SpringBoot拦截器Filter的使用方法详解

前言：

最新Servlet 3.0拦截器的使用

1.pom.xml添加需要使用的依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>
 <groupId>top.ytheng</groupId>
 <artifactId>springboot-demo</artifactId>
 <version>0.0.1</version>
 <packaging>jar</packaging>
 
 <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.5.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>
  

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
    
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
    
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-devtools</artifactId>
      <optional>true</optional>
       <scope>true</scope>
    </dependency>
  </dependencies>

  <build>
    <!-- 打包的名称 -->
    <finalName>myspringboot</finalName>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

2.添加Filter拦截器

package top.ytheng.demo.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//Servlet3.0特性
//urlPatterns:拦截的url地址
//filterName:拦截器名称
@WebFilter(urlPatterns="/api/*", filterName="loginFilter")
public class LoginFilter implements Filter{

  /*
   * 容器加载完成调用
   * */
  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    // TODO Auto-generated method stub
    System.out.println("filter init...");
  }
  
  /*
   *  请求被拦截的时候调用
   * */
  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    // TODO Auto-generated method stub
    System.out.println("doFilter...");
    
    HttpServletRequest req = (HttpServletRequest)request;
    HttpServletResponse resp = (HttpServletResponse)response;
    
    String username = req.getParameter("username");
    if(username.equals("theng")) {
      chain.doFilter(request, response);
    } else {
      //重定向
      resp.sendRedirect("/filter.html");
      return;
    }
    
  }

  /*
   * 容器被销毁的时候调用
   * */
  @Override
  public void destroy() {
    // TODO Auto-generated method stub
    System.out.println("filter destroy...");
  }
  
}								 
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