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springboot过滤器、拦截器相关知识

request.getParameterNames()不会消耗HTTP请求的输入流。

当处理application/json或multipart/form-data（特别是包含文件上传时）等类型的请求体时，这些内容通常不会通过getParameter或getParameterNames等方法直接访问，因为这些方法主要用于处理URL编码的表单数据。需要通过getInputStream()或getReader()等方法来读取整个请求体，并将其解析为相应的数据结构（如JSON对象或MultipartFile列表）。调用getInputStream()、getReader()等来读取请求体时，读取后会被关闭或消耗，意味着你不能在同一个请求中再次调用这些方法（除非你使用了某种形式的缓存或包装机制）。

getParameterNames()和getParameter()等方法访问的是请求参数，而不是请求体本身，因此它们不会消耗请求体。

HTTP请求体在Servlet容器中通常只能被读取一次，因为ServletInputStream和BufferedReader（后者通常是通过HttpServletRequest.getReader()获得的）在读取数据后不会将读取位置重置回开始。这意味着一旦你读取了请求体，你就无法在同一个请求中再次读取它，除非你在第一次读取时就已经将内容存储起来（比如复制到一个字节数组或字符流中）。

示例：在拦截器中读取Json参数

Java配置文件

@Configuration  
public class CustomWebMvcConfig implements WebMvcConfigurer {  @Autowired  private CustomInterceptor customInterceptor;  @Override  public void addInterceptors(InterceptorRegistry registry) {  registry.addInterceptor(customInterceptor)  .addPathPatterns("/**"); // 拦截所有请求，或根据需要调整  }  @Bean  public FilterRegistrationBean<FormDataToJsonFilter> formDataToJsonFilter() {  FilterRegistrationBean<FormDataToJsonFilter> registrationBean = new FilterRegistrationBean<>();  registrationBean.setFilter(new FormDataToJsonFilter());  registrationBean.addUrlPatterns("/*"); // 拦截所有请求  return registrationBean;  }  
}

过滤器

public class FormDataToJsonFilter implements Filter {  @Override  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)  throws IOException, ServletException {  HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;ServletRequest requestWrapper = new JsonParamRequestWrapper(httpServletRequest);filterChain.doFilter(requestWrapper, servletResponse);//   }  }

自定义的HttpServletRequestWrapper

这个包装类将允许读取请求体，并且不会阻止其他组件（如Controller）再次读取它。

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;  public class JsonParamRequestWrapper extends HttpServletRequestWrapper {  private final String body;  public JsonParamRequestWrapper (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);  }  }  } finally {  if (bufferedReader != null) {  bufferedReader.close();  }  }  body = stringBuilder.toString();  }  @Override  public BufferedReader getReader() throws IOException {  return new BufferedReader(new InputStreamReader(new ByteArrayInputStream(body.getBytes())));  }  @Override  public ServletInputStream getInputStream() throws IOException {  final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes());  return new ServletInputStream() {  @Override  public boolean isFinished() {  return byteArrayInputStream.available() == 0;  }  @Override  public boolean isReady() {  return true;  }  @Override  public int read() throws IOException {  return byteArrayInputStream.read();  }  };  }  // Getter for the body (if needed)  public String getBody() {  return this.body;  }  
}

拦截器

@Component  
public class CustomInterceptor implements HandlerInterceptor {  private final RestTemplate restTemplate = new RestTemplate();  private final ObjectMapper objectMapper = new ObjectMapper();  @Override  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {  if ("POST".equalsIgnoreCase(request.getMethod())) {  JsonParamRequestWrapper requestWrapper = new JsonParamRequestWrapper(request);String body = requestWrapper.getRequestBody();logger.info("请求体:" + body);String sign = "";String data = "";// 进行验签逻辑boolean isValid = verifySignature(sign, data);if (!isValid) {response.setStatus(HttpServletResponse.SC_FORBIDDEN);return false;}}  // 继续执行下一个拦截器或目标处理器  return true;  } // 验签方法  private boolean validateSignature(String body) {  // 验签逻辑  return true; }  }