cannot change version of project facet Dynamic Web Module to 3.

1、先勾选change java从1.5到1.8 点apply ，然后再勾选Dynamic Web Module3.0，选择下面的further 设置好输出文件夹，最后点击应用

2、项目中maven dependence找不到：项目右键 ---maven ---update project

3、项目中配置错误：maven Dynamic web module 3.0 requires java 1.6  or newer 解决方案：

<!-- 官方文档 -->  

<!-- http://maven.apache.org/plugins/maven-compiler-plugin/examples/set-compiler-source-and-target.html -->  

<build>  

    <plugins>  

        <plugin>  

            <groupId>org.apache.maven.plugins</groupId>  

            <artifactId>maven-compiler-plugin</artifactId>  

            <version>3.3</version>  

            <configuration>  

                <!-- 指定source和target的版本 -->                 

                <source>1.8</source>  

                <target>1.8</target>  

            </configuration>  

        </plugin>  

    </plugins>  

</build>  

4、https://github.com/源码网站

5、项目创建是遇到could not caculate build plan

Could not calculate build plan: Failure to transfer org.apache.maven.plugins:maven-surefire-plugin:pom:2.7.1
from http://repo1.maven.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact org.apache.maven.plugins:maven-surefire-plugin:pom:2.7.1
from/to central (http://repo1.maven.org/maven2): Access denied to http://repo1.maven.org/maven2/org/apache/maven/plugins/maven-surefire-plugin/2.7.1/maven-surefire-plugin-2.7.1.pom. Error code 407, Proxy Authentication Required ( The ISA Server requires authorization
to fulfill the request. Access to the Web Proxy service is denied.  ) log4j-test01 Unknown Maven Problem

解决方法如下：

（1）将C:\User\.m2\repository\org\apache\maven\plugins\maven-deploy-plugin目录下的文件夹删除，

（2）然后右击项目Maven->Update Project->Update Dependencies（如果更新无效，选择强制更新如下图）



6、web.xml is missing and <failOnMissingWebXml> is set to true错误解决方案

解决方案：

1.在视图Project Explorer中，选择Deployment Descriptor项目并鼠标右键。

2.选择Generate Deployment Descriptor Stub，如图2。