cvc-elt.1.a：找不到元素'project'的声明

Question

错误：cvc elt.1.a:找不到元素'project'的声明

我经常犯这个错误。每当我使用maven创建项目时，它就会开始显示此错误。我甚至在插件标签下提到了"maven war插件"，然后更新和刷新了项目。

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.myfirstmvcapp</groupId>
<artifactId>helloworldabc</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>helloworldabc Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.3.1</version>
</plugin>
</plugins>
<finalName>helloworldabc</finalName>
</build>
</project>

Answer 1

我找到了这个问题的解决方案，感谢@M.Deinum在问题下面评论了这个解决方案。

我所做的只是在标签中的链接中添加https，而不是http。

这是以前的代码：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.myfirstmvcapp</groupId>
<artifactId>helloworldabc</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>helloworldabc Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.3.1</version>
</plugin>
</plugins>
<finalName>helloworldabc</finalName>
</build>
</project>

这是最新的代码，所需要的只是在项目标记的最后一个链接中向xsd链接添加https而不是http。

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.myfirstmvcapp</groupId>
<artifactId>helloworldabc</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>helloworldabc Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.3.1</version>
</plugin>
</plugins>
<finalName>helloworldabc</finalName>
</build>
</project>

Answer 2

我不得不使用https用于所有这些，即

<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

以使警告在VSCode中消失。