（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

/*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();
        }
    }

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 {
    }
}

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
    }
}