Let us see how to use request.getParameter[] method in the servlet class, to retrieve the input values from HTML page. Friends it is base concept on retrieving the input data, so observe very carefully, also this is the first example we are seeing on retrieving the values form the input pages.
Hmmm let us calculate sum of two numbers [ by taking these numbers from the input HTML page ]
Directory Structure
Files Required
- index.html
- OngetParameter.java
- web.xml
index.html
Number1:
Number2:
OngetParameter.java
package java4s; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class OngetParameter extends HttpServlet { protected void doPost[HttpServletRequest req,HttpServletResponse res]throws ServletException,IOException { PrintWriter pw=res.getWriter[]; res.setContentType["text/html"]; String n1=req.getParameter["n1"]; String n2=req.getParameter["n2"]; int result=Integer.parseInt[n1]+Integer.parseInt[n2]; pw.println["Sum of two numbers " +result]; pw.close[]; } }
web.xml
sumOfTwoNumbers java4s.OngetParameter sumOfTwoNumbers /sum index.html
Explanation:
- Once we run the application, browser will display index.html as front page. Because we have given index.html in welcome file list [ line number 14 in web.xml ]
- Enter input values and press ‘Calculate Sum‘ button
- Now come to OngetParameter.java > just retrieve the input values like req.getParameter[“n1”] & req.getParameter[“n2”]
- getParameter[] is the method in request object, which returns String value always
- So convert that string output to Integer [ line number 21]
- Integer.parseInt[-String-] gives integer value
- Output
Output
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Applies To
OParameterCollection
Description
This method returns a specified OParameter object.
Usage
OParameter GetParameter[int index] const
OParameter GetParameter[const char *pname] const
index | An index from 0 to OParameterCollection.GetCount[]-1. |
pname | The name of the parameter, as stated when the parameter was created with Add. |
Remarks
OParameter objects are obtained either by name or index from an OParameterCollection object. The OParameterCollection object is obtained from an ODatabase with the GetParameters method.
Return Value
An OParameter object which will be open on success, closed on failure.
Example
This example checks the status of the "deptno" parameter.
// we have an open ODatabase named odb
OParameterCollection params = odb.GetParameters[];
OParameter pdeptno = params.GetParameter["deptno"];
pstatus = pdeptno.GetStatus[];
javax.servlet
Interface ServletRequest
All Known Subinterfaces:HttpServletRequestAll Known Implementing Classes:HttpServletRequestWrapper,
ServletRequestWrapperpublic 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
.
HttpServletRequest
AsyncContext
| getAsyncContext[] Gets the AsyncContext that was created or reinitialized by the most recent invocation of startAsync[] or startAsync[ServletRequest,ServletResponse] on this request.
|
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.
|
DispatcherType
| getDispatcherType[] Gets the dispatcher type of this request. |
ServletInputStream
| getInputStream[] Retrieves the body of the request as binary data using a ServletInputStream .
|
java.lang.String
| getLocalAddr[] Returns the Internet Protocol [IP] address of the interface on which the request was received. |
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
| 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. |
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 instead.
|
java.lang.String
| getRemoteAddr[] Returns the Internet Protocol [IP] address of the client or last proxy that sent the request. |
java.lang.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[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 to which the request was sent. |
int
| getServerPort[] Returns the port number to which the request was sent. |
ServletContext
| getServletContext[] Gets the servlet context to which this ServletRequest was last dispatched. |
boolean
| isAsyncStarted[] Checks if this request has been put into asynchronous mode. |
boolean
| isAsyncSupported[] Checks if this request supports asynchronous operation. |
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. |
AsyncContext
| startAsync[] Puts this request into asynchronous mode, and initializes its AsyncContext with the original [unwrapped] ServletRequest and ServletResponse objects.
|
AsyncContext
| startAsync[ServletRequest servletRequest,
ServletResponse servletResponse] Puts this request into asynchronous mode, and initializes its AsyncContext with the given request and response objects.
|
getAttribute
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 ServletRequest#setAttribute
. 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.*
.
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
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
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 character encoding, or null
if the request does not specify a character encoding
setCharacterEncoding
void setCharacterEncoding[java.lang.String env] throws java.io.UnsupportedEncodingExceptionOverrides 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:java.io.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
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
ServletInputStream getInputStream[] throws java.io.IOExceptionRetrieves 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 java.io.IOException
- if an input or output exception occurred getParameter
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.
name
- a String
specifying the name of the parameter Returns:a String
representing the single value of the parameterSee Also:getParameterValues[java.lang.String]
getParameterNames
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
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 valuesSee Also:getParameter[java.lang.String]
getParameterMap
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
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
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
java.lang.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 servergetServerPort
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
java.io.BufferedReader getReader[] throws java.io.IOExceptionRetrieves 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 IllegalStateException
- if
getInputStream[]
method has been called on this request java.io.IOException
- if an input or output exception occurredSee Also:getInputStream[]
getRemoteAddr
java.lang.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
java.lang.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[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 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.
name
- a String
specifying the name of the attributeo
- the Object
to be stored removeAttribute
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.
name
- a String
specifying the name of the attribute to remove getLocale
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
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
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[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
is that this method can take a relative path.
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
getRealPath
java.lang.String getRealPath[java.lang.String path]Deprecated. As of Version 2.1 of the Java Servlet API, use
ServletContext#getRealPath
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 numberSince:Servlet 2.4
getLocalName
java.lang.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:Servlet 2.4 getLocalAddr
java.lang.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:Servlet 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 numberSince:Servlet 2.4
getServletContext
ServletContext getServletContext[]Gets the servlet context to which this ServletRequest was last dispatched. Returns: the servlet context to which this ServletRequest was last dispatchedSince:Servlet 3.0
startAsync
AsyncContext startAsync[] throws java.lang.IllegalStateExceptionPuts this request into asynchronous mode, and initializes its
AsyncContext
with the original [unwrapped] ServletRequest and ServletResponse objects. Calling this method will cause committal of the associated response to be delayed until AsyncContext#complete
is called on the returned AsyncContext
, or
the asynchronous operation has timed out.
Calling AsyncContext#hasOriginalRequestAndResponse[]
on the returned AsyncContext will return true
. Any filters invoked in the outbound direction after this request was put into asynchronous mode may use this as an indication that any request and/or response wrappers that they added during their inbound invocation need not stay around for the duration of the asynchronous operation, and therefore any of their associated resources may be released.
This method
clears the list of AsyncListener
instances [if any] that were registered with the AsyncContext returned by the previous call to one of the startAsync methods, after calling each AsyncListener at its onStartAsync
method.
Subsequent invocations of this method, or its overloaded variant, will return the same AsyncContext instance, reinitialized as appropriate.
Returns:the [re]initialized AsyncContext Throws:IllegalStateException
- if this request is
within the scope of a filter or servlet that does not support asynchronous operations [that is, isAsyncSupported[]
returns false], or if this method is called again without any asynchronous dispatch [resulting from one of the AsyncContext#dispatch
methods], is called outside the scope of any such dispatch, or is called again within the scope of the same dispatch, or if the response has already been
closedSince:Servlet 3.0 startAsync
AsyncContext startAsync[ServletRequest servletRequest, ServletResponse servletResponse] throws java.lang.IllegalStateExceptionPuts this request into asynchronous mode, and initializes its
AsyncContext
with the given request and response objects. The ServletRequest and ServletResponse arguments must be the same instances, or instances of ServletRequestWrapper
and ServletResponseWrapper
that wrap them, that were passed to the service
method of the
Servlet or the doFilter
method of the Filter, respectively, in whose scope this method is being called.
Calling this method will cause committal of the associated response to be delayed until AsyncContext#complete
is called on the returned AsyncContext
, or the asynchronous operation has timed out.
Calling AsyncContext#hasOriginalRequestAndResponse[]
on the returned AsyncContext will return false
, unless the passed in ServletRequest and ServletResponse arguments are the original ones or do not carry any application-provided
wrappers. Any filters invoked in the outbound direction after this request was put into asynchronous mode may use this as an indication that some of the request and/or response wrappers that they added during their inbound invocation may need to stay in place for the duration of the asynchronous operation, and their associated resources may not be released. A ServletRequestWrapper applied during the inbound invocation of a filter may be released by the outbound
invocation of the filter only if the given servletRequest
, which is used to initialize the AsyncContext and will be returned by a call to AsyncContext#getRequest[]
, does not contain said ServletRequestWrapper. The same holds true for ServletResponseWrapper instances.
This method clears the list of AsyncListener
instances [if any] that were registered with the AsyncContext returned by the previous call to one of the startAsync methods, after calling each AsyncListener at its onStartAsync
method.
Subsequent invocations of this method, or its zero-argument variant, will return the same AsyncContext instance, reinitialized as appropriate. If a call to this method is followed by a call to its zero-argument variant, the specified [and possibly wrapped] request and response objects will remain locked in on the returned AsyncContext.
Parameters:servletRequest
- the ServletRequest used to initialize the AsyncContextservletResponse
- the ServletResponse used to
initialize the AsyncContext Returns:the [re]initialized AsyncContext Throws:IllegalStateException
- if this request is within the scope of a filter or servlet that does not support asynchronous operations [that is, isAsyncSupported[]
returns false], or if this method is called again without any asynchronous dispatch [resulting from one of the AsyncContext#dispatch
methods], is called outside the scope of any such dispatch, or is called again within the scope of the same dispatch, or if the response has already been closedSince:Servlet 3.0 isAsyncStarted
boolean isAsyncStarted[]Checks if this request has been put into asynchronous mode.
A ServletRequest is put into asynchronous mode by calling
startAsync[]
or startAsync[ServletRequest,ServletResponse]
on it.
This method returns false if this request was put into asynchronous mode, but has since been dispatched using one of the AsyncContext#dispatch
methods or released from asynchronous
mode via a call to AsyncContext#complete
.
isAsyncSupported
boolean isAsyncSupported[]Checks if this request supports asynchronous operation.
Asynchronous operation is disabled for this request if this request is within the scope of a filter or servlet that has not been annotated or flagged in the deployment descriptor as being able to support asynchronous handling.
Returns:true if this request supports asynchronous operation, false otherwiseSince:Servlet 3.0getAsyncContext
AsyncContext getAsyncContext[]Gets the AsyncContext that was created or reinitialized by the most recent invocation of
startAsync[]
or startAsync[ServletRequest,ServletResponse]
on this request. Returns:the AsyncContext that was created or reinitialized by the most recent invocation of
startAsync[]
or startAsync[ServletRequest,ServletResponse]
on this request Throws:IllegalStateException
- if this request has not been put into asynchronous mode, i.e., if neither
startAsync[]
nor startAsync[ServletRequest,ServletResponse]
has been calledSince:Servlet 3.0 getDispatcherType
DispatcherType getDispatcherType[]Gets the dispatcher type of this request.
The dispatcher type of a request is used by the container to select the filters that need to be applied to the request: Only filters with matching dispatcher type and url patterns will be applied.
Allowing a filter that has been configured for multiple dispatcher types to query a request for its dispatcher type allows the filter to process the request differently depending on its dispatcher type.
The initial dispatcher type of a request is defined as
DispatcherType.REQUEST
. The dispatcher type of a request dispatched via RequestDispatcher#forward[ServletRequest,
ServletResponse]
or RequestDispatcher#include[ServletRequest,
ServletResponse]
is given as DispatcherType.FORWARD
or DispatcherType.INCLUDE
, respectively, while the dispatcher type of an asynchronous request dispatched via one of the AsyncContext#dispatch
methods is given as DispatcherType.ASYNC
. Finally, the dispatcher type of a request dispatched to an error page by the container's error handling mechanism is given as DispatcherType.ERROR
.
DispatcherType
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