统一日志输出打印POST请求参数

众所周知，request.getInputStream()只能调一次。如果希望在请求进入Controller之前统一打印请求参数（拦截器或过滤器），又不影响业务，我们只能将获取到的输入流缓存起来，后续都从缓存中获取即可。
首先，自定义一个ServletInputStream

1. package com.cjs.example.log.filter;
3. import javax.servlet.ReadListener;
4. import javax.servlet.ServletInputStream;
5. import java.io.ByteArrayInputStream;
6. import java.io.IOException;
8. /**
9. * @Author: ChengJianSheng
10. * @Date: 2023/3/6
11. */
12. public class CustomServletInputStream extends ServletInputStream {
14.     private ByteArrayInputStream inputStream;
16.     public CustomServletInputStream(byte[] body) {
17.         this.inputStream = new ByteArrayInputStream(body);
18.     }
20.     @Override
21.     public boolean isFinished() {
22.         return inputStream.available() == 0;
23.     }
25.     @Override
26.     public boolean isReady() {
27.         return true;
28.     }
30.     @Override
31.     public void setReadListener(ReadListener readListener) {
33.     }
35.     @Override
36.     public int read() throws IOException {
37.         return inputStream.read();
38.     }
39. }

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然后，自定义一个HttpServletRequestWrapper

1. package com.cjs.example.log.filter;
3. import org.apache.commons.io.IOUtils;
5. import javax.servlet.ServletInputStream;
6. import javax.servlet.http.HttpServletRequest;
7. import javax.servlet.http.HttpServletRequestWrapper;
8. import java.io.*;
10. /**
11. * @Author: ChengJianSheng
12. * @Date: 2023/3/6
13. */
14. public class CustomHttpServletRequestWrapper extends HttpServletRequestWrapper {
16.     private byte[] body;
18.     public CustomHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
19.         super(request);
20.         body = IOUtils.toByteArray(request.getInputStream());
21.     }
23.     @Override
24.     public ServletInputStream getInputStream() throws IOException {
25.         return new CustomServletInputStream(body);
26.     }
28.     @Override
29.     public BufferedReader getReader() throws IOException {
30.         return new BufferedReader(new InputStreamReader(getInputStream(), getCharacterEncoding()));
31.     }
32. }

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接下来，写一个过滤器，在过滤器中打印请求参数

1. package com.cjs.example.log.filter;
3. import org.apache.commons.io.IOUtils;
4. import org.slf4j.Logger;
5. import org.slf4j.LoggerFactory;
7. import javax.servlet.*;
8. import javax.servlet.http.HttpServletRequest;
9. import java.io.IOException;
11. /**
12. * @Author: ChengJianSheng
13. * @Date: 2023/3/6
14. */
15. public class LogFilter implements Filter {
17.     private final static Logger logger = LoggerFactory.getLogger(LogFilter.class);
19.     @Override
20.     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
21.         CustomHttpServletRequestWrapper requestWrapper = new CustomHttpServletRequestWrapper((HttpServletRequest) servletRequest);
22.         printLog(requestWrapper);
23.         filterChain.doFilter(requestWrapper, servletResponse);
24.     }
26.     private void printLog(CustomHttpServletRequestWrapper requestWrapper) throws IOException {
27.         logger.info("请求URL: {}", requestWrapper.getRequestURL());
28.         String method = requestWrapper.getMethod();
29.         if ("GET".equalsIgnoreCase(method)) {
30.             logger.info("请求参数: {}", requestWrapper.getQueryString());
31.         } else if ("POST".equalsIgnoreCase(method) && "application/json".equalsIgnoreCase(requestWrapper.getContentType())) {
32.             String body = IOUtils.toString(requestWrapper.getInputStream(), requestWrapper.getCharacterEncoding());
33.             logger.info("请求参数: {}", body);
34.         }
35.     }
36. }

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请求经过过滤器的时候，首先在构造CustomHttpServletRequestWrapper的时候将请求中的InputStream转成字节数字缓存到内存中，然后后面每次再getInputStream()的时候都从缓存中取出内容并返回一个新的ServletInputStream
最后，定义一个配置类

1. package com.cjs.example.log.config;
3. import com.cjs.example.log.filter.LogFilter;
4. import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
5. import org.springframework.context.annotation.Bean;
6. import org.springframework.context.annotation.Configuration;
8. /**
9. * @Author: ChengJianSheng
10. * @Date: 2023/3/6
11. */
12. @Configuration
13. public class CustomLogAutoConfiguration {
14.     @Bean
15.     @ConditionalOnMissingBean
16.     public LogFilter logFilter() {
17.         return new LogFilter();
18.     }
19. }

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在resources/META-INF/spring.factories中新增一行自动配置

1. org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.cjs.example.log.config.CustomLogAutoConfiguration

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