# Class RewriteValve

java.lang.Object
org.apache.catalina.util.LifecycleBase
org.apache.catalina.util.LifecycleMBeanBase
org.apache.catalina.valves.ValveBase
org.apache.catalina.valves.rewrite.RewriteValve

All Implemented Interfaces:
  `MBeanRegistration, Contained, JmxEnabled, Lifecycle, Valve`

public class RewriteValve extends ValveBase
Note: Extra caution should be used when adding a Rewrite Rule. When specifying a regex to match for in a Rewrite Rule, certain regex could allow an attacker to DoS your server, as Java's regex parsing is vulnerable to "catastrophic backtracking" (also known as "Regular expression Denial of Service", or ReDoS). There are some open source tools to help detect vulnerable regex, though in general it is a hard problem. A good defence is to use a regex debugger on your desired regex, and read more on the subject of catastrophic backtracking.

See Also:
  - OWASP ReDoS

- ## Nested Class Summary

  ### Nested classes/interfaces inherited from interface Lifecycle

  `Lifecycle.SingleUse`

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected boolean`
  `context`
  Will be set to true if the valve is associated with a context.
  `protected boolean`
  `enabled`
  enabled this component
  `protected ThreadLocal<Boolean>`
  `invoked`
  If rewriting occurs, the whole request will be processed again.
  `protected Map<String, RewriteMap>`
  `maps`
  Maps to be used by the rules.
  `protected ArrayList<String>`
  `mapsConfiguration`
  Maps configuration.
  `protected String`
  `resourcePath`
  Relative path to the configuration file.
  `protected RewriteRule[]`
  `rules`
  The rewrite rules that the valve will use.

  ### Fields inherited from class ValveBase

  `asyncSupported, container, containerLog, next, sm`

  ### Fields inherited from class LifecycleMBeanBase

  `mserver`

  ### Fields inherited from interface Lifecycle

  `AFTER_DESTROY_EVENT, AFTER_INIT_EVENT, AFTER_START_EVENT, AFTER_STOP_EVENT, BEFORE_DESTROY_EVENT, BEFORE_INIT_EVENT, BEFORE_START_EVENT, BEFORE_STOP_EVENT, CONFIGURE_START_EVENT, CONFIGURE_STOP_EVENT, PERIODIC_EVENT, START_EVENT, STOP_EVENT`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `RewriteValve()`
  Create a new RewriteValve instance.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `String`
  `getConfiguration()`
  Get the rewrite configuration.
  `boolean`
  `getEnabled()`
  Get whether the rewrite valve is enabled.
  `protected void`
  `initInternal()`
  Subclasses implement this method to perform any instance initialisation required.
  `void`
  `invoke(Request request, Response response)`
  Perform request processing as required by this Valve.
  `protected void`
  `parse(BufferedReader reader)`
  Parse the rewrite configuration from the given reader.
  `static Object`
  `parse(String line)`
  This factory method will parse a line formed like:
  `protected static void`
  `parseCondFlag(String line, RewriteCond condition, String flag)`
  Parser for RewriteCond flags.
  `protected static void`
  `parseRuleFlag(String line, RewriteRule rule, String flag)`
  Parser for RewriteRule flags.
  `void`
  `setConfiguration(String configuration)`
  Set the rewrite configuration.
  `void`
  `setEnabled(boolean enabled)`
  Set whether the rewrite valve is enabled.
  `protected void`
  `startInternal()`
  Start this component and implement the requirements of `LifecycleBase.startInternal()`.
  `protected void`
  `stopInternal()`
  Stop this component and implement the requirements of `LifecycleBase.stopInternal()`.

  ### Methods inherited from class ValveBase

  `backgroundProcess, getContainer, getDomainInternal, getNext, getObjectNameKeyProperties, isAsyncSupported, setAsyncSupported, setContainer, setNext, toString`

  ### Methods inherited from class LifecycleMBeanBase

  `destroyInternal, getDomain, getObjectName, postDeregister, postRegister, preDeregister, preRegister, register, setDomain, unregister, unregister`

  ### Methods inherited from class LifecycleBase

  `addLifecycleListener, destroy, findLifecycleListeners, fireLifecycleEvent, getState, getStateName, getThrowOnFailure, init, removeLifecycleListener, setState, setState, setThrowOnFailure, start, stop`

  ### Methods inherited from class Object

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

- ## Field Details

  - ### rules

    protected RewriteRule[] rules
    The rewrite rules that the valve will use.

  - ### invoked

    protected ThreadLocal<Boolean> invoked
    If rewriting occurs, the whole request will be processed again.

  - ### resourcePath

    protected String resourcePath
    Relative path to the configuration file. Note: If the valve's container is a context, this will be relative to /WEB-INF/.

  - ### context

    protected boolean context
    Will be set to true if the valve is associated with a context.

  - ### enabled

    protected boolean enabled
    enabled this component

  - ### maps

    protected Map<String, RewriteMap> maps
    Maps to be used by the rules.

  - ### mapsConfiguration

    protected ArrayList<String> mapsConfiguration
    Maps configuration.

- ## Constructor Details

  - ### RewriteValve

    public RewriteValve()
    Create a new RewriteValve instance.

- ## Method Details

  - ### getEnabled

    public boolean getEnabled()
    Get whether the rewrite valve is enabled.
    Returns:
      `true` if the valve is enabled

  - ### setEnabled

    public void setEnabled(boolean enabled)
    Set whether the rewrite valve is enabled.
    Parameters:
      `enabled` - `true` to enable the valve

  - ### initInternal

    protected void initInternal() throws LifecycleException
    Description copied from class: `LifecycleBase`
    Subclasses implement this method to perform any instance initialisation required.
    Overrides:
      `initInternal` in class `ValveBase`
    Throws:
      `LifecycleException` - If the initialisation fails

  - ### startInternal

    protected void startInternal() throws LifecycleException
    Description copied from class: `ValveBase`
    Start this component and implement the requirements of `LifecycleBase.startInternal()`.
    Overrides:
      `startInternal` in class `ValveBase`
    Throws:
      `LifecycleException` - if this component detects a fatal error that prevents this component from being used

  - ### setConfiguration

    public void setConfiguration(String configuration) throws Exception
    Set the rewrite configuration.
    Parameters:
      `configuration` - The rewrite configuration string
    Throws:
      `Exception` - if the configuration cannot be parsed

  - ### getConfiguration

    public String getConfiguration()
    Get the rewrite configuration.
    Returns:
      The rewrite configuration string

  - ### parse

    protected void parse(BufferedReader reader) throws LifecycleException
    Parse the rewrite configuration from the given reader.
    Parameters:
      `reader` - The reader containing the rewrite configuration
    Throws:
      `LifecycleException` - if the configuration cannot be parsed

  - ### stopInternal

    protected void stopInternal() throws LifecycleException
    Description copied from class: `ValveBase`
    Stop this component and implement the requirements of `LifecycleBase.stopInternal()`.
    Overrides:
      `stopInternal` in class `ValveBase`
    Throws:
      `LifecycleException` - if this component detects a fatal error that prevents this component from being used

  - ### invoke

    public void invoke(Request request, Response response) throws IOException, ServletException
    Description copied from interface: `Valve`

    Perform request processing as required by this Valve.

    An individual Valve MAY perform the following actions, in the specified order:

    - Examine and/or modify the properties of the specified Request and Response.
    - Examine the properties of the specified Request, completely generate the corresponding Response, and return control to the caller.
    - Examine the properties of the specified Request and Response, wrap either or both of these objects to supplement their functionality, and pass them on.
    - If the corresponding Response was not generated (and control was not returned), call the next Valve in the pipeline (if there is one) by executing `getNext().invoke()`.
    - Examine, but not modify, the properties of the resulting Response (which was created by a subsequently invoked Valve or Container).

    A Valve MUST NOT do any of the following things:

    - Change request properties that have already been used to direct the flow of processing control for this request (for instance, trying to change the virtual host to which a Request should be sent from a pipeline attached to a Host or Context in the standard implementation).
    - Create a completed Response AND pass this Request and Response on to the next Valve in the pipeline.
    - Consume bytes from the input stream associated with the Request, unless it is completely generating the response, or wrapping the request before passing it on.
    - Modify the HTTP headers included with the Response after the `getNext().invoke()` method has returned.
    - Perform any actions on the output stream associated with the specified Response after the `getNext().invoke()` method has returned.
    Parameters:
      `request` - The servlet request to be processed
      `response` - The servlet response to be created
    Throws:
      `IOException` - if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
      `ServletException` - if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet

  - ### parse

    public static Object parse(String line)
    This factory method will parse a line formed like:

    Example: `RewriteCond %{REMOTE_HOST} ^host1.* [OR]`

    Parameters:
      `line` - A line from the rewrite configuration
    Returns:
      The condition, rule or map resulting from parsing the line

  - ### parseCondFlag

    protected static void parseCondFlag(String line, RewriteCond condition, String flag)
    Parser for RewriteCond flags.
    Parameters:
      `line` - The configuration line being parsed
      `condition` - The current condition
      `flag` - The flag

  - ### parseRuleFlag

    protected static void parseRuleFlag(String line, RewriteRule rule, String flag)
    Parser for RewriteRule flags.
    Parameters:
      `line` - The configuration line being parsed
      `rule` - The current rule
      `flag` - The flag