SpringBoot从入门到精通教程（二）- 拦截器用法和场景案例分析

偏执的太偏执、 2022-01-31 05:23 152阅读 0赞

## 需求背景 ##

> 在项目中需要全局拦截用户请求，针对一些特定请求，可进行特殊业务处理和请求过滤

## 技术点 ##

主要使用了两个对象

1. HandlerInterceptorAdapter对象（org.springframework.web.servlet.handler.HandlerInterceptorAdapter）

2. WebMvcConfigurationSupport对象（org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport）

对于第2点，不同于SpringBoot2中，SpringBoot1使用的是WebMvcConfigurerAdapter对象（org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter）

## 案例说明 ##

场景案例分析：

> 1. 拦截所有请求，对特定请求可以进行特殊处理和过滤  
> 2. 可对一批请求，验证固化的一些请求参数  
> 3. 有时需要在拦截器中注入服务层对象，调用业务相关逻辑方法  
> 4. 开启跨域请求访问功能

## 代码演示 ##

举两个例子

**1. 定义拦截器，拦截所有请求**

WebConfig类

package com.md.demo;
    
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
    import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
    
    /**
     * 拦截器定义
     * 
     * @author Minbo.He
     */
    @Configuration
    public class WebConfig extends WebMvcConfigurationSupport {
    
    	/**
    	 * 可定义多个拦截器
    	 */
    	@Override
    	public void addInterceptors(InterceptorRegistry registry) {
    		// 定义过滤拦截的url名称，拦截所有请求
    		registry.addInterceptor(new MyHttpInterceptor()).addPathPatterns("/**");
    //		registry.addInterceptor(其他拦截器).addPathPatterns("/**");
    		super.addInterceptors(registry);
    	}
    
    }

MyHttpInterceptor类

package com.md.demo;
    
    import java.io.PrintWriter;
    import java.util.Map;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.stereotype.Component;
    import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
    
    /**
     * 拦截处理类
     * 
     * @author Minbo.He
     */
    @Component
    public class MyHttpInterceptor extends HandlerInterceptorAdapter {
    
    	protected static Logger logger = LoggerFactory.getLogger(MyHttpInterceptor.class);
    	
    	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
    			throws Exception {
    		String url = request.getRequestURL().toString();
    		String method = request.getMethod();
    		String uri = request.getRequestURI();
    		String queryString = "";
    		// 去掉最后一个空格
    		Map<String, String[]> params = request.getParameterMap();
    		for (String key : params.keySet()) {
    			String[] values = params.get(key);
    			for (int i = 0; i < values.length; i++) {
    				String value = values[i];
    				queryString += key + "=" + value + "&";
    			}
    		}
    		queryString = queryString.equals("") ? null : queryString.substring(0, queryString.length() - 1);
    		logger.info(String.format("请求参数, url: %s, method: %s, params: %s", url, method, queryString));
    		
    		// hello不做拦截
    		if (uri.equals("/hello")) {
    			return true;
    		}
    		
    		// 其他拦截请求（请求必须都带上用户id）
    		String userId = request.getParameter("userId");
    		if (userId != null) {
    			return true;
    
    		} else {
    			this.output(response, "{\n" 
    					+ "\"code\": \"4001\",\n" 
    					+ "\"message\": \"参数错误\"\n" 
    					+ "}");
    			return false;
    		}
    	}
    
    	/**
    	 * 输出结果
    	 */
    	private void output(HttpServletResponse response, String result) throws Exception {
    		response.setHeader("content-type", "text/html;charset=UTF-8");
    		response.setCharacterEncoding("UTF-8");
    		PrintWriter out = response.getWriter();
    		out.println(result);
    	}
    }

**2. 开启跨域请求访问功能**

package com.md.demo;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.context.annotation.Bean;
    import org.springframework.web.cors.CorsConfiguration;
    import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
    import org.springframework.web.filter.CorsFilter;
    
    /**
     * 程序主入口
     * 
     * @author Minbo
     *
     */
    @SpringBootApplication
    public class Application {
    
    	public static void main(String[] args) {
    		SpringApplication.run(Application.class, args);
    	}
    
    	/**
    	 * 开启过滤器功能
    	 * 
    	 * @return
    	 */
    	private CorsConfiguration buildConfig() {
    		CorsConfiguration corsConfiguration = new CorsConfiguration();
    		corsConfiguration.addAllowedOrigin("*");
    		corsConfiguration.addAllowedHeader("*");
    		corsConfiguration.addAllowedMethod("*");
    		return corsConfiguration;
    	}
    
    	/**
    	 * 跨域过滤器
    	 * 
    	 * @return
    	 */
    	@Bean
    	public CorsFilter corsFilter() {
    		UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
    		source.registerCorsConfiguration("/**", buildConfig());
    		return new CorsFilter(source);
    	}
    }

## 完整源码下载 ##

我的[Github源码地址：][Github]

[https://github.com/hemin1003/spring-boot-study/tree/master/spring-boot2-study/spring-boot2-parent][Github]

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## 下一章教程 ##

[SpringBoot从入门到精通教程（三）- RocketMQ集成和场景案例分析][SpringBoot_- RocketMQ]

## 该系列教程 ##

[SpringBoot从入门到精通教程][SpringBoot]

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[Github]: https://github.com/hemin1003/spring-boot-study/tree/master/spring-boot2-study/spring-boot2-parent
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