Eclipse出现：One or more constraints have not been satisfied。的解决办法

 One or more constraints have not been satisfied.

解决办法：

1. Go to project Build Path and change the Java Library version to 1.8
2. Go to Eclipse Preferences -> Java -> Compiler -> Change compliance level to 1.8
3. Right click on project -> Properties -> Project Facets
4. Uncheck Dynamic Web Module and click Apply (also uncheck JavaServer Faces if you had that)
5. Change the Java facet version to 1.8 and click Apply
6. Add the Dyanmic Web Module v3.0, apply.

Eclipse's facets configuration is buggy. Make sure you keep hitting Apply between checking and unchecking of facets.

项目的pom.xml中添加：

<build>
<finalName>data-exchange</finalName>
<plugins>
　　<plugin>
　　　　<groupId>org.apache.maven.plugins</groupId>
　　　　<artifactId>maven-compiler-plugin</artifactId>
　　　　<version>3.3</version>
　　　　<configuration>
　　　　<encoding>UTF-8</encoding>
　　　　<source>1.8</source>
　　　　<target>1.8</target>
　　　　</configuration>
　　</plugin>
</plugins>
</build>