Servlet and JSP

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Servlet and JSP
C. Edward Chow
Related references Head First Servlets
JSPhttp//tomcat.apache.org/tomcat-5.5-doc/index.
htmlJavaServer Pages (JSP) Specfication, Version
2.0 Servlet API Specification, Version 2.4 Java
Tutorial Book on JDBC J2EE tutorial on
Servlet J2EE tutorial on JSP J2EE tutorial on
Java Standard Tag Library
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Servlet

• A servlet is a JavaTM technology-based Web
  component, managed by a container, that generates
  dynamic content. --- Servlet API Specification,
  Version 2.4
• The servlet container is a part of a Web server
  or application server that provides the network
  services over which requests and responses are
  sent, decodes MIME-based requests, and formats
  MIME-based responses. A servlet container also
  contains and manages servlets through their
  lifecycle

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Web App Processing with Servlet
URL
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Web App Processing with Servlet
Apache forwards HTTP request to Tomcat Using AJP
protocol
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Web App Processing with Servlet
Tomcat uses the mapping info in a configuration
file called web.xml of the web application to
find the right servlet
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Web App Processing with Servlet
Tomcat uses the mapping info in a configuration
file called web.xml of the web application to
find the right servlet
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Web App Processing with Servlet
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Web App Processing with Servlet
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What Container Provides?

• Communication Support (to web server no socket
  code)
• Lifecycle Management of Servlet(loading
  instantiating initializing invoking garbage
  collection fault tolerance)
• Multithread Support(create threat for each
  servlet request)
• Declarative Security(use XML deployment
  descriptor to configure/modify security without
  having to hard-code it into servlet code)
• JSP Support(translating that JSP code into real
  java)

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What a Simple Servlet looks Like?

• import javax.servlet.
• import javax.servlet.http.
• import java.io.
• public class SimpleServlet extends HttpServlet
• public void doGet (HttpServletRequest request,
  HttpServletResponse response) throws IOException
  
• PrintWriter out response.getWriter()
• java.util.Date today new
  java.util.Date()
• out.println("lthtmlgtltbodygtlth1gtThis is a
  simple web page generated by SimpleServlet with
  date info.lt/h1gtltbrgtToday is "today"lt/bodygtlt/html
  gt")

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What a Servlet Code looks Like?

• package com.example.web
• import com.example.model.
• import javax.servlet.
• import javax.servlet.http.
• import java.io.
• import java.util.
• public class BeerSelect extends HttpServlet
• public void doPost (HttpServletRequest
  request,
• HttpServletResponse
  response)
• throws IOException, ServletException
• String c request.getParameter("color")
• BeerExpert be new BeerExpert()
• List result be.getBrands(c)
• request.setAttribute("styles", result)
• RequestDispatcher view
• request.getRequestDispatcher("result.jsp")
  
• view.forward(request, response)

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How Does Container Find Right Servlet?

• Using the Deployment Descriptor web.xml
• ltweb-app xmlns"http//java.sun.com/xml/ns/j2ee"
  xmlnsxsi"http//www.w3.org/2001/XMLSchema-instan
  ce" xsischemaLocation"http//java.sun.com/xml/ns
  /j2ee http//java.sun.com/xml/ns/j2ee/web-app_2_4.
  xsd" version"2.4"gt
• ltservletgt
•   ltservlet-namegt CS301 Simple Servletlt/servlet-nam
  egt
•   ltservlet-classgt SimpleServletlt/servlet-classgt
•   lt/servletgt
• ltservlet-mappinggt
•   ltservlet-namegt CS301 Simple Servletlt/servlet-nam
  egt
•   lturl-patterngt /s1lt/url-patterngt
• lt/servlet-mappinggt
• lt/web-appgt
• This mapping improves flexibility and security.
  How?

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A Simple Web Application Following
Model-View-Controller Design Pattern
Servlet
Controllere.g. BeerSelect.java
Class Beer //Business//Logic
ltJSP gt
Model e.g., BeerExpert.java
Viewe.g. result.jsp
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File Structure in A Java Web Development
Environment
ltwebappgt Web.xml lt/webappgt
ltresult.jsp gt
BeerExpert.java
BeerSelect.java
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File Structure in a Java Web Deployment
Environment
ltwebappgt Web.xml lt/webappgt
Form.html
ltresult.jsp gt
BeerExpert.java
BeerSelect.java
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Java-base Web Application Development Environment
Setup

• We will use the tomcat 5.5.12 java-based web
  container and share jdk1.5.0_03 in
  cs301/public_html/java
• cp r cs301/public_html/tomcatChow
  ltlogingt/public_html
• It contains examples with
• The above MVC Beer-v1 web application
• Servlet with JDBC using mysql
• JSP pages using SQL tags provided by JavaServer
  Page Standard Tag Library (JSTL).
• Set up Environment Variable for JAVA_HOME and
  CATALINA_HOME
• Setup server.xml with your own tomcat port number
  and mysql Datasource info.
• Setup tomcat-users.xml with user and admin
  passwords

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JDK Environment Setup

• For CSH user, (check echo SHELL) edit your
  .cshrc file with the following
• setenv JAVA_HOME /users/server/students/cs301/publ
  ic_html/java/jdk1.5.0_03
• setenv path /users/server/students/cs301/public_h
  tml/java/jdk1.5.0_03/binPATH
• setenv CATALINA_HOME /users/server/students/ltlogin
  gt/public_html/tomcatChow
• For BASH user, (check echo SHELL) edit
  .bash_profile
• PATH/users/server/students/cs301/public_html/java
  /jdk1.5.0_03/binPATHHOME/bin
• JAVA_HOME/users/server/students/cs301/public_html
  /java/jdk1.5.0_03
• CATALINA_HOME/users/server/students/ltlogingt/publi
  c_html/tomcatChow
• export PATH JAVA_HOME CATALINA_HOME
• Once this is setup you can use CATALINA_HOME in
  shell commands, e.g., cd CATALINA_HOME to get
  to your own tomcat directory.

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Setup Server Ports in server.xml

• Edit the server.xml in CATALINA_HOME/conf
  directory
• Change the port number so that we can all run
  tomcat on CS Unix machines.
• Spread out using windom or your designated server
  machine as php exercises. Make sure you shutdown
  server after you exercise run
  CATALINA_HOME/bin/shutdown.sh
• Find the lines with the following content
• lt!-- Define a non-SSL HTTP/1.1 Connector on port
  8080 --gt
• ltConnector port"8080" maxHttpHeaderSize"8192
  "
• maxThreads"150" minSpareThreads"25"
  maxSpareThreads"75"
• enableLookups"false"
  redirectPort"8443" acceptCount"100"
• connectionTimeout"20000"
  disableUploadTimeout"true" /gt
• Replace port 8080 with 9ltlast 3 digits of your
  SIDgt in ltConnectorgt element.
• Find ltServer port"8005" shutdown"SHUTDOWN"gt
• Replace port 8005 with 7ltlast 3 digits of your
  SIDgt in ltServergt element.

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Setup Database Resource in Server.xml

• To share the Database connections among web
  application, we add the following ltContextgt and
  ltResourcegt tags to server.xml before lt/hostgt
• ltContext path"/sql" docBase"sql"
• debug"5" reloadable"true"
  crossContext"true"gt
• ltResource name"jdbc/InventoryDB"
  auth"Container"
• type"javax.sql.DataSource"
• maxActive"100" maxIdle"30" maxWait"10000"
• username"cs301" passwordXXXXXXXX"
• driverClassName"com.mysql.jdbc.Driver"
• url"jdbcmysql//blanca.uccs.edu3306
  /cs301db?autoReconnecttrue"/gt
• lt/Contextgt

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Basic Commands for compilation and Start/Shutdown
Tomcat

• Javac classpath CATALINA_HOME/common/lib/servlet
  -api.jarclasses. d classes src/com/example/web/
  BeerSelect.java-d specifies that compiled
  classes should be put in the classes directory.
  Here CATALINA_HOME is an environment variable
  with full path to the install directory of
  tomcat.
• Often we use ant (or asant for Sun App Server)
  utility or IDE such as NetBeans/IBM RSA to
  facilitate the compilation and deployment web
  applications. They contain the basic compilation
  commands as above.
• Here are the commands for shutdown/start tomcat.
  We often needs to do that after creating a new
  classes or DD.Some application servers
  automatically scan new files and redeploy
• cd CATALINA_HOME
• bin/shutdown.sh
• bin/startup.sh

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Servlet with JDBC demo

• import java.sql.
• import javax.sql.
• public class InventoryDBServlet extends
  HttpServlet
• Driver D
• Connection con
• Statement stmtPrintWriter out
  response.getWriter()
• try
• Class.forName("org.gjt.mm.mysql.Driver").new
  Instance()
• catch(java.lang.ClassNotFoundException e)
  
• System.err.print("ClassNotFoundException
  e.getMessage())
• String url"jdbcmysql//blanca.uccs.edu3306/"da
  tabase"?user"user"password"passwd
• con DriverManager.getConnection(url)
• stmt con.createStatement()
• String sqlcmd "select from inventory"
• ResultSet rs stmt.executeQuery(sqlcmd)
• while (rs.next())
• StringBuffer itemName new
  StringBuffer(rs.getString(1))
• StringBuffer amount new
  StringBuffer(rs.getString(2))

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JSP with JSTL SQL Tag Demo

• lt_at_ taglib prefix"c" uri"http//java.sun.com/jsp
  /jstl/core" gt
• lt_at_ taglib uri"http//java.sun.com/jsp/jstl/sql"
  prefix"sql" gt
• ltsqlquery var"rs" dataSource"jdbc/InventoryDB"gt
  select price.item, price.unitPrice,
  inventory.amount from price, inventory where
  price.item inventory.item
• lt/sqlquerygt
• lthtmlgt ltheadgt lttitlegtDBcataloglt/titlegt lt/headgt
  ltbodygt
• lth2gtDB Catalog Retrieval Resultslt/h2gt
• lttable border1gt lttr bgcolor"EEDDCC"gtltthgtitemlt/
  thgtltthgtunitPricelt/thgtltthgtamountlt/thgtlt/trgt ltcset
  var"counter" value"1" /gt ltcforEach
  var"row" items"rs.rows"gt ltcchoosegt
  ltcwhen test"counter mod 2 0"gt lttr
  bgcolor"99EEFF"gt lt/cwhengt
  ltcotherwisegt lttr bgcolor"99FFAA"gt
  lt/cotherwisegt lt/cchoosegt lttd
  aligncentergtrow.itemlt/tdgt lttd
  alignrightgtrow.unitPricelt/tdgt lttd
  alignrightgtrow.amountlt/tdgt lt/trgt ltcset
  var"counter" value"counter1" /gt
  lt/cforEachgt
• lt/tablegt lt/bodygt lt/htmlgt

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JSP with SQLUPDATE Parameter Access

• Demo http//windom.uccs.edu9888/sql/passwd.jsp
• Source
• lt_at_ taglib prefix"c" uri"http//java.sun.com/jsp
  /jstl/core" gt
• lt_at_ taglib uri"http//java.sun.com/jsp/jstl/sql"
  prefix"sql" gt
• lt!-- cset tag need to terminate with /gt --gt
• ltcset var"login" value"param.login" /gt
• ltcset var"password" value"param.password"
  /gt
• ltcif test"!empty login and !empty password"gt
• ltsqlupdate var"result" dataSource"jdbc/Inv
  entoryDB"
• sql"insert into password values (?, ?)"
  gt
• ltsqlparam value"login" /gt
• ltsqlparam value"password" /gt
• lt/sqlupdategt
• lt/cifgt
• Note that we really do not need to set
  login/password variable. Just use directly in
  ltsqlparam value"param.login" /gt and in
  ltcifgt