构建可重复读取Request/Response

Java构建可重复读取的Request和Response

为什么要可重复读取的req和resp

Request和Response本质上都是输入输出流，网络IO流。Request通过InputStream获取输入数据，Response通过OutputStream获取输出数据。因为流中的数据不是一直存储的，读取了就消失了，意思是只能读取一次。所以在像Servlet中拦截器这一部分，拦截Req和Resp的数据并读取，进行相应的操作，因此要对Req和Resp的数据进行保存一份，否者接下来就无法再次获取。

构建可重复读Request，应用在请求拦截器

public class RepeatedRequestWrapper extends HttpServletRequestWrapper {
    // req数据
    private final byte[] body;

    public RepeatedlyRequestWrapper(HttpServletRequest request, ServletResponse response) throws IOException {
        super(request);
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
		// TODO 获取req的二进制数据，自己实现这部分（就是输入流转字符串）
        body = xxxUtil.reqToString(request.getInputStream()).getBytes("UTF-8");
    }

    @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();
            }

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

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

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

            @Override
            public void setReadListener(ReadListener readListener) {

            }
        };
    }
}

构建可重复读Response，应用在响应拦截器

public class RepeatedResponseWrapper extends HttpServletResponseWrapper {

    private ByteArrayOutputStream byteArrayOutputStream;

    private ServletOutputStream servletOutputStream;

    public RepeatedResponseWrapper(HttpServletResponse response) {
        super(response);
        byteArrayOutputStream = new ByteArrayOutputStream();
        servletOutputStream = new ServletOutputStream() {
            @Override
            public boolean isReady() {
                return false;
            }

            @Override
            public void setWriteListener(WriteListener writeListener) {

            }

            @Override
            public void write(int b) throws IOException {
                response.getOutputStream().write(b);
                // 同时写入字节数组
                byteArrayOutputStream.write(b);
            }
        };
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return servletOutputStream;
    }

    public byte[] toByteArray() {
        return byteArrayOutputStream.toByteArray();
    }
}