一个过滤敏感词的filter,看书学到的,小结之:
?? 一个过滤敏感词的filter,看书学到的,小结之:
原理是将内容输出到response时,response将缓存起来,在filter中替换,然后再输出到客户端浏览器.因为默认的response不能缓存输出内容,
因此要自定义response,可以通过扩展HttpServletResponseWrapper 获得,
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import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
public class HttpCharacterResponseWrapper extends HttpServletResponseWrapper {
?private CharArrayWriter charArrayWriter = new CharArrayWriter();
?public HttpCharacterResponseWrapper(HttpServletResponse response) {
??super(response);
?}
?@Override
?public PrintWriter getWriter() throws IOException {
??return new PrintWriter(charArrayWriter);
?}
?public CharArrayWriter getCharArrayWriter() {
??return charArrayWriter;
?}
}
?filter需要将自定义的response传到servlet中,代码如下:
?
public class OutputReplaceFilter implements Filter {
?private Properties pp = new Properties();
?public void init(FilterConfig config) throws ServletException {
??String file = config.getInitParameter("file");
??String realPath = config.getServletContext().getRealPath(file);
??try {
???pp.load(new FileInputStream(realPath));
??} catch (IOException e) {
??}
?}
?public void doFilter(ServletRequest req, ServletResponse res,
???FilterChain chain) throws IOException, ServletException {
??// 自定义的 response
??HttpCharacterResponseWrapper response = new HttpCharacterResponseWrapper(
????(HttpServletResponse) res);
??// 提交给 Servlet 或者下一个 Filter
??chain.doFilter(req, response);
??// 得到缓存在自定义 response 中的输出内容
??String output = response.getCharArrayWriter().toString();
??// 修改,替换
??for (Object obj : pp.keySet()) {
???String key = (String) obj;
???output = output.replace(key, pp.getProperty(key));
??}
??// 输出
??PrintWriter out = res.getWriter();
??out.write(output);
??out.println("<!-- Generated at " + new java.util.Date() + " -->");
?}
?public void destroy() {
?}