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spring boot 实现拦截器
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‎README.md

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3. **[Spring Boot 异常处理](./docs/advanced/springboot-handle-exception.md)**
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4. [使用 spring-boot-devtools 进行热部署](./docs/basis/spring-boot-devtools.md)
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5. **[ Spring Boot JPA 基础：常见操作解析](./docs/basis/springboot-jpa.md)**
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6. **[JPA 中非常重要的连表查询就是这么简单]()**
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7. [整合 SpringBoot+Mybatis](./docs/basis/springboot-mybatis.md) 、[SpirngBoot2.0+ 的 SpringBoot+Mybatis 多数据源配置](./docs/basis/springboot-mybatis-mutipledatasource.md)
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6. **[JPA 中非常重要的连表查询就是这么简单](./docs/basis/springboot-jpa-lianbiao.md)**
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7. [SpringBoot 实现过滤器](./docs/basis/springboot-filter.md)
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8. [整合 SpringBoot+Mybatis](./docs/basis/springboot-mybatis.md) 、[SpirngBoot2.0+ 的 SpringBoot+Mybatis 多数据源配置](./docs/basis/springboot-mybatis-mutipledatasource.md)
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### 进阶
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‎docs/basis/springboot-filter.md

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### 1. Filter 介绍
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Filter 过滤器这个概念应该大家不会陌生，特别是对与从 Servlet 开始入门学 Java 后台的同学来说。那么这个东西我们能做什么呢？Filter 过滤器主要是用来过滤用户请求的，它允许我们对用户请求进行前置处理和后置处理，比如实现 URL 级别的权限控制、过滤非法请求等等。
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如果我们需要自定义 Filter 的话非常简单，只需要实现 `javax.Servlet.Filter` 接口，然后重写里面的 3 个方法即可！
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`Filter.java`
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```java
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public interface Filter {
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//初始化过滤器后执行的操作
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default void init(FilterConfig filterConfig) throws ServletException {
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}
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// 对请求进行过滤
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void doFilter(ServletRequest var1, ServletResponse var2, FilterChain var3) throws IOException, ServletException;
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// 销毁过滤器后执行的操作，主要用户对某些资源的回收
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default void destroy() {
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}
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}
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```
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### 2. Filter是如何实现拦截的？
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`Filter`接口中有一个叫做 `doFilter` 的方法，这个方法实现了对用户请求的过滤。具体流程大体是这样的：
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1. 用户发送请求到 web 服务器,请求会先到过滤器；
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2. 过滤器会对请求进行一些处理比如过滤请求的参数、修改返回给客户端的 response 的内容、判断是否让用户访问该接口等等。
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3. 用户请求响应完毕。
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4. 进行一些自己想要的其他操作。
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![](https://my-blog-to-use.oss-cn-beijing.aliyuncs.com/2019-7/filter1.png)
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### 3. 如何自定义Filter
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下面提供两种方法。
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#### 3.1自己手动注册配置实现
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自定义的 Filter 需要实现`javax.Servlet.Filter`接口，并重写接口中定义的3个方法。
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`MyFilter.java`
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```java
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/**
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* @author shuang.kou
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*/
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@Component
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public class MyFilter implements Filter {
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private static final Logger logger = LoggerFactory.getLogger(MyFilter.class);
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@Override
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public void init(FilterConfig filterConfig) {
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logger.info("初始化过滤器：", filterConfig.getFilterName());
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}
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@Override
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public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
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//对请求进行预处理
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logger.info("过滤器开始对请求进行预处理：");
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HttpServletRequest request = (HttpServletRequest) servletRequest;
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String requestUri = request.getRequestURI();
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System.out.println("请求的接口为：" + requestUri);
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long startTime = System.currentTimeMillis();
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//通过 doFilter 方法实现过滤功能
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filterChain.doFilter(servletRequest, servletResponse);
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// 上面的 doFilter 方法执行结束后用户的请求已经返回
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long endTime = System.currentTimeMillis();
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System.out.println("该用户的请求已经处理完毕，请求花费的时间为：" + (endTime - startTime));
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}
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@Override
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public void destroy() {
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logger.info("销毁过滤器");
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}
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}
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```
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`MyFilterConfig.java`
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```java
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@Configuration
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public class MyFilterConfig {
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@Autowired
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MyFilter myFilter;
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@Bean
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public FilterRegistrationBean<MyFilter> thirdFilter() {
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FilterRegistrationBean<MyFilter> filterRegistrationBean = new FilterRegistrationBean<>();
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filterRegistrationBean.setFilter(myFilter);
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filterRegistrationBean.setUrlPatterns(new ArrayList<>(Arrays.asList("/api/*")));
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return filterRegistrationBean;
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}
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}
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```
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#### 3.2 通过提供好的一些注解实现
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在自己的过滤器的类上加上`@WebFilter` 然后在这个注解中通过它提供好的一些参数进行配置。
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```java
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@WebFilter(filterName = "MyFilterWithAnnotation", urlPatterns = "/api/*")
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public class MyFilterWithAnnotation implements Filter {
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......
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}
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```
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另外，为了能让 Spring 找到它，你需要在启动类上加上 `@ServletComponentScan` 注解。
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‎source-code/basis/springboot-filter/src/main/java/github/javaguide/springbootfilter/SpringbootFilterApplication.java

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import org.springframework.boot.SpringApplication;
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import org.springframework.boot.autoconfigure.SpringBootApplication;
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import org.springframework.boot.web.servlet.ServletComponentScan;
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@SpringBootApplication
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@ServletComponentScan
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public class SpringbootFilterApplication {
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public static void main(String[] args) {

‎source-code/basis/springboot-filter/src/main/java/github/javaguide/springbootfilter/config/MyFilterConfig.java

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package github.javaguide.springbootfilter.config;
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import github.javaguide.springbootfilter.filter.MyFilter;
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import github.javaguide.springbootfilter.filter.MyFilter2;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.boot.web.servlet.FilterRegistrationBean;
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import org.springframework.context.annotation.Bean;
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import org.springframework.context.annotation.Configuration;
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import java.util.ArrayList;
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import java.util.Arrays;
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@Configuration
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public class MyFilterConfig {
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@Autowired
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MyFilter myFilter;
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@Autowired
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MyFilter2 myFilter2;
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@Bean
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public FilterRegistrationBean<MyFilter> myFilter() {
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FilterRegistrationBean<MyFilter> filterRegistrationBean = new FilterRegistrationBean<>();
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filterRegistrationBean.setOrder(1);
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filterRegistrationBean.setFilter(myFilter);
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filterRegistrationBean.setUrlPatterns(new ArrayList<>(Arrays.asList("/api/*")));
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return filterRegistrationBean;
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}
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@Bean
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public FilterRegistrationBean<MyFilter2> myFilter2() {
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FilterRegistrationBean<MyFilter2> filterRegistrationBean = new FilterRegistrationBean<>();
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filterRegistrationBean.setOrder(2);
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filterRegistrationBean.setFilter(myFilter2);
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filterRegistrationBean.setUrlPatterns(new ArrayList<>(Arrays.asList("/api/*")));
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return filterRegistrationBean;
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}
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}

‎source-code/basis/springboot-filter/src/main/java/github/javaguide/springbootfilter/filter/MyFilter.java

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package github.javaguide.springbootfilter.filter;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.stereotype.Component;
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import javax.servlet.Filter;
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import javax.servlet.FilterChain;
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import javax.servlet.FilterConfig;
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import javax.servlet.ServletException;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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import javax.servlet.http.HttpServletRequest;
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import java.io.IOException;
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/**
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* @author shuang.kou
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*/
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@Component
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public class MyFilter implements Filter {
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private static final Logger logger = LoggerFactory.getLogger(MyFilter.class);
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@Override
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public void init(FilterConfig filterConfig) {
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logger.info("初始化过滤器");
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}
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@Override
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public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
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//对请求进行预处理
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logger.info("过滤器开始对请求进行预处理：");
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HttpServletRequest request = (HttpServletRequest) servletRequest;
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String requestUri = request.getRequestURI();
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System.out.println("请求的接口为：" + requestUri);
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long startTime = System.currentTimeMillis();
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//通过 doFilter 方法实现过滤功能
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filterChain.doFilter(servletRequest, servletResponse);
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// 上面的 doFilter 方法执行结束后用户的请求已经返回
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long endTime = System.currentTimeMillis();
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System.out.println("该用户的请求已经处理完毕，请求花费的时间为：" + (endTime - startTime));
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}
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@Override
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public void destroy() {
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logger.info("销毁过滤器");
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}
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}

‎source-code/basis/springboot-filter/src/main/java/github/javaguide/springbootfilter/filter/MyFilter2.java

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package github.javaguide.springbootfilter.filter;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.stereotype.Component;
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import javax.servlet.Filter;
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import javax.servlet.FilterChain;
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import javax.servlet.FilterConfig;
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import javax.servlet.ServletException;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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import javax.servlet.http.HttpServletRequest;
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import java.io.IOException;
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/**
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* @author shuang.kou
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*/
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@Component
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public class MyFilter2 implements Filter {
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private static final Logger logger = LoggerFactory.getLogger(MyFilter2.class);
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@Override
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public void init(FilterConfig filterConfig) {
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logger.info("初始化过滤器2");
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}
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@Override
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public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
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//对请求进行预处理
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logger.info("过滤器开始对请求进行预处理2：");
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HttpServletRequest request = (HttpServletRequest) servletRequest;
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String requestUri = request.getRequestURI();
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System.out.println("请求的接口为2：" + requestUri);
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long startTime = System.currentTimeMillis();
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//通过 doFilter 方法实现过滤功能
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filterChain.doFilter(servletRequest, servletResponse);
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// 上面的 doFilter 方法执行结束后用户的请求已经返回
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long endTime = System.currentTimeMillis();
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System.out.println("该用户的请求已经处理完毕，请求花费的时间为2：" + (endTime - startTime));
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}
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@Override
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public void destroy() {
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logger.info("销毁过滤器2");
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}
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}

‎source-code/basis/springboot-filter/src/main/java/github/javaguide/springbootfilter/filter/MyFilterWithAnnotation.java

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package github.javaguide.springbootfilter.filter;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import javax.servlet.Filter;
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import javax.servlet.FilterChain;
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import javax.servlet.FilterConfig;
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import javax.servlet.ServletException;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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import javax.servlet.annotation.WebFilter;
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import javax.servlet.http.HttpServletRequest;
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import java.io.IOException;
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@WebFilter(filterName = "MyFilterWithAnnotation", urlPatterns = "/api/annotation/*")
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public class MyFilterWithAnnotation implements Filter {
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private static final Logger logger = LoggerFactory.getLogger(MyFilterWithAnnotation.class);
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@Override
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public void init(FilterConfig filterConfig) {
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logger.info("初始化过滤器");
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}
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@Override
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public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
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//对请求进行预处理
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logger.info("过滤器开始对请求进行预处理：");
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HttpServletRequest request = (HttpServletRequest) servletRequest;
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String requestUri = request.getRequestURI();
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System.out.println("请求的接口为：" + requestUri);
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long startTime = System.currentTimeMillis();
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//通过 doFilter 方法实现过滤功能
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filterChain.doFilter(servletRequest, servletResponse);
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// 上面的 doFilter 方法执行结束后用户的请求已经返回
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long endTime = System.currentTimeMillis();
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System.out.println("该用户的请求已经处理完毕，请求花费的时间为：" + (endTime - startTime));
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}
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@Override
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public void destroy() {
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logger.info("销毁过滤器");
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}
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}

‎source-code/basis/springboot-filter/src/main/java/github/javaguide/springbootfilter/web/MyController.java

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package github.javaguide.springbootfilter.web;
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import org.springframework.web.bind.annotation.GetMapping;
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import org.springframework.web.bind.annotation.RequestMapping;
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import org.springframework.web.bind.annotation.RestController;
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@RestController
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@RequestMapping("/api")
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public class MyController {
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@GetMapping("/hello")
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public String getHello() throws InterruptedException {
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Thread.sleep(1000);
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return "Hello";
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}
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}

‎source-code/basis/springboot-filter/src/main/resources/application.properties

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