API java : ServletRequest

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.

Author:

Various

See Also:

HttpServletRequest

Method Summary
Object	getAttribute(String name)           Returns the value of the named attribute as an Object, or null if no attribute of the given name exists.
Enumeration	getAttributeNames()           Returns an Enumeration containing the names of the attributes available to this request.
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.
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.
String	getLocalAddr()           Returns the Internet Protocol (IP) address of the interface on which the request was received.
Locale	getLocale()           Returns the preferred Locale that the client will accept content in, based on the Accept-Language header.
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.
String	getLocalName()           Returns the host name of the Internet Protocol (IP) interface on which the request was received.
int	getLocalPort()           Returns the Internet Protocol (IP) port number of the interface on which the request was received.
String	getParameter(String name)           Returns the value of a request parameter as a String, or null if the parameter does not exist.
Map	getParameterMap()           Returns a java.util.Map of the parameters of this request.
Enumeration	getParameterNames()           Returns an Enumeration of String objects containing the names of the parameters contained in this request.
String[]	getParameterValues(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.
String	getProtocol()           Returns the name and version of the protocol the request uses in the form protocol/majorVersion.minorVersion, for example, HTTP/1.1.
BufferedReader	getReader()           Retrieves the body of the request as character data using a BufferedReader.
String	getRealPath(String path)           Deprecated. As of Version 2.1 of the Java Servlet API, use ServletContext.getRealPath(java.lang.String) instead.
String	getRemoteAddr()           Returns the Internet Protocol (IP) address of the client or last proxy that sent the request.
String	getRemoteHost()           Returns the fully qualified name of the client or the last proxy that sent the request.
int	getRemotePort()           Returns the Internet Protocol (IP) source port of the client or last proxy that sent the request.
RequestDispatcher	getRequestDispatcher(String path)           Returns a RequestDispatcher object that acts as a wrapper for the resource located at the given path.
String	getScheme()           Returns the name of the scheme used to make this request, for example, http, https, or ftp.
String	getServerName()           Returns the host name of the server to which the request was sent.
int	getServerPort()           Returns the port number to which the request was sent.
boolean	isSecure()           Returns a boolean indicating whether this request was made using a secure channel, such as HTTPS.
void	removeAttribute(String name)           Removes an attribute from this request.
void	setAttribute(String name, Object o)           Stores an attribute in this request.
void	setCharacterEncoding(String env)           Overrides the name of the character encoding used in the body of this request.

 

Method Detail

getAttribute

Object getAttribute(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

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

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 character encoding, or null if the request does not specify a character encoding

setCharacterEncoding

void setCharacterEncoding(String env)
                          throws 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(). Otherwise, it has no effect.

Parameters:

env - String containing the name of the character encoding.

Throws:

UnsupportedEncodingException - if this ServletRequest is still in a state where a character encoding may be set, but the specified encoding is invalid

getContentLength

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

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

ServletInputStream getInputStream()
                                  throws 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:

IllegalStateException - if the getReader() method has already been called for this request

IOException - if an input or output exception occurred

getParameter

String getParameter(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

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

String[] getParameterValues(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

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

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

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

String getServerName()

Returns the host name of the server to which the request was sent. It is the value of the part before ":" in the Host header value, if any, or the resolved server name, or the server IP address.

Returns:

a String containing the name of the server

getServerPort

int getServerPort()

Returns the port number to which the request was sent. It is the value of the part after ":" in the Host header value, if any, or the server port where the client connection was accepted on.

Returns:

an integer specifying the port number

getReader

BufferedReader getReader()
                         throws 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:

UnsupportedEncodingException - if the character set encoding used is not supported and the text cannot be decoded

IllegalStateException - if getInputStream() method has been called on this request

IOException - if an input or output exception occurred

See Also:

getInputStream()

getRemoteAddr

String getRemoteAddr()

Returns the Internet Protocol (IP) address of the client or last proxy 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

String getRemoteHost()

Returns the fully qualified name of the client or the last proxy 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

void setAttribute(String name,
                  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 object passed in is null, the effect is the same as calling removeAttribute(java.lang.String).
It is warned that when the request is dispatched from the servlet resides in a different web application by RequestDispatcher, the object set by this method may not be correctly retrieved in the caller servlet.

Parameters:

name - a String specifying the name of the attribute

o - the Object to be stored

removeAttribute

void removeAttribute(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

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

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

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

RequestDispatcher getRequestDispatcher(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. If it is relative, it must be relative against the current servlet.

Returns:

a RequestDispatcher object that acts as a wrapper for the resource at the specified path, or null if the servlet container cannot return a RequestDispatcher

See Also:

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

getRealPath

String getRealPath(String path)

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

getRemotePort

int getRemotePort()

Returns the Internet Protocol (IP) source port of the client or last proxy that sent the request.

Returns:

an integer specifying the port number

Since:

2.4

getLocalName

String getLocalName()

Returns the host name of the Internet Protocol (IP) interface on which the request was received.

Returns:

a String containing the host name of the IP on which the request was received.

Since:

2.4

getLocalAddr

String getLocalAddr()

Returns the Internet Protocol (IP) address of the interface on which the request was received.

Returns:

a String containing the IP address on which the request was received.

Since:

2.4

getLocalPort

int getLocalPort()

Returns the Internet Protocol (IP) port number of the interface on which the request was received.

Returns:

an integer specifying the port number

Since:

2.4