filter得到request的body/content
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {

HttpServletRequest req = (HttpServletRequest) request;

int length = req.getContentLength();
if (length > 0) {
BufferedRequestWrapper bufferedRequest = new BufferedRequestWrapper(req,length);

InputStream is = bufferedRequest.getInputStream();
byte[] content = new byte[length];

int pad = 0;
while(pad < length){
pad += is.read(content, pad, length);
}

request = bufferedRequest;
}
chain.doFilter(request, response);
}


BufferedRequestWrapper .java

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class BufferedRequestWrapper extends HttpServletRequestWrapper {

ByteArrayInputStream bais;

BufferedServletInputStream bsis;

byte[] buffer;

public BufferedRequestWrapper(HttpServletRequest req,int length) throws IOException {
super(req);
// Read InputStream and store its content in a buffer.
InputStream is = req.getInputStream();
buffer = new byte[length];

int pad = 0;
while(pad < length){
pad += is.read(buffer, pad, length);
}
}

public ServletInputStream getInputStream() {
try {
// Generate a new InputStream by stored buffer
bais = new ByteArrayInputStream(buffer);
// Istantiate a subclass of ServletInputStream
// (Only ServletInputStream or subclasses of it are accepted by the
// servlet engine!)
bsis = new BufferedServletInputStream(bais);
} catch (Exception ex) {
ex.printStackTrace();
} finally {
}
return bsis;
}

}