filter拦截（Response输出压缩）此案例基础知识面广
Response两种输出方式：1.getOutputStream().writer();2.getWriter().writer();但不能同时存在
1.配置文件
2.定义
GzipFilter类并 implements Filter
public class GzipFilter implements Filter {
@Override
public void doFilter(ServletRequest req, ServletResponse resp,FilterChain chain) throws IOException, ServletException {
HttpServletRequest request=(HttpServletRequest) req;
HttpServletResponse response=(HttpServletResponse) resp;
MyResponse myresponse=new MyResponse(response);
chain.doFilter(request,
myresponse);
//response.getWriter
response.getOutputStream
//取出缓冲数据压缩后输出
byte out[]=myresponse.getBuffer();
System.out.println("压缩前："+out.length);
byte gzipout[]=gzip(out);
System.out.println("压缩后："+gzipout.length);
//设置头信息，以压缩方式打开
//设置头信息，以压缩方式打开
response.setHeader("content-encoding", "gzip");
response.setHeader("content-length", gzipout.length+"");
response.
getOutputStream().
write(gzipout);
//分别对应下面橙色A/B/C处
}
public byte[]
gzip(byte b[]) throws IOException{
//压缩
ByteArrayOutputStream bout=new ByteArrayOutputStream();
GZIPOutputStream gout=new GZIPOutputStream(bout);
gout.write(b);
gout.close();
return bout.toByteArray();
}
class MyResponse extends HttpServletResponseWrapper{ //A处对应上面response
class MyResponse extends HttpServletResponseWrapper{ //A处对应上面response
private ByteArrayOutputStream bout=new ByteArrayOutputStream();
//定义缓冲区
数组字节流
private PrintWriter pw;
private HttpServletResponse response;
public MyResponse(HttpServletResponse response) {
super(response);
this.response=response;
}
//response输出数据方式一：response.getOutputStream().write("xxxx");
@Override
public
ServletOutputStream
getOutputStream() throws IOException { //
B
处对应上面getOutputStream
return new MyServletOutputStream(bout);
//response.getOutputStream.write(); 因
ServletOutputStream是abstract类，不能直接 new
}
//response输出数据方式二：response.getWriter().write("xxxx");
@Override
public
PrintWriter
getWriter() throws IOException{
//
pw=new PrintWriter(bout);
//字符流向字节流写数据，会查编码，默认GB2312,所以要注意乱码问题
pw=new PrintWriter(new OutputStreamWriter(bout,response.getCharacterEncoding()));
//用于解决PrintWriter().writer()的乱码问题
return pw;
//MyResponse.getWriter.write("xxx");
}
//将缓冲区中的数据返回
public byte[]
getBuffer(){
if(pw!=null){
pw.close();
//保证数据会写入缓冲区，当用PrintWrier输出时，此判断有效
}
return bout.toByteArray();
}
}
class MyServletOutputStream extends ServletOutputStream{ /
/
B
处对应上面getOutputStream
，
private ByteArrayOutputStream bout;
public MyServletOutputStream(ByteArrayOutputStream bout){
this.bout=bout;
}
@Override
public void
write(int b) throws IOException {
//覆写write方法//
c
处对应上面write
bout.write(b);
}
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
}
@Override
public void destroy() {
// TODO Auto-generated method stub
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String data="中国";
//response.getOutputStream().write(
data.getBytes("UTF-8"));
//一定要指编码，用于解决getOutputStream().write输出乱码
response.getWriter().write(data); //getWriter().writer输出的乱码问题在拦截代码中处理。
}