自定义filter ，通过HttpServletResponseWrapper 加密返回值。无法获取content做处理，又或者取到但是乱码。该如何解决？

• Z时代
• 2024-02-20
• 分类：IT

开放对外接口，要对返回数据做加密。我通过filter来拦截请求做处理。通过自定义wapper来对返回数据操作。

  HttpServletResponse httpServletResponse = (HttpServletResponse) servletResponse;
        EncryptResponseWrapper encryptResponseWrapper = new EncryptResponseWrapper(httpServletResponse);
        encryptResponseWrapper.setCharacterEncoding("UTF-8");
        filterChain.doFilter(servletRequest,encryptResponseWrapper);

newBIng提供了一种实现方式，但是实际测试并没有什么用，flushbuffer完全没有执行：

public class EncryptResponseWrapper extends HttpServletResponseWrapper {
    private CharArrayWriter charArrayWriter = new CharArrayWriter();
    public EncryptResponseWrapper(HttpServletResponse response) {
        super(response);
    }
    @Override
    public PrintWriter getWriter() throws IOException {
        return new PrintWriter(charArrayWriter);
    }
    @Override
    public void flushBuffer() throws IOException {
        // 获取原始响应对象
        HttpServletResponse response = (HttpServletResponse) getResponse();
        // 获取响应内容
        String content = charArrayWriter.toString();
        // 对响应内容进行加密
        String encryptedContent = DesUtils.getEncryptString(content);
        // 将加密后的内容写入原始响应对象
        response.getWriter().write(encryptedContent);
        // 刷新缓冲区
        super.flushBuffer();
    }
}

然后上网百度了别人的实现，都是先获取content，在做加密。
我用他们的方法无法获取到content，dofilter后的代码不会执行。

但是发现使用newbing提供的CharArrayWriter 能获取content。
但是获取content中文乱码。即使设置了UTF-8也没用。

EncryptResponseWrapper encryptResponseWrapper = new EncryptResponseWrapper(httpServletResponse);
        encryptResponseWrapper.setCharacterEncoding("UTF-8");
        filterChain.doFilter(servletRequest,encryptResponseWrapper);
        String content = encryptResponseWrapper.getCharArrayWriter().toString();
        // 对响应内容进行加密
        String encryptedContent = DesUtils.getEncryptString(content);
        // 将加密后的内容写入原始响应对象
        servletResponse.getWriter().write(encryptedContent);

package com.wondersgroup.wdls.js.wapper;
import com.wondersgroup.wdls.js.web.utils.DesUtils;
import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.*;
/**
 * @author xuxuehui
 * @create 2023 - 08 - 18 9:39
 */
public class EncryptResponseWrapper extends HttpServletResponseWrapper {
    private CharArrayWriter charArrayWriter = null;
    private PrintWriter writer = null;
    private ServletOutputStream out = null;
    public EncryptResponseWrapper(HttpServletResponse response) throws IOException{
        super(response);
        charArrayWriter = new CharArrayWriter();
        out = new WapperOutputStream(charArrayWriter);
        writer = new PrintWriter(new OutputStreamWriter(new WapperOutputStream(charArrayWriter),this.getCharacterEncoding()));
    }
    @Override
    public PrintWriter getWriter() throws IOException {
        return writer;
    }
    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return out;
    }
    public CharArrayWriter getCharArrayWriter() {
        return charArrayWriter;
    }
    @Override
    public void flushBuffer() throws IOException {
        if (out!=null){
            out.flush();
        }
        if (writer !=null){
            writer.flush();
        }
    }
    @Override
    public void reset() {
        charArrayWriter.reset();
    }
    public String getResponseData() throws IOException{
        flushBuffer();
        return charArrayWriter.toString();
    }
    private class WapperOutputStream extends ServletOutputStream{
        private CharArrayWriter charArrayWriter = null;
        public WapperOutputStream(CharArrayWriter charArrayWriter){
            this.charArrayWriter = charArrayWriter;
        }
        @Override
        public void write(int b) throws IOException{
            charArrayWriter.write(b);
        }
        @Override
        public boolean isReady() {
            return false;
        }
        @Override
        public void setWriteListener(WriteListener listener) {
        }
    }
}

又做了一些更改，但都是无用功。代码改动版本太多了，就不贴了；

如何解决编码问题，又或者new bing给的玩意能用，但是需要加东西。搞了太久，头都炸了。

回答：

writer = new PrintWriter(new OutputStreamWriter(new WapperOutputStream(charArrayWriter), "UTF-8"));

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