java 过滤器获取请求返回的数据

Java 过滤器可以通过 HttpServletRequestWrapper 类来获取请求返回的数据。

实现步骤如下：

1. 创建一个类 MyHttpServletRequestWrapper，继承 HttpServletRequestWrapper 类，并实现 getReader() 和 getInputStream() 方法：

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.*;

public class MyHttpServletRequestWrapper extends HttpServletRequestWrapper {
    private final String body;

    public MyHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        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, "UTF-8"));
                char[] charBuffer = new char[128];
                int bytesRead;
                while ((bytesRead = bufferedReader.read(charBuffer)) != -1) {
                    stringBuilder.append(charBuffer, 0, bytesRead);
                }
            } else {
                stringBuilder.append("");
            }
        } catch (IOException ex) {
            throw ex;
        } finally {
            if (inputStream != null) {
                inputStream.close();
            }
            if (bufferedReader != null) {
                bufferedReader.close();
            }
        }
        body = stringBuilder.toString();
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes("UTF-8"));
        ServletInputStream servletInputStream = new ServletInputStream() {
            public int read() throws IOException {
                return byteArrayInputStream.read();
            }

            public boolean isFinished() {
                return false;
            }

            public boolean isReady() {
                return false;
            }

            public void setReadListener(ReadListener readListener) {
            }
        };
        return servletInputStream;
    }

    @Override
    public BufferedReader getReader() throws IOException {
        return new BufferedReader(new InputStreamReader(this.getInputStream()));
    }

    public String getBody() {
        return this.body;
    }
}

2. 在过滤器中获取请求返回的数据，并对其进行处理：

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

public class MyFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;

        // 将请求包装成 MyHttpServletRequestWrapper 类
        MyHttpServletRequestWrapper myRequestWrapper = new MyHttpServletRequestWrapper(request);

        // 获取请求返回的数据
        String requestBody = myRequestWrapper.getBody();

        // 对请求返回的数据进行处理，如打印日志、修改数据等

        // 将请求转发给下一个过滤器或 Servlet
        filterChain.doFilter(myRequestWrapper, servletResponse);
    }

    @Override
    public void destroy() {

    }
}

在上面的示例代码中，我们将 HttpServletRequest 包装成了 MyHttpServletRequestWrapper 类，并通过 getBody() 方法获取请求返回的数据。在 doFilter() 方法中，我们可以对请求返回的数据进行处理，如打印日志、修改数据等。最后，将包装后的请求传递给下一个过滤器或 Servlet。