java在filter中获取POST请求中request参数以及解决ServletInputStream重复读取的问题

想要回去GET请求中的请求参数，可以直接使用request.getParamMap()方法。但是POST请求的requestBody参数就必须使用流的方式来获取。

            BufferedReader reader = null;
            String body = null;
            try {
                reader = new BufferedReader(new InputStreamReader(request.getInputStream()));
                body = IOUtils.read(reader).replaceAll("\t|\n|\r", "");
            } catch (IOException e) {
                logger.error("流读取错误："+e);
                return;
            }finally {
                if (null != reader){
                    try {
                        reader.close();
                    } catch (IOException e) {
                        logger.error("流关闭错误："+e);
                    }
                }
            }
            Map<String,Object> paramMap = JSON.parseObject(body);

这样将获取body中的所有json格式的参数信息。可以根据需求，进行验签或校验等一系列操作。但是当我们chain.doFilter(request, response)，惊喜的发现接口400了！！
WHAT？？！！
嘿嘿o(￣▽￣)ｄ
我们都知道，读取流的时候是有标志的，读取一次移动一次，读取到哪里，移动到哪里，读到最后，返回-1，表示读取完成。再次读取需要重置位置，但是ServletInputStream中是没有重置方法的，也就是说流只能被读取一次。神奇！！Σ(⊙▽⊙"a 此时的流已经被读取一次，相当于已经作废，此时请求接口必然是报错的。
行吧，你既然不让我重复读，那我就把你的流拿过来封装成自己的流，这样我想读多少次就读多少次！ψ(｀∇´)ψ
加入jar包：javax.servlet

        <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>

实现HttpServletRequestWrapper类

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.*;
import java.net.URLDecoder;
import java.util.*;

/**
 * @author zhoumin
 * @create 2018-10-31 16:13
 */
public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {
    private Map<String, String[]> paramsMap;

    @Override
    public Map getParameterMap() {
        return paramsMap;
    }

    @Override
    public String getParameter(String name) {// 重写getParameter，代表参数从当前类中的map获取
        String[] values = paramsMap.get(name);
        if (values == null || values.length == 0) {
            return null;
        }
        return values[0];
    }

    @Override
    public String[] getParameterValues(String name) {// 同上
        return paramsMap.get(name);
    }

    @Override
    public Enumeration getParameterNames() {
        return Collections.enumeration(paramsMap.keySet());
    }

    private String getRequestBody(InputStream stream) {
        String line = "";
        StringBuilder body = new StringBuilder();
        int counter = 0;

        // 读取POST提交的数据内容
        BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
        try {
            while ((line = reader.readLine()) != null) {
                if (counter > 0) {
                    body.append("rn");
                }
                body.append(line);
                counter++;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return body.toString();
    }

    private HashMap<String, String[]> getParamMapFromPost(HttpServletRequest request) {

        String body = "";
        try {
            body = getRequestBody(request.getInputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }
        HashMap<String, String[]> result = new HashMap<String, String[]>();

        if (null == body || 0 == body.length()) {
            return result;
        }

        return parseQueryString(body);
    }

    // 自定义解码函数
    private String decodeValue(String value) {
        if (value.contains("%u")) {
            return Encodes.urlDecode(value);
        } else {
            try {
                return URLDecoder.decode(value, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                return "";// 非UTF-8编码
            }
        }
    }

    public HashMap<String, String[]> parseQueryString(String s) {
        String valArray[] = null;
        if (s == null) {
            throw new IllegalArgumentException();
        }
        HashMap<String, String[]> ht = new HashMap<String, String[]>();
        StringTokenizer st = new StringTokenizer(s, "&");
        while (st.hasMoreTokens()) {
            String pair = (String) st.nextToken();
            int pos = pair.indexOf('=');
            if (pos == -1) {
                continue;
            }
            String key = pair.substring(0, pos);
            String val = pair.substring(pos + 1, pair.length());
            if (ht.containsKey(key)) {
                String oldVals[] = (String[]) ht.get(key);
                valArray = new String[oldVals.length + 1];
                for (int i = 0; i < oldVals.length; i++) {
                    valArray[i] = oldVals[i];
                }
                valArray[oldVals.length] = decodeValue(val);
            } else {
                valArray = new String[1];
                valArray[0] = decodeValue(val);
            }
            ht.put(key, valArray);
        }
        return ht;
    }

    private Map<String, String[]> getParamMapFromGet(HttpServletRequest request) {
        return parseQueryString(request.getQueryString());
    }

    private final byte[] body; // 报文

    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        body = readBytes(request.getInputStream());

        // 首先从POST中获取数据
        if ("POST".equals(request.getMethod().toUpperCase())) {
            paramsMap = getParamMapFromPost(this);
        } else {
            paramsMap = getParamMapFromGet(this);
        }

    }

    @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 arg0) {

            }
        };
    }

    private static byte[] readBytes(InputStream in) throws IOException {
        BufferedInputStream bufin = new BufferedInputStream(in);
        int buffSize = 1024;
        ByteArrayOutputStream out = new ByteArrayOutputStream(buffSize);

        byte[] temp = new byte[buffSize];
        int size = 0;
        while ((size = bufin.read(temp)) != -1) {
            out.write(temp, 0, size);
        }
        bufin.close();

        byte[] content = out.toByteArray();
        return content;
    }

}

解码

/**
     * URL 解码, Encode默认为UTF-8.
     */
    public static String urlDecode(String part) {
        try {
            return URLDecoder.decode(part, DEFAULT_URL_ENCODING);
        } catch (UnsupportedEncodingException e) {
            throw new InvalidTokenException(part);
        }
    }

那么上面读取参数的代码修改为：

             ServletRequest requestWrapper = new BodyReaderHttpServletRequestWrapper(
                    (HttpServletRequest) request);
            BufferedReader reader = null;
            String body = null;
            try {
                reader = new BufferedReader(new InputStreamReader(requestWrapper.getInputStream()));
                body = IOUtils.read(reader).replaceAll("\t|\n|\r", "");
            } catch (IOException e) {
                logger.error("流读取错误："+e);
                return;
            }finally {
                if (null != reader){
                    try {
                        reader.close();
                    } catch (IOException e) {
                        logger.error("流关闭错误："+e);
                    }
                }
            }
            Map<String,Object> paramMap = JSON.parseObject(body);
            .
            .
            .
            chain.doFilter(requestWrapper, response);

OK!又是打酱油的一天。(づ｡◕ᴗᴗ◕｡)づ