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ServletRequest (Servlet and JavaServer Pages API Documentation)

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javax.servlet
Interface ServletRequest

All Known Subinterfaces:: HttpServletRequest

All Known Implementing Classes:: HttpServletRequestWrapper, ServletRequestWrapper

public interface ServletRequest

Defines an object to provide client request information to a servlet. The servlet container creates a ServletRequest object and passes it as an argument to the servlet's service method.

A ServletRequest object provides data including parameter name and values, attributes, and an input stream. Interfaces that extend ServletRequest can provide additional protocol-specific data (for example, HTTP data is provided by HttpServletRequest.

Version:: $Version$
Author:: Various
See Also:: HttpServletRequest

Method Summary

java.lang.Object getAttribute(java.lang.String name)
          Returns the value of the named attribute as an Object, or null if no attribute of the given name exists.

java.util.Enumeration getAttributeNames()
          Returns an Enumeration containing the names of the attributes available to this request.

java.lang.String getCharacterEncoding()
          Returns the name of the character encoding used in the body of this request.

int getContentLength()
          Returns the length, in bytes, of the request body and made available by the input stream, or -1 if the length is not known.

java.lang.String getContentType()
          Returns the MIME type of the body of the request, or null if the type is not known.

ServletInputStream getInputStream()
          Retrieves the body of the request as binary data using a ServletInputStream.

java.util.Locale getLocale()
          Returns the preferred Locale that the client will accept content in, based on the Accept-Language header.

java.util.Enumeration getLocales()
          Returns an Enumeration of Locale objects indicating, in decreasing order starting with the preferred locale, the locales that are acceptable to the client based on the Accept-Language header.

java.lang.String getParameter(java.lang.String name)
          Returns the value of a request parameter as a String, or null if the parameter does not exist.

java.util.Map getParameterMap()
          Returns a java.util.Map of the parameters of this request.

java.util.Enumeration getParameterNames()
          Returns an Enumeration of String objects containing the names of the parameters contained in this request.

java.lang.String[] getParameterValues(java.lang.String name)
          Returns an array of String objects containing all of the values the given request parameter has, or null if the parameter does not exist.

java.lang.String getProtocol()
          Returns the name and version of the protocol the request uses in the form protocol/majorVersion.minorVersion, for example, HTTP/1.1.

java.io.BufferedReader getReader()
          Retrieves the body of the request as character data using a BufferedReader.

java.lang.String getRealPath(java.lang.String path)
          Deprecated. As of Version 2.1 of the Java Servlet API, use ServletContext.getRealPath(java.lang.String) instead.

java.lang.String getRemoteAddr()
          Returns the Internet Protocol (IP) address of the client that sent the request.

java.lang.String getRemoteHost()
          Returns the fully qualified name of the client that sent the request.

RequestDispatcher getRequestDispatcher(java.lang.String path)
          Returns a RequestDispatcher object that acts as a wrapper for the resource located at the given path.

java.lang.String getScheme()
          Returns the name of the scheme used to make this request, for example, http, https, or ftp.

java.lang.String getServerName()
          Returns the host name of the server that received the request.

int getServerPort()
          Returns the port number on which this request was received.

boolean isSecure()
          Returns a boolean indicating whether this request was made using a secure channel, such as HTTPS.

void removeAttribute(java.lang.String name)
          Removes an attribute from this request.

void setAttribute(java.lang.String name, java.lang.Object o)
          Stores an attribute in this request.

void setCharacterEncoding(java.lang.String env)
          Overrides the name of the character encoding used in the body of this request.

Method Detail

getAttribute


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

Returns the value of the named attribute as an Object, or null if no attribute of the given name exists.

Attributes can be set two ways. The servlet container may set attributes to make available custom information about a request. For example, for requests made using HTTPS, the attribute javax.servlet.request.X509Certificate can be used to retrieve information on the certificate of the client. Attributes can also be set programatically using setAttribute(java.lang.String, java.lang.Object). This allows information to be embedded into a request before a RequestDispatcher call.

Attribute names should follow the same conventions as package names. This 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 the attribute does not exist

getAttributeNames


public java.util.Enumeration getAttributeNames()

Returns an Enumeration containing the names of the attributes available to this request. This method returns an empty Enumeration if the request has no attributes available to it.

Returns:: an Enumeration of strings containing the names of the request's attributes

getCharacterEncoding


public java.lang.String getCharacterEncoding()

Returns the name of the character encoding used in the body of this request. This method returns null if the request does not specify a character encoding

Returns:: a String containing the name of the chararacter encoding, or null if the request does not specify a character encoding

setCharacterEncoding


public void setCharacterEncoding(java.lang.String env)
                          throws java.io.UnsupportedEncodingException

Overrides the name of the character encoding used in the body of this request. This method must be called prior to reading request parameters or reading input using getReader().

Throws:: java.io.UnsupportedEncodingException - if this is not a valid encoding

getContentLength


public int getContentLength()

Returns the length, in bytes, of the request body and made available by the input stream, or -1 if the length is not known. For HTTP servlets, same as the value of the CGI variable CONTENT_LENGTH.

Returns:: an integer containing the length of the request body or -1 if the length is not known

getContentType


public java.lang.String getContentType()

Returns the MIME type of the body of the request, or null if the type is not known. For HTTP servlets, same as the value of the CGI variable CONTENT_TYPE.

Returns:: a String containing the name of the MIME type of the request, or null if the type is not known

getInputStream


public ServletInputStream getInputStream()
                                  throws java.io.IOException

Retrieves the body of the request as binary data using a ServletInputStream. Either this method or getReader() may be called to read the body, not both.

Returns:: a ServletInputStream object containing the body of the request
Throws:: java.lang.IllegalStateException - if the getReader() method has already been called for this request; java.io.IOException - if an input or output exception occurred

getParameter


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

Returns the value of a request parameter as a String, or null if the parameter does not exist. Request parameters are extra information sent with the request. For HTTP servlets, parameters are contained in the query string or posted form data.

You should only use this method when you are sure the parameter has only one value. If the parameter might have more than one value, use getParameterValues(java.lang.String).

If you use this method with a multivalued parameter, the value returned is equal to the first value in the array returned by getParameterValues.

If the parameter data was sent in the request body, such as occurs with an HTTP POST request, then reading the body directly via getInputStream() or getReader() can interfere with the execution of this method.

Parameters:: name - a String specifying the name of the parameter
Returns:: a String representing the single value of the parameter
See Also:: getParameterValues(java.lang.String)

getParameterNames


public java.util.Enumeration getParameterNames()

Returns an Enumeration of String objects containing the names of the parameters contained in this request. If the request has no parameters, the method returns an empty Enumeration.

Returns:: an Enumeration of String objects, each String containing the name of a request parameter; or an empty Enumeration if the request has no parameters

getParameterValues


public java.lang.String[] getParameterValues(java.lang.String name)

Returns an array of String objects containing all of the values the given request parameter has, or null if the parameter does not exist.

If the parameter has a single value, the array has a length of 1.

Parameters:: name - a String containing the name of the parameter whose value is requested
Returns:: an array of String objects containing the parameter's values
See Also:: getParameter(java.lang.String)

getParameterMap


public java.util.Map getParameterMap()

Returns a java.util.Map of the parameters of this request. Request parameters are extra information sent with the request. For HTTP servlets, parameters are contained in the query string or posted form data.

Returns:: an immutable java.util.Map containing parameter names as keys and parameter values as map values. The keys in the parameter map are of type String. The values in the parameter map are of type String array.

getProtocol


public java.lang.String getProtocol()

Returns the name and version of the protocol the request uses in the form protocol/majorVersion.minorVersion, for example, HTTP/1.1. For HTTP servlets, the value returned is the same as the value of the CGI variable SERVER_PROTOCOL.

Returns:: a String containing the protocol name and version number

getScheme


public java.lang.String getScheme()

Returns the name of the scheme used to make this request, for example, http, https, or ftp. Different schemes have different rules for constructing URLs, as noted in RFC 1738.

Returns:: a String containing the name of the scheme used to make this request

getServerName


public java.lang.String getServerName()

Returns the host name of the server that received the request. For HTTP servlets, same as the value of the CGI variable SERVER_NAME.

Returns:: a String containing the name of the server to which the request was sent

getServerPort


public int getServerPort()

Returns the port number on which this request was received. For HTTP servlets, same as the value of the CGI variable SERVER_PORT.

Returns:: an integer specifying the port number

getReader


public java.io.BufferedReader getReader()
                                 throws java.io.IOException

Retrieves the body of the request as character data using a BufferedReader. The reader translates the character data according to the character encoding used on the body. Either this method or getInputStream() may be called to read the body, not both.

Returns:: a BufferedReader containing the body of the request
Throws:: java.io.UnsupportedEncodingException - if the character set encoding used is not supported and the text cannot be decoded; java.lang.IllegalStateException - if getInputStream() method has been called on this request; java.io.IOException - if an input or output exception occurred
See Also:: getInputStream()

getRemoteAddr


public java.lang.String getRemoteAddr()

Returns the Internet Protocol (IP) address of the client that sent the request. For HTTP servlets, same as the value of the CGI variable REMOTE_ADDR.

Returns:: a String containing the IP address of the client that sent the request

getRemoteHost


public java.lang.String getRemoteHost()

Returns the fully qualified name of the client that sent the request. If the engine cannot or chooses not to resolve the hostname (to improve performance), this method returns the dotted-string form of the IP address. For HTTP servlets, same as the value of the CGI variable REMOTE_HOST.

Returns:: a String containing the fully qualified name of the client

setAttribute


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

Stores an attribute in this request. Attributes are reset between requests. This method is most often used in conjunction with RequestDispatcher.

Attribute names should follow the same conventions as package names. Names beginning with java.*, javax.*, and com.sun.*, are reserved for use by Sun Microsystems.
If the value passed in is null, the effect is the same as calling removeAttribute(java.lang.String).

Parameters:: name - a String specifying the name of the attribute; o - the Object to be stored

removeAttribute


public void removeAttribute(java.lang.String name)

Removes an attribute from this request. This method is not generally needed as attributes only persist as long as the request is being handled.

Attribute names should follow the same conventions as package names. Names beginning with java.*, javax.*, and com.sun.*, are reserved for use by Sun Microsystems.

Parameters:: name - a String specifying the name of the attribute to remove

getLocale


public java.util.Locale getLocale()

Returns the preferred Locale that the client will accept content in, based on the Accept-Language header. If the client request doesn't provide an Accept-Language header, this method returns the default locale for the server.

Returns:: the preferred Locale for the client

getLocales


public java.util.Enumeration getLocales()

Returns an Enumeration of Locale objects indicating, in decreasing order starting with the preferred locale, the locales that are acceptable to the client based on the Accept-Language header. If the client request doesn't provide an Accept-Language header, this method returns an Enumeration containing one Locale, the default locale for the server.

Returns:: an Enumeration of preferred Locale objects for the client

isSecure


public boolean isSecure()

Returns a boolean indicating whether this request was made using a secure channel, such as HTTPS.

Returns:: a boolean indicating if the request was made using a secure channel

getRequestDispatcher


public RequestDispatcher getRequestDispatcher(java.lang.String path)

Returns a 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 specified may be relative, although it cannot extend outside the current servlet context. If the path begins with a "/" it is interpreted as relative to the current context root. This method returns null if the servlet container cannot return a RequestDispatcher.

The difference between this method and ServletContext.getRequestDispatcher(java.lang.String) is that this method can take a relative path.

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:: RequestDispatcher, ServletContext.getRequestDispatcher(java.lang.String)

getRealPath


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

Deprecated. As of Version 2.1 of the Java Servlet API, use ServletContext.getRealPath(java.lang.String) instead.