org.apache.catalina.filters

## Class AddDefaultCharsetFilter

- java.lang.Object
- - org.apache.catalina.filters.FilterBase
  - - org.apache.catalina.filters.AddDefaultCharsetFilter

All Implemented Interfaces:
  Filter

    public class AddDefaultCharsetFilter
    extends FilterBase

Filter that explicitly sets the default character set for media subtypes of the "text" type to ISO-8859-1, or another user defined character set. RFC2616 explicitly states that browsers must use ISO-8859-1 if no character set is defined for media with subtype "text". However, browsers may attempt to auto-detect the character set. This may be exploited by an attacker to perform an XSS attack. Internet Explorer has this behaviour by default. Other browsers have an option to enable it.
This filter prevents the attack by explicitly setting a character set. Unless the provided character set is explicitly overridden by the user - in which case they deserve everything they get - the browser will adhere to an explicitly set character set, thus preventing the XSS attack.

### Nested Class Summary

Nested Classes
`static class` `AddDefaultCharsetFilter.ResponseWrapper` Wrapper that adds a character set for text media types if no character set is specified.

### Field Summary

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

`sm`

### Constructor Summary

Constructors
Constructor and Description
`AddDefaultCharsetFilter()`

### Method Summary

Methods
`void` `doFilter(ServletRequest request, ServletResponse response, FilterChain chain)` The `doFilter` 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.
`protected Log` `getLogger()`
`void` `init(FilterConfig filterConfig)` Called by the web container to indicate to a filter that it is being placed into service.
`void` `setEncoding(String encoding)`

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

`destroy, isConfigProblemFatal`

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

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

### Constructor Detail

#### AddDefaultCharsetFilter

    public AddDefaultCharsetFilter()

### Method Detail

#### setEncoding

    public void setEncoding(String encoding)

#### getLogger

    protected Log getLogger()

Specified by:
  `getLogger` in class `FilterBase`

#### init

    public void init(FilterConfig filterConfig)
              throws ServletException

Description copied from interface: `javax.servlet.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.
The web container cannot place the filter into service if the init method either
1.Throws a ServletException
2.Does not return within a time period defined by the web container

Specified by:
  `init` in interface `Filter`
Overrides:
  `init` in class `FilterBase`
Throws:
  `ServletException`

#### doFilter

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

Description copied from interface: `javax.servlet.Filter`
The `doFilter` 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.

A typical implementation of this method would follow the following pattern:-
1. Examine the request
2. Optionally wrap the request object with a custom implementation to filter content or headers for input filtering
3. Optionally wrap the response object with a custom implementation to filter content or headers for output filtering
4. a) Either invoke the next entity in the chain using the FilterChain object (`chain.doFilter()`),
4. b) or not pass on the request/response pair to the next entity in the filter chain to block the request processing
5. Directly set headers on the response after invocation of the next entity in the filter chain.

Throws:
  `IOException`
  `ServletException`