org.w3c.www.protocol.http.proxy
Class ProxyDispatcher

java.lang.Object
  org.w3c.www.protocol.http.proxy.ProxyDispatcher

All Implemented Interfaces:

PropertyMonitoring, PropRequestFilter, RequestFilter

public class ProxyDispatcher
extends java.lang.Object
implements PropRequestFilter, PropertyMonitoring

The proxy dispatcher applies some rules to a request. The goal of that filter is to allow special pre-processing of requests based, on their target host, before sending them off the net.

The filter is configured through a rule file whose format is described by the following BNF: rule-file=(record)*
record=EOL|comment|rule
comment=#(^EOL)*EOL
rule=rule-lhs(SPACE)*rule-rhs
rule-lhs=(token) |(token (. token)*
rule-lhr=forbid|direct|redirect |proxy|authorization|proxyauth
forbid=FORBID|forbid
direct=DIRECT|direct
redirect=(REDIRECT|proxy) url
proxy=(PROXY|proxy) url
url=any valid URL
authorization=(AUTHORIZATION|authorization user password
proxyauth=(PROXYAUTH|proxyauth user password url


A sample rule file looks like this: # Some comments edu proxy http://class.w3.org:8001/ org proxy http://class.w3.org:8001/ fr direct www.evilsite.com redirect http://www.goodsite.com/warning.html www.w3.org direct 138.96.24 direct www.playboy.com forbid default proxy http://cache.inria.fr:8080/

The algorithm used to lookup rules is the following:

• Split all rules left hand side into its components, eg H1.H2.H3 is splitted into { H1, H2, H3 }, then reverse the components and map that to the rule. In our example above, { org, w3, www} would be mapped to direct.
• Split the fully qualified host name into its components, eg, A.B.C is splitted into { A, B, C } and reverse it.
• Find the longest match in the mapping table of rules, and get apply the given rule.

In our example, a request to www.isi.edu would match the edu rule, and a request for www.w3.org would match the direct rule, for example.

Three rules are defined:

direct

Run that request directly against the target host.

forbid

Emit a forbid message, indicating that the user is not allowed to contact this host.

proxy

Run that request through the given proxy.

proxyauth

Run that request through a proxy with the right proxy credentials.

For numeric IP addresses, the most significant part is the beginning, so {A, B, C} are deducted directly. In the example { 138, 96, 24 } is mapped to direct.

If no rules are applied, then the default rule (root rule) is applied. See the example.

Field Summary

protected boolean	check_rules
static java.lang.String	CHECK_RULES_LAST_MODIFIED_P Name of the property turning that filter in debug mode.
protected boolean	debug Are we in debug mode ?
static java.lang.String	DEBUG_P Name of the property turning that filter in debug mode.
protected static java.lang.String	disabled
protected long	lastParsingTime
protected ObservableProperties	props The properties we initialized ourself from.
static java.lang.String	RULE_P Name of the property giving the rule file URL.
protected RuleNode	rules The current set of rules to apply.

Constructor Summary

ProxyDispatcher()
Empty constructor, for dynamic instantiation.

Method Summary

boolean	exceptionFilter(Request request, HttpException ex) Filter requests when an error occurs during the process.
Reply	ingoingFilter(Request request) Filter requests before they are emitted.
void	initialize(HttpManager manager) Initialize this filter, using the provided manager.
protected boolean	needsParsing()
Reply	outgoingFilter(Request request, Reply reply) Filter requests after processing.
protected void	parseRules() Parse the default set of rules.
protected void	parseRules(java.io.InputStream in) Parse the given input stream as a rule file.
boolean	propertyChanged(java.lang.String name) PropertyMonitoring implementation - Commit property changes.
void	sync() We don't maintain cached infos.

Methods inherited from class java.lang.Object

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

Field Detail

RULE_P

public static final java.lang.String RULE_P

Name of the property giving the rule file URL.

See Also:

Constant Field Values

DEBUG_P

public static final java.lang.String DEBUG_P

Name of the property turning that filter in debug mode.

See Also:

Constant Field Values

CHECK_RULES_LAST_MODIFIED_P

public static final java.lang.String CHECK_RULES_LAST_MODIFIED_P

Name of the property turning that filter in debug mode.

See Also:

Constant Field Values

props

protected ObservableProperties props

The properties we initialized ourself from.

rules

protected RuleNode rules

The current set of rules to apply.

debug

protected boolean debug

Are we in debug mode ?

check_rules

protected boolean check_rules

disabled

protected static final java.lang.String disabled

See Also:

Constant Field Values

lastParsingTime

protected long lastParsingTime

Constructor Detail

ProxyDispatcher

public ProxyDispatcher()

Empty constructor, for dynamic instantiation.

Method Detail

parseRules

protected void parseRules(java.io.InputStream in)
                   throws java.io.IOException,
                          RuleParserException

Parse the given input stream as a rule file.

Parameters:

in - The input stream to parse.

Throws:

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

RuleParserException - if parsing failed.

parseRules

protected void parseRules()

Parse the default set of rules.

IOf the rules cannot be parsed, the filter emits an error message to standard error, and turn itself into transparent mode.

needsParsing

protected boolean needsParsing()

ingoingFilter

public Reply ingoingFilter(Request request)

Filter requests before they are emitted. Look for a matching rule, and if found apply it before continuing the process. If a forbid rule was apply, this method will return with a forbidden message.

Specified by:

ingoingFilter in interface RequestFilter

Parameters:

request - The request to filter.

Returns:

A Reply instance, if processing is not to be continued, falseotherwise.

exceptionFilter

public boolean exceptionFilter(Request request,
                               HttpException ex)

Filter requests when an error occurs during the process. This filter tries to do a direct connection if it is needed

Specified by:

exceptionFilter in interface RequestFilter

Parameters:

reques - The request to filter.

reply - It's associated reply.

Returns:

Always null.

outgoingFilter

public Reply outgoingFilter(Request request,
                            Reply reply)

Filter requests after processing. This filter doesn't do any post-processing.

Specified by:

outgoingFilter in interface RequestFilter

Parameters:

reques - The request to filter.

reply - It's associated reply.

Returns:

Always null.

propertyChanged

public boolean propertyChanged(java.lang.String name)

PropertyMonitoring implementation - Commit property changes.

Specified by:

propertyChanged in interface PropertyMonitoring

Parameters:

name - The name of the property that has changed.

Returns:

A boolean true if change was commited, false otherwise.

initialize

public void initialize(HttpManager manager)

Description copied from interface: PropRequestFilter

Initialize this filter, using the provided manager. During initialization, it is up to the filter to install itself in the manager, by invoking the appropriate setFilter method.

Specified by:

initialize in interface PropRequestFilter

Parameters:

manager - The HttpManager initializing the filter.

sync

public void sync()

We don't maintain cached infos.

Specified by:

sync in interface RequestFilter