将几个Filter整合成一个Filter

CAS-Client的客户端配置还是多Filter，这个对于接入系统比较繁琐，我试着将这几个Filter合并成一个。

FilterChainProxy ：其职责是给web.xml使用，接受其他需要合并的Filter的参数，初始化其他Filter.

FilterInvocation：doFilter的参数的封装，取得路径信息等。

VirtualFilterChain：实现FilterChain，

代码如下：

FilterChainProxy

public class FilterChainProxy extends AbstractConfigurationFilter {

Logger logger = Logger.getLogger(FilterChainProxy.class);

private Filter[] filters;

/* (non-Javadoc)
* @see javax.servlet.Filter#destroy()
*/
public void destroy() {

for (int i = 0; i < filters.length; i++) {
if (filters[i] != null) {
if (logger.isDebugEnabled()) {
logger.debug("Destroying Filter defined in ApplicationContext: '" + filters[i].toString() + "'");
}

filters[i].destroy();
}
}

}

/* (non-Javadoc)
* @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
ServletException {
FilterInvocation fi = new FilterInvocation(request, response, chain);

if (filters.length == 0) {
if (logger.isDebugEnabled()) {
logger.debug(fi.getRequestUrl()+" has an empty filter list");
}
chain.doFilter(request, response);

return;
}

VirtualFilterChain virtualFilterChain = new VirtualFilterChain(fi, filters);
virtualFilterChain.doFilter(fi.getRequest(), fi.getResponse());

}

/* (non-Javadoc)
* @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
*/
public void init(FilterConfig filterConfig) throws ServletException {
filters = obtainAllDefinedFilters();

for (int i = 0; i < filters.length; i++) {
if (filters[i] != null) {
if (logger.isDebugEnabled()) {
logger.debug("Initializing Filter defined in ApplicationContext: '" + filters[i].toString() + "'");
}
filters[i].init(filterConfig);
}
}

}
/**
* 初始化单点登录需要的过滤器
* @return
*/
private Filter[] obtainAllDefinedFilters() {

Set<Filter> list = new LinkedHashSet<Filter>();
// SingleSignOutFilter
list.add(new SingleSignOutFilter());
// AuthenticationFilter
list.add(new AuthenticationFilter());
// Cas20ProxyReceivingTicketValidationFilter
list.add(new Cas20ProxyReceivingTicketValidationFilter());
// AssertionThreadLocalFilter
list.add(new AssertionThreadLocalFilter());
// HttpServletRequestWrapperFilter
list.add(new HttpServletRequestWrapperFilter());

return (Filter[]) list.toArray(new Filter[0]);
}

VirtualFilterChain

private class VirtualFilterChain implements FilterChain {
private FilterInvocation fi;
private Filter[] additionalFilters;
private int currentPosition = 0;

public VirtualFilterChain(FilterInvocation filterInvocation, Filter[] additionalFilters) {
this.fi = filterInvocation;
this.additionalFilters = additionalFilters;
}

public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
if (currentPosition == additionalFilters.length) {
if (logger.isDebugEnabled()) {
logger.debug(fi.getRequestUrl()
+ " reached end of additional filter chain; proceeding with original chain");
}

fi.getChain().doFilter(request, response);
} else {
currentPosition++;

if (logger.isDebugEnabled()) {
logger.debug(fi.getRequestUrl() + " at position " + currentPosition + " of "
+ additionalFilters.length + " in additional filter chain; firing Filter: '"
+ additionalFilters[currentPosition - 1] + "'");
}

additionalFilters[currentPosition - 1].doFilter(request, response, this);
}
}

}

FilterInvocation

public class FilterInvocation {
private FilterChain chain;
private ServletRequest request;
private ServletResponse response;

public FilterInvocation(ServletRequest request, ServletResponse response, FilterChain chain) {
if ((request == null) || (response == null) || (chain == null)) {
throw new IllegalArgumentException("Cannot pass null values to constructor");
}

if (!(request instanceof HttpServletRequest)) {
throw new IllegalArgumentException("Can only process HttpServletRequest");
}

if (!(response instanceof HttpServletResponse)) {
throw new IllegalArgumentException("Can only process HttpServletResponse");
}

this.request = request;
this.response = response;
this.chain = chain;
}

public FilterChain getChain() {
return chain;
}

/**
* Indicates the URL that the user agent used for this request.<P>The returned URL does <b>not</b> reflect
* the port number determined from a {@link org.acegisecurity.util.PortResolver}.</p>
*
* @return the full URL of this request
*/
public String getFullRequestUrl() {
return UrlUtils.getFullRequestUrl(this);
}

public HttpServletRequest getHttpRequest() {
return (HttpServletRequest) request;
}

public HttpServletResponse getHttpResponse() {
return (HttpServletResponse) response;
}

public ServletRequest getRequest() {
return request;
}

/**
* Obtains the web application-specific fragment of the URL.
*
* @return the URL, excluding any server name, context path or servlet path
*/
public String getRequestUrl() {
return UrlUtils.getRequestUrl(this);
}

public ServletResponse getResponse() {
return response;
}

public String toString() {
return "FilterInvocation: URL: " + getRequestUrl();
}
}