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

java 复制代码

@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

java 复制代码

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。

java 复制代码

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

java 复制代码

@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; 
    }  
  
}