Model View Controller 模型 视图 控制器

Model

• 业务处理：业务逻辑（Service）
• 数据持久层CRUD（Dao）

View

• 展示数据
• 提供链接发起Servlet请求（a,form,img...）

Controkler（Servlet）

• 接受用户的请求（req：请求参数，Session信息。。。。）
• 交给业务层处理对应的代码
• 控制视图的跳转

登录——>接收用户的登录请求——>处理用户的请求（获取用户登录的参数，username，password）——>交给业务层处理业务（判断用户名密码是否正确：事务）——>Dao层查询用户名和密码是否正确——>数据库

Filter

Filter：过滤器。用来过滤网站的数据

1、开发步骤

1. 导包
2. 实现Filter接口重写Filter方法

代码

web.xml

<?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>ss</servlet-name>
        <servlet-class>servlet.showServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ss</servlet-name>
        <url-pattern>/ss</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ss</servlet-name>
        <url-pattern>/servlet/ss</url-pattern>
    </servlet-mapping>

    <filter>
        <filter-name>filter</filter-name>
        <filter-class>Filter.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>filter</filter-name>
        <url-pattern>/servlet/*</url-pattern>
    </filter-mapping>
</web-app>

CharacterEncodingFilter.java

package Filter;

import javax.servlet.*;
import java.io.IOException;

public class CharacterEncodingFilter implements Filter {

    //初始化
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("CharacterEncodingFilter初始化");
    }

    //销毁
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //filterChain 链

        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        servletResponse.setContentType("text/html;charset=UTF-8");

        System.out.println("执行前........");

        filterChain.doFilter(servletRequest, servletResponse);

        System.out.println("执行后........");
    }

    public void destroy() {

    }
}

showServlet

package servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class showServlet extends HttpServlet {
    @Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    resp.setCharacterEncoding("utf-8");
   // resp.setContentType("text/html");

    resp.getWriter().write("你好，世界");
}

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

pom.xml

<?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-Filter</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.3.3</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet.jsp.jstl</groupId>
            <artifactId>jstl-api</artifactId>
            <version>1.2</version>
        </dependency>

        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>


        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
    </dependencies>

</project>

结果

未过滤

过滤