使用ServletInputStream在攔截器或過濾器中應(yīng)用后重寫

更新時(shí)間：2021年10月26日 11:08:35 作者：閆-先生

這篇文章主要介紹了使用ServletInputStream在攔截器或過濾器中應(yīng)用后重寫，具有很好的參考價(jià)值，希望對大家有所幫助。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教

ServletInputStream在攔截器或過濾器應(yīng)用后重寫

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(shù)據(jù)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();
        }
};

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

導(dǎo)致在controller中無法獲取請求參數(shù)

問題描述

在攔截器種使用了request.getInputStream()或者getReader()，然后在controller接口種使用了@requestbody ，導(dǎo)致controller中無法獲取入?yún)?，?bào)錯(cuò)：HttpMessageNotReadableException: Required request body is missing：

原因分析

ServletRequest中g(shù)etReader()和getInputStream()只能調(diào)用一次。而又由于@RequestBody注解獲取輸出參數(shù)的方式也是根據(jù)流的方式獲取的。所以我們前面使用流獲取后，后面的@RequestBody就獲取不到對應(yīng)的輸入流了。

為什么取不到輸入流了？？？因?yàn)榱鲗?yīng)的是數(shù)據(jù)，數(shù)據(jù)放在內(nèi)存中，有的是部分放在內(nèi)存中。

read 一次標(biāo)記一次當(dāng)前位置（mark position），第二次read就從標(biāo)記位置繼續(xù)讀（從內(nèi)存中copy）數(shù)據(jù)。

所以這就是為什么讀了一次第二次是空了。怎么讓它不為空呢？只要inputstream 中的pos 變成0就可以重寫讀取當(dāng)前內(nèi)存中的數(shù)據(jù)。

javaAPI中有一個(gè)方法public void reset() 這個(gè)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(diào)用該方法！ServletInputStream是不能調(diào)用reset方法，這就導(dǎo)致了只能調(diào)用一次getInputStream()。

如何處理

重寫HttpServletRequestWrapper把request保存下來，然后通過過濾器把保存下來的request再填充進(jìn)去，這樣就可以多次讀取request了。

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(jìn)入了過濾器。。。。。");
			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(dòng)類中注冊過濾器