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使用ServletInputStream在拦截器或过滤器中应用后重写

︶ㄣSDDLL学院 メ
SDDLL学院V管理员 / 阅读
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这篇文章主要介绍了使用ServletInputStream在拦截器或过滤器中应用后重写，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教

这篇文章主要介绍了使用ServletInputStream在拦截器或过滤器中应用后重写，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教

ServletInputStream在拦截器或过滤器应用后重写

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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中数据的代码
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();
        }
};

在拦截器种使用了request.getInputStream()或者getReader()

导致在controller中无法获取请求参数

问题描述

在拦截器种使用了request.getInputStream()或者getReader()，然后在controller接口种使用了@requestbody ，导致controller中无法获取入参，报错：HttpMessageNotReadableException: Required request body is missing：

原因分析

ServletRequest中getReader()和getInputStream()只能调用一次。而又由于@RequestBody注解获取输出参数的方式也是根据流的方式获取的。所以我们前面使用流获取后，后面的@RequestBody就获取不到对应的输入流了。

为什么取不到输入流了？？？因为流对应的是数据，数据放在内存中，有的是部分放在内存中。

read 一次标记一次当前位置（mark position），第二次read就从标记位置继续读（从内存中copy）数据。

所以这就是为什么读了一次第二次是空了。 怎么让它不为空呢？只要inputstream 中的pos 变成0就可以重写读取当前内存中的数据。

javaAPI中有一个方法public void reset() 这个方法就是可以重置pos为起始位置，但是不是所有的IO读取流都可以调用该方法！ServletInputStream是不能调用reset方法，这就导致了只能调用一次getInputStream()。

如何处理

重写HttpServletRequestWrapper把request保存下来，然后通过过滤器把保存下来的request再填充进去，这样就可以多次读取request了。

第一步：定义过滤器

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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("进入了过滤器。。。。。");
            filterChain.doFilter(requestWrapper, servletResponse);
        }
    }
 
    @Override
    public void destroy() {
    }
}

第二步：重写RequestWrapper类

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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：在启动类中注册过滤器

使用ServletInputStream在拦截器或过滤器中应用后重写

以上为个人经验，希望能给大家一个参考，也希望大家多多支持米米素材网。

原文链接：https://blog.csdn.net/u011110968/article/details/80228567