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From ol...@apache.org
Subject svn commit: r657143 - in /httpcomponents/httpclient/trunk/src/site: apt/index.apt apt/ntlm.apt apt/primer.apt resources/images/ resources/images/browser.png resources/images/httpclient.png site.xml
Date Fri, 16 May 2008 17:35:13 GMT
Author: olegk
Date: Fri May 16 10:35:13 2008
New Revision: 657143

URL: http://svn.apache.org/viewvc?rev=657143&view=rev
Log:
Added document on NTLM support; ported HTTP client programming primer from WIKI

Added:
    httpcomponents/httpclient/trunk/src/site/apt/ntlm.apt   (with props)
    httpcomponents/httpclient/trunk/src/site/apt/primer.apt   (with props)
    httpcomponents/httpclient/trunk/src/site/resources/images/
    httpcomponents/httpclient/trunk/src/site/resources/images/browser.png   (with props)
    httpcomponents/httpclient/trunk/src/site/resources/images/httpclient.png   (with props)
Modified:
    httpcomponents/httpclient/trunk/src/site/apt/index.apt
    httpcomponents/httpclient/trunk/src/site/site.xml

Modified: httpcomponents/httpclient/trunk/src/site/apt/index.apt
URL: http://svn.apache.org/viewvc/httpcomponents/httpclient/trunk/src/site/apt/index.apt?rev=657143&r1=657142&r2=657143&view=diff
==============================================================================
--- httpcomponents/httpclient/trunk/src/site/apt/index.apt (original)
+++ httpcomponents/httpclient/trunk/src/site/apt/index.apt Fri May 16 10:35:13 2008
@@ -62,7 +62,7 @@
 
     * Tunneled HTTPS connections through HTTP proxies, via the CONNECT method.
 
-    * Basic, Digest authentication schemes. Please note NTLM is currently not supported.
+    * Basic, Digest authentication schemes. Please note NTLM is supported only partially.
 
     * Plug-in mechanism for custom authentication schemes.
 

Added: httpcomponents/httpclient/trunk/src/site/apt/ntlm.apt
URL: http://svn.apache.org/viewvc/httpcomponents/httpclient/trunk/src/site/apt/ntlm.apt?rev=657143&view=auto
==============================================================================
--- httpcomponents/httpclient/trunk/src/site/apt/ntlm.apt (added)
+++ httpcomponents/httpclient/trunk/src/site/apt/ntlm.apt Fri May 16 10:35:13 2008
@@ -0,0 +1,183 @@
+~~ $HeadURL$
+~~ $Revision$
+~~ $Date$
+~~
+~~ ====================================================================
+~~ Licensed to the Apache Software Foundation (ASF) under one
+~~ or more contributor license agreements.  See the NOTICE file
+~~ distributed with this work for additional information
+~~ regarding copyright ownership.  The ASF licenses this file
+~~ to you under the Apache License, Version 2.0 (the
+~~ "License"); you may not use this file except in compliance
+~~ with the License.  You may obtain a copy of the License at
+~~
+~~   http://www.apache.org/licenses/LICENSE-2.0
+~~
+~~ Unless required by applicable law or agreed to in writing,
+~~ software distributed under the License is distributed on an
+~~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+~~ KIND, either express or implied.  See the License for the
+~~ specific language governing permissions and limitations
+~~ under the License.
+~~ ====================================================================
+~~
+~~ This software consists of voluntary contributions made by many
+~~ individuals on behalf of the Apache Software Foundation.  For more
+~~ information on the Apache Software Foundation, please see
+~~ <http://www.apache.org/>.
+
+    ----------
+    NTLM support in HttpClient
+    ----------
+    ----------
+    ----------
+
+NTLM support in HttpClient
+
+    Currently HttpClient 4.0 does not provide support for the NTLM authentication scheme
+    out of the box and probably never will. The reasons for that are legal rather than
+    technical.
+
+* Background
+
+    NTLM is a proprietary authentication scheme developed by Microsoft and optimized for
+    Windows operating system.
+
+    Until year 2008 there was no official, publicly available, complete documentation of
+    the protocol. {{{http://davenport.sourceforge.net/ntlm.html}Unofficial}} 3rd party
+    protocol descriptions existed as a result of reverse-engineering efforts. It was not
+    really known whether the protocol based on the reverse-engineering were complete or
+    even correct.
+
+    Microsoft published {{{http://download.microsoft.com/download/a/e/6/ae6e4142-aa58-45c6-8dcf-a657e5900cd3/%5BMS-NLMP%5D.pdf}MS-NLMP}}
+    and {{{http://download.microsoft.com/download/a/e/6/ae6e4142-aa58-45c6-8dcf-a657e5900cd3/%5BMS-NTHT%5D.pdf}MS-NTHT}}
+    specifications in February 2008 as a part of its
+    {{{http://www.microsoft.com/interop/principles/default.mspx}Interoperability
+    Principles initiative}}. Unfortunately, it is still not entirely clear whether NTLM
+    encryption algorithms are covered by any patents held by Microsoft, which would make
+    commercial users of open-source NTLM implementations liable for the use of Microsoft
+    intellectual property.
+
+* Enabling NTLM support in HttpClient 4.x
+
+    The good news is HttpClient is fully NTLM capable right out of the box.
+    HttpClient ships with the NTLM  authentication scheme, which, if configured
+    to use an external NTLM engine, can handle NTLM challenges and authenticate
+    against NTLM servers.
+
+----------------------------------------
+public interface NTLMEngine {
+
+    String generateType1Msg(
+            String domain,
+            String workstation) throws NTLMEngineException;
+
+    String generateType3Msg(
+            String username,
+            String password,
+            String domain,
+            String workstation,
+            String challenge) throws NTLMEngineException;
+
+}
+----------------------------------------
+
+* Using Samba JCIFS as an NTLM engine
+
+    Follow these instructions to build an NTLMEngine implementation using JCIFS library
+
+    <<!!!!DISCLAIMER !!!! HttpComponents project DOES _NOT_ SUPPORT the code provided
below. 
+    Use it as is at your own discretion>>.
+
+    * Download the latest release of the JCIFS library from the 
+    {{{http://jcifs.samba.org/}Samba}} web site
+
+    * Implement NTLMEngine interface
+
+----------------------------------------
+import jcifs.ntlmssp.Type1Message;
+import jcifs.ntlmssp.Type2Message;
+import jcifs.ntlmssp.Type3Message;
+import jcifs.util.Base64;
+
+import org.apache.http.impl.auth.NTLMEngine;
+import org.apache.http.impl.auth.NTLMEngineException;
+
+public class JCIFSEngine implements NTLMEngine {
+
+    public String generateType1Msg(
+            String domain, 
+            String workstation) throws NTLMEngineException {
+
+        Type1Message t1m = new Type1Message(
+                Type1Message.getDefaultFlags(),
+                domain,
+                workstation);
+        return Base64.encode(t1m.toByteArray());
+    }
+
+    public String generateType3Msg(
+            String username, 
+            String password, 
+            String domain,
+            String workstation, 
+            String challenge) throws NTLMEngineException {
+        Type2Message t2m;
+        try {
+            t2m = new Type2Message(Base64.decode(challenge));
+        } catch (IOException ex) {
+            throw new NTLMEngineException("Invalid Type2 message", ex);
+        }
+        Type3Message t3m = new Type3Message(
+                t2m, 
+                password, 
+                domain, 
+                username, 
+                workstation);
+        return Base64.encode(t3m.toByteArray());
+    }
+
+}
+----------------------------------------
+
+    * Implement AuthSchemeFactory interface
+
+----------------------------------------
+import org.apache.http.auth.AuthScheme;
+import org.apache.http.auth.AuthSchemeFactory;
+import org.apache.http.impl.auth.NTLMScheme;
+import org.apache.http.params.HttpParams;
+
+public class NTLMSchemeFactory implements AuthSchemeFactory {
+
+    public AuthScheme newInstance(final HttpParams params) {
+        return new NTLMScheme(new JCIFSEngine());
+    }
+
+}
+----------------------------------------
+
+    * Register NTLMSchemeFactory with the HttpClient instance you want to NTLM 
+    enable.
+
+----------------------------------------
+httpclient.getAuthSchemes().register("ntlm", new NTLMSchemeFactory());
+----------------------------------------
+
+    * Set NTCredentials for the web server you are going to access.
+
+----------------------------------------
+httpclient.getCredentialsProvider().setCredentials(
+    new AuthScope("myserver", -1), 
+    new NTCredentials("username", "password", "MYSERVER", "MYDOMAIN"));
+-----------------------------------------------------------
+
+    * You are done.
+
+
+* Why this code is not distributed with HttpClient 
+
+    JCIFS is licensed under the Lesser General Public License (LGPL). This license 
+    is not compatible with the Apache Licenses under which all Apache Software is 
+    released. Lawyers of the Apache Software Foundation are currently investigating 
+    under which conditions Apache software is allowed to make use of LGPL software.

Propchange: httpcomponents/httpclient/trunk/src/site/apt/ntlm.apt
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Propchange: httpcomponents/httpclient/trunk/src/site/apt/ntlm.apt
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    svn:keywords = Date Author Id Revision HeadURL

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    svn:mime-type = text/plain

Added: httpcomponents/httpclient/trunk/src/site/apt/primer.apt
URL: http://svn.apache.org/viewvc/httpcomponents/httpclient/trunk/src/site/apt/primer.apt?rev=657143&view=auto
==============================================================================
--- httpcomponents/httpclient/trunk/src/site/apt/primer.apt (added)
+++ httpcomponents/httpclient/trunk/src/site/apt/primer.apt Fri May 16 10:35:13 2008
@@ -0,0 +1,670 @@
+~~ $HeadURL$
+~~ $Revision$
+~~ $Date$
+~~
+~~ ====================================================================
+~~ Licensed to the Apache Software Foundation (ASF) under one
+~~ or more contributor license agreements.  See the NOTICE file
+~~ distributed with this work for additional information
+~~ regarding copyright ownership.  The ASF licenses this file
+~~ to you under the Apache License, Version 2.0 (the
+~~ "License"); you may not use this file except in compliance
+~~ with the License.  You may obtain a copy of the License at
+~~
+~~   http://www.apache.org/licenses/LICENSE-2.0
+~~
+~~ Unless required by applicable law or agreed to in writing,
+~~ software distributed under the License is distributed on an
+~~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+~~ KIND, either express or implied.  See the License for the
+~~ specific language governing permissions and limitations
+~~ under the License.
+~~ ====================================================================
+~~
+~~ This software consists of voluntary contributions made by many
+~~ individuals on behalf of the Apache Software Foundation.  For more
+~~ information on the Apache Software Foundation, please see
+~~ <http://www.apache.org/>.
+
+    ----------
+    Client HTTP Programming Primer
+    ----------
+    ----------
+    ----------
+
+Client HTTP Programming Primer
+
+* About
+
+    This document is intended for people who suddenly have to or want to implement
+    an application that automates something usually done with a browser,
+    but are missing the background to understand what they actually need to do.
+    It provides guidance on the steps required to implement a program that
+    interacts with a web site which is designed to be used with a browser.
+    It does not save you from eventually learning the background of what
+    you are doing, but it should help you to get started quickly and learn
+    the details later.
+
+    This document has evolved from discussions on the HttpClient mailing lists.
+    Although it refers to HttpClient, the concepts described here apply equally
+    to HttpComponents or SUN's {{{http://java.sun.com/j2se/1.4.2/docs/api/java/net/HttpURLConnection.html}HttpURLConnection}}

+    or any other HTTP communication library for any programming language. So you 
+    might find it useful even if you're not using Java and HttpClient.
+
+    The existence of this document does not imply that the HttpClient community
+    feels responsible for teaching you how to program a client HTTP application.
+    It is merely a way for us to reduce the noise on the mailing list without
+    just leaving the newbies out in the cold.
+
+* Scenario
+
+    Let's assume that you have some kind of repetitive, web-based task that
+    you want to automate. Something like:
+
+    * goto page http://xxx.yyy.zzz/login.html
+
+    * enter username and password in a web form and hit the "login" button
+
+    * navigate to a specific page
+
+    * check the number/headline/whatever shown on that page
+
+    []
+
+    At this time, we don't have a specific example which could be developed
+    into a sample application. So this document is all bla-bla, and you will
+    have to work out the details - all the details - yourself. Such is life.
+
+* Caveat
+
+    This scenario describes a hobbyist usage of HTTP, in other words:
+    <<a bad practice>>. Web sites are designed for user interaction, not
+    as an application programming interface (API). The interface of a
+    web site is the user interface displayed by a browser. The HTTP
+    communication between the browser and the server is an internal API,
+    subject to change without notice.
+
+    A web site can be redesigned at any point in time. The server then
+    sends different documents and a browser will display the new content.
+    The user easily adjusts to click the appropriate links, and the browser
+    communicates via HTTP as specified by the new documents from the server.
+    Your application that only mimicks a browser will simply break.
+
+    Nevertheless, implementing this scenario will help you to get
+    familiar with HTTP communication. It is also "good enough" for
+    hobbyists applications, for example if you want to download the
+    latest installment of your favorite daily webcomic to install
+    it as the screen background. There is no big damage if such an
+    application breaks.
+
+    If you want to implement a solid application, you should use only
+    published APIs. For example, to check for new mail on your webmail
+    account, you should ask the webmail provider for POP or IMAP access.
+    These are standardized protocols supported my most EMail client applications.
+    If you want to have a newsticker, look for RSS feeds from the provider and
+    applications that display them.
+
+    As another example, if you want to perform a web search, there are
+    search companies that provide an API for using their search engines.
+    Unlike the examples before, such APIs are proprietary. You will still
+    have to implement an application, but then you are using a published API
+    that the provider will not change without notice.
+
+
+* Not a Browser
+
+    HttpClient is not a browser. Here's the difference.
+
+    <<Browser>>
+
+[images/browser.png] Browser
+
+    The figure shows some of the components you will find in a browser.
+    To the left, there is the user interface. The browser needs a rendering
+    engine to display pages, and to interpret user input such as mouse clicks
+    somewhere on the displayed page. There is a layout engine which computes
+    how an HTML page should be displayed, including cascading style sheets
+    and images. A JavaScript interpreter runs JavaScript code embedded in
+    or referenced from HTML pages. Events from the user interface are passed
+    to the JavaScript interpreter for processing.
+    On the top, there are interfaces for plugins that can handle Applets,
+    embedded media objects like PDF files, Quicktime movies and Flash animations,
+    or ActiveX controls that can do anything.
+
+    In the center of the figure you can find internal components. Browsers
+    have a cache of recently accessed documents and image files. They need
+    to remember cookies and passwords entered by the user. Such information
+    can be kept in memory or stored persistently in the file system at the
+    bottom of the figure, to be available again when the browser is restarted.
+    Certificates for secure communication are almost always stored persistently.
+    To the right of the figure is the network. Browsers support many protocols
+    on different levels of abstraction. There are application protocols
+    such as FTP and HTTP to retrieve documents from servers, and transport
+    layer protocols such as TLS/SSL and Socks to establish connections for
+    the application protocols.
+
+    One characteristic of browsers that is not shown in the figure is tolerance
+    for bad input. There needs to be tolerance for invalid user input to make
+    the browser user friendly. There also needs to be tolerance for malformed
+    documents retrieved from servers, and for flaws in server behavior when
+    executing protocols, to make as many websites as possible accessible to
+    the user.
+
+    <<HTTP Client>>
+
+[images/httpclient.png] HTTP Client
+
+    The figure shows some of the components you will find in a browser,
+    and highlights the scope of HttpClient. The primary responsibility
+    of HttpClient is the HTTP protocol, executed directly or through an
+    HTTP proxy. It provides interfaces and default implementations for
+    cookie and password management, but not for persisting such data.
+    User interfacing, HTML parsing, plugins or non-HTTP application level
+    protocols are not in the scope of HttpClient. It does provide interfaces
+    to plug in transport layer protocols, but it does not implement such
+    protocols.
+
+    All the rest of a browser's functionality you require needs to be
+    provided by your application. HttpClient executes HTTP requests, but it
+    will not and can not assemble them. Since HttpClient does not interface
+    with the user, nor interpret content such as HTML files, there is
+    little or no tolerance for bad data passed to the API. There is some
+    tolerance for flaws in server behavior, but there are limits to the
+    deviations HttpClient can handle.
+
+* Terminology
+
+    This section introduces some important terms you have to know to
+    understand the rest of this document.
+
+    <<<HTTP Message>>>
+    
+    consists of a header section and an optional entity. There are two kinds 
+    of messages, requests and responses. They differ in the format of the 
+    first line, but both can have header fields and an optional entity.
+
+    <<<HTTP Request>>> 
+    
+    is sent from a client to a server. The first line includes the URI for 
+    which the request is sent, and a method that the server should execute 
+    for the client.
+
+    <<<HTTP Response>>>
+    
+    is sent from a server to a client in response to a request. The first
+    line includes a status code that tells about success or failure of
+    the request. HTTP defines a set of status codes, like 200 for success
+    and 404 for not found. Other protocols based on HTTP can define
+    additional status codes.
+
+    <<<Method>>>
+    
+    is an operation requested from the server. HTTP defines a set of
+    operations, the most frequent being GET and POST. Other protocols
+    based on HTTP can define additional methods.
+
+    <<<Header Fields>>>
+    
+    are name-value pairs, where both name and value are text. The name of
+    a header field is not case sensitive. Multiple values can be assigned
+    to the same name. RFC 2616 defines a wide range
+    of header fields for handling various aspects of the HTTP protocol.
+    Other specifications, like RFC 2617 and RFC 2965, define additional
+    headers. Some of the defined headers are for general use, others are
+    meant for exclusive use with either requests or responses, still others
+    are meant for use only with an entity.
+
+    <<<Entity>>>
+    
+    is data sent with an HTTP message. For example, a response can contain
+    the page or image you are downloading as an entity, or a request can
+    include the parameters that you entered into a web form.
+    The entity of an HTTP message can have an arbitrary data format, which
+    is usually specified as a MIME type in a header field.
+
+    <<<Session>>>
+    
+    is a series of requests from a single source to a server. The server
+    can keep session data, and needs to recognize the session to which
+    each incoming request belongs. For example, if you execute a web search,
+    the server will only return one page of search results. But it keeps
+    track of the other results and makes them available when you click on
+    the link to the "next" page. The server needs to know from the request
+    that it is you and your session for which more results are requested,
+    and not me and my session. That's because I searched for something else.
+
+    <<<Cookies>>>
+    
+    are the preferred way for servers to track sessions. The server supplies
+    a piece of data, called a cookie, in response to a request. The server
+    expects the client to send that piece of data in a header field with each
+    following request of the same session.
+    The cookie is different for each session, so the server can identify to
+    which session a request belongs by looking at the cookie. If the cookie
+    is missing from a request, the server will not respond as expected.
+
+* Step by Step 
+
+** GET the Login Page
+
+    Create and execute a GET request for the login page.
+    Just use the link you would type into the browser as the URL.
+    This is what a browser does when you enter a URL in the address bar
+    or when you click on a link that points to another web page.
+
+    Inspect the response from the server:
+
+    * do you get the page you expected?
+
+    []
+
+    It should be sent as the entity of the response to your request.
+    The entity is also referred to as the response body.
+
+    * do you get a session cookie?
+
+    []
+
+    Cookies are sent in a header field named Set-Cookie or Set-Cookie2.
+    It is possible that you don't get a session cookie until you log in.
+    If there is no session cookie in the response, you'll have to do perform
+    step 2 later, after you reach the point where the cookie is set.
+
+    If you do not get the page you expect, check the URL you are requesting.
+    If it is correct, the server may use a browser detection. You will have
+    to set the header field User-Agent to a value used by a popular browser
+    to pretend that the request is coming from that browser.
+
+    If you can't get the login page, get the home page instead now.
+    Get the login page in the next step, when you establish the session.
+
+** Establish the Session
+
+    Create and execute another GET request for a page.
+    You can simply request the login page again, or some other page
+    of which you know the URL. Do NOT try to get a page which would
+    be returned in response to submitting a web form. Use something
+    you can reach simply by clicking on a link in the browser. Something
+    where you can see the URL in the browser status line while the
+    mouse pointer is hovering over the link.
+
+    This step is important when developing the application. Once you know
+    that your application does establish the session correctly, you may
+    be able to remove it. Only if you couldn't get the login page directly
+    and had to get the home page first, you know you have to leave it in.
+
+    Inspect the request being sent to the server.
+
+    * is the session cookie sent with the request?
+
+    []
+
+    You can see what is sent to the server by enabling the wire log
+    for HttpClient. You only need to see the request headers, not the body.
+    The session cookie should be sent in a header field called Cookie.
+    There may be several of those, and other cookies might be sent as well.
+
+    Inspect the response from the server:
+
+    * do you get another session cookie?
+
+    []
+
+    You should not get another session cookie. If you get the same session
+    cookie as before, the server behaves a little strange but that should
+    not be a problem. If you get a new session cookie, then the server did
+    not recognize the session for the request. Usually, this happens if the
+    request did not contain the session cookie. But servers might use other
+    means to track sessions, or to detect session hijacking.
+
+    If the session cookie is not sent in the request, one of two things
+    has gone wrong. Either the cookie was not detected in the previous
+    response, or the cookie was not selected for being sent with the new
+    request.
+
+    HttpClient automatically parses cookies sent in responses and puts them
+    into a cookie store. HttpClient uses a configurable cookie policy
+    to decide whether a cookie being sent from a server is correct.
+    The default policy complies strictly with RFC 2109, but many servers
+    do not. Play around with the cookie policies until the cookie is
+    accepted and put into the cookie store.
+
+    If the cookie is accepted from the previous response but still not
+    sent with the new request, make sure that HttpClient uses the same
+    cookie store object. Unless you explicitly manage cookie store 
+    objects (not recommended for newbies!), this will be the case if you 
+    use the same HttpClient object to execute both requests.
+
+    If the cookie is still not sent with the request, make sure that the
+    URL you are requesting is in the scope for the cookie. Cookies are
+    only sent to the domain and path specified in the cookie scope.
+    A cookie for host "jakarta.apache.org" will not be sent to host
+    "tomcat.apache.org". A cookie for domain ".apache.org" will be sent
+    to both. A cookie for host "apache.org", without the leading dot,
+    will not be sent to "jakarta.apache.org". The latter case can be
+    resolved by using a different cookie spec that adds the leading dot.
+    In the other cases, use a URL that in the cookie scope to establish
+    the session.
+
+    If the session cookie is sent with the request, but a new session cookie
+    is set in the response anyway, check whether there are cookies other
+    than the session cookie in the request. Some servers are incapable of
+    detecting multiple cookies sent in individual header fields. HttpClient
+    can be advised to put all cookies into a single header field.
+
+    If that doesn't help, you are in trouble. The server may use additional
+    means to track the session, for example the header field named Referer.
+    Set that field to the URL of the previous request.
+    ({{{http://mail-archives.apache.org/mod_mbox/jakarta-httpclient-user/200602.mbox/%3c19b.44e04b45.31166eaa@aol.com%3e}see
this mail}})
+
+    If that doesn't help either, you will have to compare the request from
+    your application to a corresponding one generated by a browser. The
+    instructions in step 5 for POST requests apply for GET requests as well.
+    It's even simpler with GET, since you don't have an entity.
+
+** Analyze the Form
+
+    Now it is time to analyze the form defined in the HTML markup of the page.
+    A form in HTML is a set of name-value-pairs called parameters, where some
+    of the values can be entered in the browser. By analyzing the HTML markup,
+    you can learn which parameters you have to define and how to send them
+    to the server.
+
+    Look for the <form> tag in the page source. There may be several forms in
+    the page, but they can not be nested. Locate the form you want to submit.
+    Locate the matching </form> tag. Everything in between the two may be
+    relevant. Let's start with the attributes of the <form> tag:
+
+    <<<method=>>>
+ 
+    specifies the method used for submitting the form. If it is GET or
+    not specified at all, then you need to create a GET request. The parameters
+    will be added as a query string to the URL. If the method is POST, you
+    need to create a POST request. The parameters will be put in the entity
+    of the request, also referred to as the request body.
+    How to do that is discussed in step 5.
+
+    <<<action=>>>
+ 
+    specifies the URL to which the request has to be sent. Do not try to
+    get this URL from the address bar of your browser! A browser will
+    automatically follow redirects and only displays the final URL, which
+    can be different from the URL in this attribute.
+    It is possible that the URL includes a query string that specifies
+    some parameters. If so, keep that in mind.
+
+    <<<enctype=>>>
+ 
+    specifies the MIME type for the entity of the request generated by the
+    form. The two common cases are url-encoded (default) and multipart-mime.
+    Note that these terms are just informally used here, the exact values
+    that need to be written in an HTML document are specified elsewhere.
+    This attribute is only used for the POST method. If the method is GET,
+    the parameters will always be url-encoded, but not in an entity.
+
+    <<<accept-charset=>>>
+    
+    specifies the character set that the browser should allow for user input.
+    It will not be discussed here, but you will have to consider this value
+    if you experience charset related problems.
+
+    Except for optional query parameters in the action attribute, the parameters
+    of a form are specified by HTML tags between <form> and </form>.
+    The following is a list of tags that can be used to define parameters.
+    Except where stated otherwise, they have a name attribute which specifies
+    the name of the parameter. The value of the parameter usually depends on
+    user input.
+
+----------------------------------------
+<input type="text" name="...">
+<input type="password" name="...">
+----------------------------------------
+
+    specify single-line input fields. Using the return key in one of these
+    fields will submit the form, so the value really is a single line of
+    input from the user.
+
+----------------------------------------
+<input type="text" readonly name="..." value="...">
+<input type="hidden" name="..." value="...">
+----------------------------------------
+
+    specify a parameter that can not be changed by the user.
+    The value of the parameter is given by the value attribute.
+
+----------------------------------------
+<input type="radio" name="..." value="...">
+<input type="checkbox" name="..." value="...">
+----------------------------------------
+
+    specify a parameter that can be included or omitted. There usually is
+    more than one tag with the same name. For radio buttons, only one can
+    be selected and the value of the parameter is the value of the selected
+    radio button. For checkboxes, more than one can be selected. There will
+    be one name-value-pair for each selected checkbox, with the same name
+    for all of them.
+
+----------------------------------------
+<input type="submit" name="..." value="...">
+<button type="submit" name="..." value="...">
+----------------------------------------
+
+    specify a button to submit the form. The parameter will only be added
+    to the form if that button is used to submit. If another button is used,
+    or the form is submitted by pressing the return key in a text input field,
+    the parameter is not part of the submitted form data. If the name attribute
+    is missing, no parameter is added to the form data for that button.
+
+----------------------------------------
+<textarea name="...">
+<textarea value="..." readonly>
+----------------------------------------
+
+    specify a multi-line input field. In the readonly case, the value of
+    the parameter is the text between the <textarea> and </textarea> tags.
+
+----------------------------------------
+<select name="..." multiple>}}}
+  <option value="...">...</option>}}}
+  <option value="...">...</option>}}}
+  ...
+</select>
+----------------------------------------
+
+    specify a selection list or drop-down menu. If the multiple attribute is
+    not present, only one option can be selected. There will be one
+    name-value-pair for each selected option, with the same name for all of them.
+    If there is no value attribute, the value for that option is
+    the text between <option> and </option>.
+
+----------------------------------------
+<input type="image" name="...">
+----------------------------------------
+
+    specifies an image that can be clicked to submit the form. If that image
+    is clicked to submit the form, two parameters are added to the form data.
+    The name attribute is suffixed with ".x" and ".y", the values for the
+    parameters are the relative coordinates of the mouse pointer within the
+    image at the time of the click, in pixel. If the name attribute is missing,
+    no parameters will be added to the form data.
+
+----------------------------------------
+<input type="file" name="...">
+----------------------------------------
+    
+    specifies a file selection box. The user can select a file that should
+    be sent as part of the form data. This is only possible if the encoding
+    is multipart-mime. Unlike other parameters, the file is not mapped to a
+    simple name-value-pair. File upload is not a topic for beginners.
+
+    These tags are used to define parameters in static HTML. With dynamic HTML,
+    in particular JavaScript, the parameter values can be changed before the
+    form is submitted. If that is the case, you are in trouble. Learn JavaScript,
+    analyze the code that is executed, and modify your application to match
+    that behavior.
+
+
+** Analyze the Form, Again
+
+    After you have determined the action URL and name-value-pairs of
+    a form, you should exit the program you used to get the HTML source,
+    start it again and repeat the analysis with the new page.
+
+    Most parameters will be the same for both pages. But some parameters,
+    in particular those from hidden input fields, may change from session
+    to session, or even with every request. The same can be the case with
+    the action URL.
+
+    Parameters that remain the same can be hard-coded in your program.
+    If parameters change (except for user input), then your application
+    has to request the page with the form and extract the dynamic parameters
+    at runtime. If you're lucky you can locate them by simple string searches.
+    If you're unlucky, you need an HTML parser to make sense of the page.
+    HTML parsing is out of scope for HttpClient, but you'll find some
+    HTML parsers mentioned in the mailing list archives.
+
+    Note that a redesign of the form on the server can break your application
+    at any time. Whenever that happens, you have to repeat the analysis with
+    the new form returned by the server after the redesign, and adjust your
+    application accordingly.
+
+
+** POST the Form
+
+    After analyzing the form, it is time to create a request that matches
+    what a browser would generate. If the method is GET, just add the
+    name-value-pairs for all parameters to the query string. If the method
+    is POST, things are a little more complicated.
+
+    It depends on the server how closely you have to match browser behavior.
+    For example, a servlet will not distinguish between parameters in the
+    query string and url-encoded parameters of the entity. But other server
+    side code might make that distinction. The safe way is always to match
+    browser behavior exactly.
+
+    HttpClient supports both encoding types, url-encoded and multipart-mime.
+    To send parameters url-encoded, use the POST request and add the parameters
+    directly there. To send parameters in multipart-mime, collect the parameters
+    in a multipart-encoded request entity and add set the entity for the 
+    POST request. You will also find support for file upload in the multipart 
+    package. Note that these techniques are mutually exclusive, they can not be 
+    combined. Parameters defined in the query string of the URL can remain there.
+
+    Send the request. Inspect the response from the server:
+
+    * do you get a status code 303 or 307?
+    
+    []
+
+    That is called a redirect. Follow redirects to the ultimate page
+    and inspect that response. See step 6 on following redirects.
+
+    * do you get the page you expected?
+
+    []
+
+    If the server response to your POST request indicates a problem,
+    try to enable or disable the expect-continue handshake, or switch
+    the protocol version to HTTP/1.0. If that doesn't help...
+
+    Inspect the request you are sending:
+
+    * are there significant differences to the request of a browser?
+
+    []
+
+    There is a variety of sniffer programs you can use to grep the
+    browser request. Some of them are mentioned in the responses
+    to {{{http://mail-archives.apache.org/mod_mbox/jakarta-httpclient-user/200603.mbox/%3c981224FF5B88B349B7C1FED584D2620E02A2CBB2@CORPUSMX50B.corp.emc.com%3e
this question}on the mailing list}}.
+
+    Candidates for problems are missing or wrong parameters, and differences
+    in the header fields. The parameters are all up to you. As a general rule
+    for the header fields, you should send the same as the browser does. The
+    order of the fields does not matter.
+
+    But there's a caveat: some header fields are controlled by HttpClient and
+    can not be set explicitly. Other header fields are used to indicate
+    capabilities which a browser has, but your application probably has not.
+    For these, the request from your application has to and should differ.
+    Here is a possibly incomplete list of headers that need special consideration:
+
+    <<<Host:>>>
+
+    controlled by HttpClient. The value is usually obtained from the URL
+    you are posting to. It is possible to set a different value, called
+    a "virtual host".
+
+    <<<Content-Type:>>>
+    
+    <<<Content-Length:>>>
+    
+    <<<Transfer-Encoding:>>>
+    
+    controlled by HttpClient. The values are obtained from the request entity.
+
+    <<<Connection:>>>
+    
+    usually controlled by HttpClient to handle connection keep-alive.
+    Leave it alone or set the value to "close".
+
+    <<<Content-Encoding:>>>
+    
+    used to indicate the capability to process compressed responses.
+    Do not set this, unless you are prepared to implement decompression.
+
+** Follow Redirects
+
+    It is quite common for servers to respond with a 303 or 307 status code
+    to a POST request. These redirects indicate that your application has to
+    send another request to retrieve the actual result of the operation you
+    have triggered with the POST request.
+
+    HttpClient can be configured to follow some redirects automatically.
+    Others it is not allowed to follow automatically, since RFC 2616 specifies
+    that a user interaction should take place. We will make sure that HttpClient
+    is compliant with this requirement, but we can't stop you from implementing
+    a different behavior in your application. The Location header field in the
+    redirect response indicates the URL from which to fetch the actual page.
+    It is common practice that servers return a relative URL as the location,
+    although the specification requires an absolute URL.
+
+    Note that there may be more than one redirect in succession. Your
+    application then has to follow the redirect for a redirect, but make sure
+    that you do not enter an infinite loop. If you find that there are more
+    than two redirects in succession, something probably is fishy.
+
+
+** Logout
+
+    Your application can send as many GET and POST requests and follow as many
+    redirects as is required. But you should remember that there is a session
+    tracked by the server. Once your application is done, and if the web site
+    does provide a logout link, you should send a final request to log out.
+    This will tell the server that the session data can be discarded. If the
+    server prevents multiple logins with the same user ID and your application
+    has to run repeatedly, logout may even be required.
+
+* Further Reading
+
+    ReferenceMaterials: a list of technical specifications for HTTP and related 
+    stuff.
+
+    * {{{http://www.w3.org/TR/html4/interact/forms.html} HTML 4.01 Specification, 
+    Section on Forms}}: Includes how browsers have to generate the data to submit 
+    to the server.
+
+    * {{{http://www.webreference.com/html/tutorial13/} Giving Form to Forms}}:
+    Explains how to define HTML forms and what is submitted to the server.
+    Probably easier to digest than the HTML 4.01 Specification.
+
+    * {{{http://java.sun.com/developer/technicalArticles/InnerWorkings/BackstageSession/index.html}

+    JDC and Session Management}}: Details of a real site using session tracking, 
+    login forms and redirects.
+
+    * {{{http://jakarta.apache.org/commons/fileupload/} Commons File Upload}}:
+    Server-side library for parsing multipart requests.
+
+    * {{{http://www.cs.tut.fi/~jkorpela/forms/file.html} Tutorial on File Upload 
+    in HTML}}
+    
+    []
\ No newline at end of file

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Modified: httpcomponents/httpclient/trunk/src/site/site.xml
URL: http://svn.apache.org/viewvc/httpcomponents/httpclient/trunk/src/site/site.xml?rev=657143&r1=657142&r2=657143&view=diff
==============================================================================
--- httpcomponents/httpclient/trunk/src/site/site.xml (original)
+++ httpcomponents/httpclient/trunk/src/site/site.xml Fri May 16 10:35:13 2008
@@ -51,6 +51,10 @@
       <item name="Download" href="download.html"/>
       <item name="Examples" href="examples.html"/>
     </menu>
+    <menu name="Documentation">
+      <item name="Client HTTP Programming Primer" href="primer.html"/>
+      <item name="NTLM support" href="ntlm.html"/>
+    </menu>
     <menu name="Modules">
       <item name="HttpClient" href="httpclient/index.html"/>
       <item name="HttpMime" href="httpmime/index.html"/>



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