|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
@TransactionType(value=NOT_SUPPORTED) public interface ServletContext
Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file.
There is one context per "web application" per Java Virtual Machine. (A "web
application" is a collection of servlets and content installed under a
specific subset of the server's URL namespace such as /catalog
and possibly installed via a .war
file.)
The ServletContext
object is contained within the
ServletConfig
object, which the Web server provides the servlet when
the servlet is initialized.
This Java Card interface is a subset of the Java Servlet API 2.4 ServletContext interface. Some methods have been pruned in an effort to reduce the size of this interface and its implementations and/or eliminate dependencies on unsupported features.
Servlet.getServletConfig()
,
ServletConfig.getServletContext()
Method Summary | |
---|---|
Object |
getAttribute(String name)
Returns the servlet container attribute with the given name, or null if there is no attribute by that name. |
Enumeration |
getAttributeNames()
Returns an Enumeration containing the attribute names
available within this servlet context. |
ServletContext |
getContext(String uripath)
Returns a ServletContext object that corresponds to a
specified URL on the server. |
String |
getInitParameter(String name)
Returns a String containing the value of the named
context-wide initialization parameter, or null if the
parameter does not exist. |
Enumeration |
getInitParameterNames()
Returns the names of the context's initialization parameters as an Enumeration of String objects, or an empty
Enumeration if the context has no initialization
parameters. |
int |
getMajorVersion()
Returns the major version of the Java Servlet API that this servlet container supports. |
String |
getMimeType(String file)
Returns the MIME type of the specified file, or null if
the MIME type is not known. |
int |
getMinorVersion()
Returns the minor version of the Servlet API that this servlet container supports. |
RequestDispatcher |
getNamedDispatcher(String name)
Returns a RequestDispatcher object that acts as a wrapper for the
named servlet. |
String |
getRealPath(String path)
Returns a String containing the real path for a given
virtual path. |
RequestDispatcher |
getRequestDispatcher(String path)
Returns a RequestDispatcher object that acts as a wrapper for the
resource located at the given path. |
InputStream |
getResourceAsStream(String path)
Returns the resource located at the named path as an InputStream object. |
String |
getServerInfo()
Returns the name and version of the servlet container on which the servlet is running. |
String |
getServletContextName()
Returns the name of this web application corresponding to this ServletContext as specified in the deployment descriptor for this web application by the display-name element. |
void |
log(String msg)
Writes the specified message to a servlet log file, usually an event log. |
void |
log(String message,
Throwable throwable)
Writes an explanatory message and a stack trace for a given Throwable exception to the servlet log file. |
void |
removeAttribute(String name)
Removes the attribute with the given name from the servlet context. |
void |
setAttribute(String name,
Object object)
Binds an object to a given attribute name in this servlet context. |
Method Detail |
---|
ServletContext getContext(String uripath)
ServletContext
object that corresponds to a
specified URL on the server.
This method allows servlets to gain access to the context for various
parts of the server, and as needed obtain RequestDispatcher
objects from the context. The given path must be begin with "/", is
interpreted relative to the server's document root and is matched against
the context roots of other web applications hosted on this container.
In a security conscious environment, the servlet container may return
null
for a given URL.
uripath
- a String
specifying the context path of another
web application in the container.
ServletContext
object that corresponds to the
named URL, or null if either none exists or the container wishes
to restrict this access.RequestDispatcher
int getMajorVersion()
int getMinorVersion()
String getMimeType(String file)
null
if
the MIME type is not known. The MIME type is determined by the
configuration of the servlet container, and may be specified in a web
application deployment descriptor. Common MIME types are
"text/html"
and "image/gif"
.
file
- a String
specifying the name of a file
String
specifying the file's MIME typeInputStream getResourceAsStream(String path)
InputStream
object.
The data in the InputStream
can be of any type or length.
The path must begin with a "/" and is interpreted as relative to the
current context root. This method returns null
if
no resource exists at the specified path.
This method allows the servlet container to make a resource available to
servlets from any source. Resources can be located on a file system,
in a database, or in a .war
file.
This method is different from
java.lang.Class.getResourceAsStream
, which uses a class
loader. This method allows servlet containers to make a resource
available to a servlet from any location, without using a class loader.
path
- a String
specifying the path to the resource
InputStream
returned to the servlet, or
null
if no resource exists at the specified pathRequestDispatcher getRequestDispatcher(String path)
RequestDispatcher
object that acts as a wrapper for the
resource located at the given path. A RequestDispatcher
object can be used to forward a request to the resource or to include the
resource in a response. The resource can be dynamic or static.
The pathname must begin with a "/" and is interpreted as relative to the
current context root. Use getContext
to obtain a
RequestDispatcher
for resources in foreign contexts. This
method returns null
if the ServletContext
cannot return a RequestDispatcher
.
path
- a String
specifying the pathname to the
resource
RequestDispatcher
object that acts as a wrapper
for the resource at the specified path, or null
if
the ServletContext
cannot return a
RequestDispatcher
RequestDispatcher
,
getContext(java.lang.String)
RequestDispatcher getNamedDispatcher(String name)
RequestDispatcher
object that acts as a wrapper for the
named servlet.
Servlets may be given names via server
administration or via a web application deployment descriptor. A servlet
instance can determine its name using
ServletConfig.getServletName()
.
This method returns null
if the
ServletContext
cannot return a
RequestDispatcher
for any reason.
name
- a String
specifying the name of a servlet to
wrap
RequestDispatcher
object that acts as a wrapper
for the named servlet, or null
if the
ServletContext
cannot return a
RequestDispatcher
RequestDispatcher
,
getContext(java.lang.String)
,
ServletConfig.getServletName()
void log(String msg)
msg
- a String
specifying the message to be written
to the log filevoid log(String message, Throwable throwable)
Throwable
exception to the servlet log file. The name and
type of the servlet log file is specific to the servlet container,
usually an event log.
message
- a String
that describes the error or exceptionthrowable
- the Throwable
error or exceptionString getRealPath(String path)
String
containing the real path for a given
virtual path. For example, the path "/index.html" returns the absolute
file path on the server's filesystem would be served by a request for
"http://host/contextPath/index.html", where contextPath is the context
path of this ServletContext..
The real path returned will be in a form appropriate to the computer and
operating system on which the servlet container is running, including the
proper path separators. This method returns null
if the
servlet container cannot translate the virtual path to a real path for
any reason (such as when the content is being made available from a
.war
archive).
path
- a String
specifying a virtual path
String
specifying the real path, or null if the
translation cannot be performedString getServerInfo()
The form of the returned string is servername/versionnumber.
For example, the JavaServer Web Development Kit may return the string
JavaServer Web Dev Kit/1.0
.
The servlet container may return other optional information after the
primary string in parentheses, for example,
JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86)
.
String
containing at least the servlet container
name and version numberString getInitParameter(String name)
String
containing the value of the named
context-wide initialization parameter, or null
if the
parameter does not exist.
This method can make available configuration information useful to an entire "web application". For example, it can provide a webmaster's email address or the name of a system that holds critical data.
name
- a String
containing the name of the parameter
whose value is requested
String
containing at least the servlet container
name and version numberServletConfig.getInitParameter(java.lang.String)
Enumeration getInitParameterNames()
Enumeration
of String
objects, or an empty
Enumeration
if the context has no initialization
parameters.
Enumeration
of String
objects
containing the names of the context's initialization parametersServletConfig.getInitParameter(java.lang.String)
Object getAttribute(String name)
null
if there is no attribute by that name. An attribute
allows a servlet container to give the servlet additional information not
already provided by this interface. See your server documentation for
information about its attributes. A list of supported attributes can be
retrieved using getAttributeNames
.
The attribute is returned as a java.lang.Object
or some
subclass. Attribute names should follow the same convention as package
names. The Java Servlet API specification reserves names matching
java.*
, javax.*
,
javacard.*
, javacardx.*
,
com.sun.*
, and sun.*
.
name
- a String
specifying the name of the attribute
Object
containing the value of the attribute,
or null
if no attribute exists matching the given
namegetAttributeNames()
Enumeration getAttributeNames()
Enumeration
containing the attribute names
available within this servlet context. Use the getAttribute(java.lang.String)
method with an attribute name to get the value of an attribute.
Enumeration
of attribute namesgetAttribute(java.lang.String)
void setAttribute(String name, Object object)
If listeners are configured on the ServletContext
the
container notifies them accordingly.
If a null value is passed, the effect is the same as calling
removeAttribute()
.
Attribute names should follow the same convention as package names. The
Java Servlet API specification reserves names matching
java.*
, javax.*
,
javacard.*
, javacardx.*
,
com.sun.*
, and sun.*
.
name
- a String
specifying the name of the attributeobject
- an Object
representing the attribute to be
boundvoid removeAttribute(String name)
getAttribute(java.lang.String)
to retrieve the
attribute's value will return null
.
If listeners are configured on the ServletContext
the
container notifies them accordingly.
name
- a String
specifying the name of the attribute
to be removedString getServletContextName()
|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |