java后台怎么获取前台传过来的json字符串

public String getRequestPostStr(HttpServletRequest request) throws IOException{
byte buffer[] = getRequestPostBytes(request);
String charEncoding = request.getCharacterEncoding();
if(charEncoding == null){
charEncoding = "UTF-8";
}
return new String(buffer,charEncoding);
}
public byte[] getRequestPostBytes(HttpServletRequest request) throws IOException{
int contentLength = request.getContentLength();
if(contentLength<0){
return null;
}
byte[] buffer = new byte[contentLength];
for(int i = 0;i<contentLength;){
int readlen = request.getInputStream().read(buffer,i,contentLength - i);
if(readlen == -1){
break;
}
i += readlen;
}
return buffer;
}