问题描述
用Eclipse创建Maven结构的web项目的时候选择了Artifact Id为maven-artchetype-webapp，由于这个catalog比较老，用的servlet还是2.3的，而一般现在都是用3.0，在Project Facets里面修改Dynamic web module为3.0的时候就会出现Cannot change version of project facet Dynamic web module to 3.0，如图：
其实在右边可以看到改到3.0需要的条件以及有冲突的facets，4
解决这个问题的步骤如下：
1.把Servlet改成3.0，打开项目的web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="schedule-console" version="3.0">
2.修改项目的设置，在Navigator下打开项目.settings目录下的org.eclipse.jdt.core.prefs
把1.5改成1.7
eclipse.preferences.version=1
org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.7
org.eclipse.jdt.core.compiler.compliance=1.7
org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
org.eclipse.jdt.core.compiler.source=1.7
3. 打开org.eclipse.wst.common.component
本文件不用修改
<?xml version="1.0" encoding="UTF-8"?><project-modules id="moduleCoreId" project-version="1.5.0">
<wb-module deploy-name="xband-schedule-console">
<wb-resource deploy-path="/" source-path="/target/m2e-wtp/web-resources"/>
<wb-resource deploy-path="/" source-path="/src/main/webapp" tag="defaultRootSource"/>
<wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/java"/>
<wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/resources"/>
<dependent-module archiveName="xband-schedule-core-1.0-SNAPSHOT.jar" deploy-path="/WEB-INF/lib" handle="module:/resource/xband-schedule-core/xband-schedule-core">
<dependency-type>uses</dependency-type>
</dependent-module>
<property name="java-output-path" value="/xband-schedule-console/target/classes"/>
<property name="context-root" value="schedule-console"/>
</wb-module>
</project-modules>
4. 打开org.eclipse.wst.common.project.facet.core.xml
把1.5改成1.7
<?xml version="1.0" encoding="UTF-8"?>
<faceted-project>
<fixed facet="wst.jsdt.web"/>
<installed facet="jst.web" version="3.0"/>
<installed facet="wst.jsdt.web" version="1.0"/>
<installed facet="java" version="1.7"/>
</faceted-project>
