1 /* 2  * Licensed to the Apache Software Foundation (ASF) under one 3  * or more contributor license agreements.  See the NOTICE file 4  * distributed with this work for additional information 5  * regarding copyright ownership.  The ASF licenses this file 6  * to you under the Apache License, Version 2.0 (the 7  * "License"); you may not use this file except in compliance 8  * with the License.  You may obtain a copy of the License at 9  *10  *     http://www.apache.org/licenses/LICENSE-2.011  *12  * Unless required by applicable law or agreed to in writing, software13  * distributed under the License is distributed on an "AS IS" BASIS,14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.15  * See the License for the specific language governing permissions and16  * limitations under the License.17  */18 19  //apache的软件所有权声明，意思就是说hadoop所有权是属于apache的。在其其他产品中如tomcat中经常可以看到20 21 package org.apache.hadoop;22 23 import java.lang.annotation.*;24 //只导入了Java的注释包中的类。一是说明它没有级联其他hadoop类，二是说明这个类基本上就是一个注释类了25 /**26  * A package attribute that captures the version of Hadoop that was compiled.27  */28  //意思是这是个包属性类，当hadoop编译的时候捕捉其版本号29 @Retention(RetentionPolicy.RUNTIME)30 @Target(ElementType.PACKAGE)31 //两个注释。恶补了一下后知道第一个是注释后能让JVM实时通过反射得到注释信息。32 //第二个就是指定这个注释类的目标，就是用在什么地方，具体可以用在类上、属性上等等，这个是说这个注释类是33 //用来注释包的34 public @interface HadoopVersionAnnotation {35 //@interface是说这个类是个注释类。36   /**37    * Get the Hadoop version38    * @return the version string "0.6.3-dev"39    */40   String version();41   //得到hadoop的版本号42   /**43    * Get the username that compiled Hadoop.44    */45   String user();46   //得到编译这个hadoop类时的所属用户47   /**48    * Get the date when Hadoop was compiled.49    * @return the date in unix ‘date‘ format50    */51   String date();52   //当hadoop编译的时候得到时间，而且是unix格式的时间53   /**54    * Get the url for the subversion repository.55    */56   String url();57   //得到SVN版本库的地址58   /**59    * Get the subversion revision.60    * @return the revision number as a string (eg. "451451")61    */62   String revision();63   //得到SVN版本库的补丁号64 }

 1 package org.apache.hadoop; 2  3 import java.lang.annotation.*; 4  5 @Retention(RetentionPolicy.RUNTIME) 6 @Target(ElementType.PACKAGE) 7 public class HadoopVersionAnnotation extends java.lang.annotation.Annotation{ 8      9     private String version;10     11     public void setVersion(String version) {12         this.version = version;13     }14     public String getVersion{15         return version;16     }17     18     private String user;19     20     public void setUser(String user) {21         this.user = user;22     }23     public String getUser{24         return user;25     }26     27     private String date;28     29     public void setDate(String date) {30         this.date = date;31     }32     public String getDate{33         return date;34     }35     36     private String url;37     38     public void setUrl(String url) {39         this.url = url;40     }41     public String getUrl{42         return url;43     }44     45     private String revision;46     47     public void setRevision(String revision) {48         this.revision = revision;49     }50     public String getRevision{51         return revision;52     }53 54 }