import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.zip.GZIPOutputStream;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
//全站压缩过滤器
public class GzipFilter implements Filter {
public void destroy() {
}
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest)req;
HttpServletResponse response = (HttpServletResponse)resp;
GzipHttpServletResponse gresponse = new GzipHttpServletResponse(response);
chain.doFilter(request, gresponse);//放行
//压缩代码写在此处
//找一个内存缓冲字节流
ByteArrayOutputStream baos = new ByteArrayOutputStream();
//把数据压缩到缓冲字节流流中
GZIPOutputStream gout = new GZIPOutputStream(baos);
//取出数据：压缩后的
byte b[] = gresponse.getOldBytes();//原始字节
System.out.println("原有数据大小："+b.length);
gout.write(b);
gout.close();//保证所有的数据都进入内存缓存流
//取出压缩后的数据
b = baos.toByteArray();
System.out.println("压缩后的数据大小："+b.length);
//输出前一定要告知客户端压缩方式
response.setHeader("Content-Encoding", "gzip");
response.setContentLength(b.length);//告知客户端正文的大小
//用服务器的响应对象输出
ServletOutputStream out = response.getOutputStream();
out.write(b);
}
public void init(FilterConfig filterConfig) throws ServletException {
}
}
class GzipHttpServletResponse extends HttpServletResponseWrapper{
private ByteArrayOutputStream baos = new ByteArrayOutputStream();
private PrintWriter pw;
public GzipHttpServletResponse(HttpServletResponse response){
super(response);
}
//把原始数据封装到一个缓冲流中
@Override
public ServletOutputStream getOutputStream() throws IOException {
return new MyServletOutputStream(baos);
}
//字符流：把原始数据封装到一个缓冲流中
@Override
public PrintWriter getWriter() throws IOException {
pw = new PrintWriter(new OutputStreamWriter(baos, super.getCharacterEncoding()));//字符流转成字节流编码会丢失
return pw;
}
//返回baos中的缓存数据：原始
public byte[] getOldBytes(){
try {
if(pw!=null){
pw.close();
}
baos.flush();
} catch (IOException e) {
e.printStackTrace();
}
return baos.toByteArray();
}
}
class MyServletOutputStream extends ServletOutputStream{
private ByteArrayOutputStream baos;
public MyServletOutputStream(ByteArrayOutputStream baos){
this.baos = baos;
}
@Override
public void write(int b) throws IOException {
baos.write(b);
}
}