解决因生成javadoc失败导致Maven打包失败问题

方案就是设置javadoc生成失败时不导致整个打包失败：

 1             <plugin>
 2                 <groupId>org.apache.maven.plugins</groupId>
 3                 <artifactId>maven-javadoc-plugin</artifactId>
 4                 <version>2.8</version>
 5                 <executions>
 6                     <execution>
 7                         <id>attach-javadocs</id>
 8                         <goals>
 9                             <goal>jar</goal>
10                         </goals>
11                         <configuration>
12                          <failOnError>false</failOnError>
13                         </configuration>
14                     </execution>
15                 </executions>
16             </plugin>