（简易详细）spring boot 使用拦截器实现拦截前端请求并返回json到前端页面

灰太狼 2023-10-09 15:24 61阅读 0赞

## 一、核心方法代码returnJson ##

/*返回客户端数据*/
    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) {
            } finally {
                if (writer != null)
                    writer.close();
            }
        }

## 二、使用案例 ##

### 1.**实现**HandlerInterceptor**接口与核心代码** ###

package com.aa.daemon.controller;
     
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.servlet.HandlerInterceptor;
    import org.springframework.web.servlet.ModelAndView;
     
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.io.PrintWriter;
     
    @Configuration
    public class TestInterceptor implements HandlerInterceptor {
     
        @Override
        public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse
    httpServletResponse, Object o) throws Exception {
            System.out.println("前置拦截器");
            String name = httpServletRequest.getParameter("name");
            if(name.equals("admin")) {
                return true;
            }
            returnJson(httpServletResponse,"{\"code\":400,\"msg\":\"name is error!\"}");
            return false;
        }
        /*返回客户端数据*/
        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) {
            } finally {
                if (writer != null)
                    writer.close();
            }
        }
        @Override
        public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
     
        }
     
        @Override
        public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
     
        }
    }

### 2.注册拦截器 ###

package com.yixiecha.daemon.controller;
     
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
    import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
     
    @Configuration
    public class WebMvcConfigurer extends WebMvcConfigurerAdapter {
     
        public void addInterceptors(InterceptorRegistry registry) {
            registry.addInterceptor(new TestInterceptor()).addPathPatterns("/**");// 对‘/daemon/**’路径的接口进行拦截
        }
    }

### 3.OK完毕 ###

## 三、扩展 ##

**因为我们的核心方法代码returnJson需要传入的json字符串所以我们可以利用工具类将对象转为json字符串，这样大大方便了我们使用**

**配置工具类**，参考我的博客

[（fastjson）java 如何将String(字符串)与JSON互转\_\_揽的博客-CSDN博客][fastjson_java _String_JSON_-CSDN]

[fastjson_java _String_JSON_-CSDN]: https://blog.csdn.net/qq_59747594/article/details/128721677?spm=1001.2014.3001.5501