post请求体内容无法重复获取

post请求体内容无法重复获取

原文链接 https://zhhll.icu/2020/javaweb/问题/6.post请求体内容无法重复获取/

为什么会无法重复读取呢？

以tomcat为例，在进行请求体读取时实际底层调用的是org.apache.catalina.connector.Request的getInputStream()方法，而该方法返回的是CoyoteInputStream输入流

public ServletInputStream getInputStream() throws IOException {
    

    if (usingReader) {
    
        throw new IllegalStateException(sm.getString("coyoteRequest.getInputStream.ise"));
    }

    usingInputStream = true;
    if (inputStream == null) {
    
        inputStream = new CoyoteInputStream(inputBuffer);
    }
    return inputStream;

}

在使用CoyoteInputStream进行读取时

public int read(byte[] b, int off, int len) throws IOException {
    
  // 如果流关闭，则抛出异常
    if (closed) {
    
        throw new IOException(sm.getString("inputBuffer.streamClosed"));
    }
// 如果已经读完了，则返回-1
    if (checkByteBufferEof()) {
    
        return -1;
    }
    int n = Math.min(len, bb.remaining());
    bb.get(b, off, n);
    return n;
}

而流读取完毕都会进行close，这个流close之后，close状态就置为了true，所以导致流无法进行二次读取

那么如何解决呢？将tomcat的Request类进行重新实现吗？代价太大了，sun公司当初在设计的时候就已经提供了解决方法，对于请求和响应，sun公司提供了包装类，可以HttpServletRequestWrapper类包装原始的request对象，实现了HttpServletRequest接口的所有方法，内部调用了所包装的request对象的对应方法；相应的也有HttpServletResponseWrapper类来包装原始的response对象继承HttpServletRequestWrapper来进行方法重写，可以使用HttpServletResponseWrapper和HttpServletRequestWrapper来进行定制响应和请求

public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {
    
		// 存储请求体
    private byte[] body;

    private HttpServletRequest orgRequest;

    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
    
        super(request);
        this.orgRequest = request;
        body = HttpHelper.getBody(request);
    }

    public HttpServletRequest getOrgRequest() {
    
        return this.orgRequest;
    }

  // 重写读取，从存储的字节数组中读
    @Override
    public BufferedReader getReader() throws IOException {
    
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }

  // 重写读取，从存储的字节数组中读
    @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 boolean isFinished() {
    
                return false;
            }

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

            @Override
            public void setReadListener(ReadListener readListener) {
    

            }
        };
    }
}