接口请求一切正常，但是会报错Required request body is missing的错误
百般查询和debug后都未查到问题，最后还是在stackOverFlow中找解决方案：
stackoverflow.com/questions/3…
原因是：我新增了一个Filter用于打印请求和返回日志，部分代码如下：
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
this.preHandle(request, (HttpServletResponse) response);
chain.doFilter(request, response);
this.afterCompletion((HttpServletRequest) request, (HttpServletResponse) response);
}
private void preHandle(HttpServletRequest request, HttpServletResponse response) {
try {
RequestWrapper requestWrapper = new RequestWrapper((HttpServletRequest) request);
log.info("request params：{}", JSON.toJSON(requestWrapper.getBody()));
} catch (Exception e) {
log.info("log error ignore", e);
}
}
复制代码@Slf4j
public class RequestWrapper extends HttpServletRequestWrapper {
private final String body;
public RequestWrapper(HttpServletRequest request) {
super(request);
StringBuilder stringBuilder = new StringBuilder();
BufferedReader bufferedReader = null;
InputStream inputStream = null;
try {
inputStream = request.getInputStream();
if (inputStream != null) {
bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
char[] charBuffer = new char[128];
int bytesRead = -1;
while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
stringBuilder.append(charBuffer, 0, bytesRead);
}
} else {
stringBuilder.append("");
}
} catch (IOException ex) {
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
log.error("inputStream close error", e);
}
}
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (IOException e) {
log.error("bufferedReader close error", e);
}
}
}
body = stringBuilder.toString();
}
@Override
public ServletInputStream getInputStream() throws IOException {
final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes());
ServletInputStream servletInputStream = new ServletInputStream() {
@Override
public boolean isFinished() {
return false;
}
@Override
public boolean isReady() {
return false;
}
@Override
public void setReadListener(ReadListener readListener) {
}
@Override
public int read() throws IOException {
return byteArrayInputStream.read();
}
};
return servletInputStream;
}
@Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(this.getInputStream()));
}
public String getBody() {
return this.body;
}
}
复制代码开始总是找不到原因，最后是上述链接里的一番话，才让我恍然大悟，找到根源
inputstream只可以读取一次！ ，看到这句话，基本问题就迎刃而解了。最简单的方式就是在filter里不要读取inputstream，当然如果你想读取的话，可以采用下面的方式，思路也是上图中说的：decorate the httpServletRequest。代码如下：
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
RequestWrapper requestWrapper = new RequestWrapper((HttpServletRequest) request);
this.preHandle(requestWrapper, (HttpServletResponse) response);
//此处传封装后的HttpServletRequest
chain.doFilter(requestWrapper, response);
this.afterCompletion((HttpServletRequest) request, (HttpServletResponse) response);
}
复制代码RequestWrapper不用改，封装HttpServletRequest之后，doFilter也传入封装的HttpServletRequest即可。
总结
一. 为什么inputStream只可以读取一次
InputStream read方法内部会记录position，用于记录当前流读取到的位置，若已读完，read方法会返回-1，(经常和inputStream打交道的，应该都会while(read() != -1) ，用这种方式读取inputStream)。若读取完再次读取的话可以调用inputStream.reset方法，此方法的前提是此方法markSupported返回true。HttpServletRequest使用的是ServletInputStream，看源码可知ServletInputStream没有实现reset和markSupported方法，那么ServletInputStream无法reset之后再次读取，所以inputStream只可以读取一次！ （我要是对基础有深刻的了解，就不会查这么久了。）
public synchronized void reset() throws IOException {
throw new IOException("mark/reset not supported");
}
/**
* Tests if this input stream supports the <code>mark</code> and
* <code>reset</code> methods. Whether or not <code>mark</code> and
* <code>reset</code> are supported is an invariant property of a
* particular input stream instance. The <code>markSupported</code> method
* of <code>InputStream</code> returns <code>false</code>.
*
* @return <code>true</code> if this stream instance supports the mark
* and reset methods; <code>false</code> otherwise.
* @see java.io.InputStream#mark(int)
* @see java.io.InputStream#reset()
*/
public boolean markSupported() {
return false;
}
复制代码