Servlet Filter Response Pre Post

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package com.cv.servlet.filter.response;

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

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

import org.apache.log4j.Logger;

/**
 * Servlet Filter implementation class CharResponseWrapper
 
 @author Chandra Vardhan
 
 */
public class CharResponseWrapper extends HttpServletResponseWrapper {
  private static final Logger LOGGER = Logger
      .getLogger(CharResponseWrapper.class);

  private CharArrayWriter output;

  public String toString() {
    LOGGER.info("LOGGER : CharResponseWrapper toString()");
    return output.toString();
  }

  public CharResponseWrapper(HttpServletResponse response) {
    super(response);
    output = new CharArrayWriter();
    LOGGER.info("LOGGER : CharResponseWrapper CharResponseWrapper(HttpServletResponse)");
  }

  public PrintWriter getWriter() {
    LOGGER.info("LOGGER : CharResponseWrapper getWriter()");
  
    return new PrintWriter(output);
    
  }
}


 

    
package com.cv.servlet.filter.response;

import java.io.IOException;
import java.io.OutputStream;

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;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

/**
 * Servlet Filter implementation class PrePostFilter
 
 @author Chandra Vardhan
 
 */

public class PrePostFilter implements Filter {

  private static final Logger LOGGER = Logger
      .getLogger(PrePostFilter.class);

  private ServletContext context;

  public void init(FilterConfig fConfigthrows ServletException {
    LOGGER.info("init ... ResponseChangeFilter");
    this.context = fConfig.getServletContext();
    this.context.log("ResponseChangeFilter initialized");
  }

  public void doFilter(ServletRequest request, ServletResponse response,
      FilterChain chainthrows IOException, ServletException {
    LOGGER.info("doFilter ... ResponseChangeFilter BEFORE filter");
    OutputStream out = response.getOutputStream();
    out.write("<HR>PRE<HR>".getBytes());
    CharResponseWrapper wrapper = new CharResponseWrapper(
        (HttpServletResponseresponse);
    chain.doFilter(request, wrapper);
    out.write(wrapper.toString().getBytes());
    out.write("<HR>POST<HR>".getBytes());
    out.close();
  }

  public void destroy() {
    // we can close resources here
    LOGGER.info("destroy ... RequestParameterChangeFilter");
  }

}


 

    
package com.cv.servlet.filter.response;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

/**
 * Servlet Filter implementation class TestServlet
 
 @author Chandra Vardhan
 
 */
public class TestServlet extends HttpServlet {

  private static final Logger LOGGER = Logger
      .getLogger(PrePostFilter.class);

  private static final long serialVersionUID = 1L;

  /**
   @see HttpServlet#HttpServlet()
   */
  public TestServlet() {
    super();
  }

  /**
   @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doGet(HttpServletRequest request,
      HttpServletResponse responsethrows ServletException, IOException {
    LOGGER.info("LOGGER : TestServlet doGet(HttpServletRequest,HttpServletResponse)");
    LOGGER.info("LOGGER : Provided output Test chandra vardhan kodam");
    response.getWriter().print("Test chandra vardhan kodam");

  }

  /**
   @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
   *      response)
   */
  protected void doPost(HttpServletRequest request,
      HttpServletResponse responsethrows ServletException, IOException {
    LOGGER.info("LOGGER : TestServlet doPost(HttpServletRequest ,HttpServletResponse )");
    doGet(request, response);
  }

}



<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<br>
<br>
<a href="TestServlet">Click here to get response...</a>
</body>
</html>



#By default enabling Console appender
# Root logger option
log4j.rootLogger=INFO, stdout

# Redirect log messages to console
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%-5p [%c]:%L -->> %m%n

# Redirect log messages to a log file
#log4j.appender.file=org.apache.log4j.RollingFileAppender
#log4j.appender.file.File=C:\\servlet-application.log
#log4j.appender.file.MaxFileSize=5MB
#log4j.appender.file.MaxBackupIndex=10
#log4j.appender.file.layout=org.apache.log4j.PatternLayout
#log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n




<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <artifactId>ServletFilterResponsePrePost</artifactId> <version>1.0</version> <packaging>war</packaging> <properties> <log4j.version>1.2.16</log4j.version> <java.version>1.8</java.version> </properties> <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.3</version> <configuration> <source>${java.version}</source> <target>${java.version}</target> </configuration> </plugin> <plugin> <artifactId>maven-war-plugin</artifactId> <version>2.6</version> <configuration> <warSourceDirectory>WebContent</warSourceDirectory> <failOnMissingWebXml>false</failOnMissingWebXml> </configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>3.0-alpha-1</version> </dependency> <dependency> <groupId>commons-fileupload</groupId> <artifactId>commons-fileupload</artifactId> <version>1.3.1</version> </dependency> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>${log4j.version}</version> </dependency> <dependency> <groupId>javax.servlet.jsp</groupId> <artifactId>jsp-api</artifactId> <version>2.0</version> </dependency> <dependency> <groupId>jstl</groupId> <artifactId>jstl</artifactId> <version>1.2</version> </dependency> <dependency> <groupId>taglibs</groupId> <artifactId>standard</artifactId> <version>1.1.2</version> </dependency> </dependencies> <groupId>com.cv.servlet.filter.response</groupId> </project>




 
<?xml version="1.0" encoding="UTF-8"?> 
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> <servlet> <servlet-name>TestServlet</servlet-name> <servlet-class>com.cv.servlet.filter.response.TestServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>TestServlet</servlet-name> <url-pattern>/TestServlet</url-pattern> </servlet-mapping> <filter> <filter-name>PrePostFilter</filter-name> <filter-class>com.cv.servlet.filter.response.PrePostFilter</filter-class> </filter> <filter-mapping> <filter-name>PrePostFilter</filter-name> <url-pattern>/TestServlet</url-pattern> </filter-mapping> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> </web-app>


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