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[[custom-error-pages]]
=== Creating Custom Error Pages

The following sections describe several ways to create custom error pages in Jetty.

==== Defining error pages in web.xml

You can use the standard webapp configuration file located in `webapp/WEB-INF/web.xml` to map errors to specific URLs with the `error-page` element.
This element creates a mapping between the error-code or exception-type to the location of a resource in the web application.

* `error-code` - an integer value
* `exception-type` - a fully qualified class name of a Java Exception type
* `location` - location of the resource in the webapp relative to the root of the web application. Value should start with `/`.

Error code example:

[source, xml, subs="{sub-order}"]
----
<error-page>
  <error-code>404</error-code>
  <location>/jspsnoop/ERROR/404</location>
</error-page>

----

Exception example:

[source, xml, subs="{sub-order}"]
----
<error-page>
  <exception-type>java.io.IOException</exception-type>
  <location>/jspsnoop/IOException</location>
</error-page>

----

The error page mappings created with the error-page element will redirect to a normal URL within the web application and will be handled as a normal request to that location and thus may be static content, a JSP or a filter and/or servlet.
When handling a request generated by an error redirection, the following request attributes are set and are available to generate dynamic content:

javax.servlet.error.exception::
  The exception instance that caused the error (or null).
javax.servlet.error.exception_type::
  The class name of the exception instance that caused the error (or null).
javax.servlet.error.message::
  The error message.
javax.servlet.error.request_uri::
  The URI of the request with an error.
javax.servlet.error.servlet_name::
  The Servlet name of the servlet that the request was
  dispatched to.
javax.servlet.error.status_code::
  The status code of the error (e.g. 404, 500 etc.).

==== Configuring error pages context files

You can use context IoC XML files to configure the default error page mappings with more flexibility than is available with `web.xml`, specifically with the support of error code ranges.
Context files are normally located in `${jetty.base}/webapps/` (see `DeployerManager` for more details) and an example of more flexible error page mapping is below:

[source, xml, subs="{sub-order}"]
----
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "http://www.eclipse.org/jetty/configure_9_3.dtd">

<Configure class="org.eclipse.jetty.webapp.WebAppContext">
  <Set name="contextPath">/test</Set>
  <Set name="war">
    <SystemProperty name="jetty.base" default="."/>/webapps/test
  </Set>

  <!-- by Code -->
  <Get name="errorHandler">
    <Call name="addErrorPage">
      <Arg type="int">404</Arg>
      <Arg type="String">/jspsnoop/ERROR/404</Arg>
    </Call>
  </Get>

  <!-- by Exception -->
  <Get name="errorHandler">
    <Call name="addErrorPage">
      <Arg>
        <Call class="java.lang.Class" name="forName">
          <Arg type="String">java.io.IOException</Arg>
        </Call>
      </Arg>
      <Arg type="String">/jspsnoop/IOException</Arg>
    </Call>
  </Get>

  <!-- by Code Range -->
  <Get name="errorHandler">
    <Call name="addErrorPage">
      <Arg type="int">500</Arg>
      <Arg type="int">599</Arg>
      <Arg type="String">/dump/errorCodeRangeMapping</Arg>
    </Call>
  </Get>
</Configure>

----

==== Custom ErrorHandler class

If no error page mapping is defined, or if the error page resource itself has an error, then the error page will be generated by an instance of `ErrorHandler` configured either the Context or the Server.
An `ErrorHandler` may extend the `ErrorHandler` class and may totally replace the handle method to generate an error page, or it can implement some or all of the following methods to partially modify the error pages:

[source, java, subs="{sub-order}"]
----
void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException
void handleErrorPage(HttpServletRequest request, Writer writer, int code, String message) throws IOException
void writeErrorPage(HttpServletRequest request, Writer writer, int code, String message, boolean showStacks) throws IOException
void writeErrorPageHead(HttpServletRequest request, Writer writer, int code, String message) throws IOException
void writeErrorPageBody(HttpServletRequest request, Writer writer, int code, String message, boolean showStacks) throws IOException
void writeErrorPageMessage(HttpServletRequest request, Writer writer, int code, String message, String uri) throws IOException
void writeErrorPageStacks(HttpServletRequest request, Writer writer) throws IOException
----

An `ErrorHandler` instance may be set on a Context by calling the `ContextHandler.setErrorHandler` method. This can be done by embedded code or via context IoC XML.
For example:

[source, xml, subs="{sub-order}"]
----
<Configure class="org.eclipse.jetty.server.handler.ContextHandler">
  ...
  <Set name="errorHandler">
    <New class="com.acme.handler.MyErrorHandler"/>
  </Set>
  ...
</Configure>
----

An `ErrorHandler` instance may be set on the entire server by setting it as a dependent bean on the Server instance.
This can be done by calling `Server.addBean(Object)` via embedded code or in `jetty.xml` IoC XML:

[source, xml, subs="{sub-order}"]
----
<Configure id="Server" class="org.eclipse.jetty.server.Server">
  ...
  <Call name="addBean">
    <Arg>
      <New class="com.acme.handler.MyErrorHandler"/>
    </Arg>
  </Call>
  ...
</Configure>
----

==== Server level 404 error

It is possible to get a 'page not found' when a request is made to the server for a resource that is outside of any registered contexts.
As an example, you have a domain name pointing to your public server IP, yet no context is registered with Jetty to serve pages for that domain.
As a consequence, the server, by default, gives a listing of all contexts running on the server.

One of the quickest ways to avoid this behavior is to create a catch all context.
Create a "root" web app mapped to the "/" URI, and use the `index.html` redirect to whatever place with a header directive.
