用过滤器转换amr音频

package cn.zq.amrplay.web.filter; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import cn.zq.amrplay.util.AudioUtils; /** * <p>此过滤器用来拦截所有以amr后缀结尾的请求，并转换成mp3流输出，输出<strong>MIME</strong>类型为audio/mpeg。</p> * @author Riccio Zhang * */ public class Amr2Mp3Filter implements Filter{ /** * mp3扩展名对应的MIME类型，值为"audio/mpeg" */ public final static String MP3_MIME_TYPE = "audio/mpeg"; public void init(FilterConfig filterConfig) throws ServletException {} public void destroy() {} public void doFilter(ServletRequest req, ServletResponse resp, FilterChain filterChain) throws IOException, ServletException { HttpServletRequest request; HttpServletResponse response; try { request = (HttpServletRequest) req; response = (HttpServletResponse) resp; } catch (ClassCastException e) { throw new ServletException("non-HTTP request or response"); } String requstURI = request.getRequestURI(); String contextPath = request.getContextPath(); String resPath = requstURI; //去掉requstURI中contextPath部分和参数部分 if(contextPath.length() > 0) { resPath = resPath.substring(contextPath.length()); } int index = 0; if((index = resPath.lastIndexOf("?")) != -1) { resPath = resPath.substring(0, index); } String resRealPath = req.getServletContext().getRealPath(resPath); String mp3ResRealPath = resRealPath.replaceFirst(".amr$", ".mp3"); File mp3File = new File(mp3ResRealPath); if(!mp3File.exists()) { File amrFile = new File(resRealPath); if(!amrFile.exists()) { filterChain.doFilter(request, response); return; } AudioUtils.amr2mp3(amrFile.getAbsolutePath(), mp3File.getAbsolutePath()); } response.setContentLength((int)mp3File.length()); response.setContentType(MP3_MIME_TYPE); InputStream in = new FileInputStream(mp3File); OutputStream out = response.getOutputStream(); try { byte[] buf = new byte[1024]; int len = -1; while((len = in.read(buf)) != -1) { out.write(buf, 0, len); } } finally { try { in.close(); } catch (Exception e) { e.printStackTrace(); } out.flush(); } } }