异常：getReader() has already been called for this request

太过爱你忘了你带给我的痛 2022-05-22 04:11 221阅读 0赞

一个流不能读两次异常，这种异常一般出现在框架或者拦截器中读取了request中的流的数据，我们在业务代码中再次读取（如@requestBody），由于流中的数据已经没了，所以第二次读取的时候就会抛出异常。

解决方案：定义一个过滤器将流中的数据读取到一个数组中，并重写getInputStream()和getRead()方法，后续获取流中的数据的时候，直接去数组中读取，代码实现如下：

class DealStreamFilter extends AbstractWebFilter { 
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            logger.info("进入DealStreamFilter。。。。。。");
            ServletRequest requestWrapper = null;
            if (servletRequest instanceof HttpServletRequest) {
                requestWrapper = new BodyReaderHttpServletRequestWrapper((HttpServletRequest) servletRequest);
            }
            if (null == requestWrapper) {
                filterChain.doFilter(servletRequest, servletResponse);
            } else {
                filterChain.doFilter(requestWrapper, servletResponse);
            }
        }
    
        static class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper { 
    
            private final byte[] body;
    
            public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
                super(request);
                body = toByteArray(request.getInputStream());
            }
    
            private byte[] toByteArray(InputStream in) throws IOException {
    
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024 * 4];
                int n = 0;
                while ((n = in.read(buffer)) != -1) {
                    out.write(buffer, 0, n);
                }
                return out.toByteArray();
            }
    
            @Override
            public BufferedReader getReader() throws IOException {
                return new BufferedReader(new InputStreamReader(getInputStream()));
            }
    
    
            @Override
            public ServletInputStream getInputStream() throws IOException {
                final ByteArrayInputStream bais = new ByteArrayInputStream(body);
                return new ServletInputStream() {
                    @Override
                    public int read() throws IOException {
                        return bais.read();
                    }
                };
            }
        }
    }

将过滤器配置到配置文件：

<bean id="dealStreamFilter" class="com.pingan.apollo.filter.DealStreamFilter">
        <property name="patterns" >
            <list>
                <value>/loan/device/report.do</value>
            </list>
        </property>
        <property name="order" >
            <value>-999999</value>
        </property>
    </bean>