From 3f57d35d71e8a93c915a2518e33f1b119ed0c2a4 Mon Sep 17 00:00:00 2001
From: cuijiawang <cuijiawang@aizerobyte.com>
Date: Thu, 6 Feb 2025 10:17:26 +0800
Subject: [PATCH] filter

---
 pom.xml                                       |  8 ++++
 .../java/stu/base/filter/FilterConfig.java    | 25 +++++++++++++
 src/main/java/stu/base/filter/MyFilter.java   | 37 +++++++++++++++++++
 src/main/java/stu/base/filter/filter.md       | 20 ++++++++++
 4 files changed, 90 insertions(+)
 create mode 100644 src/main/java/stu/base/filter/FilterConfig.java
 create mode 100644 src/main/java/stu/base/filter/MyFilter.java
 create mode 100644 src/main/java/stu/base/filter/filter.md

diff --git a/pom.xml b/pom.xml
index 8c60447..e27a6fa 100644
--- a/pom.xml
+++ b/pom.xml
@@ -20,6 +20,14 @@
         <lombok.version>1.18.30</lombok.version>
     </properties>
     <dependencies>
+        <!-- filter -->
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>javax.servlet-api</artifactId>
+            <version>4.0.1</version>
+            <scope>provided</scope>
+        </dependency>
+        <!-- filter end -->
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter</artifactId>
diff --git a/src/main/java/stu/base/filter/FilterConfig.java b/src/main/java/stu/base/filter/FilterConfig.java
new file mode 100644
index 0000000..2a9c3b5
--- /dev/null
+++ b/src/main/java/stu/base/filter/FilterConfig.java
@@ -0,0 +1,25 @@
+package stu.base.filter;
+
+import org.springframework.boot.web.servlet.FilterRegistrationBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * @Author cuiJiaWang
+ * @Create 2025-02-06 10:03
+ */
+@Configuration
+public class FilterConfig {
+
+    @Bean
+    public FilterRegistrationBean<MyFilter> customFilterRegistration() {
+        FilterRegistrationBean<MyFilter> registrationBean = new FilterRegistrationBean<>();
+        MyFilter myFilter = new MyFilter();
+        registrationBean.setFilter(myFilter);
+        registrationBean.addUrlPatterns("/*");
+        registrationBean.setOrder(1); // 设置过滤器的执行顺序
+
+        registrationBean.addInitParameter("encoding", "UTF-8"); // 添加初始化参数
+        return registrationBean;
+    }
+}
diff --git a/src/main/java/stu/base/filter/MyFilter.java b/src/main/java/stu/base/filter/MyFilter.java
new file mode 100644
index 0000000..9b1e8b0
--- /dev/null
+++ b/src/main/java/stu/base/filter/MyFilter.java
@@ -0,0 +1,37 @@
+package stu.base.filter;
+
+import javax.servlet.FilterConfig;
+import javax.servlet.*;
+import java.io.IOException;
+
+/**
+ * @Author cuiJiaWang
+ * @Create 2025-02-06 09:54
+ */
+public class MyFilter implements Filter {
+
+    /*
+        Web 容器在启动时，会触发每个Filter实例的 init 方法调用并传递一个FilterConfig对象，
+        该配置允许过滤器获取初始化参数以及ServletContext上下文对象，从而加载任何所需的资源。
+        该方法在Filter的整个生命周期中仅会在初始化时被调用一次。
+     */
+    @Override
+    public void init(FilterConfig filterConfig) throws ServletException {
+    }
+
+    /*
+        每一次请求都会调用该方法
+    */
+    @Override
+    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
+        filterChain.doFilter(servletRequest, servletResponse);
+    }
+
+    /*
+        Web 容器在销毁时，会执行一次
+        清理过滤器所有持有的资源（如内存、文件句柄、线程等）
+    */
+    @Override
+    public void destroy() {
+    }
+}
diff --git a/src/main/java/stu/base/filter/filter.md b/src/main/java/stu/base/filter/filter.md
new file mode 100644
index 0000000..25fb802
--- /dev/null
+++ b/src/main/java/stu/base/filter/filter.md
@@ -0,0 +1,20 @@
+## 过滤器
+### 什么是Filter
+`Filter`是 Java Servlet 规范的一部分，定义在`javax.servlet`包中，`Filter`可以对`Servlet`容器的所有 HTTP 请求（`HttpServletRequest`）和响应（`HttpServletResponse`）进行预处理或后处理操作。
+
+
+### 使用
+- 在启动类或者任意配置类上加上`@ServletComponentScan`注解来让 Spring Boot 自动扫描并注册这些过滤器。
+```java
+@WebFilter(urlPatterns = "/*", filterName = "myFilter")
+public class MyFilter implements Filter{}
+
+@ServletComponentScan(basePackages ="stu.base.filter") // 指定扫描包路径
+public class StuApplication {}
+```
+- 使用 `FilterRegistrationBean` 进行注册
+- 直接使用 `@Component` 注解
+```java
+@Component    //默认会应用到所有请求路径
+public class MyFilter implements Filter{}
+```