Cannot change version of project facet Dynamic Web Module to 3.1 （Eclipse Maven唯一解决方式）

If you want to use version 3.1 you need to use the following schema:

• http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd

Note that 3.0 and 3.1 are different: in 3.1 there's no Sun mentioned, so simply changing 3_0.xsd to 3_1.xsd won't work

<?
xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee"></web-app>

Also, make sure you're depending on the latest versions in your pom.xml. That is,

<plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-war-plugin</artifactId><version>2.4</version><configuration>...</configuration></plugin>

and

<dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version><scope>provided</scope></dependency>

Also, you should compile with Java 7 or 8:

<plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.1</version><configuration><source>1.7</source><target>1.7</target></configuration></plugin>

2016-02-20

加入，假设还有错，依照以下配置进行改动

Another way is to edit the project facet configuration file itself: [code]org.eclipse.wst.common.project.facet.core.xml

Change the dynamic web module version in this line to 3.0 - 

<installed facet="jst.web" version="2.5"/>

And then:

1. Right-click on the project (in the Project Explorer panel).
2. Select Maven » Update Project (or press Alt+F5)

You'll find this file in the 

.settings

 directory within the Eclipse project.

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