标签:ServletException 16 filter 过滤器 import servlet javax
16-filter过滤器
怎么都理解不了的东西,只不过是需要点拨而已,愿所有人都找到适合自己的方法
概述
本文主要讲解过滤器,过滤器其实是在servlet前面增加了一层,用来处理统一的请求或者响应的过滤处理
常见应用:
- web服务器有一些垃圾请求,后台不应该处理,或者应该报错
- 处理乱码问题
重点
写一个过滤器只要实现javax.servlet
包下的Filter接口,重写里面的init,destroy,doFilter几个接口即可
过滤器的初始化是在tomacat启动的时候完成的
销毁是在web服务器关闭的时候完成的
另外过滤器是可以传递的,从一个filter传到其他filter,也必须通过FilterChain
传递
实践
Servlet1.java
package com.kuang.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 功能描述
*
* @since 2022-08-23
*/
public class Servlet1 extends HttpServlet {
private static final long serialVersionUID = 7727991466501115729L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.getWriter().write("你好世界");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
CharacterEncodingFilter.java
package com.kuang.filter;
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 java.io.IOException;
/**
* 功能描述
*
* @since 2022-08-23
*/
public class CharacterEncodingFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("过滤器初始化");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
throws IOException, ServletException {
servletRequest.setCharacterEncoding("utf-8");
servletResponse.setCharacterEncoding("utf-8");
servletResponse.setContentType("text/html;charset=utf-8");
System.out.println("chain 传递前");
filterChain.doFilter(servletRequest, servletResponse);
System.out.println("chain 传递后");
}
@Override
public void destroy() {
System.out.println("过滤器销毁");
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<servlet>
<servlet-name>s1</servlet-name>
<servlet-class>com.kuang.servlet.Servlet1</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>s1</servlet-name>
<url-pattern>/s1</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>s1</servlet-name>
<url-pattern>/servlet/s1</url-pattern>
</servlet-mapping>
<filter>
<filter-name>f1</filter-name>
<filter-class>com.kuang.filter.CharacterEncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>f1</filter-name>
<url-pattern>/servlet/*</url-pattern>
</filter-mapping>
</web-app>
子pom
<?xml version="1.0" encoding="UTF-8"?>
<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">
<parent>
<artifactId>JavaWeb-Study</artifactId>
<groupId>org.example</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>08-Filter</artifactId>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
</project>
父pom
<?xml version="1.0" encoding="UTF-8"?>
<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>org.example</groupId>
<artifactId>JavaWeb-Study</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<modules>
<module>01-HelloServlet</module>
<module>02-ServletContext</module>
<module>03-Download</module>
<module>04-VerificationCode</module>
<module>05-Login</module>
<module>06-Cookie</module>
<module>07-Session</module>
<module>08-Filter</module>
</modules>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.2</version>
</dependency>
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>jasper</artifactId>
<version>6.0.53</version>
</dependency>
</dependencies>
</project>
标签:ServletException,16,filter,过滤器,import,servlet,javax 来源: https://www.cnblogs.com/Oh-mydream/p/16618571.html
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