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

原创
2020/12/24 20:27
阅读数 1.4W

在 Filter 中对 request 中的 body 进行参数签名校验, 会报如下错误: 

getReader() has already been called for this request

原因是 request.getReader() 和 request.getInputStream() 都是只能调用一次

并且 getReader() 方法底层也是调用 getInputStream() 来实现的.

所以我们要使用 HttpServletRequestWrapper 来实现自定义的 CustomHttpServletRequestWrapper, 把 body 保存在 CustomHttpServletRequestWrapper 中, 并且重写 getInputStream() 方法

public class CustomHttpServletRequestWrapper extends HttpServletRequestWrapper{

	private byte[] body;

	public CustomHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
		super(request);
		
		BufferedReader reader = request.getReader();
		try (StringWriter writer = new StringWriter()) {
			int read;
            char[] buf = new char[1024 * 8];
    		while ((read = reader.read(buf)) != -1) {
    			writer.write(buf, 0, read);
    		}
    		this.body = writer.getBuffer().toString().getBytes();
        }
	}
	
	public byte[] getBody() {
		return body;
	}
	
	@Override
	public ServletInputStream getInputStream() throws IOException {
		ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body);
		return new ServletInputStream() {
			
			@Override
			public int read() throws IOException {
				return byteArrayInputStream.read();
			}
			
			@Override
			public void setReadListener(ReadListener listener) {
			}
			
			@Override
			public boolean isReady() {
				return true;
			}
			
			@Override
			public boolean isFinished() {
				return false;
			}
		};
	}
}

然后, 获取 body 就调用 CustomHttpServletRequestWrapper 中的 getBody() 方法, 后面就使用

filterChain.doFilter(customHttpServletRequestWrapper, response);

就 OK 了

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