The plugin automatically ensures the classes are rebuilt and up-to-date before deployment. If you change the source of a class and your IDE automatically compiles it in the background, the plugin picks up the changed class.
You do not need to assemble the webapp into a WAR, saving time during the development cycle. Once invoked, you can configure the plugin to run continuously, scanning for changes in the project and automatically performing a hot redeploy when necessary. Any changes you make are immediately reflected in the running instance of Jetty, letting you quickly jump from coding to testing, rather than going through the cycle of: code, compile, reassemble, redeploy, test.
2020-05-14
？？？，不啟動項目你怎么輸入網站
2018-01-15
mvn：一種代碼管理工具，也負責依賴包的管理。比如你可以加入jetty的maven插件像這樣：
<plugins>
? ? ? ? <plugin>
? ? ? ? ? <groupId>org.eclipse.jetty</groupId>
? ? ? ? ? <artifactId>jetty-maven-plugin</artifactId>
? ? ? ? ? <version>9.4.8.v20171121</version>
? ? ? ? </plugin>
? ? ? </plugins>
jetty：servlet容器。也可以認為是運行環境。Javaweb程序的根基是servlet(jsp也是特殊的servlet，框架的根基也是。)，頁面的呈現啊、頁面的跳轉啊所有網頁的相關功能都是由servlet來處理。Javase部分并不負責servlet運行相關的條件，需要外部容器，這個容器可以是各種各樣的，例如jetty、tomcat。這里的容器也可以看成你工程的“服務器”了。Linux部署完成這些容器后，打包發布工程，本地點擊瀏覽器就能看見你的網頁了。
mvn jetty:run：則是要求工程運行到jetty的命令，意思是：“工程??！你在jetty里面奔跑起來吧！”，官網對它的描述是：
The plugin automatically ensures the classes are rebuilt and up-to-date before deployment. If you change the source of a class and your IDE automatically compiles it in the background, the plugin picks up the changed class.
You do not need to assemble the webapp into a WAR, saving time during the development cycle. Once invoked, you can configure the plugin to run continuously, scanning for changes in the project and automatically performing a hot redeploy when necessary. Any changes you make are immediately reflected in the running instance of Jetty, letting you quickly jump from coding to testing, rather than going through the cycle of: code, compile, reassemble, redeploy, test.
這里面提到了只要運行起來，每次修改完成代碼后，其實也不需要重新啟動了。
以上是我的理解。