interceptor or controller 获取流异常

　　最近做一个拦截器获取参数的需求 (还有一个在 controller 获取 request 的流的时候也出现了同样的问题。)，本来运行的好好的，可是迭代了几个版本之后，发现所有获取流的方法都出现了问题。经过排查发现是加了几个拦截器。而 request.getInputStream() 只可以读一次。所以导致后续从request获取数据全部是空，才出现的异常。所以我们可以通过 filter 将request存起来，这样用的时候就不会出异常了。

1. 工具类

import javax.servlet.http.HttpServletRequest;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;

public class HttpHelper {
    public static String getBodyString(HttpServletRequest request) throws IOException {
        StringBuilder sb = new StringBuilder();
        InputStream inputStream = null;
        BufferedReader reader = null;
        try {
            inputStream = request.getInputStream();
            reader = new BufferedReader(new InputStreamReader(inputStream, Charset.forName("UTF-8")));
            String line = "";
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return sb.toString();
    }
}

2. 包装类处理流

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;

public class RequestReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {

    private final byte[] body;

    public RequestReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        body = HttpHelper.getBodyString(request).getBytes(Charset.forName("UTF-8"));
    }

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

    @Override
    public ServletInputStream getInputStream() throws IOException {

        final ByteArrayInputStream bais = new ByteArrayInputStream(body);

        return new ServletInputStream() {

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

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

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

            @Override
            public void setReadListener(ReadListener readListener) {

            }
        };
    }
}

3. 添加过滤器

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


public class HttpServletRequestReplacedFilter implements Filter {
    @Override
    public void destroy() {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain) throws IOException, ServletException {
        ServletRequest requestWrapper = null;
        if(request instanceof HttpServletRequest) {
            requestWrapper = new RequestReaderHttpServletRequestWrapper((HttpServletRequest) request);
        }
        //获取请求中的流如何，将取出来的字符串，再次转换成流，然后把它放入到新request对象中。
        // 在chain.doFiler方法中传递新的request对象
        if(requestWrapper == null) {
            chain.doFilter(request, response);
        } else {
            chain.doFilter(requestWrapper, response);
        }
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {

    }
}

4. 注册过滤器

@Configuration
public class RpcAuthenticationConfiguration {

    @Bean
    public FilterRegistrationBean httpServletRequestReplacedRegistration() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new HttpServletRequestReplacedFilter());
        registration.addUrlPatterns("/*");
        registration.setName("httpServletRequestReplacedFilter");
        registration.setOrder(1);
        return registration;
    }
}

。