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LES FILTRES EN JAVA (javax.servlet.filter)

Created with colorer-take5 library. Type 'xml'

<filter>
        <filter-name>Path Mapped Filter</filter-name>
        <filter-class>filters.ExampleFilter</filter-class>

    <init-param>
        <param-name>attribute</param-name>
        <param-value>filters.ExampleFilter.PATH_MAPPED</param-value>

    </init-param>
    </filter>

Created with colorer-take5 library. Type 'xml'

 <!-- Define filter mappings for the defined filters -->

<filter-mapping>
        <filter-name>Path Mapped Filter</filter-name>
    <url-pattern>/servlet/*</url-pattern>

    </filter-mapping>

Created with colorer-take5 library. Type 'xml'

 <init-param>
        <param-name>attribute</param-name>
        <param-value>filters.ExampleFilter.SERVLET_MAPPED</param-value>

    </init-param>

Created with colorer-take5 library. Type 'java'

/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0

*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package filters;


import java.io.IOException;
import javax.servlet.Filter;

import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;


/**
* Example filter that can be attached to either an individual servlet
* or to a URL pattern. This filter performs the following functions:
* <ul>

* <li>Attaches itself as a request attribute, under the attribute name
* defined by the value of the <code>attribute</code> initialization

* parameter.</li>
* <li>Calculates the number of milliseconds required to perform the
* servlet processing required by this request, including any

* subsequently defined filters, and logs the result to the servlet
* context log for this application.
* </ul>
*

* @author Craig McClanahan
* @version $Revision: 267129 $ $Date: 2004-03-18 11:40:35 -0500 (Thu, 18 Mar 2004) $

*/

public final class ExampleFilter implements Filter {


// ----------------------------------------------------- Instance Variables


/**
* The request attribute name under which we store a reference to ourself.
*/
private String attribute = null;


/**
* The filter configuration object we are associated with. If this value
* is null, this filter instance is not currently configured.
*/

private FilterConfig filterConfig = null;


// --------------------------------------------------------- Public Methods


/**
* Take this filter out of service.

*/
public void destroy() {

this.attribute = null;

this.filterConfig = null;

}


/**
* Time the processing that is performed by all subsequent filters in the

* current filter stack, including the ultimately invoked servlet.
*
* @param request The servlet request we are processing
* @param result The servlet response we are creating

* @param chain The filter chain we are processing
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet error occurs

*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)

throws IOException, ServletException {

// Store ourselves as a request attribute (if requested)
if (attribute != null)

request.setAttribute(attribute, this);

// Time and log the subsequent processing
long startTime = System.currentTimeMillis();

chain.doFilter(request, response);
long stopTime = System.currentTimeMillis();

filterConfig.getServletContext().log
(this.toString() + ": " + (stopTime - startTime) +

" milliseconds");

}


/**
* Place this filter into service.
*

* @param filterConfig The filter configuration object
*/
public void init(FilterConfig filterConfig) throws ServletException {

this.filterConfig = filterConfig;
this.attribute = filterConfig.getInitParameter("attribute");

}


/**
* Return a String representation of this object.
*/
public String toString() {

if (filterConfig == null)
return ("InvokerFilter()");

StringBuffer sb = new StringBuffer("InvokerFilter(");
sb.append(filterConfig);

sb.append(")");
return (sb.toString());

}

}

Created with colorer-take5 library. Type 'java'

/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0

*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet;

import java.io.IOException;

    /** 
    * A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both.

        * <br><br>
    * Filters perform filtering in the <code>doFilter</code> method. Every Filter has access to 
    ** a FilterConfig object from which it can obtain its initialization parameters, a

    ** reference to the ServletContext which it can use, for example, to load resources
    ** needed for filtering tasks.

    ** <p>
    ** Filters are configured in the deployment descriptor of a web application
    ** <p>

    ** Examples that have been identified for this design are<br>
    ** 1) Authentication Filters <br>
    ** 2) Logging and Auditing Filters <br>

    ** 3) Image conversion Filters <br>
        ** 4) Data compression Filters <br>
    ** 5) Encryption Filters <br>

    ** 6) Tokenizing Filters <br>
    ** 7) Filters that trigger resource access events <br>
    ** 8) XSL/T filters <br>

    ** 9) Mime-type chain Filter <br>
     * @since    Servlet 2.3

    */

public interface Filter {

    /** 
    * Called by the web container to indicate to a filter that it is being placed into

    * service. The servlet container calls the init method exactly once after instantiating the
    * filter. The init method must complete successfully before the filter is asked to do any
    * filtering work. <br><br>


         * The web container cannot place the filter into service if the init method either<br>
        * 1.Throws a ServletException <br>
        * 2.Does not return within a time period defined by the web container 

    */
    public void init(FilterConfig filterConfig) throws ServletException;

    
    
    /**
    * The <code>doFilter</code> method of the Filter is called by the container
    * each time a request/response pair is passed through the chain due

    * to a client request for a resource at the end of the chain. The FilterChain passed in to this
    * method allows the Filter to pass on the request and response to the next entity in the
    * chain.<p>
    * A typical implementation of this method would follow the following pattern:- <br>

    * 1. Examine the request<br>
    * 2. Optionally wrap the request object with a custom implementation to
    * filter content or headers for input filtering <br>

    * 3. Optionally wrap the response object with a custom implementation to
    * filter content or headers for output filtering <br>
    * 4. a) <strong>Either</strong> invoke the next entity in the chain using the FilterChain object (<code>chain.doFilter()</code>), <br>   

    ** 4. b) <strong>or</strong> not pass on the request/response pair to the next entity in the filter chain to block the request processing<br>
    ** 5. Directly set headers on the response after invocation of the next entity in the filter chain.

    **/
    public void doFilter ( ServletRequest request, ServletResponse response, FilterChain chain ) throws IOException, ServletException;

    /**
    * Called by the web container to indicate to a filter that it is being taken out of service. This 
    * method is only called once all threads within the filter's doFilter method have exited or after
    * a timeout period has passed. After the web container calls this method, it will not call the

    * doFilter method again on this instance of the filter. <br><br>
    * 
         * This method gives the filter an opportunity to clean up any resources that are being held (for
    * example, memory, file handles, threads) and make sure that any persistent state is synchronized

    * with the filter's current state in memory.
    */

    public void destroy();


}

Created with colorer-take5 library. Type 'java'

public void init(FilterConfig filterConfig) throws ServletException {

    this.filterConfig = filterConfig;

        this.attribute = filterConfig.getInitParameter("attribute");

    }

Created with colorer-take5 library. Type 'java'

public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
    throws IOException, ServletException {

    // Store ourselves as a request attribute (if requested)
    if (attribute != null)

        request.setAttribute(attribute, this);

    // Time and log the subsequent processing
    long startTime = System.currentTimeMillis();

        chain.doFilter(request, response);
    long stopTime = System.currentTimeMillis();

    filterConfig.getServletContext().log
        (this.toString() + ": " + (stopTime - startTime) +

         " milliseconds");

    }

B) Cas d’un filtre qui modifie la réponse

Created with colorer-take5 library. Type 'java'

public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
    throws IOException, ServletException {

    
    PrintWriter out = response.getWriter();

    
    CharResponseWrapper wrapper = new CharResponseWrapper(
               (HttpServletResponse)response);

    chain.doFilter(request, wrapper);    
    
    String strAvant = wrapper.toString();

    String strApres = avant.replace("bonjour", "good morning");

    
    out.write(strApres);
    out.close();

    
}

Created with colorer-take5 library. Type 'java'

import java.io.CharArrayWriter;
import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

public class CharResponseWrapper extends
HttpServletResponseWrapper {
private CharArrayWriter output;

public String toString() {
return output.toString();

}

public CharResponseWrapper(HttpServletResponse response){
super(response);

           output = new CharArrayWriter();
}

public PrintWriter getWriter(){

           return new PrintWriter(output);
}
}