# Class RequestFilter

java.lang.Object
org.apache.catalina.filters.FilterBase
org.apache.catalina.filters.RequestFilter

All Implemented Interfaces:
  `Filter`

Direct Known Subclasses:
  `RemoteAddrFilter`, `RemoteHostFilter`

public abstract class RequestFilter extends FilterBase
Implementation of a Filter that performs filtering based on comparing the appropriate request property (selected based on which subclass you choose to configure into your Container's pipeline) against the regular expressions configured for this Filter.

This filter is configured by setting the `allow` and/or `deny` properties to a regular expressions (in the syntax supported by `Pattern`) to which the appropriate request property will be compared. Evaluation proceeds as follows:

- The subclass extracts the request property to be filtered, and calls the common `process()` method.
- If there is a deny expression configured, the property will be compared to the expression. If a match is found, this request will be rejected with a "Forbidden" HTTP response.
- If there is an allow expression configured, the property will be compared to the expression. If a match is found, this request will be allowed to pass through to the next filter in the current pipeline.
- If a deny expression was specified but no allow expression, allow this request to pass through (because none of the deny expressions matched it).
- The request will be rejected with a "Forbidden" HTTP response.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected Pattern`
  `allow`
  The regular expression used to test for allowed requests.
  `protected Pattern`
  `deny`
  The regular expression used to test for denied requests.
  `protected int`
  `denyStatus`
  The HTTP response status code that is used when rejecting denied request.

  ### Fields inherited from class org.apache.catalina.filters.FilterBase

  `sm`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `RequestFilter()`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `abstract void`
  `doFilter(ServletRequest request, ServletResponse response, FilterChain chain)`
  Extract the desired request property, and pass it (along with the specified request and response objects) to the protected `process()` method to perform the actual filtering.
  `String`
  `getAllow()`
  `String`
  `getDeny()`
  `int`
  `getDenyStatus()`
  `protected boolean`
  `isConfigProblemFatal()`
  Determines if an exception when calling a setter or an unknown configuration attribute triggers the failure of this filter which in turn will prevent the web application from starting.
  `protected void`
  `process(String property, ServletRequest request, ServletResponse response, FilterChain chain)`
  Perform the filtering that has been configured for this Filter, matching against the specified request property.
  `void`
  `setAllow(String allow)`
  Set the regular expression used to test for allowed requests for this Filter, if any.
  `void`
  `setDeny(String deny)`
  Set the regular expression used to test for denied requests for this Filter, if any.
  `void`
  `setDenyStatus(int denyStatus)`
  Set response status code that is used to reject denied request.

  ### Methods inherited from class org.apache.catalina.filters.FilterBase

  `getLogger, init`

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

  ### Methods inherited from interface javax.servlet.Filter

  `destroy`

- ## Field Details

  - ### allow

    protected Pattern allow
    The regular expression used to test for allowed requests.

  - ### deny

    protected Pattern deny
    The regular expression used to test for denied requests.

  - ### denyStatus

    protected int denyStatus
    The HTTP response status code that is used when rejecting denied request. It is 403 by default, but may be changed to be 404.

- ## Constructor Details

  - ### RequestFilter

    public RequestFilter()

- ## Method Details

  - ### getAllow

    public String getAllow()
    Returns:
      the regular expression used to test for allowed requests for this Filter, if any; otherwise, return `null`.

  - ### setAllow

    public void setAllow(String allow)
    Set the regular expression used to test for allowed requests for this Filter, if any.
    Parameters:
      `allow` - The new allow expression

  - ### getDeny

    public String getDeny()
    Returns:
      the regular expression used to test for denied requests for this Filter, if any; otherwise, return `null`.

  - ### setDeny

    public void setDeny(String deny)
    Set the regular expression used to test for denied requests for this Filter, if any.
    Parameters:
      `deny` - The new deny expression

  - ### getDenyStatus

    public int getDenyStatus()
    Returns:
      response status code that is used to reject denied request.

  - ### setDenyStatus

    public void setDenyStatus(int denyStatus)
    Set response status code that is used to reject denied request.
    Parameters:
      `denyStatus` - The status code for deny

  - ### doFilter

    public abstract void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
    Extract the desired request property, and pass it (along with the specified request and response objects) to the protected `process()` method to perform the actual filtering. This method must be implemented by a concrete subclass.
    Parameters:
      `request` - The servlet request to be processed
      `response` - The servlet response to be created
      `chain` - The filter chain
    Throws:
      `IOException` - if an input/output error occurs
      `ServletException` - if a servlet error occurs

  - ### isConfigProblemFatal

    protected boolean isConfigProblemFatal()
    Description copied from class: `FilterBase`
    Determines if an exception when calling a setter or an unknown configuration attribute triggers the failure of this filter which in turn will prevent the web application from starting.
    Overrides:
      `isConfigProblemFatal` in class `FilterBase`
    Returns:
      `true` if a problem should trigger the failure of this filter, else `false`

  - ### process

    protected void process(String property, ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
    Perform the filtering that has been configured for this Filter, matching against the specified request property.
    Parameters:
      `property` - The request property on which to filter
      `request` - The servlet request to be processed
      `response` - The servlet response to be processed
      `chain` - The filter chain
    Throws:
      `IOException` - if an input/output error occurs
      `ServletException` - if a servlet error occurs