Spring拦截器拦截request与response业务数据

来源：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 {@Autowiredprivate ResponseHolder responseHolder;private Logger logger = LogManager.getLogger(ResponseInterceptor.class);@Overridepublic boolean preHandle(HttpServletRequest var1, HttpServletResponse var2, Object var3) throws Exception{return true;}@Overridepublic void postHandle(HttpServletRequest var1, HttpServletResponse var2, Object var3, ModelAndView var4) throws Exception{//do noting}@Overridepublic 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！

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