JavaWeb05Servlet

2021/10/13 14:44:40

编程Tag： import http servlet resp javax req JavaWeb05Servlet

本文主要是介绍JavaWeb05Servlet，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

JavaWeb05Servlet

1.Servlet概述

2.HelloServlet

新建项目

父项目中的jar包，子项目可以直接使用，子项目中的jar包，父项目不能使用

<?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>com.mingmao</groupId>
    <artifactId>Javaweb-02-servlet</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>servlet-01</module>
    </modules>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
        <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>
            <scope>provided</scope>
        </dependency>
    </dependencies>

</project>

<?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-02-servlet</artifactId>
        <groupId>com.mingmao</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>servlet-01</artifactId>
    <packaging>war</packaging>

    <name>servlet-01 Maven Webapp</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <finalName>servlet-01</finalName>
        <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
            <plugins>
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.1.0</version>
                </plugin>
                <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-war-plugin</artifactId>
                    <version>3.2.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>2.5.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>2.8.2</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

</web-app>

编写servlet程序

package com.mingmao.servlet;

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

public class HelloServlet extends HttpServlet {
    // 由于get,post只是请求实现的不同方式，所以可以相互调用，因为业务逻辑都一样
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //ServletOutputStream outputStream = resp.getOutputStream();
        PrintWriter writer = resp.getWriter();//响应流
        writer.print("Hello,Servlet!");
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

<!--    注册servlet-->
    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.mingmao.servlet.HelloServlet</servlet-class>
    </servlet>

<!--    servlet的请求路径-->
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
</web-app>

配置Tomcat

启动测试

3.Servlet原理

4.Mapping问题

自己写404页面

package com.mingmao.servlet;

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

public class ErrorServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter writer = resp.getWriter();
        writer.print("<h1>404</h1>");
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

<!--    注册servlet-->
    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.mingmao.servlet.HelloServlet</servlet-class>
    </servlet>
<!--    servlet的请求路径-->
   <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

<!--    404-->
    <servlet>
        <servlet-name>error</servlet-name>
        <servlet-class>com.mingmao.servlet.ErrorServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>error</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>

</web-app>

优先级问题

5.ServletContext

写代码

package com.mingmao.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 HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("hello");//后台输出
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.mingmao.servlet.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

</web-app>

启动

ServletContext

1.共享数据

package com.mingmao.servlet;

import javax.servlet.ServletContext;
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 HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // this.getInitParameter(); 初始化参数 几乎不用
        //this.getServletConfig(); servlet配置
        //this.getServletContext(); servlet上下文
        ServletContext servletContext = this.getServletContext();

        String username="小明";//数据
        servletContext.setAttribute("username",username);//将数据保存在ServletContext中
    }

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

package com.mingmao.servlet;

import javax.servlet.ServletContext;
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 GetServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        String username = (String) servletContext.getAttribute("username");

        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        resp.getWriter().print(username);
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.mingmao.servlet.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>getc</servlet-name>
        <servlet-class>com.mingmao.servlet.GetServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getc</servlet-name>
        <url-pattern>/getc</url-pattern>
    </servlet-mapping>

</web-app>

先启动hello，再启动getc

2.获得参数

package com.mingmao.servlet;

import javax.servlet.ServletContext;
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 ServletDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();

        String url = servletContext.getInitParameter("url");
        resp.getWriter().print(url);
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

<!--    配置一些web应用的初始化参数-->
    <context-param>
        <param-name>url</param-name>
        <param-value>jdbc:mysql://localhost:3306/mybatis</param-value>
    </context-param>

    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.mingmao.servlet.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>getc</servlet-name>
        <servlet-class>com.mingmao.servlet.GetServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getc</servlet-name>
        <url-pattern>/getc</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>gp</servlet-name>
        <servlet-class>com.mingmao.servlet.ServletDemo03</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>gp</servlet-name>
        <url-pattern>/gp</url-pattern>
    </servlet-mapping>

</web-app>

3.请求转发

package com.mingmao.servlet;

import javax.servlet.ServletContext;
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 ServletDemo04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        servletContext.getRequestDispatcher("/gp").forward(req,resp);
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

<!--    配置一些web应用的初始化参数-->
    <context-param>
        <param-name>url</param-name>
        <param-value>jdbc:mysql://localhost:3306/mybatis</param-value>
    </context-param>

    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.mingmao.servlet.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>getc</servlet-name>
        <servlet-class>com.mingmao.servlet.GetServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getc</servlet-name>
        <url-pattern>/getc</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>gp</servlet-name>
        <servlet-class>com.mingmao.servlet.ServletDemo03</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>gp</servlet-name>
        <url-pattern>/gp</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>sd4</servlet-name>
        <servlet-class>com.mingmao.servlet.ServletDemo04</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>sd4</servlet-name>
        <url-pattern>/sd4</url-pattern>
    </servlet-mapping>

</web-app>

4.读取资源文件

username=root
password=123456

package com.mingmao.servlet;

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

public class ServletDemo05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        InputStream resourceAsStream = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");
        Properties properties = new Properties();
        properties.load(resourceAsStream);
        String username = properties.getProperty("username");
        String password = properties.getProperty("password");
        resp.getWriter().print(username+":"+password);
    }

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

  <servlet>
        <servlet-name>sd5</servlet-name>
        <servlet-class>com.mingmao.servlet.ServletDemo05</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>sd5</servlet-name>
        <url-pattern>/sd5</url-pattern>
    </servlet-mapping>

6.HttpServletResponse

下载文件

package com.mingmao.servlet;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;

public class FileServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取下载文件的路径
        //String realPath = this.getServletContext().getRealPath("/1.png");
        //String realPath="D:\\file\\Javaweb-02-servlet\\response\\src\\main\\resources\\图片.png"; 中文还是无法下载
        String realPath="D:\\file\\Javaweb-02-servlet\\response\\src\\main\\resources\\1.png";
        //2.获取下载的文件名
        String fileName = realPath.substring(realPath.lastIndexOf("\\" + 1));
        //3.让浏览器支持下载
        resp.setHeader("Content-Disposition","attachment;filename"+URLEncoder.encode(fileName,"utf-8"));
        //4.获取下载文件的输入流
        FileInputStream fileInputStream = new FileInputStream(realPath);
        //5.创建缓冲区
        int len=0;
        byte[] bytes = new byte[1024];
        //6.获取输出流对象
        ServletOutputStream outputStream = resp.getOutputStream();
        //7.将输入流写入缓冲区,使用输出流输出到客户端
        while((len=fileInputStream.read(bytes))!=-1){
            outputStream.write(bytes,0,len);
        }
        fileInputStream.close();
        outputStream.close();
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>filedown</servlet-name>
        <servlet-class>com.mingmao.servlet.FileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>filedown</servlet-name>
        <url-pattern>/down</url-pattern>
    </servlet-mapping>

</web-app>

验证码

package com.mingmao.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import static java.awt.Color.white;

public class ImageServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //让浏览器3s自动刷新一次
        resp.setHeader("refresh","3");
        //在内存中创建一个图片
        BufferedImage bufferedImage = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
        //得到图片
        Graphics2D graphics = (Graphics2D)bufferedImage.getGraphics();
        //设置图片的背景颜色
        graphics.setColor(Color.white);
        graphics.fillRect(0,0,80,20);
        //给图片写数据
        graphics.setColor(Color.blue);
        graphics.setFont(new Font(null,Font.BOLD,20));
        graphics.drawString(makeNum(),0,20);
        //告诉浏览器，这个请求用图片方式打开
        resp.setContentType("image/jpg");
        //网站存在缓存，不让浏览器缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragma","no-cache");
        //把图片写给浏览器
        boolean write = ImageIO.write(bufferedImage, "jpg",resp.getOutputStream());
    }

    //生成随机数
    private String makeNum(){
        Random random = new Random();
        String num = random.nextInt(9999999) + "";
        //不足7位用0填充
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i < 7-num.length(); i++) {
            stringBuffer.append("0");
        }
        num = stringBuffer.toString() + num;
        return num;
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>filedown</servlet-name>
        <servlet-class>com.mingmao.servlet.FileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>filedown</servlet-name>
        <url-pattern>/down</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>ImageServlet</servlet-name>
        <servlet-class>com.mingmao.servlet.ImageServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ImageServlet</servlet-name>
        <url-pattern>/img</url-pattern>
    </servlet-mapping>

</web-app>

重定向

package com.mingmao.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 RedirectServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.sendRedirect("/r/img");
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>filedown</servlet-name>
        <servlet-class>com.mingmao.servlet.FileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>filedown</servlet-name>
        <url-pattern>/down</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>ImageServlet</servlet-name>
        <servlet-class>com.mingmao.servlet.ImageServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ImageServlet</servlet-name>
        <url-pattern>/img</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>RedirectServlet</servlet-name>
        <servlet-class>com.mingmao.servlet.RedirectServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>RedirectServlet</servlet-name>
        <url-pattern>/red</url-pattern>
    </servlet-mapping>

</web-app>

测试

<html>
<body>
<h2>Hello World!</h2>

<form action="${pageContext.request.contextPath}/login" method="get">
    用户名：<input type="text" name="username"></br>
    密码：<input type="password" name="password"></br>
    <input type="submit"></br>
</form>

</body>
</html>

package com.mingmao.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 RequestTest extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>filedown</servlet-name>
        <servlet-class>com.mingmao.servlet.FileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>filedown</servlet-name>
        <url-pattern>/down</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>ImageServlet</servlet-name>
        <servlet-class>com.mingmao.servlet.ImageServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ImageServlet</servlet-name>
        <url-pattern>/img</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>RedirectServlet</servlet-name>
        <servlet-class>com.mingmao.servlet.RedirectServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>RedirectServlet</servlet-name>
        <url-pattern>/red</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>RequestTest</servlet-name>
        <servlet-class>com.mingmao.servlet.RequestTest</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>RequestTest</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

</web-app>

测试2

<html>
<body>
<h2>Hello World!</h2>

<form action="${pageContext.request.contextPath}/login" method="get">
    用户名：<input type="text" name="username"></br>
    密码：<input type="password" name="password"></br>
    <input type="submit"></br>
</form>

</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: user
  Date: 2021/10/11
  Time: 14:54
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<h1>success</h1>

</body>
</html>

package com.mingmao.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 RequestTest extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //处理请求
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        System.out.println(username+":"+password);
        resp.sendRedirect("/r/success.jsp");
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

<servlet>
    <servlet-name>filedown</servlet-name>
    <servlet-class>com.mingmao.servlet.FileServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>filedown</servlet-name>
    <url-pattern>/down</url-pattern>
</servlet-mapping>

<servlet>
    <servlet-name>ImageServlet</servlet-name>
    <servlet-class>com.mingmao.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>ImageServlet</servlet-name>
    <url-pattern>/img</url-pattern>
</servlet-mapping>

<servlet>
    <servlet-name>RedirectServlet</servlet-name>
    <servlet-class>com.mingmao.servlet.RedirectServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>RedirectServlet</servlet-name>
    <url-pattern>/red</url-pattern>
</servlet-mapping>

<servlet>
    <servlet-name>RequestTest</servlet-name>
    <servlet-class>com.mingmao.servlet.RequestTest</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>RequestTest</servlet-name>
    <url-pattern>/login</url-pattern>
</servlet-mapping>

</web-app>

7.HttpServletRequest

获取前端传递的参数与请求转发

<%--
  Created by IntelliJ IDEA.
  User: user
  Date: 2021/10/12
  Time: 8:34
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录</title>
</head>
<body>

<h1>登录</h1>
<div style="text-align: center">
    <form action="${pageContext.request.contextPath}/login" method="post">
        用户名：<input type="text" name="username"></br>
        密码：<input type="password" name="password"></br>
        爱好：
        <input type="checkbox" name="hobbys" value="唱歌">唱歌
        <input type="checkbox" name="hobbys" value="跳舞">跳舞
        <input type="checkbox" name="hobbys" value="运动">运动 </br>
        <input type="submit">
    </form>
</div>

</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: user
  Date: 2021/10/12
  Time: 8:48
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<h1>登陆成功</h1>

</body>
</html>

package com.mingmao.servlet;

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

public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        //获取参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String[] hobbys = req.getParameterValues("hobbys");
        //后台输出
        System.out.println(username+":"+password);
        System.out.println(Arrays.toString(hobbys));
        //重定向
        //resp.sendRedirect(req.getContextPath()+"/success.jsp");
        req.getRequestDispatcher("/success.jsp").forward(req,resp);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>com.mingmao.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
</web-app>

8.cookie

新建项目

<?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>com.mingmao</groupId>
  <artifactId>javaweb-session-cookie</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <dependencies>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <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>
      <scope>provided</scope>
    </dependency>
  </dependencies>

</project>

保存会话的两种技术

package com.mingmao.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;

//保存用户上一次访问的时间
public class CookieDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //解决中文乱码
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        PrintWriter out = resp.getWriter();

        //服务器从客户端获取cookie
        Cookie[] cookies = req.getCookies();
        if(cookies!=null){
            out.write("您上一次访问的时间是：");
            for (Cookie cookie : cookies) {
                //获取cookie的名字
                if(cookie.getName().equals("LastLoginTime")){
                    //获取cookie中的值
                    long lastLoginTime = Long.parseLong(cookie.getValue());
                    Date date = new Date(lastLoginTime);
                    out.write(date.toLocaleString());
                }
            }
        }else{
            out.write("这是您第一次访问本站！");
        }

        //服务器给客户端响应一个cookie
        Cookie cookie = new Cookie("LastLoginTime", System.currentTimeMillis()+"");
        cookie.setMaxAge(24*60*60);// 设置cookie有效期为1天
        resp.addCookie(cookie);
    }

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app metadata-complete="true" version="3.1"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <servlet>
        <servlet-name>CookieDemo1</servlet-name>
        <servlet-class>com.mingmao.servlet.CookieDemo1</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CookieDemo1</servlet-name>
        <url-pattern>/c1</url-pattern>
    </servlet-mapping>
</web-app>

关于cookie

删除cookie：

package com.mingmao.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;

public class CookieDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //创建一个cookie，名字必须和要删除的cookie名字相同
        Cookie cookie = new Cookie("LastLoginTime", System.currentTimeMillis()+"");
        cookie.setMaxAge(0);
        resp.addCookie(cookie);
    }

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

中文数据传递

package com.mingmao.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.Date;

//中文数据传递
public class CookieDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //解决中文乱码
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        PrintWriter out = resp.getWriter();

        //服务器从客户端获取cookie
        Cookie[] cookies = req.getCookies();
        if(cookies!=null){
            out.write("您的用户名是：");
            for (Cookie cookie : cookies) {
                //获取cookie的名字
                if(cookie.getName().equals("name")){
                    //获取cookie中的值
                    out.write(URLDecoder.decode(cookie.getValue(),"utf-8"));//解码，此处不解码也可以
                }
            }
        }else{
            out.write("这是您第一次访问本站！");
        }

        //服务器给客户端响应一个cookie
        Cookie cookie = new Cookie("name", URLEncoder.encode("小明","utf-8"));//编码，此处不编码也可以
        resp.addCookie(cookie);
    }

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

9.session

session

package com.mingmao.servlet;

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

public class SessionDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //解决中文乱码
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        //得到session
        HttpSession session = req.getSession();
        //给session存内容
        session.setAttribute("name","小明");

        //获取session的id
        String id = session.getId();
        //判断session是不是新创建的
        if(session.isNew()){
            resp.getWriter().write("session创建成功,id为："+id);
        }else{
            resp.getWriter().write("session已经在服务器中存在了,id为："+id);
        }

    }

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

获取session对象

package com.mingmao.pojo;

public class Persion {
    private String name;
    private int age;

    public Persion() {
    }

    public Persion(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Persion{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

package com.mingmao.servlet;

import com.mingmao.pojo.Persion;

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

public class SessionDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //解决中文乱码
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        //得到session
        HttpSession session = req.getSession();
        //给session存内容
        session.setAttribute("name",new Persion("小明",3));

        //获取session的id
        String id = session.getId();
        //判断session是不是新创建的
        if(session.isNew()){
            resp.getWriter().write("session创建成功,id为："+id);
        }else{
            resp.getWriter().write("session已经在服务器中存在了,id为："+id);
        }

    }

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

package com.mingmao.servlet;

import com.mingmao.pojo.Persion;

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

public class SessionDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //解决中文乱码
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        //得到session
        HttpSession session = req.getSession();
        Persion persion = (Persion) session.getAttribute("name");
        System.out.println(persion);
    }

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

手动注销session

package com.mingmao.servlet;

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

public class SessionDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        HttpSession session = req.getSession();
        session.removeAttribute("name");
        session.invalidate();
    }

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

自动注销session

<!--    设置session默认的失效时间-->
    <session-config>
<!--        15分钟后session自动失效-->
        <session-timeout>15</session-timeout>
    </session-config>

session与cookie的区别

10.学习视频

学习视频

这篇关于JavaWeb05Servlet的文章就介绍到这儿，希望我们推荐的文章对大家有所帮助，也希望大家多多支持为之网！

JavaWeb05Servlet

JavaWeb05Servlet

1.Servlet概述

2.HelloServlet

新建项目

编写servlet程序

配置Tomcat

启动测试

3.Servlet原理

4.Mapping问题

自己写404页面

优先级问题

5.ServletContext

写代码

启动

ServletContext

6.HttpServletResponse

下载文件

验证码

重定向

测试

测试2

7.HttpServletRequest

获取前端传递的参数与请求转发

8.cookie

新建项目

会话与甜点session and cookie

保存会话的两种技术

cookie

关于cookie

中文数据传递

9.session

session

获取session对象

手动注销session

自动注销session

session与cookie的区别

10.学习视频

相关编程文章