場景：API的參數都是經過加密的，於是在過濾器中，將獲取到的請求的參數先解密再去進行處理

一、實現Filter接口

public class TestFilter implements Filter {

    private Logger logger = LoggerFactory.getLogger(this.getClass());

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        logger.info("TestFilter init");
    }

    @Override
    
 
public void destroy() {
        logger.info("TestFilter destroy");
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        HttpServletResponse httpServletResponse 
 
= (HttpServletResponse) response;
        String servletPath = httpServletRequest.getServletPath();

        String body = HttpHelper.getBodyString(httpServletRequest);
        JSONObject param = JSONObject.parseObject(body);
        if (param == null) {
            logger.info("參數為空");
            
 
return;
        }
        String data = param.getString("data");
        String time = param.getString("time");
        ServletRequestWrapper requestWrapper = new ServletRequestWrapper(httpServletRequest,
                param.toString().getBytes(Charset.forName("UTF-8")));

        // 參數解密 解密過程省略
        //.............
        param.put("data", decryptParam); //將解密後的data取代加密的data
        requestWrapper.setBody(param.toString().getBytes(Charset.forName("UTF-8")));
        
         try {
            // 捕獲異常
            chain.doFilter(requestWrapper, response);
        } catch (Exception e) {
            logger.error("", e);
        }
    }

}        

二、設置過濾的接口

在TestFilter上添加 @WebFilter(filterName = "testFilter", urlPatterns = "/test/*") ，表示在test下的所有接口都經過過濾器

三、啟動過濾器

在Application中添加 @ServletComponentScan

SpringBoot中使用過濾器