Servlet--HttpServletRequest接口，HttpServletResponse接口

public void sendRedirect(String location)
throws IOException {

if (isCommitted())
throw new IllegalStateException
(sm.getString("coyoteResponse.sendRedirect.ise"));

// Ignore any call from an included servlet
if (included)
return;

// Clear any data content that has been buffered
resetBuffer();

// Generate a temporary redirect to the specified location
try {
String absolute = toAbsolute(location);
setStatus(SC_FOUND);
setHeader("Location", absolute);
} catch (IllegalArgumentException e) {
setStatus(SC_NOT_FOUND);
}

// Cause the response to be finished (from the application perspective)
setSuspended(true);

}

/**
* Convert (if necessary) and return the absolute URL that represents the
* resource referenced by this possibly relative URL.  If this URL is
* already absolute, return it unchanged.
*
* @param location URL to be (possibly) converted and then returned
*
* @exception IllegalArgumentException if a MalformedURLException is
*  thrown when converting the relative URL to an absolute one
*/
private String toAbsolute(String location) {

if (location == null)
return (location);

boolean leadingSlash = location.startsWith("/");

if (leadingSlash || !hasScheme(location)) {

redirectURLCC.recycle();

String scheme = request.getScheme();
String name = request.getServerName();
int port = request.getServerPort();

try {
redirectURLCC.append(scheme, 0, scheme.length());
redirectURLCC.append("://", 0, 3);
redirectURLCC.append(name, 0, name.length());
if ((scheme.equals("http") && port != 80)
|| (scheme.equals("https") && port != 443)) {
redirectURLCC.append(':');
String portS = port + "";
redirectURLCC.append(portS, 0, portS.length());
}
if (!leadingSlash) {
String relativePath = request.getDecodedRequestURI();
int pos = relativePath.lastIndexOf('/');
relativePath = relativePath.substring(0, pos);

String encodedURI = null;
final String frelativePath = relativePath;
if (SecurityUtil.isPackageProtectionEnabled() ){
try{
encodedURI = (String)AccessController.doPrivileged(
new PrivilegedExceptionAction(){
public Object run() throws IOException{
return urlEncoder.encodeURL(frelativePath);
}
});
} catch (PrivilegedActionException pae){
IllegalArgumentException iae =
new IllegalArgumentException(location);
iae.initCause(pae.getException());
throw iae;
}
} else {
encodedURI = urlEncoder.encodeURL(relativePath);
}
redirectURLCC.append(encodedURI, 0, encodedURI.length());
redirectURLCC.append('/');
}
redirectURLCC.append(location, 0, location.length());
} catch (IOException e) {
IllegalArgumentException iae =
new IllegalArgumentException(location);
iae.initCause(e);
throw iae;
}

return redirectURLCC.toString();

} else {

return (location);

}

}