Google Git
Sign in
chromium/chromium/src/third_party/httpcomponents-client/master/./binary-distribution/tutorial/html/statemgmt.html
blob: 503ae28283e7e5cdcf5d66d15c81bb483c2cfe79 [file] [log] [blame]
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Chapter&nbsp;3.&nbsp;HTTP state management</title><link rel="stylesheet" type="text/css" href="css/hc-tutorial.css"><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"><link rel="home" href="index.html" title="HttpClient Tutorial"><link rel="up" href="index.html" title="HttpClient Tutorial"><link rel="prev" href="connmgmt.html" title="Chapter&nbsp;2.&nbsp;Connection management"><link rel="next" href="authentication.html" title="Chapter&nbsp;4.&nbsp;HTTP authentication"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div xmlns:fo="http://www.w3.org/1999/XSL/Format" class="banner"><a class="bannerLeft" href="http://www.apache.org/" title="Apache Software Foundation"><img style="border:none;" src="images/asf_logo_wide.gif"></a><a class="bannerRight" href="http://hc.apache.org/httpcomponents-client-ga/" title="Apache HttpComponents Client"><img style="border:none;" src="images/hc_logo.png"></a><div class="clear"></div></div><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter&nbsp;3.&nbsp;HTTP state management</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="connmgmt.html">Prev</a>&nbsp;</td><th width="60%" align="center">&nbsp;</th><td width="20%" align="right">&nbsp;<a accesskey="n" href="authentication.html">Next</a></td></tr></table><hr></div><div class="chapter" title="Chapter&nbsp;3.&nbsp;HTTP state management"><div class="titlepage"><div><div><h2 class="title"><a name="statemgmt"></a>Chapter&nbsp;3.&nbsp;HTTP state management</h2></div></div></div>
<p>Originally HTTP was designed as a stateless, request / response oriented protocol that
made no special provisions for stateful sessions spanning across several logically related
request / response exchanges. As HTTP protocol grew in popularity and adoption more and more
systems began to use it for applications it was never intended for, for instance as a
transport for e-commerce applications. Thus, the support for state management became a
necessity.</p>
<p>Netscape Communications, at that time a leading developer of web client and server
software, implemented support for HTTP state management in their products based on a
proprietary specification. Later, Netscape tried to standardise the mechanism by publishing
a specification draft. Those efforts contributed to the formal specification defined through
the RFC standard track. However, state management in a significant number of applications is
still largely based on the Netscape draft and is incompatible with the official
specification. All major developers of web browsers felt compelled to retain compatibility
with those applications greatly contributing to the fragmentation of standards
compliance.</p>
<div class="section" title="3.1.&nbsp;HTTP cookies"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e669"></a>3.1.&nbsp;HTTP cookies</h2></div></div></div>
<p>An HTTP cookie is a token or short packet of state information that the HTTP agent and the
target server can exchange to maintain a session. Netscape engineers used to refer to it
as a "magic cookie" and the name stuck.</p>
<p>HttpClient uses the <code class="interfacename">Cookie</code> interface to represent an
abstract cookie token. In its simplest form an HTTP cookie is merely a name / value pair.
Usually an HTTP cookie also contains a number of attributes such as version, a domain
for which is valid, a path that specifies the subset of URLs on the origin server to
which this cookie applies, and the maximum period of time for which the cookie is valid.</p>
<p>The <code class="interfacename">SetCookie</code> interface represents a
<code class="literal">Set-Cookie</code> response header sent by the origin server to the HTTP
agent in order to maintain a conversational state.
The <code class="interfacename">SetCookie2</code> interface extends SetCookie with
<code class="literal">Set-Cookie2</code> specific methods.</p>
<p>The <code class="interfacename">ClientCookie</code> interface extends
<code class="interfacename">Cookie</code> interface with additional client specific
functionality such as the ability to retrieve original cookie attributes exactly as they were
specified by the origin server. This is important for generating the
<code class="literal">Cookie</code> header because some cookie specifications require that the
<code class="literal">Cookie</code> header should include certain attributes only if they were
specified in the <code class="literal">Set-Cookie</code> or <code class="literal">Set-Cookie2</code>
header.</p>
<div class="section" title="3.1.1.&nbsp;Cookie versions"><div class="titlepage"><div><div><h3 class="title"><a name="d5e686"></a>3.1.1.&nbsp;Cookie versions</h3></div></div></div>
<p>Cookies compatible with Netscape draft specification but non-compliant with the
official specification are considered to be of version 0. Standard compliant cookies
are expected to have version 1. HttpClient may handle cookies differently depending
on the version.</p>
<p>Here is an example of re-creating a Netscape cookie:</p>
<pre class="programlisting">
BasicClientCookie netscapeCookie = new BasicClientCookie("name", "value");
netscapeCookie.setVersion(0);
netscapeCookie.setDomain(".mycompany.com");
netscapeCookie.setPath("/");
</pre>
<p>Here is an example of re-creating a standard cookie. Please note that standard
compliant cookie must retain all attributes as sent by the origin server:</p>
<pre class="programlisting">
BasicClientCookie stdCookie = new BasicClientCookie("name", "value");
stdCookie.setVersion(1);
stdCookie.setDomain(".mycompany.com");
stdCookie.setPath("/");
stdCookie.setSecure(true);
// Set attributes EXACTLY as sent by the server
stdCookie.setAttribute(ClientCookie.VERSION_ATTR, "1");
stdCookie.setAttribute(ClientCookie.DOMAIN_ATTR, ".mycompany.com");
</pre>
<p>Here is an example of re-creating a <code class="literal">Set-Cookie2</code> compliant
cookie. Please note that standard compliant cookie must retain all attributes as
sent by the origin server:</p>
<pre class="programlisting">
BasicClientCookie2 stdCookie = new BasicClientCookie2("name", "value");
stdCookie.setVersion(1);
stdCookie.setDomain(".mycompany.com");
stdCookie.setPorts(new int[] {80,8080});
stdCookie.setPath("/");
stdCookie.setSecure(true);
// Set attributes EXACTLY as sent by the server
stdCookie.setAttribute(ClientCookie.VERSION_ATTR, "1");
stdCookie.setAttribute(ClientCookie.DOMAIN_ATTR, ".mycompany.com");
stdCookie.setAttribute(ClientCookie.PORT_ATTR, "80,8080");
</pre>
</div>
</div>
<div class="section" title="3.2.&nbsp;Cookie specifications"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e696"></a>3.2.&nbsp;Cookie specifications</h2></div></div></div>
<p>The <code class="interfacename">CookieSpec</code> interface represents a cookie management
specification. The cookie management specification is expected to enforce:</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
<p>rules of parsing <code class="literal">Set-Cookie</code> and optionally
<code class="literal">Set-Cookie2</code> headers.</p>
</li><li class="listitem">
<p>rules of validation of parsed cookies.</p>
</li><li class="listitem">
<p>formatting of <code class="literal">Cookie</code> header for a given host, port and path
of origin.</p>
</li></ul></div>
<p>HttpClient ships with several <code class="interfacename">CookieSpec</code>
implementations:</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
<p title="Netscape draft:">
<b>Netscape draft:&nbsp;</b>
This specification conforms to the original draft specification published
by Netscape Communications. It should be avoided unless absolutely necessary
for compatibility with legacy code.
</p>
</li><li class="listitem">
<p title="RFC 2109:">
<b>RFC 2109:&nbsp;</b>
Older version of the official HTTP state management specification
superseded by RFC 2965.
</p>
</li><li class="listitem">
<p title="RFC 2965:">
<b>RFC 2965:&nbsp;</b>
The official HTTP state management specification.
</p>
</li><li class="listitem">
<p title="Browser compatibility:">
<b>Browser compatibility:&nbsp;</b>
This implementation strives to closely mimic the (mis)behavior of common web
browser applications such as Microsoft Internet Explorer and Mozilla
FireFox.
</p>
</li><li class="listitem">
<p title="Best match:">
<b>Best match:&nbsp;</b>
'Meta' cookie specification that picks up a cookie policy based on the
format of cookies sent with the HTTP response. It basically aggregates all
above implementations into one class.
</p>
</li><li class="listitem">
<p title="Ignore cookies:">
<b>Ignore cookies:&nbsp;</b>
All cookies are ignored.
</p>
</li></ul></div>
<p>It is strongly recommended to use the <code class="literal">Best Match</code> policy and let
HttpClient pick up an appropriate compliance level at runtime based on the execution
context.</p>
</div>
<div class="section" title="3.3.&nbsp;HTTP cookie and state management parameters"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e739"></a>3.3.&nbsp;HTTP cookie and state management parameters</h2></div></div></div>
<p>These are parameters that be used to customize HTTP state management and the behaviour of
individual cookie specifications:</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
<p title="CookieSpecPNames.DATE_PATTERNS='http.protocol.cookie-datepatterns':">
<b><code class="constant">CookieSpecPNames.DATE_PATTERNS</code>='http.protocol.cookie-datepatterns':&nbsp;</b>
defines valid date patterns to be used for parsing non-standard
<code class="literal">expires</code> attribute. Only required for compatibility
with non-compliant servers that still use <code class="literal">expires</code> defined
in the Netscape draft instead of the standard <code class="literal">max-age</code>
attribute. This parameter expects a value of type
<code class="interfacename">java.util.Collection</code>. The collection
elements must be of type <code class="classname">java.lang.String</code> compatible
with the syntax of <code class="classname">java.text.SimpleDateFormat</code>. If
this parameter is not set the choice of a default value is
<code class="interfacename">CookieSpec</code> implementation specific.
</p>
</li><li class="listitem">
<p title="CookieSpecPNames.SINGLE_COOKIE_HEADER='http.protocol.single-cookie-header':">
<b><code class="constant">CookieSpecPNames.SINGLE_COOKIE_HEADER</code>='http.protocol.single-cookie-header':&nbsp;</b>
defines whether cookies should be forced into a single
<code class="literal">Cookie</code> request header. Otherwise, each cookie is
formatted as a separate <code class="literal">Cookie</code> header. This parameter
expects a value of type <code class="classname">java.lang.Boolean</code>. If this
parameter is not set, the choice of a default value is CookieSpec
implementation specific. Please note this parameter applies to strict cookie
specifications (RFC 2109 and RFC 2965) only. Browser compatibility and
netscape draft policies will always put all cookies into one request
header.
</p>
</li><li class="listitem">
<p title="ClientPNames.COOKIE_POLICY='http.protocol.cookie-policy':">
<b><code class="constant">ClientPNames.COOKIE_POLICY</code>='http.protocol.cookie-policy':&nbsp;</b>
defines the name of a cookie specification to be used for HTTP state
management. This parameter expects a value of type
<code class="classname">java.lang.String</code>. If this parameter is not set,
valid date patterns are <code class="interfacename">CookieSpec</code>
implementation specific.
</p>
</li></ul></div>
</div>
<div class="section" title="3.4.&nbsp;Cookie specification registry"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e770"></a>3.4.&nbsp;Cookie specification registry</h2></div></div></div>
<p>HttpClient maintains a registry of available cookie specifications using
the <code class="classname">CookieSpecRegistry</code> class. The following specifications are
registered per default:</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
<p title="compatibility:">
<b>compatibility:&nbsp;</b>
Browser compatibility (lenient policy).
</p>
</li><li class="listitem">
<p title="netscape:">
<b>netscape:&nbsp;</b>
Netscape draft.
</p>
</li><li class="listitem">
<p title="rfc2109:">
<b>rfc2109:&nbsp;</b>
RFC 2109 (outdated strict policy).
</p>
</li><li class="listitem">
<p title="rfc2965:">
<b>rfc2965:&nbsp;</b>
RFC 2965 (standard conformant strict policy).
</p>
</li><li class="listitem">
<p title="best-match:">
<b>best-match:&nbsp;</b>
Best match meta-policy.
</p>
</li><li class="listitem">
<p title="ignoreCookies:">
<b>ignoreCookies:&nbsp;</b>
All cookies are ignored.
</p>
</li></ul></div>
</div>
<div class="section" title="3.5.&nbsp;Choosing cookie policy"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e799"></a>3.5.&nbsp;Choosing cookie policy</h2></div></div></div>
<p>Cookie policy can be set at the HTTP client and overridden on the HTTP request level
if required.</p>
<pre class="programlisting">
HttpClient httpclient = new DefaultHttpClient();
// force strict cookie policy per default
httpclient.getParams().setParameter(
ClientPNames.COOKIE_POLICY, CookiePolicy.RFC_2965);
HttpGet httpget = new HttpGet("http://www.broken-server.com/");
// Override the default policy for this request
httpget.getParams().setParameter(
ClientPNames.COOKIE_POLICY, CookiePolicy.BROWSER_COMPATIBILITY);
</pre>
</div>
<div class="section" title="3.6.&nbsp;Custom cookie policy"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e803"></a>3.6.&nbsp;Custom cookie policy</h2></div></div></div>
<p>In order to implement a custom cookie policy one should create a custom implementation
of the <code class="interfacename">CookieSpec</code> interface, create a
<code class="interfacename">CookieSpecFactory</code> implementation to create and
initialize instances of the custom specification and register the factory with
HttpClient. Once the custom specification has been registered, it can be activated the
same way as a standard cookie specification.</p>
<pre class="programlisting">
CookieSpecFactory csf = new CookieSpecFactory() {
public CookieSpec newInstance(HttpParams params) {
return new BrowserCompatSpec() {
@Override
public void validate(Cookie cookie, CookieOrigin origin)
throws MalformedCookieException {
// Oh, I am easy
}
};
}
};
DefaultHttpClient httpclient = new DefaultHttpClient();
httpclient.getCookieSpecs().register("easy", csf);
httpclient.getParams().setParameter(
ClientPNames.COOKIE_POLICY, "easy");
</pre>
</div>
<div class="section" title="3.7.&nbsp;Cookie persistence"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e809"></a>3.7.&nbsp;Cookie persistence</h2></div></div></div>
<p>HttpClient can work with any physical representation of a persistent cookie store that
implements the <code class="interfacename">CookieStore</code> interface. The default
<code class="interfacename">CookieStore</code> implementation called
<code class="classname">BasicCookieStore</code> is a simple implementation backed by a
<code class="classname">java.util.ArrayList</code>. Cookies stored in an
<code class="classname">BasicClientCookie</code> object are lost when the container object
get garbage collected. Users can provide more complex implementations if
necessary.</p>
<pre class="programlisting">
DefaultHttpClient httpclient = new DefaultHttpClient();
// Create a local instance of cookie store
CookieStore cookieStore = new MyCookieStore();
// Populate cookies if needed
BasicClientCookie cookie = new BasicClientCookie("name", "value");
cookie.setVersion(0);
cookie.setDomain(".mycompany.com");
cookie.setPath("/");
cookieStore.addCookie(cookie);
// Set the store
httpclient.setCookieStore(cookieStore);
</pre>
</div>
<div class="section" title="3.8.&nbsp;HTTP state management and execution context"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e818"></a>3.8.&nbsp;HTTP state management and execution context</h2></div></div></div>
<p>In the course of HTTP request execution HttpClient adds the following state management
related objects to the execution context:</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
<p title="ClientContext.COOKIESPEC_REGISTRY='http.cookiespec-registry':">
<b><code class="constant">ClientContext.COOKIESPEC_REGISTRY</code>='http.cookiespec-registry':&nbsp;</b>
<code class="classname">CookieSpecRegistry</code> instance representing the actual
cookie specification registry. The value of this attribute set in the local
context takes precedence over the default one.
</p>
</li><li class="listitem">
<p title="ClientContext.COOKIE_SPEC='http.cookie-spec':">
<b><code class="constant">ClientContext.COOKIE_SPEC</code>='http.cookie-spec':&nbsp;</b>
<code class="interfacename">CookieSpec</code> instance representing the actual
cookie specification.
</p>
</li><li class="listitem">
<p title="ClientContext.COOKIE_ORIGIN='http.cookie-origin':">
<b><code class="constant">ClientContext.COOKIE_ORIGIN</code>='http.cookie-origin':&nbsp;</b>
<code class="classname">CookieOrigin</code> instance representing the actual
details of the origin server.
</p>
</li><li class="listitem">
<p title="ClientContext.COOKIE_STORE='http.cookie-store':">
<b><code class="constant">ClientContext.COOKIE_STORE</code>='http.cookie-store':&nbsp;</b>
<code class="interfacename">CookieStore</code> instance representing the actual
cookie store. The value of this attribute set in the local context takes
precedence over the default one.
</p>
</li></ul></div>
<p>The local <code class="interfacename">HttpContext</code> object can be used to customize
the HTTP state management context prior to request execution, or to examine its state after
the request has been executed:</p>
<pre class="programlisting">
HttpClient httpclient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpGet httpget = new HttpGet("http://localhost:8080/");
HttpResponse response = httpclient.execute(httpget, localContext);
CookieOrigin cookieOrigin = (CookieOrigin) localContext.getAttribute(
ClientContext.COOKIE_ORIGIN);
System.out.println("Cookie origin: " + cookieOrigin);
CookieSpec cookieSpec = (CookieSpec) localContext.getAttribute(
ClientContext.COOKIE_SPEC);
System.out.println("Cookie spec used: " + cookieSpec);
</pre>
</div>
<div class="section" title="3.9.&nbsp;Per user / thread state management"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d5e849"></a>3.9.&nbsp;Per user / thread state management</h2></div></div></div>
<p>One can use an individual local execution context in order to implement per user (or
per thread) state management. A cookie specification registry and cookie store defined in
the local context will take precedence over the default ones set at the HTTP client
level.</p>
<pre class="programlisting">
HttpClient httpclient = new DefaultHttpClient();
// Create a local instance of cookie store
CookieStore cookieStore = new BasicCookieStore();
// Create local HTTP context
HttpContext localContext = new BasicHttpContext();
// Bind custom cookie store to the local context
localContext.setAttribute(ClientContext.COOKIE_STORE, cookieStore);
HttpGet httpget = new HttpGet("http://www.google.com/");
// Pass local context as a parameter
HttpResponse response = httpclient.execute(httpget, localContext);
</pre>
</div>
</div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="connmgmt.html">Prev</a>&nbsp;</td><td width="20%" align="center">&nbsp;</td><td width="40%" align="right">&nbsp;<a accesskey="n" href="authentication.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter&nbsp;2.&nbsp;Connection management&nbsp;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&nbsp;Chapter&nbsp;4.&nbsp;HTTP authentication</td></tr></table></div></body></html>