hadoop初识之七：linux 中eclipse 读写HDFS文件

/opt/tools/workspace/npl_hdfs/src/main/java/com/npl/hadoop/senier/hdfs
--==================添加hadoop jar 包========================
    =》pom.xml配置以下两项，hadoop jar包会自动添加到工程中【Maven Dependencies】中
         <dependency>
           <groupId>org.apache.hadoop</groupId>
           <artifactId>hadoop-client</artifactId>
           <version>2.5.0-mr1-cdh5.3.10</version>
         </dependency>
         <dependency>
           <groupId>junit</groupId>
           <artifactId>junit</artifactId>
           <version>4.10</version>
         </dependency>
  =》copy hdfs配置文件core-site.xml,hdfs-site.xml 到elipse项目中
     cp /opt/modules/hadoop-2.5.0-cdh5.3.6/etc/hadoop/core-site.xml 
 /opt/modules/hadoop-2.5.0-cdh5.3.6/etc/hadoop/hdfs-site.xml 
 /opt/tools/workspace/npl_hdfs/src/main/resources
  =》cope log4j.properties 到项目中，使控制台输出中不显示关于log4j警告信息
     cp /opt/modules/hadoop-2.5.0-cdh5.3.6/etc/hadoop/log4j.properties 
     /opt/tools/workspace/npl_hdfs/src/main/resources/
  =>读文件系统
  public static FileSystem getFileSystem() throws IOException {

// read:core-site.xml,core-default.xml,dfs-site.xml,hdfs-default.xml
Configuration conf = new Configuration();


// get filesystem
FileSystem fileSystem = FileSystem.get(conf);


//System.out.println(fileSystem);
return fileSystem;
}
  =》读文件
        public static void read(String fileName) throws IOException{
                // get filesystem
                FileSystem fileSystem = getFileSystem();
                //read path
                Path readPath=new Path(fileName);
                //opeh file
                FSDataInputStream inStream=fileSystem.open(readPath);


                try {
                        //read
                        IOUtils.copyBytes(inStream,System.out , 4096, false);
                } catch (Exception e) {
                        e.printStackTrace();
                }finally{
                       IOUtils.closeStream(inStream);
                }
        }
 =》写文件
  /*
* write data
*/
public static void write(String fileName) throws IOException{
FileSystem fileSystem=getFileSystem();
//write path
String putFileName="/user/npl/put-wc.input";
Path writePath=new Path(putFileName);
//Output Stream
FSDataOutputStream outStream=fileSystem.create(writePath);

//File input stream
FileInputStream inStream=new FileInputStream(new File("/opt/modules/hadoop-2.5.0-cdh5.3.6/wc.input"));

try {
IOUtils.copyBytes(inStream, outStream, 2046, false);
} catch (Exception e) {
e.printStackTrace();
}finally{
IOUtils.closeStream(inStream);
IOUtils.closeStream(outStream);
}

}