“Web Enabled Commercial Application Development Using HTML, DHTML, PERL, Java Script” Download
Monthly Archives: April 2013
Create a servlet filter that logs all access to and from servlets in an application and prints the following to System.out: a. the time the request was received b. the time the response was sent c. how much time it took to process the request d. the URL of the resource requested e. the IP address of the visitor
ex22.java
import java.io.*;
import java.util.*;
import javax.servlet.http.*;
import javax.servlet.*;
import java.util.*;
public class ex22 implements Filter
{
ServletContext context;
public void doFilter(ServletRequest req,ServletResponse res,FilterChain chain) throws IOException,ServletException
{
HttpServletRequest request=(HttpServletRequest)req;
PrintWriter out=res.getWriter();
Date myreqdate=new Date();
System.out.println("request received on "+myreqdate);
// Note the start time.
long startTime = System.currentTimeMillis();
String mylog=new String(request.getRemoteHost()+"tried to access"+request.getRequestURL()+"on Time"+new Date());
context.log(mylog);
chain.doFilter(req,res);
//Note the end time.
long endTime = System.currentTimeMillis();
Date myresdate=new Date();
context.log("Response receive on"+myresdate);
long diff =endTime-startTime;
context.log("Start time : " + startTime);
context.log("End time: " + endTime);
context.log("Time take to process the request is "+diff);
}
public void init(FilterConfig confy)
{
context=confy.getServletContext();
}
public void destroy()
{
}
}
Apply these filter to servlet file.
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class FilterEx extends HttpServlet
{
public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
{
PrintWriter out = res.getWriter();
res.setContentType("text/html");
out.println("Testing");
try
{
Thread.sleep(1000);
}
catch(Exception e)
{
out.println(e);
}
}
}
web.xml
<servlet>
<servlet-name>FilterEx</servlet-name>
<servlet-class>FilterEx</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FilterEx</servlet-name>
<url-pattern>/FilterEx</url-pattern>
</servlet-mapping>
<filter>
<filter-name>ex22</filter-name>
<filter-class>ex22</filter-class>
</filter>
<filter-mapping>
<filter-name>ex22</filter-name>
<servlet-name>FilterEx</servlet-name>
</filter-mapping>
Write a code in JDBC where a maximum limit of database connections has been reached?
Use DatabaseMetaData.getMaxConnections() and compare to the number of connections currently open. Note that a return value of zero can mean unlimited
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
public class Main {
private static final String DRIVER = "com.mysql.jdbc.Driver";
private static final String URL = "jdbc:mysql://localhost/yourDatabase";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
public static void main(String[] args) throws Exception {
Class.forName(DRIVER);
Connection connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
DatabaseMetaData metadata = connection.getMetaData();
int maxConnection = metadata.getMaxConnections();
System.out.println("Maximum Connection = " + maxConnection);
connection.close();
}
}
JDBC Transaction
JDBCTransaction.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
public class JDBCTransaction extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
Connection connection = null;
Statement statement = null;
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
connection=DriverManager.getConnection("jdbc:odbc:studentora","scott","tiger");
//Here we set auto commit to false so no changes will take
//effect immediately.
connection.setAutoCommit(false);
statement = connection.createStatement();
//Execute the queries
statement.executeUpdate("UPDATE stud SET name='abc' WHERE rollno = 2");
//No changes has been made in the database yet, so now we will commit
//the changes.
connection.commit();
}
catch (ClassNotFoundException ex)
{
ex.printStackTrace();
}
catch (SQLException ex)
{
ex.printStackTrace();
try
{
//An error occured so we rollback the changes.
connection.rollback();
}
catch (SQLException ex1)
{
ex1.printStackTrace();
}
}
finally
{
try
{
if (statement != null)
statement.close();
if (connection != null)
connection.close();
}
catch (SQLException ex)
{
ex.printStackTrace();
}
}
}
}
Pass the initialization parameter to JSP Page
web.xml
<servlet>
<servlet-name>InitPage</servlet-name>
<jsp-file>/InitPage.jsp</jsp-file>
<init-param>
<param-name>firstName</param-name>
<param-value>abc</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>InitPage</servlet-name>
<url-pattern>/InitPage</url-pattern>
</servlet-mapping>
InitPage.jsp
<HTML>
<HEAD><TITLE>JSP Init Test</TITLE></HEAD>
<BODY BGCOLOR="#FDF5E6">
<H2>Init Parameters:</H2>
<UL>
<LI>First name: <%= firstName %>
</UL>
</BODY></HTML>
<%!
private String firstName = "First name is missing.";
public void jspInit()
{
ServletConfig config = getServletConfig();
if (config.getInitParameter("firstName") != null)
{
firstName = config.getInitParameter("firstName");
}
}
%>
Example of callablestatement with function
To create the function follow these syntax:
create or replace function incr(rln IN number) RETURN number is
begin
update stud set name=’mno’ where rollno=rln;
return ( SQL%ROWCOUNT);
END incr;
callablestatement3.java
import java.sql.*;
class callablestatement3
{
public static void main(String args[])
{
Connection con;
CallableStatement cs;
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:studentora","scott","tiger");
cs=con.prepareCall("{?=call incr(?)}");
cs.registerOutParameter(1,Types.INTEGER);
cs.setInt(2,1);
cs.execute();
System.out.println("Rows : "+cs.getInt(1));
con.close();
}
catch(ClassNotFoundException e)
{
System.out.println(e);
}
catch(SQLException e)
{
System.out.println(e);
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Example of Callable Statement with input and output parameter
//procedure with input and output parameter
create or replace procedure test(roll IN number,nm OUT varchar) as
begin
select name into nm from stud where rollno=roll;
end;
/
callablestatement1.java
import java.sql.*;
class callablestatement1
{
public static void main(String args[])
{
Connection con;
CallableStatement cs;
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:studentora","scott","tiger");
cs=con.prepareCall("{call test(?,?)}");
cs.registerOutParameter(2,Types.VARCHAR);
cs.setInt(1,1);
cs.execute();
String nm=cs.getString(2);
System.out.println("Name="+nm);
con.close();
}
catch(ClassNotFoundException e)
{
System.out.println(e);
}
catch(SQLException e)
{
System.out.println(e);
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Example of Callable Statement
To Run following example follow the stpes.
Step 1: create a DSN
(Control Panel -> Administrative Tools -> Data Sources (ODBC) -> Add User DSN -> provide the name of DSN, username and server name (For example : DSN NAME : studora, username: scott , server name : localhost) )
Step 2: create a procedure named remove like these
create table stud (rollno number,name varchar2(15),city varchar2(25));
insert into stud values(1,’abc’,’rajkot’);
create or replace procedure remove (name1 varchar2) as
begin
delete from stud where name=name1;
end;
/
//To execute the procedure from sql prompt :
execute remove(‘abc’);
step 3 :
import java.sql.*;
class callablestatement
{
public static void main(String args[])
{
Connection con;
CallableStatement cs;
try
{
//with DSN
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
// provide the username and password
con=DriverManager.getConnection("jdbc:odbc:studentora","scott","tiger");
cs=con.prepareCall("{call remove(?)}");
cs.setString(1,"abc");
cs.executeUpdate();
System.out.println("Record deleted");
cs.close();
con.commit();
con.close();
}
catch(Exception e)
{
System.out.println(e);
}
}
}
Web Technology & Application Development – 2640002 