HttpServletRequestWrapper使用：解决HttpServletRequest只能读取一次流后无法获取的问题，封装request.getInputStream()

文章目录

1.背景

​ 在过滤器中获取请求的参数信息，并对参数信息进行校验。

2.过滤器

package com.qin.filter;

import com.qin.common.util.RequestWrapper;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;


/**
 * 这个类留着给多次获取request中的参数流使用
 * 原理和springsession类似，将request重写
 */
@Configuration
@WebFilter(filterName="requestFilter", urlPatterns="/**")
@Order(0)
public class RequestFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        ServletRequest requestWrapper = null;
        if(request instanceof HttpServletRequest) {
            requestWrapper = new RequestWrapper((HttpServletRequest) request);
        }
        if(requestWrapper == null) {
            chain.doFilter(request, response);
        } else {
            chain.doFilter(requestWrapper, response);
        }
    }

    @Override
    public void destroy() {

    }
}

3.RequestWrapper

package com.qin.common.util;

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) throws IOException {
        super(request);
        StringBuilder stringBuilder = new StringBuilder();
        BufferedReader bufferedReader = null;
        try {
            InputStream 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) {
            throw ex;
        } finally {
            if (bufferedReader != null) {
                try {
                    bufferedReader.close();
                } catch (IOException ex) {
                    throw ex;
                }
            }
        }
        body = stringBuilder.toString();
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes());
        ServletInputStream servletInputStream = new ServletInputStream() {
            public boolean isFinished() {
                return false;
            }
            public boolean isReady() {
                return false;
            }
            public void setReadListener(ReadListener readListener) {}
            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;
    }

}

4.业务处理（获取请求参数并且加密）

public String encryptParam(HttpServletRequest request){
    // request.getInputStream()为上述RequestWrapper包装的方法
    ServletInputStream inputStream = request.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        int contentLength = request.getContentLength();
        byte[] bytes = new byte[contentLength];
        int lens = -1;
        while ((lens = inputStream.read(bytes, 0, contentLength)) != -1) {
            baos.write(bytes, 0, lens);
        }
    //加密baos
    
}