springboot 获取到的inputStream为空的问题

springboot在接收http请求的时候读取的request的inputStream，造成我们想自己读取inputStream的时候发现inputStream已经无法读取了。

为了读取inputStream，我们应该在springboot读取之前把inputStream的内容暂存先来。

1 这里要使用一个类HttpServletRequestWrapper，我们写一个类继承这个类，把传入的request中的inputStream转为byte[] 暂存下来，重写其中的getInputStream方法，每次返回由暂存的byte转换而来的 inputStream。

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Collection;
import java.util.stream.Collectors;

import javax.servlet.ReadListener;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.Part;

import org.springframework.web.bind.annotation.RequestMethod;

public class InputStreamHttpServletRequestWrapper extends HttpServletRequestWrapper {
    private final byte[] streamBody;
    private static final int BUFFER_SIZE = 4096;

    public InputStreamHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        byte[] bytes = new byte[0];
        String uri = request.getRequestURI();
        if (Objects.isNull(request.getHeader("Content-Type")) || request.getHeader("Content-Type").contains("multipart/form-data;")) {
            bytes = inputStream2Byte(request.getInputStream());
        } else if (isFormPost(request)) {
            // 从ParameterMap获取参数，并保存以便多次获取
            bytes = params2Byte(request);
        } else {
            bytes = inputStream2Byte(request.getInputStream());
        }

        streamBody = bytes;
        // this.setRequest(this);
    }

    private boolean isFormPost(HttpServletRequest request) {
        return RequestMethod.POST.name().equals(request.getMethod());
    }

    private byte[] params2Byte(HttpServletRequest request) {
        byte[] bytes = request.getParameterMap().entrySet().stream().map(entry -> {
            String result;
            String[] value = entry.getValue();
            if (value != null && value.length > 1) {
                result = Arrays.stream(value).map(s -> entry.getKey() + "=" + s).collect(Collectors.joining("&"));
            } else {
                result = entry.getKey() + "=" + value[0];
            }

            return result;
        }).collect(Collectors.joining("&")).getBytes();
        return bytes;
    }

    private byte[] inputStream2Byte(InputStream inputStream) throws IOException {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        byte[] bytes = new byte[BUFFER_SIZE];
        int length;
        while ((length = inputStream.read(bytes, 0, BUFFER_SIZE)) != -1) {
            outputStream.write(bytes, 0, length);
        }

        return outputStream.toByteArray();
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        ByteArrayInputStream inputStream = new ByteArrayInputStream(streamBody);

        return new ServletInputStream() {
            @Override
            public boolean isFinished() {
                return false;
            }

            @Override
            public boolean isReady() {
                return false;
            }

            @Override
            public void setReadListener(ReadListener listener) {

            }

            @Override
            public int read() throws IOException {
                return inputStream.read();
            }
        };
    }

    @Override
    public BufferedReader getReader() throws IOException {
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }
}

2.这里要使用一个神奇的filter：HiddenHttpMethodFilter

在这个类中调用之前定义的 InputStreamHttpServletRequestWrapper类，并把实例化之后的类传入以后的filter中，这样以后所有的 ServletRequest 都是我们自己定义的了。

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.filter.HiddenHttpMethodFilter;
import org.springframework.web.filter.OncePerRequestFilter;

import com.esri.rest.configure.helper.InputStreamHttpServletRequestWrapper;

public class InputStreamWrapperFilter extends HiddenHttpMethodFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {

        ServletRequest servletRequest = new InputStreamHttpServletRequestWrapper(request);

        filterChain.doFilter(servletRequest, response);

    }

}

3，最后一步：把filter加入springboot 配置

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.web.filter.HiddenHttpMethodFilter;

import com.esri.rest.filter.InputStreamWrapperFilter;

@Configuration
public class RequestConfig { 

    @Bean
    @Order(1)
    public HiddenHttpMethodFilter hiddenHttpMethodFilter() {
        return new InputStreamWrapperFilter();
    }
}