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ServletConfig Interface
ServletConfig Interface
A servlet configuration object used by a servlet
container to pass information to a servlet
during initialization.
during initialization.
This object can be used to get
configuration information from web.xml file.
If the configuration
information is modified from the web.xml file, we don't need to change the
servlet. So it is easier to manage the web application if any specific content
is modified from time to time.
Advantage of ServletConfig
The core advantage of
ServletConfig is that you don't need to edit the servlet file if information is
modified from the web.xml file.
Method Summary
|
|
java.lang.String |
getInitParameter
(java.lang.String name) Returns a String containing the value of the named initialization parameter,
or null if the parameter does not exist. |
java.util.Enumeration |
getInitParameterNames
() Returns the names of the servlet's initialization parameters as an Enumeration of Stringobjects, or an empty Enumeration if the servlet has no initialization parameters. |
java.lang.String |
|
Method Detail
|
getServletName
java.lang.String getServletName()
Returns the name of this servlet instance. The
name may be provided via server administration, assigned in the web application
deployment descriptor, or for an unregistered (and thus unnamed) servlet
instance it will be the servlet's class name.
Returns:
the name of the servlet instance
getServletContext
ServletContext getServletContext()
Returns a reference to the
ServletContext in which the caller is executing.
Returns:
a
ServletContext object, used by the caller to interact
with its servlet container
See Also:
getInitParameter
java.lang.String getInitParameter(java.lang.String name)
Returns a
String containing the value of the named initialization parameter,
or null if the parameter does not exist.
Parameters:
name - a String specifying the name of
the initialization parameter
Returns:
a
String containing the value of the initialization parameter
getInitParameterNames
java.util.Enumeration getInitParameterNames()
Returns the names of the servlet's initialization
parameters as an
Enumeration of String objects, or an emptyEnumeration if the servlet has no
initialization parameters.
Returns:
an
Enumeration of String objects containing the names of the servlet's initialization
parameters
How to
get the object of ServletConfig
- getServletConfig()
method of Servlet
interface returns the object of ServletConfig.
Syntax of
getServletConfig() method
1. public ServletConfig getServletConfig();
Example of
getServletConfig() method
1. ServletConfig config=getServletConfig();
2. //Now we can call the methods of ServletConfig interface
Syntax
to provide the initialization parameter for a servlet
The init-param sub-element of
servlet is used to specify the initialization parameter for a servlet.
1. <web-app>
2. <servlet>
3. ......
4.
5. <init-param>
6. <param-name>parametername</param-name>
7. <param-value>parametervalue</param-value>
8. </init-param>
9. ......
10. </servlet>
11. </web-app>
Example of
ServletConfig to get initialization parameter
In this example, we are getting
the one initialization parameter from the web.xml file and printing this
information in the servlet.
DemoServlet.java
1. import java.io.*;
2. import javax.servlet.*;
3. import javax.servlet.http.*;
4.
5. public class DemoServlet extends HttpServlet {
6. public void doGet(HttpServletRequest request, HttpServletResponse response)
7. throws ServletException, IOException {
8.
9. response.setContentType("text/html");
10. PrintWriter out = response.getWriter();
11.
12. ServletConfig config=getServletConfig();
13. String driver=config.getInitParameter("driver");
14. out.print("Driver is: "+driver);
15.
16. out.close();
17. }
18.
19. }
web.xml
1. <web-app>
2.
3. <servlet>
4. <servlet-name>DemoServlet</servlet-name>
5. <servlet-class>DemoServlet</servlet-class>
6.
7. <init-param>
8. <param-name>driver</param-name>
9. <param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>
10. </init-param>
11.
12. </servlet>
13.
14. <servlet-mapping>
15. <servlet-name>DemoServlet</servlet-name>
16. <url-pattern>/servlet1</url-pattern>
17. </servlet-mapping>
18.
19. </web-app>
Example of
ServletConfig to get all the initialization parameters
In this example, we are getting
all the initialization parameter from the web.xml file and printing this information
in the servlet.
DemoServlet.java
1. import java.io.IOException;
2. import java.io.PrintWriter;
3. import java.util.Enumeration;
4.
5. import javax.servlet.ServletConfig;
6. import javax.servlet.ServletException;
7. import javax.servlet.http.HttpServlet;
8. import javax.servlet.http.HttpServletRequest;
9. import javax.servlet.http.HttpServletResponse;
10.
11.
12. public class DemoServlet extends HttpServlet {
13. public void doGet(HttpServletRequest request, HttpServletResponse response)
14. throws ServletException, IOException {
15.
16. response.setContentType("text/html");
17. PrintWriter out = response.getWriter();
18.
19. ServletConfig config=getServletConfig();
20. Enumeration<String> e=config.getInitParameterNames();
21.
22. String str="";
23. while(e.hasMoreElements()){
24. str=e.nextElement();
25. out.print("<br>Name: "+str);
26. out.print(" value: "+config.getInitParameter(str));
27. }
28.
29. out.close();
30. }
31.
32. }
web.xml
1. <web-app>
2.
3. <servlet>
4. <servlet-name>DemoServlet</servlet-name>
5. <servlet-class>DemoServlet</servlet-class>
6.
7. <init-param>
8. <param-name>username</param-name>
9. <param-value>system</param-value>
10. </init-param>
11.
12. <init-param>
13. <param-name>password</param-name>
14. <param-value>oracle</param-value>
15. </init-param>
16.
17. </servlet>
18.
19. <servlet-mapping>
20. <servlet-name>DemoServlet</servlet-name>
21. <url-pattern>/servlet1</url-pattern>
22. </servlet-mapping>
23.
24. </web-app>
SendRedirect in servlet
SendRedirect in servlet
- sendRedirect method
- Syntax of sendRedirect()
method
- Example of
RequestDispatcher interface
The sendRedirect() method of HttpServletResponseinterface
can be used to redirect response to another resource, it may be servlet, jsp or
html file.
It accepts relative as well as
absolute URL.
It works at client side because
it uses the url bar of the browser to make another request. So, it can work
inside and outside the server.
Difference between forward() and sendRedirect() method
There are many differences
between the forward() method of RequestDispatcher and sendRedirect() method of
HttpServletResponse interface. They are given below:
|
forward()
method
|
sendRedirect()
method
|
|
The
forward() method works at server side.
|
The
sendRedirect() method works at client side.
|
|
It
sends the same request and response objects to another servlet.
|
It
always sends a new request.
|
|
It
can work within the server only.
|
It
can be used within and outside the server.
|
|
Example:
request.getRequestDispacher("servlet2").forward(request,response);
|
Example:
response.sendRedirect("servlet2");
|
Syntax of sendRedirect() method
1. public void sendRedirect(String URL)throws IOException;
Example of sendRedirect() method
1. response.sendRedirect("http://www.google.com");
Full
example of sendRedirect method in servlet
|
In
this example, we are redirecting the request to the google server. Notice
that sendRedirect method works at client side, that is why we can our request
to anywhere. We can send our request within and outside the server.
|
DemoServlet.java
1. import java.io.*;
2. import javax.servlet.*;
3. import javax.servlet.http.*;
4.
5. public class DemoServlet extends HttpServlet{
6. public void doGet(HttpServletRequest req,HttpServletResponse res)
7. throws ServletException,IOException
8. {
9. res.setContentType("text/html");
10. PrintWriter pw=res.getWriter();
11.
12. response.sendRedirect("http://www.google.com");
13.
14. pw.close();
15. }}
Creating
custom google search using sendRedirect
In this example, we are using
sendRedirect method to send request to google server with the request data.
index.html
1. <!DOCTYPE html>
2. <html>
3. <head>
4. <meta charset="ISO-8859-1">
5. <title>sendRedirect example</title>
6. </head>
7. <body>
8.
9.
10. <form action="MySearcher">
11. <input type="text" name="name">
12. <input type="submit" value="Google Search">
13. </form>
14.
15. </body>
16. </html>
MySearcher.java
1. import java.io.IOException;
2. import javax.servlet.ServletException;
3. import javax.servlet.http.HttpServlet;
4. import javax.servlet.http.HttpServletRequest;
5. import javax.servlet.http.HttpServletResponse;
6.
7. public class MySearcher extends HttpServlet {
8. protected void doGet(HttpServletRequest request, HttpServletResponse response)
9. throws ServletException, IOException {
10.
11. String name=request.getParameter("name");
12. response.sendRedirect("https://www.google.co.in/#q="+name);
13. }
14. }
Output
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