Get parameter is the method of

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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::. About the Author .::
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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

Arguments	Description
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, 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:VariousSee Also:HttpServletRequest

---

Method Summary
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.

 

Method Detail

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.*.

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

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.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: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.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 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.

Parameters: 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 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

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 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.

Parameters: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.

Parameters: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.

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 RequestDispatcherSee 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.IllegalStateException

Puts 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.IllegalStateException

Puts 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.

Returns:true if this request has been put into asynchronous mode, false otherwiseSince:Servlet 3.0

---

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 3.0

---

getAsyncContext

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.

Returns:the dispatcher type of this requestSince: Servlet 3.0See Also:DispatcherType

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Generated on 10-February-2011 12:41

What is getParameter () method?

What are GET parameters called?

DOES GET method have parameters?

What is a return type of get parameter method?