web基礎2-servlet入門(request、response)

阿新 • • 發佈：2022-04-20

web基礎2-servlet入門

一、Servlet

1.1 servlet簡介

Servlet就是sun公司開發動態web的一門技術
Sun在這些API中提供一個介面叫做：Servlet，如果你想開發一個Servlet程式，只需要完成3個步驟：
- 編寫一個類，實現servlet介面
- 把開發好的Servlet註冊在web.xml中
- 把開發好的JAVA類部署到web伺服器中

把實現了Servlet介面的java程式叫做servlet

1.2 第一個servlet-HelloServlet

servlet在sun公司有兩個預設繼承類，Httpservlet，GenericServlet

1.2.1 構建父子工程。（也可以不用父子工程）

構建一個普通的maven專案，刪掉裡面的src目錄，以後我們的學習就在這個專案裡面建立module了。這個空的工程就是maven主工程。詳細見1.3

1.2.2 Maven環境優化

修改web.xml為最新的，換頭
將maven的結構搭建完畢

1.2.3 編寫一個servlet程式

編寫一個普通類
實現一個servlet介面，我們這裡直接繼承Httpservlet

`idea中檢視繼承關係樹`

方法一：

ctrl+H

方法二：

ctrl+alt+U

1.2.4 編寫servlet對映

為什麼需要對映：我們寫的是java程式，但是要通過瀏覽器訪問，而瀏覽器需要連線的web伺服器，所以我們需要：

在web伺服器中註冊我們寫的servlet
還需要給他一個瀏覽器能夠訪問的路徑。

<!--web.xml是配置我們web的核心配置檔案-->
<!--註冊Servelet-->
<servlet>
    <servlet-name>helloServlet</servlet-name>
    <servlet-class>com.happy.servlet.HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>helloServlet</servlet-name>
    <!--請求地址-->
    <url-pattern>/hello</url-pattern>
</servlet-mapping>

1.2.5 配置tomcat

注意：配置專案釋出的路徑即可

`1.3 關於maven 父子工程的理解`

注意：有時候用idea建立子專案的時候，parent標籤會丟失，注意檢查專案

父專案中會有

<modules>
    <module>servlet-01</module>
</modules>

子專案中會有

<parent>
    <artifactId>PureMavenWeb</artifactId>
    <groupId>org.example</groupId>
    <version>1.0-SNAPSHOT</version>
</parent>

父專案中的java子專案可以直接使用，而子專案中的父專案不能使用。同多型一樣。

二、servlet原理

三、Mapping問題

3.1 一個Servlet請求可以指定一個對映路徑

<!--web.xml是配置我們web的核心配置檔案-->
<!--註冊Servelet-->
<servlet>
    <servlet-name>helloServlet</servlet-name>
    <servlet-class>com.happy.servlet.HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>helloServlet</servlet-name>
    <!--請求地址-->
    <url-pattern>/hello</url-pattern>
</servlet-mapping>

3.2 一個Servlet可以指定多個對映路徑

<servlet>
    <servlet-name>helloServlet</servlet-name>
    <servlet-class>com.happy.servlet.HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>helloServlet</servlet-name>
    <!--請求地址-->
    <url-pattern>/hello</url-pattern>
</servlet-mapping>
<!--一個servlet對應多個對映url-->
<servlet-mapping>
    <servlet-name>helloServlet</servlet-name>
    <!--請求地址-->
    <url-pattern>/hello2</url-pattern>
</servlet-mapping>

3.3 一個Servlet可以指定通用對映路徑

<servlet-mapping>
    <servlet-name>helloServlet</servlet-name>
    <!--請求地址-->
    <url-pattern>/hello/*</url-pattern>
</servlet-mapping>

3.4 自定義字尾實現請求對映

注意：前面不能加對映的路徑，如/hello/*.do

<servlet>
    <servlet-name>helloServlet</servlet-name>
    <servlet-class>com.happy.servlet.HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>helloServlet</servlet-name>
    <!--可以自定義字尾匹配對映-->
    <url-pattern>*.do</url-pattern>
</servlet-mapping>

3.5 預設請求路徑（兜底）

<servlet>
    <servlet-name>helloServlet</servlet-name>
    <servlet-class>com.happy.servlet.HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>helloServlet</servlet-name>
    <!--可以自定義字尾匹配對映-->
    <url-pattern>/*</url-pattern>
</servlet-mapping>

3.6 優先順序匹配

指定了固有的對映路徑=》優先順序最高。

如果找不到就會走預設的處理請求/*

四、servlet重要物件和API

4.1 init-parm vs context-param

<servlet>
    <servlet-name>loginServlet</servlet-name>
    <servlet-class>com.qcc.study.servlet02.LoginServlet</servlet-class>
    <!-- 配置Servlet初始化引數 -->
    <init-param>
        <param-name>initParam</param-name>
        <param-value>qcc</param-value>
    </init-param>
    <!-- Web容器啟動時就載入並例項化該Servlet -->
    <load-on-startup>0</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>loginServlet</servlet-name>
    <url-pattern>/login</url-pattern>	
</servlet-mapping>
<!-- 配置ContextParam全域性引數 -->
<context-param>
    <param-name>contextParam</param-name>
    <param-value>admin</param-value>
</context-param>

配置在標籤中,用來初始化當前的Servlet的,屬於當前Servlet的配置,因此存放在 servletConfig物件中;

通過getServletConfig().getInitParameter("initParam")的方式獲取;

直接配置在web.xml的標籤中,屬於上下文引數,在整個web應用中都可以使用,它是全域性的,因此存放在servletContext物件中(即application物件);

通過getServletContext().getInitParameter("contextParam")的方式獲取;

4.2 ServletContext

web容器在啟動的時候，他會為每個web程式都建立一個對應的ServletContext物件，它代表了當前的web應用。(在容器啟動時候就有)

作用：

4.2.1 共享資料

我在這servlet中儲存的資料，可以在另外一個servlet獲取。

注意：實際工作中，一般不用servletContext存取資料，一般用session和cookie和request存取資料

一個servlet用於通過ServletContext來set資料

package com.happy.servlet;


import javax.servlet.ServletConfig;
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;
import java.io.PrintWriter;

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

//    <!-- 配置ContextParam全域性引數 -->
//    <context-param>
//        <param-name>happyContextParam</param-name>
//        <param-value>admin</param-value>
//    </context-param>
        String happy = servletContext.getInitParameter("happyContextParam");
        System.out.println(happy);
        int i=0;
        Object object= servletContext.getAttribute("happy");
        if (object==null){
            i=0;
        } else {
            i=(int)object+1;
        }
        servletContext.setAttribute("happy",i);

        ServletConfig servletConfig = this.getServletConfig();
        String happyServletParam = servletConfig.getInitParameter("happyServletParam");
        System.out.println(happyServletParam);
        PrintWriter writer = resp.getWriter();
        writer.println("<h1>訪問次數+1</h1>");
        writer.println("<a href='http://localhost:8080/s2/get' target='_blank'>http://localhost:8080/s2/get</a>");
        System.out.println(i);
    }

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

一個servlet用於通過ServletContext來get資料

package com.happy.servlet;

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

public class GetServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        Object happy = servletContext.getAttribute("happy");
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("訪問次數共計："+happy);

    }

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

web.xml如下

<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"
         metadata-complete="true">

    <!-- 配置ContextParam全域性引數 -->
    <context-param>
        <param-name>happyContextParam</param-name>
        <param-value>admin</param-value>
    </context-param>

    <servlet>
        <servlet-name>SetServlet</servlet-name>
        <servlet-class>com.happy.servlet.SetServlet</servlet-class>
        <init-param>
            <param-name>happyServletParam</param-name>
            <param-value>happyvalue</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>SetServlet</servlet-name>
        <url-pattern>/set/*</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>GetServlet</servlet-name>
        <servlet-class>com.happy.servlet.GetServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>GetServlet</servlet-name>
        <url-pattern>/get</url-pattern>
    </servlet-mapping>

</web-app>

4.2.2 獲取初始化引數

可以用來配置一些web應用初始化引數

注意：實際工作中一般不在web.xml中放參數，而用properties檔案等存全域性引數

 <!-- 配置ContextParam全域性引數
        可以用來配置一些web應用初始化引數-->
    <context-param>
        <param-name>happyContextParam</param-name>
        <param-value>admin</param-value>
    </context-param>

    <context-param>
        <param-name>setByConf</param-name>
        <param-value>setByConfValue</param-value>
    </context-param>

package com.happy.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;
import java.io.PrintWriter;

public class GetInitParamsServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        String setByConf = (String)servletContext.getInitParameter("setByConf");
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("setByConf："+setByConf);

    }

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

`4.2.3 請求轉發`

實際工作中一般不用ContextServlet物件的dispatcher，而用response物件的dispatcher方法

package com.happy.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;
import java.io.PrintWriter;

public class ContextDispatcherServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        servletContext.getRequestDispatcher("/get").forward(request,response);
    }

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

<servlet>
    <servlet-name>ContextDispatcherServlet</servlet-name>
    <servlet-class>com.happy.servlet.ContextDispatcherServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>ContextDispatcherServlet</servlet-name>
    <url-pattern>/cds</url-pattern>
</servlet-mapping>

4.2.4 讀取專案資原始檔

實際工作中一般不用這個api，而是用反射和類載入等載入資原始檔

前景補充知識

關於classpath

java目錄，作為source目錄
resources目錄，作為resources目錄

對回被打包到同一個路徑下：classes，我們俗稱這個路徑為classpath：

`maven構建時候，部分source目錄下面資原始檔不能打包問題`

解決方案：在build中配置resources.來防止我們資源匯出失敗的問題

<build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

獲取資原始檔

寫一個servlet呼叫context物件的獲取資原始檔的api方法getResourceAsStream

InputStream is = servletContext.getResourceAsStream("/WEB-INF/classes/db.properties");

    <servlet>
        <servlet-name>PropertiesServlet</servlet-name>
        <servlet-class>com.happy.servlet.PropertiesServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>PropertiesServlet</servlet-name>
        <url-pattern>/ps</url-pattern>
    </servlet-mapping>

package com.happy.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;
import java.io.InputStream;
import java.util.Properties;

public class PropertiesServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        InputStream is = servletContext.getResourceAsStream("/WEB-INF/classes/db.properties");
        Properties prop = new Properties();
        prop.load(is);
        String url = prop.getProperty("url");
        String username = prop.getProperty("username");
        String password = prop.getProperty("password");
        response.getWriter().println(url+" "+username+" "+password);
    }

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

效果如下：

4.3 HttpServletResponse

web伺服器接收到客戶端的http請求，針對這個請求，分別建立一個代表請求的HttpServletRequest物件，代表響應的一個httpServeletResponse。

如果要獲取客戶端請求過來的引數：找HttpServeletRequest
如果要給客戶端響應一些資訊：找HttpServeletResponse

4.3.1 HttpServletResponse簡單分類

負責向瀏覽器傳送資料的方法

ServletOutputStream getOutputStream() throws IOException;  //其他，如果老用中文會造成字元竄丟失

PrintWriter getWriter() throws IOException; 			//中文

負責向瀏覽器設定響應頭方法

void setCharacterEncoding(String var1);

void setContentLength(int var1);

void setContentLengthLong(long var1);

void setContentType(String var1);

void setBufferSize(int var1);


void setDateHeader(String var1, long var2);

void addDateHeader(String var1, long var2);

void setHeader(String var1, String var2);

void addHeader(String var1, String var2);

void setIntHeader(String var1, int var2);

void addIntHeader(String var1, int var2);

void setStatus(int var1);

響應的狀態碼：

int SC_CONTINUE = 100;
int SC_SWITCHING_PROTOCOLS = 101;
int SC_OK = 200;
int SC_CREATED = 201;
int SC_ACCEPTED = 202;
int SC_NON_AUTHORITATIVE_INFORMATION = 203;
int SC_NO_CONTENT = 204;
int SC_RESET_CONTENT = 205;
int SC_PARTIAL_CONTENT = 206;
int SC_MULTIPLE_CHOICES = 300;
int SC_MOVED_PERMANENTLY = 301;
int SC_MOVED_TEMPORARILY = 302;
int SC_FOUND = 302;
int SC_SEE_OTHER = 303;
int SC_NOT_MODIFIED = 304;
int SC_USE_PROXY = 305;
int SC_TEMPORARY_REDIRECT = 307;
int SC_BAD_REQUEST = 400;
int SC_UNAUTHORIZED = 401;
int SC_PAYMENT_REQUIRED = 402;
int SC_FORBIDDEN = 403;
int SC_NOT_FOUND = 404;
int SC_METHOD_NOT_ALLOWED = 405;
int SC_NOT_ACCEPTABLE = 406;
int SC_PROXY_AUTHENTICATION_REQUIRED = 407;
int SC_REQUEST_TIMEOUT = 408;
int SC_CONFLICT = 409;
int SC_GONE = 410;
int SC_LENGTH_REQUIRED = 411;
int SC_PRECONDITION_FAILED = 412;
int SC_REQUEST_ENTITY_TOO_LARGE = 413;
int SC_REQUEST_URI_TOO_LONG = 414;
int SC_UNSUPPORTED_MEDIA_TYPE = 415;
int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
int SC_EXPECTATION_FAILED = 417;
int SC_INTERNAL_SERVER_ERROR = 500;
int SC_NOT_IMPLEMENTED = 501;
int SC_BAD_GATEWAY = 502;
int SC_SERVICE_UNAVAILABLE = 503;
int SC_GATEWAY_TIMEOUT = 504;
int SC_HTTP_VERSION_NOT_SUPPORTED = 505;

4.3.2 HttpServletResponse常見應用

1. 向瀏覽器輸出訊息

2.`下載檔案`resp.setHeader("Content-disposition","attachment;filename"+filename);

核心：

resp.setHeader("Content-disposition","attachment;filename="+filename);

URLEncoder.encode(filename,"utf-8")) //解決檔名亂碼

要獲取下載檔案的路徑
下載檔名是啥
設定想辦法讓瀏覽器能夠支援下載我們需要的東西
獲取下載檔案的輸入流
建立快取區
獲取OutputStream物件
將FIleOutputStream流寫入到buffer緩衝區
使用outputstream將緩衝區中的資料輸出到客戶端

package com.happy.servlet;


import org.apache.commons.lang3.StringUtils;

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 DownServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
      /*  1. 要獲取下載檔案的路徑
        2. 下載檔名是啥
        3. 設定想辦法讓瀏覽器能夠支援下載我們需要的東西
        4. 獲取下載檔案的輸入流
        5. 建立快取區
        6. 獲取OutputStream物件
        7. 將FIleOutputStream流寫入到buffer緩衝區
        8. 使用outputstream將緩衝區中的資料輸出到客戶端*/
        String realPath = this.getServletContext().getRealPath("/WEB-INF/classes/書.jpg");
        System.out.println(realPath);
        String filename = realPath.substring(realPath.lastIndexOf("\\") + 1);
        System.out.println(filename);

//        resp.setHeader("Content-disposition","attachment;filename"+filename);

        String userAgent = req.getHeader("USER-AGENT");
        if (StringUtils.contains(userAgent, "MSIE") || StringUtils.contains(userAgent, "Edge")) {
            // IE瀏覽器
            filename = URLEncoder.encode(filename, "UTF-8");
        } else if (StringUtils.contains(userAgent, "Firefox") || StringUtils.contains(userAgent, "Chrome") || StringUtils.contains(userAgent, "Safari")) {
            // google,火狐瀏覽器
//            filename = new String(filename.getBytes(), "ISO-8859-1");
            filename = URLEncoder.encode(filename, "UTF-8");
        } else {
            filename = URLEncoder.encode(filename, "UTF-8");
// 其他瀏覽器
        }
        System.out.println(filename);
        resp.setHeader("Content-disposition", "attachment;filename=" + filename);


        // 建立輸入流,把檔案變成流
        FileInputStream is = new FileInputStream(realPath);
        // 建立輸出流
        ServletOutputStream os = resp.getOutputStream();
        // 建立快取區，new 一個byte【】作為byte
        byte[] buff = new byte[1024];
        int len = 0;
        try {
            System.out.println("開始讀取資料");
            while ((len = is.read(buff)) > 0) {
                os.write(buff, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            is.close();
            os.close();
        }
    }

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

3.生成驗證碼

原生生成驗證碼方法：

package com.happy.servlet;

import org.junit.jupiter.api.Test;

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

public class ImageServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        前端重新整理為windows.location.refresh
//        通過後端響應給前端設定頭資訊，響應可以設定前端所有東西
        response.setHeader("refresh","8");

        BufferedImage bufferedImage=drawNum();

//        告訴瀏覽器，這個請求的響應用圖片方式開啟
        response.setContentType("image/png");
//        取消快取
        response.setDateHeader("expires",-1);
        response.setHeader("Cache-Control","no-cache");
        response.setHeader("Pragma","no-cache");
        boolean jpg = ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
    }

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

    @Test
    public BufferedImage drawNum(){
        //        在記憶體中建立一個空白的圖片
        BufferedImage bufferedImage = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics = (Graphics2D) bufferedImage.getGraphics();
//        設定圖片的背景顏色
        graphics.setColor(Color.white);
//        畫邊框
        graphics.fillRect(0,0,80,20);
//        給圖片寫資料
        graphics.setColor(Color.blue);
        graphics.setFont(new Font(null,Font.BOLD,20));
        graphics.drawString(makeNum(),0,20);

        return bufferedImage;
    }

    public String makeNum(){
        Random random = new Random();
        String num = String.valueOf(random.nextInt(999999+1));
        StringBuffer sb = new StringBuffer(num);
        for(int i=0;i<=5-num.length();i++){
            sb.append(0);
        }
        return sb.toString();
    }
}

`4.實現重定向`

本質上是302和location設定重定向地址

response.sendRedirect();

常見場景：

使用者登陸

package com.happy.servlet;

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

public class RedirectServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        方式一
//        可以直接重定向到外部網站
//        response.sendRedirect("http://www.baidu.com");
//        也可以內部地址，要帶專案名
        response.sendRedirect("/response/image");
    }

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

所以本質上是302和location設定重定向地址

//        方式二，拆分兩步
response.setHeader("Location","/response/image");
//        response.setStatus(302);
response.setStatus(HttpServletResponse.SC_FOUND);

重定向和轉發的區別

	重定向	轉發
相同點	頁面實現跳轉	頁面實現跳轉
不同點	url位址列會發生變化	url不會產生變化

${pageContext.request.contextPath}

登陸跳轉（重定向實戰）

index.jsp作為登陸頁面如下：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登陸介面</title>
</head>
<body>

<%--這裡提交的路徑，需要尋找專案的路徑--%>
<%--<form action="/response/login" method="get">--%>
<form action="${pageContext.request.contextPath}/login" method="get">
使用者：<input type="text" name="username">
密碼：<input type="password" name="password">
<input type="submit" value="提交">
</form>
</body>
</html>

web.xml配置對映

<servlet>
    <servlet-name>FormServlet</servlet-name>
    <servlet-class>com.happy.servlet.FormServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>FormServlet</servlet-name>
    <url-pattern>/login</url-pattern>
</servlet-mapping>

處理servlet

package com.happy.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 FormServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("進入這個請求了");
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println(username+":"+password);
        response.sendRedirect("/response/success.jsp");

    }

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

4.4 HttpServletRequest

4.4.1 響應重定向和請求轉發

重定向和轉發的區別

	重定向	轉發
相同點	頁面實現跳轉	頁面實現跳轉
不同點	url位址列會發生變化	url不會產生變化
狀態碼	302	307

重定向response.sendRedirect

注意：重定地址（外部地址）要帶專案名

獲取方式：
寫死response.sendRedirect("projectContextName/success.jsp");
this.getServletContext().getContextPath()
response.sendRedirect(this.getServletContext().getContextPath()+"/success.jsp");
request.getContextPath()
response.sendRedirect(request.getContextPath()+"/success.jsp");

轉發request.getRequestDispatcher

注意：轉發地址（內部地址）不用帶專案名

轉發this.getServletContext().getRequestDispatcher

4.4.2 獲取前端引數

package com.happy.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;
import java.util.Arrays;

public class LoginServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println(username+":"+password);
        String[] hobbies = request.getParameterValues("hobbies");
        System.out.println(Arrays.toString(hobbies));
        System.out.println(this.getServletContext().getContextPath());
        System.out.println(request.getContextPath());
//        方式一：response redirect轉發
//        response.sendRedirect(this.getServletContext().getContextPath()+"/success.jsp");
//        方式二：servletContext 重定向
//        this.getServletContext().getRequestDispatcher("/success.jsp").forward(request,response);
        //方式三：request 重定向
        request.getRequestDispatcher("/success.jsp").forward(request,response);

    }

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

web基礎2-servlet入門(request、response)

web基礎2-servlet入門一、Servlet 1.1 servlet簡介 Servlet就是sun公司開發動態web的一門技術

Servlet中request、response亂碼問題完美解決

技術標籤：servlet亂碼當我們從頁面提交內容或顯示內容時可能會出現中文亂碼的現象。我們在程式碼中加上下面這兩行程式碼即可。

Servlet、request、response等

5.12、Servlet的依賴 <dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api&