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Table des matières

Cycle de vie
Création du projet
Exemple 1 - La base
Exemple 2 - Utilisation d'un Bean
Exemple 3 - Formulaire avec Bean global et session
Exemple 4 - context-param et init-param
Exemple 5 - Cookies
Exemple 6 - Affichage d'une liste dans un tableau

Un servlet utilise du code Java dans lequel est mis du code HTML.

<note>Tous les exemples ci-dessous utilisent le BeanPersonne.</note>

Cycle de vie

Création du projet

Nécessite un projet de type Dynamic Web Project. Une fois le projet généré, il faut créer la servlet. Pour cela : File|New|Servlet et choisissez comme Superclass javax.servlet.http.HttpServlet. Si la super classe n'est pas disponible, c'est que le Dynamic Web Project n'a pas été correctement créé. Ensuite cliquez sur Next|Next et demandez à implémenter les méthodes doGet et doPost en fonction des besoins.

La création d'une servlet crée automatiquement un fichier web.xml.

Si un message de type IWAE0035I No servlets exist to add apparait sous Gentoo, il faut suivre les instructions de Gentoo Archive, à savoir :

cd /usr/share/tomcat-8/lib
ln -s /usr/share/eclipse-ecj-4.4/lib/ecj.jar 
ln -s /usr/share/tomcat-servlet-api-3.1/lib/el-api.jar 
ln -s /usr/share/tomcat-servlet-api-3.1/lib/jsp-api.jar 
ln -s /usr/share/tomcat-servlet-api-3.1/
ln -s /usr/share/tomcat-servlet-api-3.1/lib/servlet-api.jar

Exemple 1 - La base

Servlet.java

package com.llgc;
 
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class Servlet
 */
@WebServlet ("/Servlet")
public class Servlet extends HttpServlet
{
  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    response.setCharacterEncoding ("UTF-8");
    PrintWriter out = response.getWriter ();
    response.setContentType ("text/html");
 
    out.println ("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
    out.println ("<html>");
    out.println ("<head>");
    out.println ("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");
    out.println ("<title>Insert title here</title>");
    out.println ("</head>");
    out.println ("<body>");
    out.println ("  <p>");
    if (15 % 2 == 0)
    {
      out.print ("15 est un nombre pair.");
    }
    else
    {
      out.print ("15 est un nombre impair.");
    }
    out.println ("    <br />");
    switch (16 % 2)
    {
      case 0:
        out.print ("16 est un nombre pair.");
        break;
      default:
        out.print ("16 est un nombre impair.");
        break;
    }
    out.println ("  </p>");
    out.println ("</body>");
    out.println ("</html>");
  }
 
  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    doGet (request, response);
  }
}

Rendu :

15 est un nombre impair. 
16 est un nombre pair.

Exemple 2 - Utilisation d'un Bean

Le Bean utilisé est celui d'une personne.

Servlet2.java

package com.llgc;
 
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class Servlet2
 */
@WebServlet ("/Servlet2")
public class Servlet2 extends HttpServlet
{
  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    response.setCharacterEncoding ("UTF-8");
    PrintWriter out = response.getWriter ();
    response.setContentType ("text/html");
 
    out.println ("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
    out.println ("<html>");
    out.println ("<head>");
    out.println ("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");
    out.println ("<title>Insert title here</title>");
    out.println ("</head>");
    out.println ("<body>");
    BeanPersonne perso1 = new BeanPersonne ();
    perso1.setTaille (170);
    perso1.setYeuxBleus (true);
    BeanPersonne perso2 = new BeanPersonne ();
    perso2.setTaille (160);
    perso2.setYeuxBleus (false);
    out.println ("  <p>");
    out.println ("    La personne 1 possède une taille de " + perso1.getTaille () + " cm et");
    if (!perso1.isYeuxBleus ())
    {
      out.print ("n'a pas");
    }
    else
    {
      out.print ("a");
    }
    out.println ("    les yeux bleus.<br />");
    out.println ("    La personne 2 possède une taille de " + perso2.getTaille () + " cm et");
    if (!perso2.isYeuxBleus ())
    {
      out.print ("n'a pas");
    }
    else
    {
      out.print ("a");
    }
    out.println ("    les yeux bleus.");
    out.println ("  </p>");
    out.println ("</body>");
    out.println ("</html>");
  }
 
  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    doGet (request, response);
  }
}

Rendu :

La personne 1 possède une taille de 170 cm et a les yeux bleus.
La personne 2 possède une taille de 160 cm et n'a pas les yeux bleus.

Exemple 3 - Formulaire avec Bean global et session

Servlet3.java

package com.llgc;
 
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
 
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class Servlet3
 */
@WebServlet ("/Servlet3")
public class Servlet3 extends HttpServlet
{
  @Override
  public void init (ServletConfig config) throws ServletException
  {
    BeanPersonne pers = new BeanPersonne ();
 
    pers.setTaille (123);
    config.getServletContext ().setAttribute ("beanApp", pers);
 
    super.init (config);
  }
 
  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    response.setCharacterEncoding ("UTF-8");
    PrintWriter out = response.getWriter ();
    BeanPersonne pers = new BeanPersonne ();
 
    request.getSession (true).setAttribute ("beanSession", pers);
 
    response.setContentType ("text/html");
 
    out.println ("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
    out.println ("<html>");
    out.println ("<head>");
    out.println ("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");
    out.println ("<title>Insert title here</title>");
    out.println ("</head>");
    out.println ("<body>");
    out.println ("  <br />");
    out.println ("  <form method=\"post\" action=\"Servlet3\">");
    out.println ("    Taille : <input name=\"taille\" type=\"text\" /> <input type=\"submit\"");
    out.println ("      value=\"Submit\" />");
    out.println ("  </form>");
    out.println ("</body>");
    out.println ("</html>");
  }
 
  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    response.setCharacterEncoding ("UTF-8");
    PrintWriter out = response.getWriter ();
    BeanPersonne persApp = (BeanPersonne) getServletContext ().getAttribute ("beanApp");
    BeanPersonne persLoc = (BeanPersonne) request.getSession (true).getAttribute ("beanSession");
    persLoc.setTaille (Integer.parseInt (request.getParameter ("taille")));
 
    response.setContentType ("text/html");
 
    out.println ("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
    out.println ("<html>");
    out.println ("<head>");
    out.println ("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");
    out.println ("<title>Insert title here</title>");
    out.println ("</head>");
    out.println ("<body>");
    out.println ("  Valeur par défaut du bean application : " + persApp.getTaille () + ".<br />");
    out.println ("  Valeur saisie du bean local : " + persLoc.getTaille ());
    out.println ("  <br />");
    out.println ("</body>");
    out.println ("</html>");
  }
}

Rendu du formulaire : Rendu de la réponse :

Valeur par défaut du bean application : 123.
Valeur saisie du bean local : 153

Exemple 4 - context-param et init-param

Ajout de 3 context-param.

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns="http://xmlns.jcp.org/xml/ns/javaee"
  xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
  version="3.1">
  <display-name>EL</display-name>
  <servlet>
    <servlet-name>Faces Servlet</servlet-name>
    <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
  </servlet>
  <context-param>
    <param-name>user</param-name>
    <param-value>utilisateur</param-value>
  </context-param>
  <context-param>
    <param-name>password</param-name>
    <param-value>mot de passe</param-value>
  </context-param>
  <context-param>
    <param-name>driver</param-name>
    <param-value>com.mysql.jdbc.Driver</param-value>
  </context-param>
  …
</web-app>

Servlet4.java

package com.llgc;
 
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class Servlet4
 */
@WebServlet (urlPatterns = "/Servlet4", initParams = { @WebInitParam (name = "user2", value = "utilisateurServlet") })
public class Servlet4 extends HttpServlet
{
 
  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    response.setCharacterEncoding ("UTF-8");
    PrintWriter out = response.getWriter ();
    response.setContentType ("text/html");
 
    out.println ("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
    out.println ("<html>");
    out.println ("<head>");
    out.println ("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");
    out.println ("<title>Insert title here</title>");
    out.println ("</head>");
    out.println ("<body>");
    out.println ("  <p>");
    out.println ("nom : " + getServletContext ().getInitParameter ("user") + "<br />");
    out.println ("pass : " + getServletContext ().getInitParameter ("password") + "<br />");
    out.println ("driver : " + getServletContext ().getInitParameter ("driver") + "<br />");
    out.println ("nom2 : " + getInitParameter ("user2"));
    out.println ("  </p>");
    out.println ("</body>");
    out.println ("</html>");
  }
 
  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    doGet (request, response);
  }
}

Rendu :

nom : utilisateur
pass : mot de passe
driver : com.mysql.jdbc.Driver
nom2 : utilisateurServlet

Exemple 5 - Cookies

Servlet5.java

package com.llgc;
 
import java.io.IOException;
import java.io.PrintWriter;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class Servlet5
 */
@WebServlet ("/Servlet5")
public class Servlet5 extends HttpServlet
{
  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    response.setCharacterEncoding ("UTF-8");
    PrintWriter out = response.getWriter ();
    String value = getCookie (request.getCookies (), "compteur");
    response.setContentType ("text/html");
    int compteur = 0;
    out.println ("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
    out.println ("<html>");
    out.println ("<head>");
    out.println ("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");
    out.println ("<title>Insert title here</title>");
    out.println ("</head>");
    out.println ("<body>");
    out.println ("  <p>");
    if (value == null)
    {
      out.println ("Pas de cookie, allez cuisiner !!!");
    }
    else
    {
      compteur = Integer.parseInt (value);
      out.println ("compteur : " + compteur);
    }
    out.println ("  </p>");
    out.println ("</body>");
    out.println ("</html>");
    compteur++;
    Cookie c = new Cookie ("compteur", "" + compteur);
    c.setMaxAge (3600);
    response.addCookie (c);
  }
 
  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
  {
    doGet (request, response);
  }
 
  // Renvoie la valeur d'un cookie.
  protected static String getCookie (Cookie[] cookies, String cookieName)
  {
    if (cookies == null)
    {
      return null;
    }
    for (int i = 0; i < cookies.length; i++)
    {
      if (cookieName.equalsIgnoreCase (cookies[i].getName ()))
      {
        return cookies[i].getValue ();
      }
    }
    return null;
  }
}

Rendu 1 :

Pas de cookie, allez cuisiner !!!

Rendu 2 :

compteur : 1

Exemple 6 - Affichage d'une liste dans un tableau

La liste est générée par une classe Java et affiche un type BeanPersonne.

Liste6.java

package com.llgc;
 
import java.util.LinkedList;
import java.util.List;
 
@ManagedBean
public class Liste6
{
  public static List <BeanPersonne> getListePersonne ()
  {
    LinkedList <BeanPersonne> liste = new LinkedList <> ();
 
    BeanPersonne personne = new BeanPersonne ();
    personne.setTaille (160);
    personne.setYeuxBleus (true);
    liste.add (personne);
 
    personne = new BeanPersonne ();
    personne.setTaille (170);
    personne.setYeuxBleus (true);
    liste.add (personne);
 
    personne = new BeanPersonne ();
    personne.setTaille (180);
    personne.setYeuxBleus (false);
    liste.add (personne);
 
    return liste;
  }
}

Servlet6.java

package com.llgc;
 
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class Servlet6
 */
@WebServlet("/Servlet6")
public class Servlet6 extends HttpServlet {
  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setCharacterEncoding ("UTF-8");
    PrintWriter out = response.getWriter ();
    response.setContentType ("text/html");
 
    List <BeanPersonne> liste = Liste6.getListePersonne ();
 
    out.println ("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">");
    out.println ("<html>");
    out.println ("<head>");
    out.println ("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");
    out.println ("<title>Insert title here</title>");
    out.println ("</head>");
    out.println ("<body>");
    out.println ("  <p>");
    out.println ("    <table border=\"1\">");
    out.println ("      <tr>");
    out.println ("        <td>Taille</td>");
    out.println ("        <td>Yeux bleus</td>");
    out.println ("      </tr>");
 
    for (BeanPersonne beanPersonne : liste)
    {
      out.println ("      <tr>");
      out.println ("        <td>" + beanPersonne.getTaille () + "</td>");
      out.println ("        <td>" + beanPersonne.isYeuxBleus () + "</td>");
      out.println ("      </tr>");
    }
    out.println ("    </table>");
 
    out.println ("  </p>");
    out.println ("</body>");
    out.println ("</html>");
	}
 
	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
 
}

Rendu :