最近有一個需要從攔截器中獲取post請求的參數的需求，這里記錄一下處理過程中出現的問題。
首先想到的就是request.getParameter(String )方法，但是這個方法只能在get請求中取到參數，post是不行的，后來想到了使用流的方式，調用request.getInputStream()獲取流，然后從流中讀取參數，如下代碼所示：
String body = "";
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) {
e.printStackTrace();
} 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();
代碼中的body就是request中的參數，我這里傳的是JSON數據：{"page": 1, "pageSize": 10}，那么body就是：body = "{"page": 1, "pageSize": 10}"，一個JSON字符串。這樣是可以成功獲取到post請求的body，但是，經過攔截器后，參數經過@RequestBody注解賦值給controller中的方法的時候，卻拋出了一個這樣的異常：
org.springframework.http.converter.HttpMessageNotReadableException: Required request body is missing
在網上查找資料后發現，request的輸入流只能讀取一次，那么這是為什么呢？下面是答案：
那是因為流對應的是數據，數據放在內存中，有的是部分放在內存中。read 一次標記一次當前位置（mark position），第二次read就從標記位置繼續讀（從內存中copy）數據。 所以這就是為什么讀了一次第二次是空了。 怎么讓它不為空呢？只要inputstream 中的pos 變成0就可以重寫讀取當前內存中的數據。javaAPI中有一個方法public void reset() 這個方法就是可以重置pos為起始位置，但是不是所有的IO讀取流都可以調用該方法！ServletInputStream是不能調用reset方法，這就導致了只能調用一次getInputStream()。
那么有什么辦法可以用戶解決呢？上面這篇博客中提到了解決方案，就是重寫HttpServletRequestWrapper把request保存下來，然后通過過濾器把保存下來的request再填充進去，這樣就可以多次讀取request了。步驟如下所示：
①寫一個類，繼承HttpServletRequestWrapper
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;
}
}
②攔截器層面
import com.alibaba.fastjson.JSON;
import com.miniprogram.api.douyin.user.req.DyuserReq;
import com.miniprogram.common.auth.VisitLimitCount;
import com.miniprogram.common.cache.RedisCache;
import com.miniprogram.common.config.InterceptorConfigMap;
import com.miniprogram.common.config.InterceptorUrlConfig;
import com.miniprogram.common.douyin.SearchEngineMapConstants;
import com.miniprogram.common.response.Response;
import com.miniprogram.common.session.*;
import com.miniprogram.common.utils.DateUtil;
import com.miniprogram.dao.common.UserLoginEntity.Users;
import com.miniprogram.service.douyin.users.UsersService;
import com.miniprogram.web.douyin.config.RequestWrapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
@Component("authSecurityInterceptor")
public class AuthSecurityInterceptor extends HandlerInterceptorAdapter {
private Logger logger = LoggerFactory.getLogger(AuthSecurityInterceptor.class);
@Autowired
private RedisCache redisCache;
@Autowired
private VisitLimitCount visitLimitCount;
@Override
public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
try {
RequestWrapper requestWrapper = new RequestWrapper(httpServletRequest);
String body = requestWrapper.getBody();
System.out.println(body);
return true;
}catch (Exception e){
logger.error("權限判斷出錯",e);
}
return false;
}
@Override
public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
}
@Override
public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
}
}
③過濾器Filter，用來把request傳遞下去
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 {
filterChain.doFilter(requestWrapper, servletResponse);
}
}
@Override
public void destroy() {
}
}
④在啟動類中注冊攔截器
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.MultipartConfigFactory;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@SpringBootApplication
// @ServletComponentScan //注冊過濾器注解
@Configuration
public class WebApplication {
public static void main(String[] args) {
SpringApplication.run(WebApplication.class, args);
}
}