Portlet API (V0.7.1) : Interface PortletContext

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## javax.portlet
Interface PortletContext

public interface PortletContext

The `PortletContext` interface defines a portlet view of the portlet container. The `PortletContext` also makes resources available to the portlet. Using the context, a portlet can access the portlet log, and obtain URL references to resources.

There is one context per "portlet web application" per Java Virtual Machine. (A "portlet web application" is a collection of portlets, servlets, and content installed under a specific subset of the server URL namespace, such as `/catalog`. They are possibly installed via a `.war` file.) As a web application, a portlet application also has a servlet context. The portlet context leverages most of its functionality from the servlet context of the portlet application.

Attibutes stored in the context are global for all users and all components in the portlet web application.

In the case of a web application marked "distributed" in its deployment descriptor, there will be one context instance for each virtual machine. In this situation, the context cannot be used as a location to share global information (because the information is not truly global). Use an external resource, such as a database to achieve sharing on a global scope.

Method Summary
`java.lang.Object` | `getAttribute(java.lang.String name)` Returns the portlet container attribute with the given name, or null if there is no attribute by that name.
`java.util.Enumeration` | `getAttributeNames()` Returns an `Enumeration` containing the attribute names available within this portlet context, or an emtpy `Enumeration` if no attributes are available.
`java.lang.String` | `getInitParameter(java.lang.String name)` Returns a String containing the value of the named context-wide initialization parameter, or `null` if the parameter does not exist.
`java.util.Enumeration` | `getInitParameterNames()` Returns the names of the context 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 Portlet API that this portlet container supports.
`java.lang.String` | `getMimeType(java.lang.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 Portlet API that this portlet container supports.
`PortletRequestDispatcher` | `getNamedDispatcher(java.lang.String name)` Returns a `PortletRequestDispatcher` object that acts as a wrapper for the named servlet.
`java.lang.String` | `getPortletContextName()` Returns the name of this portlet web application correponding to this PortletContext as specified in the `web.xml` deployment descriptor for this web application by the `display-name` element.
`java.lang.String` | `getRealPath(java.lang.String path)` Returns a `String` containing the real path for a given virtual path.
`PortletRequestDispatcher` | `getRequestDispatcher(java.lang.String path)` Returns a `PortletRequestDispatcher` object that acts as a wrapper for the resource located at the given path.
`java.net.URL` | `getResource(java.lang.String path)` Returns a URL to the resource that is mapped to a specified path.
`java.io.InputStream` | `getResourceAsStream(java.lang.String path)` Returns the resource located at the given path as an InputStream object.
`java.util.Set` | `getResourcePaths(java.lang.String path)` Returns a directory-like listing of all the paths to resources within the web application longest sub-path of which matches the supplied path argument.
`java.lang.String` | `getServerInfo()` Returns the name and version of the portlet container in which the portlet is running.
`void` | `log(java.lang.String msg)` Writes the specified message to a portlet log file, usually an event log.
`void` | `log(java.lang.String message, java.lang.Throwable throwable)` Writes an explanatory message and a stack trace for a given Throwable exception to the portlet log file.
`void` | `removeAttribute(java.lang.String name)` Removes the attribute with the given name from the portlet context.
`void` | `setAttribute(java.lang.String name, java.lang.Object object)` Binds an object to a given attribute name in this portlet context.

Method Detail

### getServerInfo

    public java.lang.String getServerInfo()

  Returns the name and version of the portlet container in which the portlet is running.

  The form of the returned string is `containername/versionnumber`.

  Returns:
    the string containing at least name and version number

### getRequestDispatcher

    public PortletRequestDispatcher getRequestDispatcher(java.lang.String path)

  Returns a `PortletRequestDispatcher` object that acts as a wrapper for the resource located at the given path. A `RequestDispatcher` object can be used include the resource in a response. The resource can be dynamic or static.

  The pathname must begin with a slash (`/` ) and is interpreted as relative to the current context root. This method returns `null` if the `PortletContext` cannot return a `PortletRequestDispatcher`.

  Parameters:
    `path` - a `String` specifying the pathname to the resource
  Returns:
    a `RequestDispatcher` object that acts as a wrapper for the resource at the specified path.
  See Also:
    `PortletRequestDispatcher`

### getNamedDispatcher

    public PortletRequestDispatcher getNamedDispatcher(java.lang.String name)

  Returns a `PortletRequestDispatcher` object that acts as a wrapper for the named servlet.

  Servlets (and also JSP pages) may be given names via server administration or via a web application deployment descriptor.

  This method returns `null` if the `PortletContext` cannot return a `RequestDispatcher` for any reason.

  Parameters:
    `name` - a `String` specifying the name of a servlet to be wrapped
  Returns:
    a `RequestDispatcher` object that acts as a wrapper for the named servlet
  See Also:
    `PortletRequestDispatcher`

### getResourceAsStream

    public java.io.InputStream getResourceAsStream(java.lang.String path)

  Returns the resource located at the given path as an InputStream object. The data in the InputStream can be of any type or length. The method returns null if no resource exists at the given path.

  In order to access protected resources the path has to be prefixed with `/WEB-INF/` (for example `/WEB-INF/myportlet/myportlet.jsp`). Otherwise, the direct path is used (for example `/myportlet/myportlet.jsp`).

  Parameters:
    `path` - the path to the resource
  Returns:
    the input stream

### getMajorVersion

    public int getMajorVersion()

  Returns the major version of the Portlet API that this portlet container supports.
  Returns:
    the major version
  See Also:
    `getMinorVersion()`

### getMinorVersion

    public int getMinorVersion()

  Returns the minor version of the Portlet API that this portlet container supports.
  Returns:
    the minor version
  See Also:
    `getMajorVersion()`

### getMimeType

    public java.lang.String getMimeType(java.lang.String file)

  Returns the MIME type of the specified file, or `null` if the MIME type is not known. The MIME type is determined by the configuration of the portlet container and may be specified in a web application deployment descriptor. Common MIME types are `text/html` and `image/gif`.
  Parameters:
    `file` - a `String` specifying the name of a file
  Returns:
    a `String` specifying the MIME type of the file

### getRealPath

    public java.lang.String getRealPath(java.lang.String path)

  Returns a `String` containing the real path for a given virtual path. For example, the path `/index.html` returns the absolute file path of the portlet container file system.

  The real path returned will be in a form appropriate to the computer and operating system on which the portlet container is running, including the proper path separators. This method returns `null` if the portlet 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).

  Parameters:
    `path` - a `String` specifying a virtual path
  Returns:
    a `String` specifying the real path, or null if the transformation cannot be performed.

### getResourcePaths

    public java.util.Set getResourcePaths(java.lang.String path)

  Returns a directory-like listing of all the paths to resources within the web application longest sub-path of which matches the supplied path argument. Paths indicating subdirectory paths end with a slash (`/`). The returned paths are all relative to the root of the web application and have a leading slash. For example, for a web application containing
  `/welcome.html
  /catalog/index.html
  /catalog/products.html
  /catalog/offers/books.html
  /catalog/offers/music.html
  /customer/login.jsp
  /WEB-INF/web.xml
  /WEB-INF/classes/com.acme.OrderPortlet.class,
  ` `getResourcePaths("/")` returns `{"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}`
  `getResourcePaths("/catalog/")` returns `{"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}`.
  Parameters:
    `path` - the partial path used to match the resources, which must start with a slash
  Returns:
    a Set containing the directory listing, or `null` if there are no resources in the web application of which the path begins with the supplied path.

### getResource

    public java.net.URL getResource(java.lang.String path)
                             throws java.net.MalformedURLException

  Returns a URL to the resource that is mapped to a specified path. The path must begin with a slash (`/`) and is interpreted as relative to the current context root.

  This method allows the portlet container to make a resource available to portlets from any source. Resources can be located on a local or remote file system, in a database, or in a `.war` file.

  The portlet container must implement the URL handlers and `URLConnection` objects that are necessary to access the resource.

  This method returns `null` if no resource is mapped to the pathname.

  Some containers may allow writing to the URL returned by this method using the methods of the URL class.

  The resource content is returned directly, so be aware that requesting a `.jsp` page returns the JSP source code. Use a `RequestDispatcher` instead to include results of an execution.

  This method has a different purpose than `java.lang.Class.getResource`, which looks up resources based on a class loader. This method does not use class loaders.

  Parameters:
    `path` - a `String` specifying the path to the resource
  Returns:
    the resource located at the named path, or `null` if there is no resource at that path
  Throws:
    `MalformedURLException` - if the pathname is not given in the correct form

### getAttribute

    public java.lang.Object getAttribute(java.lang.String name)

  Returns the portlet container attribute with the given name, or null if there is no attribute by that name. An attribute allows a portlet container to give the portlet additional information not already provided by this interface. 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 Portlet API specification reserves names matching `java.*`, `javax.*`, and `sun.*`.

  Parameters:
    `name` - a `String` specifying the name of the attribute
  Returns:
    an `Object` containing the value of the attribute, or `null` if no attribute exists matching the given name
  Throws:
    `java.lang.IllegalArgumentException` - if name is `null`.
  See Also:
    `getAttributeNames()`

### getAttributeNames

    public java.util.Enumeration getAttributeNames()

  Returns an `Enumeration` containing the attribute names available within this portlet context, or an emtpy `Enumeration` if no attributes are available. Use the `getAttribute(java.lang.String)` method with an attribute name to get the value of an attribute.
  Returns:
    an `Enumeration` of attribute names
  See Also:
    `getAttribute(java.lang.String)`

### getInitParameter

    public java.lang.String getInitParameter(java.lang.String name)

  Returns a String containing the value of the named context-wide initialization parameter, or `null` if the parameter does not exist. This method provides configuration information which may be useful for an entire "portlet web application".
  Parameters:
    `name` - a `String` containing the name of the requested parameter
  Returns:
    a `String` containing the value of the initialization parameter, or `null` if the parameter does not exist.
  Throws:
    `java.lang.IllegalArgumentException` - if name is `null`.
  See Also:
    `getInitParameterNames()`

### getInitParameterNames

    public java.util.Enumeration getInitParameterNames()

  Returns the names of the context initialization parameters as an `Enumeration` of String objects, or an empty Enumeration if the context has no initialization parameters.
  Returns:
    an `Enumeration` of `String` objects containing the names of the context initialization parameters
  See Also:
    `getInitParameter(java.lang.String)`

### log

    public void log(java.lang.String msg)

  Writes the specified message to a portlet log file, usually an event log. The name and type of the portlet log file is specific to the portlet container.

  This method mapps to the `ServletContext.log` method. The portlet container may in addition log this message in a portlet container specific log file.

  Parameters:
    `msg` - a `String` specifying the message to be written to the log file

### log

    public void log(java.lang.String message,
                    java.lang.Throwable throwable)

  Writes an explanatory message and a stack trace for a given Throwable exception to the portlet log file. The name and type of the portlet log file is specific to the portlet container, usually an event log.

  This method is mapped to the `ServletContext.log` method. The portlet container may in addition log this message in a portlet container specific log file.

  Parameters:
    `message` - a `String` that describes the error or exception
    `throwable` - the `Throwable` error or exception

### removeAttribute

    public void removeAttribute(java.lang.String name)

  Removes the attribute with the given name from the portlet context. After removal, subsequent calls to `getAttribute(java.lang.String)` to retrieve the attribute's value will return `null`.
  Parameters:
    `name` - a `String` specifying the name of the attribute to be removed
  Throws:
    `java.lang.IllegalArgumentException` - if name is `null`.

### setAttribute

    public void setAttribute(java.lang.String name,
                             java.lang.Object object)

  Binds an object to a given attribute name in this portlet context. If the name specified is already used for an attribute, this method removes the old attribute and binds the name to the new attribute.

  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 Portlet API specification reserves names matching `java.*`, `javax.*`, and `sun.*`.

  Parameters:
    `name` - a `String` specifying the name of the attribute
    `object` - an `Object` representing the attribute to be bound
  Throws:
    `java.lang.IllegalArgumentException` - if name is `null`.

### getPortletContextName

    public java.lang.String getPortletContextName()

  Returns the name of this portlet web application correponding to this PortletContext as specified in the `web.xml` deployment descriptor for this web application by the `display-name` element.
  Returns:
    The name of the web application or null if no name has been declared in the deployment descriptor.

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