Servlet and JavaServer Pages API Documentation: Interface ServletRequest

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## javax.servlet
Interface ServletRequest

All Known Subinterfaces:
  HttpServletRequest

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.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, or the IP address of the client if the name cannot be determined.
`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.

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

### 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 -1 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)`

### 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 `getReader()` 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, or the IP address of the client if the name cannot be determined. 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.

  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.

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