使用ServletInputStream在攔截器或過濾器中應用後重寫

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ServletInputStream在攔截器或過濾器應用後重寫

ServletInputStream inputStream = super.getInputStream();
StringBuilder sb = new StringBuilder();
BufferedReader reader = null;
try {
    reader = new BufferedReader(new InputStreamReader(servletInputStream, Charset.forName("UTF-8")));
    String line = "";
    while ((line = reader.readLine()) != null) {
          sb.append(line);
    }
} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (servletInputStream != null) {
       try {
           servletInputStream.close();
       } catch (IOException e) {
           e.printStackTrace();
       }
    }
    if (reader != null) {
         try {
              reader.close();
         } catch (IOException e) {
              e.printStackTrace();
         }
    }
}
//使用ServletInputStream中數據的代碼
byte[] bytes = sb.getBytes("UTF-8");
final ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
return new ServletInputStream() {
       @Override
       public boolean isFinished() {
               return false;
       }
 
        @Override
        public boolean isReady() {
               return false;
        }
 
        @Override
        public void setReadListener(ReadListener readListener) {
 
        }
 
        @Override
        public int read() throws IOException {
               return bais.read();
        }
};

在攔截器種使用瞭request.getInputStream()或者getReader()

導致在controller中無法獲取請求參數

問題描述

在攔截器種使用瞭request.getInputStream()或者getReader()，然後在controller接口種使用瞭@requestbody ，導致controller中無法獲取入參，報錯：HttpMessageNotReadableException: Required request body is missing：

原因分析

ServletRequest中getReader()和getInputStream()隻能調用一次。而又由於@RequestBody註解獲取輸出參數的方式也是根據流的方式獲取的。所以我們前面使用流獲取後，後面的@RequestBody就獲取不到對應的輸入流瞭。

為什麼取不到輸入流瞭？？？因為流對應的是數據，數據放在內存中，有的是部分放在內存中。

read 一次標記一次當前位置（mark position），第二次read就從標記位置繼續讀（從內存中copy）數據。

所以這就是為什麼讀瞭一次第二次是空瞭。 怎麼讓它不為空呢？隻要inputstream 中的pos 變成0就可以重寫讀取當前內存中的數據。

javaAPI中有一個方法public void reset() 這個方法就是可以重置pos為起始位置，但是不是所有的IO讀取流都可以調用該方法！ServletInputStream是不能調用reset方法，這就導致瞭隻能調用一次getInputStream()。

如何處理

重寫HttpServletRequestWrapper把request保存下來，然後通過過濾器把保存下來的request再填充進去，這樣就可以多次讀取request瞭。

第一步：定義過濾器

 
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
 
@WebFilter(urlPatterns = "/*", filterName = "channelFilter")
public class ChannelFilter implements Filter {
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
	}
 
	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
			throws IOException, ServletException {
		ServletRequest requestWrapper = null;
		if (servletRequest instanceof HttpServletRequest) {
			requestWrapper = new RequestWrapper((HttpServletRequest) servletRequest);
		}
		if (requestWrapper == null) {
			filterChain.doFilter(servletRequest, servletResponse);
		} else {
			System.out.println("進入瞭過濾器。。。。。");
			filterChain.doFilter(requestWrapper, servletResponse);
		}
	}
 
	@Override
	public void destroy() {
	}
}

第二步：重寫RequestWrapper類

 
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.*;
 
public class RequestWrapper extends HttpServletRequestWrapper { 
	private final String body; 
	public RequestWrapper(HttpServletRequest request) {
		super(request);
		StringBuilder stringBuilder = new StringBuilder();
		BufferedReader bufferedReader = null;
		InputStream inputStream = null;
		try {
			inputStream = request.getInputStream();
			if (inputStream != null) {
				bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
				char[] charBuffer = new char[128];
				int bytesRead = -1;
				while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
					stringBuilder.append(charBuffer, 0, bytesRead);
				}
			} else {
				stringBuilder.append("");
			}
		} catch (IOException ex) {
		} finally {
			if (inputStream != null) {
				try {
					inputStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if (bufferedReader != null) {
				try {
					bufferedReader.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		body = stringBuilder.toString();
	} 
	@Override
	public ServletInputStream getInputStream() throws IOException {
		final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes());
		ServletInputStream servletInputStream = new ServletInputStream() {
			@Override
			public boolean isFinished() {
				return false;
			}
 
			@Override
			public boolean isReady() {
				return false;
			}
 
			@Override
			public void setReadListener(ReadListener readListener) {
			}
 
			@Override
			public int read() throws IOException {
				return byteArrayInputStream.read();
			}
		};
		return servletInputStream;
	}
 
	@Override
	public BufferedReader getReader() throws IOException {
		return new BufferedReader(new InputStreamReader(this.getInputStream()));
	} 
	public String getBody() {
		return this.body;
	}
}

第三步：在啟動類中註冊過濾器

以上為個人經驗，希望能給大傢一個參考，也希望大傢多多支持WalkonNet。

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