What is the difference between a **Servlet** and **Filter**? What do you recommend to use for authorization to pages?

Servlet vs Filter

I&#39;ve created a filter to in my java webserver (appengine actually) that logs the parameters of an incoming request. I&#39;d also like to log the resulting response that my webserver writes. Although I have access to the response object, I&#39;m not sure how to get the actual string/content response out of it.

Any ideas?

How to read and copy the HTTP servlet response output stream content for logging

I&#39;m trying to find a method to redirect my request from a filter to the login page but I don&#39;t know how to redirect from servlet. I&#39;ve searched but what I find is `sendRedirect()` method. I can&#39;t find this method on my response object in the filter. What&#39;s the cause? How can I solve this?

How to redirect in a servlet filter?

I would like to block the access of some page even if the user knows the url of some pages.
For example, `/localhost:8080/user/home.xhtml` (need to do the login first) if not logged then redirect to `/index.xhtml`.

How do that in JSF ? I read in the Google that&#39;s needed a filter, but I don&#39;t know how to do that.


How implement a login filter in JSF?

Is there any annotation for a `Filter` class (for web applications) in Spring Boot? Perhaps `@Filter`?

I want to add a custom filter in my project.

[The Spring Boot Reference Guide][0] mentioned about
`FilterRegistrationBean`, but I am not sure how to use it.

  [0]: http://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/



How can I add a filter class in Spring Boot?

How can I use a servlet filter to change an incoming servlet request url from

`http://nm-java.appspot.com/Check_License/Dir_My_App/Dir_ABC/My_Obj_123`

to

`http://nm-java.appspot.com/Check_License?Contact_Id=My_Obj_123`

?

---

**Update**: according to BalusC&#39;s steps below, I came up with the following code:

    public class UrlRewriteFilter implements Filter {

        @Override
        public void init(FilterConfig config) throws ServletException {
            //
        }

        @Override
        public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws ServletException, IOException {
            HttpServletRequest request = (HttpServletRequest) req;
            String requestURI = request.getRequestURI();

            if (requestURI.startsWith(&quot;/Check_License/Dir_My_App/&quot;)) {
                String toReplace = requestURI.substring(requestURI.indexOf(&quot;/Dir_My_App&quot;), requestURI.lastIndexOf(&quot;/&quot;) + 1);
                String newURI = requestURI.replace(toReplace, &quot;?Contact_Id=&quot;);
                req.getRequestDispatcher(newURI).forward(req, res);
            } else {
                chain.doFilter(req, res);
            }
        }

        @Override
        public void destroy() {
            //
        }
    }


The relevant entry in `web.xml` look like this:

&lt;!-- language: xml --&gt;

    &lt;filter&gt;
        &lt;filter-name&gt;urlRewriteFilter&lt;/filter-name&gt;
        &lt;filter-class&gt;com.example.UrlRewriteFilter&lt;/filter-class&gt;
    &lt;/filter&gt;
    &lt;filter-mapping&gt;
        &lt;filter-name&gt;urlRewriteFilter&lt;/filter-name&gt;
        &lt;url-pattern&gt;/*&lt;/url-pattern&gt;
    &lt;/filter-mapping&gt;

I tried both server-side and client-side redirect with the expected results. It worked, thanks BalusC!

How to use a servlet filter in Java to change an incoming servlet request url?

If we define webapp specific servlet filters in WAR&#39;s own `web.xml`, then the order of execution of the filters will be the same as the order in which they are defined in the `web.xml`.

But, if we define those filters using `@WebFilter` annotation, what is the order of execution of filters, and how can we determine the order of execution?

How to define servlet filter order of execution using annotations in WAR

I want some concrete filter to be applied for all urls except for one concrete (i.e. for `/*` except for `/specialpath`).

Is there a possibility to do that?

---
sample code:

&lt;!-- language: xml --&gt;

    &lt;filter&gt;
        &lt;filter-name&gt;SomeFilter&lt;/filter-name&gt;
        &lt;filter-class&gt;org.somproject.AFilter&lt;/filter-class&gt;
    &lt;/filter&gt;
    &lt;filter-mapping&gt;
        &lt;filter-name&gt;SomeFilter&lt;/filter-name&gt;
        &lt;url-pattern&gt;/*&lt;/url-pattern&gt;   &lt;!-- the question is: how to modify this line?  --&gt;
        &lt;dispatcher&gt;REQUEST&lt;/dispatcher&gt;
        &lt;dispatcher&gt;FORWARD&lt;/dispatcher&gt;
    &lt;/filter-mapping&gt;

Can I exclude some concrete urls from &lt;url-pattern&gt; inside &lt;filter-mapping&gt;?

An existing web application is running on Tomcat 4.1.  There is an XSS issue with a page, but I can&#39;t modify the source.  I&#39;ve decided to write a servlet filter to sanitize the parameter before it is seen by the page.

I would like to write a Filter class like this:

    import java.io.*;
    import javax.servlet.*;
    
    public final class XssFilter implements Filter {
    
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
          throws IOException, ServletException
      {
        String badValue = request.getParameter(&quot;dangerousParamName&quot;);
        String goodValue = sanitize(badValue);
        request.setParameter(&quot;dangerousParamName&quot;, goodValue);
        chain.doFilter(request, response);
      }
    
      public void destroy() {
      }
    
      public void init(FilterConfig filterConfig) {
      }
    }

But `ServletRequest.setParameter` doesn&#39;t exist.

How can I change the value of the request parameter before passing the request down the chain?

Modify request parameter with servlet filter

I&#39;m trying to accessing two http request parameters in a Java Servlet filter, nothing new here, but was surprised to find that the parameters have already been consumed! Because of this, it is not available anymore in the filter chain.

It seems that this only occurs when the parameters comes in a POST request body (a form submit, for example).

Is there a way to read the parameters and NOT consume them?

So far I&#39;ve found only this reference: [Servlet Filter using request.getParameter loses Form data](http://restlet-discuss.1400322.n2.nabble.com/Servlet-Filter-using-request-getParameter-loses-Form-data-td2141035.html).

Thanks!

Http Servlet request lose params from POST body after read it once

I am trying to write a filter that can retrieve the request URL, but I&#39;m not sure how to do so.

Here is what I have so far:

    import javax.servlet.*;
    import javax.servlet.http.HttpServletRequest;
    import java.io.IOException;
    
    public class MyFilter implements Filter {
    	public void init(FilterConfig config) throws ServletException {	}
    
    	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
    		chain.doFilter(request, response);

    		String url = ((HttpServletRequest) request).getPathTranslated();
    		System.out.println(&quot;Url: &quot; + url);
    	}
    
    	public void destroy() {	}
    }

When I hit a page on my server, the only output I see is &quot;Url: null&quot;.

What is the correct way to get the requested URL from a given ServletRequest object in a Filter?

How can I get the request URL from a Java Filter?

I am using a Servlet Filter in my JSF application.  I have three groups of Web pages in my application, and I want to check Authentication for these pages in my Servlet Filter:

my Folders

&lt;!-- language: none --&gt;

    /Admin/ *.xhtml

    /Supervisor/*.xhtml
    /Employee/*.xhtml


and I am writing `web.xml` like

      
&lt;!-- language: lang-xml --&gt;

    &lt;filter&gt;
        &lt;filter-name&gt;LoginFilter&lt;/filter-name&gt;
        &lt;filter-class&gt;com.ems.admin.servlet.LoginFilter&lt;/filter-class&gt;
    &lt;/filter&gt;

    &lt;filter-mapping&gt;
        &lt;filter-name&gt;LoginFilter&lt;/filter-name&gt;
        &lt;url-pattern&gt;/Employee/*&lt;/url-pattern&gt;
    &lt;/filter-mapping&gt;
    &lt;filter-mapping&gt;
        &lt;filter-name&gt;LoginFilter&lt;/filter-name&gt;
        &lt;url-pattern&gt;/Admin/*&lt;/url-pattern&gt;
    &lt;/filter-mapping&gt;
    &lt;filter-mapping&gt;
        &lt;filter-name&gt;LoginFilter&lt;/filter-name&gt;
        &lt;url-pattern&gt;/Supervisor/*&lt;/url-pattern&gt;
    &lt;/filter-mapping&gt;


but requests like

&lt;!-- language: none --&gt;

    http://localhost:8080/EMS2/faces/Html/Admin/Upload.xhtml

are not entering into Filter.

I have to provide security to these 3 folders.

How to solve this problem ?






Giving multiple URL patterns to Servlet Filter

Here is how my `WebFilter` looks like  

    @WebFilter(&quot;/rest/*&quot;)
    public class AuthTokenValidatorFilter implements Filter {
    
    	@Override
    	public void init(final FilterConfig filterConfig) throws ServletException {
    	}
    
    	@Override
    	public void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, final FilterChain filterChain) throws IOException, ServletException {
    		final Enumeration&lt;String&gt; attributeNames = servletRequest.getAttributeNames();
    		while (attributeNames.hasMoreElements()) {
    			System.out.println(&quot;{attribute} &quot; + servletRequest.getParameter(attributeNames.nextElement()));
    		}
    
    		final Enumeration&lt;String&gt; parameterNames = servletRequest.getParameterNames();
    		while (parameterNames.hasMoreElements()) {
    			System.out.println(&quot;{parameter} &quot; + servletRequest.getParameter(parameterNames.nextElement()));
    		}
    		filterChain.doFilter(servletRequest, servletResponse);
    	}
    
    	@Override
    	public void destroy() {
    	}
    }

I tried to find out online as to how to get values for `HTTP headers` coming from request.  

I did not find anything, so I tried to enumerate on `servletRequest.getAttributeNames()` and `servletRequest.getParameterNames()` without knowing anything, but I do not get any headers.

**Question**  
How can I get all the headers coming from the request?

Servlet Filter: How to get all the headers from servletRequest?

There are Filters and Listeners functionality in Servlet. I want to know exact difference between Filter and Listener.

Difference between Filter and Listener in Servlet (Java EE)

[HandlerInterceptor][1]s in Spring can now be configured to be invoked only on certain URLs using `&lt;mvc:interceptors&gt;`.

Servlet Filters can achieve same functionality (logging, security etc). So which one should be used?

I think with Interceptors, one can use `ModelAndView` object to work with Models so it has more advantages. Can anyone draw out scenarios where Filters or Interceptors have advantages over the other?


  [1]: http://static.springsource.org/spring/docs/current/javadoc-api/org/springframework/web/servlet/HandlerInterceptor.html

Spring HandlerInterceptor vs Servlet Filters

I was trying to implement a login filter in my web app with jsf 2, following this guide:

https://stackoverflow.com/tags/servlet-filters/info

after I compiled my filter and added the .class in &quot;web-inf/classes&quot; (as the guide says) the filter worked, but i put the  wrong url to redirect to the login page so i deleted the filter.class from the folder (web-inf/classes) and tried to compile the project again , but it failed, and since then im getting &quot;package javax.servlet does not exist&quot;

it is weird because before it was working and i have javax.servlet in my pom.xml.. i tried cleaning the project, but nothing.

this is my filter class:

    package Bean;
    
    import java.io.IOException;
    
    import javax.servlet.Filter;
    import javax.servlet.FilterChain;
    import javax.servlet.FilterConfig;
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.annotation.WebFilter;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    /**
     * Created with IntelliJ IDEA.
     * User: rodrigo
     * Date: 28-04-13
     * Time: 06:54 AM
     * To change this template use File | Settings | File Templates.
     */
    @WebFilter(&quot;/Contenido/*&quot;)
    public class filtro implements Filter {
    
        @Override
        public void init(FilterConfig config) throws ServletException {
            // If you have any &lt;init-param&gt; in web.xml, then you could get them
            // here by config.getInitParameter(&quot;name&quot;) and assign it as field.
        }
    
        @Override
        public void doFilter(ServletRequest request, ServletResponse response,
                FilterChain chain) throws ServletException, IOException {
            HttpServletRequest req = (HttpServletRequest) request;
            LoginBean user = (LoginBean) req.getSession().getAttribute(&quot;user&quot;);
    
            if (user != null &amp;&amp; user.isLoggedIn()) {
                // User is logged in, so just continue request.
                chain.doFilter(request, response);
            } else {
                // User is not logged in, so redirect to index.
                HttpServletResponse res = (HttpServletResponse) response;
                res.sendRedirect(req.getContextPath() + &quot;/Contenido/Login.xhtml&quot;);
            }
        }
    
        @Override
        public void destroy() {
            // If you have assigned any expensive resources as field of
            // this Filter class, then you could clean/close them here.
        }
    }

this is the error:

 

    \Users\rodrigo\IdeaProjects\Frutemu\src\main\java\Bean\filtro.java:[5,20] error: package javax.servlet does not exist
    [ERROR] \Users\rodrigo\IdeaProjects\Frutemu\src\main\java\Bean\filtro.java:[6,20] error: package javax.servlet does not exist
    [ERROR] \Users\rodrigo\IdeaProjects\Frutemu\src\main\java\Bean\filtro.java:[7,20] error: package javax.servlet does not exist
    [ERROR] \Users\rodrigo\IdeaProjects\Frutemu\src\main\java\Bean\filtro.java:[8,20] error: package javax.servlet does not exist
    [ERROR] \Users\rodrigo\IdeaProjects\Frutemu\src\main\java\Bean\filtro.java:[9,20] error: package javax.servlet does not exist
    [ERROR] \Users\rodrigo\IdeaProjects\Frutemu\src\main\java\Bean\filtro.java:[10,20] error: package javax.servlet does not exist
    [ERROR] \Users\rodrigo\IdeaProjects\Frutemu\src\main\java\Bean\filtro.java:[11,31] error: package javax.servlet.annotation does not exist

my pom.xml:

	
	&lt;project xmlns=&quot;http://maven.apache.org/POM/4.0.0&quot; xmlns:xsi=&quot;http://www.w3.org/2001/XMLSchema-instance&quot;
		xsi:schemaLocation=&quot;http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd&quot;&gt;
		&lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
		&lt;groupId&gt;Frutemu&lt;/groupId&gt;
		&lt;artifactId&gt;Frutemu&lt;/artifactId&gt;
		&lt;packaging&gt;war&lt;/packaging&gt;
		&lt;version&gt;1.0-SNAPSHOT&lt;/version&gt;
		&lt;name&gt;Frutemu Maven Webapp&lt;/name&gt;
		&lt;url&gt;http://maven.apache.org&lt;/url&gt;
		&lt;repositories&gt;
			&lt;repository&gt;
				&lt;id&gt;prime-repo&lt;/id&gt;
				&lt;name&gt;Prime Repo&lt;/name&gt;
				&lt;url&gt;http://repository.primefaces.org&lt;/url&gt;
			&lt;/repository&gt;
		&lt;/repositories&gt;
		&lt;dependencies&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;junit&lt;/groupId&gt;
				&lt;artifactId&gt;junit&lt;/artifactId&gt;
				&lt;version&gt;3.8.1&lt;/version&gt;
				&lt;scope&gt;test&lt;/scope&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;javax.ejb&lt;/groupId&gt;
				&lt;artifactId&gt;ejb-api&lt;/artifactId&gt;
				&lt;version&gt;3.0&lt;/version&gt;
				&lt;scope&gt;provided&lt;/scope&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;org.primefaces&lt;/groupId&gt;
				&lt;artifactId&gt;primefaces&lt;/artifactId&gt;
				&lt;version&gt;3.5&lt;/version&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;org.primefaces.themes&lt;/groupId&gt;
				&lt;artifactId&gt;all-themes&lt;/artifactId&gt;
				&lt;version&gt;1.0.9&lt;/version&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;javax.faces&lt;/groupId&gt;
				&lt;artifactId&gt;jsf-api&lt;/artifactId&gt;
				&lt;version&gt;2.0&lt;/version&gt;
				&lt;scope&gt;compile&lt;/scope&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;com.sun.faces&lt;/groupId&gt;
				&lt;artifactId&gt;jsf-impl&lt;/artifactId&gt;
				&lt;version&gt;2.0.2-b10&lt;/version&gt;
				&lt;scope&gt;compile&lt;/scope&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;javax.servlet&lt;/groupId&gt;
				&lt;artifactId&gt;jstl&lt;/artifactId&gt;
				&lt;version&gt;1.2&lt;/version&gt;
			&lt;/dependency&gt;
			&lt;!-- MySQL database driver --&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;mysql&lt;/groupId&gt;
				&lt;artifactId&gt;mysql-connector-java&lt;/artifactId&gt;
				&lt;version&gt;5.1.21&lt;/version&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;org.glassfish.web&lt;/groupId&gt;
				&lt;artifactId&gt;el-impl&lt;/artifactId&gt;
				&lt;version&gt;2.2.1-b04&lt;/version&gt;
				&lt;scope&gt;provided&lt;/scope&gt;
			&lt;/dependency&gt;
			&lt;!-- OpenJPA framework --&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;org.apache.openjpa&lt;/groupId&gt;
				&lt;artifactId&gt;openjpa-all&lt;/artifactId&gt;
				&lt;version&gt;2.2.0&lt;/version&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;com.microsoft.sqlserver&lt;/groupId&gt;
				&lt;artifactId&gt;sqljdbc4&lt;/artifactId&gt;
				&lt;version&gt;4.0&lt;/version&gt;
			&lt;/dependency&gt;
			&lt;dependency&gt;
				&lt;groupId&gt;net.sf.jasperreports&lt;/groupId&gt;
				&lt;artifactId&gt;jasperreports&lt;/artifactId&gt;
				&lt;version&gt;4.1.2&lt;/version&gt;
			&lt;/dependency&gt;
		&lt;/dependencies&gt;
		&lt;build&gt;
			&lt;finalName&gt;Frutemu&lt;/finalName&gt;
			&lt;plugins&gt;
				&lt;!-- Open Jpa --&gt;
				&lt;plugin&gt;
					&lt;groupId&gt;org.apache.openjpa&lt;/groupId&gt;
					&lt;artifactId&gt;openjpa-maven-plugin&lt;/artifactId&gt;
					&lt;version&gt;2.2.0&lt;/version&gt;
					&lt;configuration&gt;
						&lt;includes&gt;**/model/*.class&lt;/includes&gt;
						&lt;addDefaultConstructor&gt;true&lt;/addDefaultConstructor&gt;
						&lt;enforcePropertyRestrictions&gt;true&lt;/enforcePropertyRestrictions&gt;
					&lt;/configuration&gt;
					&lt;executions&gt;
						&lt;execution&gt;
							&lt;id&gt;enhancer&lt;/id&gt;
							&lt;phase&gt;process-classes&lt;/phase&gt;
							&lt;goals&gt;
								&lt;goal&gt;enhance&lt;/goal&gt;
							&lt;/goals&gt;
						&lt;/execution&gt;
					&lt;/executions&gt;
				&lt;/plugin&gt;
				&lt;!-- Plugin para levantar una instancia de Tomcat 7 liviana, &#250;nica para este proyecto --&gt;
				&lt;plugin&gt;
					&lt;groupId&gt;org.apache.tomcat.maven&lt;/groupId&gt;
					&lt;artifactId&gt;tomcat7-maven-plugin&lt;/artifactId&gt;
					&lt;version&gt;2.0&lt;/version&gt;
					&lt;configuration&gt;
						&lt;url&gt;http://127.0.0.1:8080/manager/text&lt;/url&gt;
						&lt;server&gt;TomcatServer&lt;/server&gt;
						&lt;path&gt;/Frutemu&lt;/path&gt;
					&lt;/configuration&gt;
				&lt;/plugin&gt;
				&lt;plugin&gt;
					&lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
					&lt;artifactId&gt;jasperreports-maven-plugin&lt;/artifactId&gt;
					&lt;executions&gt;
						&lt;execution&gt;
							&lt;goals&gt;
								&lt;goal&gt;compile-reports&lt;/goal&gt;
							&lt;/goals&gt;
						&lt;/execution&gt;
					&lt;/executions&gt;
					&lt;dependencies&gt;
						&lt;!--note this must be repeated here to pick up correct xml validation --&gt;
						&lt;dependency&gt;
							&lt;groupId&gt;net.sf.jasperreports&lt;/groupId&gt;
							&lt;artifactId&gt;jasperreports&lt;/artifactId&gt;
							&lt;version&gt;4.1.2&lt;/version&gt;
						&lt;/dependency&gt;
					&lt;/dependencies&gt;
				&lt;/plugin&gt;
			&lt;/plugins&gt;
		&lt;/build&gt;
	&lt;/project&gt;


error: package javax.servlet does not exist

I&#39;m trying to report on every HTTP status code returned from my webapp.  However the status code does not appear to be accessible via the ServletResponse, or even if I cast it to a HttpServletResponse.  Is there a way to get access to this value within a ServletFilter?

All Servlet Filters Solutions on Gang of Coders

Total of 17 Servlet Filters Solutions