1、web.xml is missing and <failOnMissingWebXml> is set to true 提示信息应该能看懂。也就是缺少了web.xml文件，<failOnMissingWebXml>被设置成true了。
目前被顶次数最多的回答原文如下：
This is a maven error. It says that it is expecting a web.xml file in your project because it is a web application, as indicated by <packaging>war</packaging>. However, for recent web applications a web.xml file is totally optional. Maven needs to catch up to this convention. Add this to your maven pom.xml to let maven catch up and you don't need to add a useless web.xml to your project:
大意是说这是一个Maven错误，在最近的web应用开发中web.xml文件已经变得可有可无了。不过Maven还没有跟上这一变化。
This is a maven error. It says that it is expecting a web.xml file in your project because it is a web application, as indicated by <packaging>war</packaging>. However, for recent web applications a web.xml file is totally optional. Maven needs to catch up to this convention. Add this to your maven pom.xml to let maven catch up and you don't need to add a useless web.xml to your project:
大意是说这是一个Maven错误，在最近的web应用开发中web.xml文件已经变得可有可无了。不过Maven还没有跟上这一变化。
我们只要在pom.xml文件中手动添加如下配置：
<properties>
<failOnMissingWebXml>false</failOnMissingWebXml>
</properties>
2、红色感叹号，build path无报错
一般是因为缺少jar包。在保证pom.xml没有报错的情况下，顺序进行如下操作。
1）项目右键，maven download sources
2）项目右键，maven update project
3）项目右键，run as maven clean
4）project clean 选中报错项目 clean
2）项目右键，maven update project
3）项目右键，run as maven clean
4）project clean 选中报错项目 clean
如果以上步骤仍然无效，可在Problems视图查看具体错误，
Description Resource Path Location Type
Archive for required library: 'D:/DevTools/mavenrepo/org/apache/lucene/lucene-backward-codecs/5.5.4/lucene-backward-codecs-5.5.4.jar' in project 'test' cannot be read or is not a valid ZIP file test Build path Build Path Problem
在Maven仓库中查看，发现该jar包已存在，删除之，随便修改pom.xml使其重新编译，重新下载后正常。
Description Resource Path Location Type
Archive for required library: 'D:/DevTools/mavenrepo/org/apache/lucene/lucene-backward-codecs/5.5.4/lucene-backward-codecs-5.5.4.jar' in project 'test' cannot be read or is not a valid ZIP file test Build path Build Path Problem
在Maven仓库中查看，发现该jar包已存在，删除之，随便修改pom.xml使其重新编译，重新下载后正常。