springboot使用过滤器对请求参数进行处理

Dear 丶 2022-09-07 14:49 193阅读 0赞

前段时间对项目进行改造，需要实现对请求参数进行解密，再传输到控制层。参考了网上的一些文章，基本都是通过过滤器和实现RequestBodyAdvice接口进行处理。结合自己的项目要求，实现RequestBodyAdvice接口只能对参数在请求体中（@RequestBody）才生效，而项目中需要对get和post请求都进行处理，所以最后决定使用过滤器来实现。这里记录下代码实现，方便以后遇到相似的功能就不需要再去网上搜了。

首先需要继承HttpServletRequestWrapper类来自定义一个Request类，因为post请求需要使用request.getInputStream()来读取请求体中的参数，而流中的数据读取一次后就不能再读取了，这样传输到控制层就没有参数了，所以需要自定义一个request进行包装，将读取的参数处理后重新放回request中。

public class MyHttpRequest extends HttpServletRequestWrapper { 
        /** * 保存流数据 */
        private final byte[] body;
        /** * 保存参数 */
        private Map<String, String[]> params = new HashMap<>();
    
        public MyHttpRequest(HttpServletRequest request) { 
            super(request);
            body = getBodyString(request).getBytes(StandardCharsets.UTF_8);
            this.params.putAll(request.getParameterMap());
        }
    
        public MyHttpRequest(HttpServletRequest request, byte[] body) { 
            super(request);
            this.body = body;
            this.params.putAll(request.getParameterMap());
        }
    
        @Override
        public ServletInputStream getInputStream() { 
            final ByteArrayInputStream bais = new ByteArrayInputStream(body);
            return new ServletInputStream() { 
                @Override
                public boolean isFinished() { 
                    return false;
                }
    
                @Override
                public boolean isReady() { 
                    return false;
                }
    
                @Override
                public void setReadListener(ReadListener readListener) { 
                }
    
                @Override
                public int read() { 
                    return bais.read();
                }
            };
    
        }
        @Override
        public BufferedReader getReader() { 
            return new BufferedReader(new InputStreamReader(this.getInputStream()));
        }
    
        @Override
        public String getParameter(String name) { 
            String[] values = params.get(name);
            if(values == null || values.length == 0) { 
                return null;
            }
            return values[0];
        }
    
        @Override
        public Enumeration<String> getParameterNames() { 
            return Collections.enumeration(params.keySet());
        }
    
        @Override
        public String[] getParameterValues(String name) { 
            return params.get(name);
        }
    
        @Override
        public Map<String, String[]> getParameterMap() { 
            return this.params;
        }
    
        public void setParameter(Map<String, String> map) { 
            params.clear();
            map.forEach((key, value) -> params.put(key, new String[]{ value}));
        }
    
        public String getBody() { 
            return new String(body);
        }
    
        public static String getBodyString(ServletRequest request) { 
            StringBuilder sb = new StringBuilder();
            InputStream inputStream = null;
            BufferedReader reader = null;
            try { 
                inputStream = request.getInputStream();
                reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
                String line = "";
                while ((line = reader.readLine()) != null) { 
                    sb.append(line);
                }
            } catch (IOException e) { 
                e.printStackTrace();
            } finally { 
                if (inputStream != null) { 
                    try { 
                        inputStream.close();
                    } catch (IOException e) { 
                        e.printStackTrace();
                    }
                }
                if (reader != null) { 
                    try { 
                        reader.close();
                    } catch (IOException e) { 
                        e.printStackTrace();
                    }
                }
            }
            return sb.toString();
        }
    }

然后自定义一个过滤器，实现Filter接口

@WebFilter(filterName = "customParamFilter", urlPatterns = { "/*"})
    public class CustomParamFilter implements Filter { 
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { 
            HttpServletRequest request = (HttpServletRequest) servletRequest;
            MyHttpRequest requestWrapper = new MyHttpRequest(request);
            try { 
                // get请求
                if (requestWrapper.getMethod().equals(HttpMethod.GET.name())) { 
                    // 对参数进行处理，得到新的参数，将参数重新设置到request中
                    Map<String, String> params = handle(requestWrapper.getParameterMap());
                    requestWrapper.setParameter(params);
                } else {  // post请求，这里没有对x-www-form-urlencoded类型进行处理
                    String body = requestWrapper.getBody();
                    if (StringUtils.isNotEmpty(body)) { 
                        JSONObject jsonObject = JSONObject.parseObject(body);
                        // 对参数进行处理
                        Map<String, String> params = handle(jsonObject);
                        // 由于body是设置成不可变的，所以需要重新创建一个request，将body设置进去
                        requestWrapper = new MyHttpRequest(requestWrapper, JSONObject.toJSONString(params).getBytes());
                    }
                }
                filterChain.doFilter(requestWrapper, servletResponse);
            } catch (Exception ex) { 
                outErrorMessage(servletResponse, ExceptionConfig.BUSINESS_CODE, ExceptionConfig.BUSINESS_MSG);
            }
    
        }
    
        public void outErrorMessage(ServletResponse servletResponse, Integer code, String msg) throws IOException { 
            //返回json错误
            servletResponse.setCharacterEncoding("UTF-8");
            servletResponse.setContentType("application/json; charset=utf-8");
            PrintWriter out = servletResponse.getWriter();
            JSONObject res = new JSONObject();
            res.put("code", code);
            res.put("msg", msg);
            out.append(JSON.toJSONString(res));
        }
    }

类上加@WebFilter使过滤器生效即可。