Package org.apache.hadoop.lib.servlet

Class FileSystemReleaseFilter

java.lang.Object

org.apache.hadoop.lib.servlet.FileSystemReleaseFilter

All Implemented Interfaces:

javax.servlet.Filter

Direct Known Subclasses:

HttpFSReleaseFilter

@Private
public abstract class FileSystemReleaseFilter
extends java.lang.Object
implements javax.servlet.Filter

The FileSystemReleaseFilter releases back to the FileSystemAccess service a FileSystem instance.

This filter is useful in situations where a servlet request is streaming out HDFS data and the corresponding filesystem instance have to be closed after the streaming completes.

Constructor Summary

Constructors

Constructor	Description
FileSystemReleaseFilter()

Method Summary

Modifier and Type	Method	Description
void	destroy()	Destroys the filter.
void	doFilter(javax.servlet.ServletRequest servletRequest, javax.servlet.ServletResponse servletResponse, javax.servlet.FilterChain filterChain)	It delegates the incoming request to the FilterChain, and at its completion (in a finally block) releases the filesystem instance back to the FileSystemAccess service.
protected abstract FileSystemAccess	getFileSystemAccess()	Abstract method to be implemented by concrete implementations of the filter that return the FileSystemAccess service to which the filesystem will be returned to.
void	init(javax.servlet.FilterConfig filterConfig)	Initializes the filter.
static void	setFileSystem(org.apache.hadoop.fs.FileSystem fs)	Static method that sets the FileSystem to release back to the FileSystemAccess service on servlet request completion.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FileSystemReleaseFilter

public FileSystemReleaseFilter()

Method Detail

init

public void init(javax.servlet.FilterConfig filterConfig)
          throws javax.servlet.ServletException

Initializes the filter.

This implementation is a NOP.

Specified by:

init in interface javax.servlet.Filter

Parameters:

filterConfig - filter configuration.

Throws:

javax.servlet.ServletException - thrown if the filter could not be initialized.

doFilter

public void doFilter(javax.servlet.ServletRequest servletRequest,
                     javax.servlet.ServletResponse servletResponse,
                     javax.servlet.FilterChain filterChain)
              throws java.io.IOException,
                     javax.servlet.ServletException

It delegates the incoming request to the FilterChain, and at its completion (in a finally block) releases the filesystem instance back to the FileSystemAccess service.

Specified by:

doFilter in interface javax.servlet.Filter

Parameters:

servletRequest - servlet request.

servletResponse - servlet response.

filterChain - filter chain.

Throws:

java.io.IOException - thrown if an IO error occurs.

javax.servlet.ServletException - thrown if a servlet error occurs.

destroy

public void destroy()

Destroys the filter.

This implementation is a NOP.

Specified by:

destroy in interface javax.servlet.Filter

setFileSystem

public static void setFileSystem(org.apache.hadoop.fs.FileSystem fs)

Static method that sets the FileSystem to release back to the FileSystemAccess service on servlet request completion.

Parameters:

fs - a filesystem instance.

getFileSystemAccess

protected abstract FileSystemAccess getFileSystemAccess()

Abstract method to be implemented by concrete implementations of the filter that return the FileSystemAccess service to which the filesystem will be returned to.

Returns:

the FileSystemAccess service.