Filter处理HttpServletRequest & HttpServletResponse 笔记

HttpServletRequest 及HttpServletResponse 的复制 通过BufferedServletRequestWrapper和ContentCachingResponseWrapper进行处理

import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
* Created by ylzhou on 2017/6/22.
*/
public class BufferedServletRequestWrapper extends HttpServletRequestWrapper {

private byte[] buffer;

public BufferedServletRequestWrapper(HttpServletRequest request) throws IOException {
super(request);
InputStream is = request.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte buff[] = new byte[1024];
int read;
while ((read = is.read(buff)) > 0) {
baos.write(buff, 0, read);
}
this.buffer = baos.toByteArray();
}

@Override
public ServletInputStream getInputStream() throws IOException {
return new BufferedServletInputStream(this.buffer);
}
}

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import java.io.ByteArrayInputStream;
import java.io.IOException;

/**
* Created by ylzhou on 2017/6/22.
*/
public class BufferedServletInputStream extends ServletInputStream {

private ByteArrayInputStream inputStream;

public BufferedServletInputStream(byte[] buffer) {
this.inputStream = new ByteArrayInputStream(buffer);
}

@Override
public int read(byte[] b, int off, int len) throws IOException {
return inputStream.read(b, off, len);
}

@Override
public int available() throws IOException {
return inputStream.available();
}

@Override
public int read() throws IOException {
return inputStream.read();
}

@Override
public boolean isFinished() {
return false;
}

@Override
public boolean isReady() {
return false;
}

@Override
public void setReadListener(ReadListener listener) {

}
}

需要注意的是复制出的HttpServletRequest 需要关闭，而复制出的HttpServletResponse 需要回写结果

@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
if (!(servletRequest instanceof HttpServletRequest) || !(servletResponse instanceof HttpServletResponse)) {
throw new ServletException("Filter just supports HTTP requests");
}
// 复制request
HttpServletRequest bufferedWrapper = new BufferedServletRequestWrapper((HttpServletRequest) servletRequest);
// 切入
ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper(bufferedWrapper);
ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper((HttpServletResponse) servletResponse);

// 截取request值
HttpHeaders requestHeaders = new HttpHeaders();
Enumeration headerNames = requestWrapper.getHeaderNames();
while (headerNames.hasMoreElements()) {
String headerName = (String) headerNames.nextElement();
requestHeaders.add(headerName, requestWrapper.getHeader(headerName));
}
Map<String, String[]> requestParams = requestWrapper.getParameterMap();
String requestBody = "";
InputStream inputStream = null;
try {
inputStream = requestWrapper.getInputStream();
requestBody = IOUtils.toString(requestWrapper.getInputStream(), StandardCharsets.UTF_8);
} catch (IOException e) {
logger.error("获取请求body失败{}", e);
} finally {
// 由于inputStream是复制出来的，所以需要关闭
IOUtils.closeQuietly(inputStream);
}
try {
new SpanExtraInfo
.SpanExtraInfoBuild()
.requestHeaders(JSONUtils.toJson(requestHeaders))
.requestParams(JSONUtils.toJson(requestParams))
.requestBody(requestBody)
.build();
} catch (JsonProcessingException exc) {
log.warn("request info analyze error! {}",
4000
exc);
}

// 调用父，这里的需传入bufferedWrapper
super.doFilter(bufferedWrapper, responseWrapper, filterChain);
}

SpanExtraInfo spanExtraInfo = SpanExtraInfo.getInstance();
tracer.addTag("requestHeaders", spanExtraInfo.getRequestHeaders());
tracer.addTag("requestParams", spanExtraInfo.getRequestParams());
tracer.addTag("requestBody", spanExtraInfo.getRequestBody());
if (response instanceof ContentCachingResponseWrapper) {
ContentCachingResponseWrapper responseWrapper = (ContentCachingResponseWrapper) response;
HttpHeaders responseHeaders = new HttpHeaders();
for (String headerName : responseWrapper.getHeaderNames()) {
responseHeaders.add(headerName, responseWrapper.getHeader(headerName));
}
try {
tracer.addTag("responseHeaders", JSONUtils.toJson(responseHeaders));
} catch (JsonProcessingException exc) {
log.warn("responseHeaders analyze error! {}", exc);
}
try {
String responseBody = IOUtils.toString(responseWrapper.getContentInputStream(), StandardCharsets.UTF_8);
tracer.addTag("responseBody", responseBody);
// 最后需要回写下servletResponse，否则会返回一个空的servletResponse
responseWrapper.copyBodyToResponse();
} catch (IOException exc) {
log.warn("responseBody analyze error! {}", exc);
}
}