Spring拦截器拦截request与response业务数据

ゝ一世哀愁。 2021-12-11 15:47 503阅读 0赞

来源：[http://blog.csdn.net/u013979547/article/details/53449788][http_blog.csdn.net_u013979547_article_details_53449788]

Controller层的作用是处理业务逻辑并返回数据，那怎么返回数据呢？接口的请求通过HttpServletRequest和HttpServletResponse实现前后端的交互，ServletResponse中有一个getWriter()方法获取到一个PrintWriter对象，通过PrintWriter的.print()方法即可将数据通过HttpServletResponse传递给前端。

首先定义一个返回数据的module，

public class ResponseModel {
        public static final int SUCCESS = 200;

**public static final int *ERROR*** = 100;

**private** Integer **status**;

**private** String **message**;

**private** Object **data**;

**private** Locale **locale**;

**public** ResponseModel()\{  
        **this**.**status** = ***SUCCESS***;  
        **this**.**locale** = Locale.***CHINA***;  
    \}

**public** ResponseModel put(String key, Object value)\{  
        **if**(**this**.**data** == **null** || !(**data instanceof** Map))\{  
            **this**.**data** = **new** HashMap<String,Object>();  
        \}  
        Map<String, Object> map = (Map<String,Object>)**this**.**data**;  
        map.put(key,value);  
        **return this**;  
    \}

**public** Object getData()\{  
        **return data**;  
    \}

**public** ResponseModel setData(Object data)\{  
        **this**.**data** = data;  
        **return this**;  
    \}

**public** ResponseModel setErrorMsg(ErrorMsg errorMsg)\{  
        **this**.setStatus(errorMsg.getCode());  
        **this**.setMessage(errorMsg.getMessage());  
        **return this**;  
    \}  
    **public** ResponseModel setStatus(**int** status)\{  
        **this**.**status** = status;  
        **if**(***ERROR*** == status)\{  
            **this**.setMessage(**“系统错误”**);  
        \}  
        **return this**;  
    \}  
    **public** ResponseModel setMessage(String message)\{  
        **this**.**message** = message;  
        **return this**;  
    \}  
    **public int** getStatus()\{  
        **return status**;  
    \}  
    **public** String getMessage()\{  
        **return message**;  
    \}  
\}

再定义一个holder的Bean，返回module作为一个线程级变量放到Bean中，

@Component
    public class ResponseHolder {
        private static ThreadLocal<Object> model = new ThreadLocal<>();
    
        public void clean(){
            model.remove();
        }
    
        public ResponseModel getModel(){
            Object o = model.get();
            if(o == null){
                this.setModel(new ResponseModel());
                o = this.getObject();
            }
            if(o != null && o instanceof ResponseModel){
                return (ResponseModel) o;
            }else {
                return null;
            }
        }
    
        public Object getObject(){
            return model.get();
        }
    
        public void setModel(Object o){
            model.set(o);
        }
    
        public ResponseModel put(String key, Object value){
            ResponseModel responseModel = this.getModel();
            Object data = responseModel.getData();
            if(data == null || !(data instanceof Map)){
                data = new HashMap<String,Object>();
                responseModel.setData(data);
            }
            Map<String,Object> map = (Map<String,Object>) data;
            map.put(key,value);
            return responseModel;
        }
    
        public ResponseModel setData(Object data){
            ResponseModel responseModel = this.getModel();
            responseModel.setData(data);
            return responseModel;
        }
    
        public ResponseModel setErrorMsg(ErrorMsg errorMsg){
            ResponseModel responseModel = this.getModel();
            responseModel.setStatus(errorMsg.getCode());
            responseModel.setMessage(errorMsg.getMessage());
            return responseModel;
        }
    }

其中的ErrorMsg是一个错误枚举，

public enum ErrorMsg {
    
        TEST(1,"test"),
        SUCCESS(200,"交易完成"),
        LOGIN_FAIL(101,"登录失败"),
        LOGOUT_SUCCESS(104,"登出成功"),
        USER_NOT_FOUND(102,"未注册用户"),
        USER_DISABLED(103,"无效用户"),
        NO_LOGIN(105,"未登录"),
        VERIFY_CODE_ERROR(106,"验证码错误"),
        SYSTEM_ERROR(100,"系统错误");
    
        private int code;
        private String message;
    
        public int getCode(){
            return code;
        }
        public String getMessage(){
            return message;
        }
    
        ErrorMsg(int code, String message){
            this.code = code;
            this.message = message;
        }
    }

接下来定义拦截器，在每个controller完成后从holder中取出数据通过HttpServletResponse传递给前端，

@Component
    public class ResponseInterceptor implements HandlerInterceptor {
    
        @Autowired
        private ResponseHolder responseHolder;
    
        private Logger logger = LogManager.getLogger(ResponseInterceptor.class);
    
        @Override
        public boolean preHandle(HttpServletRequest var1, HttpServletResponse var2, Object var3) throws Exception{
            return true;
        }
    
        @Override
        public void postHandle(HttpServletRequest var1, HttpServletResponse var2, Object var3, ModelAndView var4) throws Exception{
            //do noting
        }
    
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object object, Exception exception) throws Exception{
            if(responseHolder == null){
                logger.error("system error", exception);
                responseHolder.setErrorMsg(ErrorMsg.SYSTEM_ERROR);
            }
            String json = JSON.toJSONString(responseHolder.getModel());
            this.returnJson(response,json);
            responseHolder.clean();
        }
    
        private void returnJson(HttpServletResponse response, String json) throws Exception{
            PrintWriter writer = null;
            response.setCharacterEncoding("UTF-8");
            response.setContentType("text/html; charset=utf-8");
            try {
                writer = response.getWriter();
                writer.print(json);
    
            } catch (IOException e) {
                logger.error("response error",e);
            } finally {
                if (writer != null)
                    writer.close();
            }
        }
    
    }

spring提供了拦截器HandlerInterceptorAdapter对应提供了三个preHandle，postHandle，afterCompletion方法。preHandle在业务处理器处理请求之前被调用，  
    postHandle在业务处理器处理请求执行完成后,生成视图之前执行，afterCompletion在DispatcherServlet完全处理完请求后被调用,可用于清理资源等 。

拦截器定义完成后，不配置是不起作用的，传统的spring项目通过XML文件配置，spring—boot是为了实现无XML配置，所以可以通过如下方式添加，

@Configuration
    public class WebAppConfig extends org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter {

@Autowired  
    **private** ResponseInterceptor **responseInterceptor**;

@Override  
    **public void** addInterceptors(InterceptorRegistry registry) \{  
        registry.addInterceptor(**responseInterceptor**).addPathPatterns(**"/\*\*"**).excludePathPatterns(**"/identifyCode/generate"**);  
    \}

这里可是整个拦截器的核心，通过实现addInterceptors接口，我们可以添加自己想加的拦截器，也能配置特殊不需要拦截的接口。代码虽简单，但值得细细揣摩，也有许多可优化的地方！

[http_blog.csdn.net_u013979547_article_details_53449788]: http://blog.csdn.net/u013979547/article/details/53449788