maven repository cache (the file ending with lastupdated) is clear, because as long as it exists, refreshing it will not re-download it. In the local repository, look down the folders one at a time according to the gav attribute, eventually delete the internal files, and refresh to re-download them!

4.6 Maven Project <Build> Build Configuration

1. Specify the name of the build package, not the default name.

<!--自定义打包名称-->
<build>
	<finalName>maven_web-1.0</finalName>
</build>

2. Specify the file format and excluded files to be included when building the package. If you add a java class to the java folder, it will be automatically packaged and compiled into the classes folder! If you add a java class to the java folder, it will be automatically compiled into the classes folder! By default, files placed according to the maven project structure will be compiled and packaged by default! In addition, we can use the resources tag to specify which static resources should be packaged in the root of the classes folder! Scenario: In mubatis, sometimes the mapping files for writing SQL statements and the mapper interface are written in a package under src./main/java, and the mapping files are not packaged.

<build>
	<resources>
        <resource>
            <!--设置资源所在目录-->
            <directory>src/main/java</directory>
            <includes>
                <!--设置包含资源类型, **表示任意包, *表示任意以xml结尾的文件-->
                <include>**/*.xml</include>
            </includes>
        </resource>
    </resources>
</build>

3. Packaging plug-in version is too low, configure a higher version of the plug-in dependencies tag to introduce the development of the required jar package! We can build/plugins/plugin tag to introduce plug-ins commonly used plug-ins: modify the jdk version, tomcat plug-in, mybatis paging plug-in, mybatis reverse engineering plug-ins and so on!

<plugins>
						<!--War包打包插件-->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.2.2</version>
            </plugin>
            <!--java编译插件, 配jdk的编译版本-->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>

            <!--tomcat 插件-->
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
                <configuration>
                    <port>8090</port>
                    <path>/</path>
                    <uriEncoding>UTF-8</uriEncoding>
                    <server>tomcat7</server>
                </configuration>
            </plugin>
        </plugins>