Request

Request对象 - 入门

获取请求行信息

GET /http_request/login?username=user&password=pass HTTP/1.1

相关API

• String getMethod()

  得到请求的方式：GET或POST

• String getRequestURI()

  Uniform Resource Identifier 统一资源标识符，代表一个资源的名字
  URI = ContextPath + ServletPath

• StringBuffer getRequestURL()

  Uniform Resource Locator 统一资源定位符，代表一个可以访问地址

• String getProtocol()

  得到协议和版本

• 【重点】String getContextPath()

  得到当前项目的访问地址

• 【重点】String getServletPath()

  得到当前Servlet的访问地址

案例

• 获取请求行信息并显示在终端上

实现

• RequestLineServlet.java

  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  
  @WebServlet("/request_line")
  public class RequestLineServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
          System.out.println("Method: " + request.getMethod());
          System.out.println("RequestURI: " + request.getRequestURI());
          System.out.println("RequestURL: " + request.getRequestURL());
          System.out.println("Protocol: " + request.getProtocol());
          System.out.println("ContextPath: " + request.getContextPath());
          System.out.println("ServletPath: " + request.getServletPath());
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

输出

Method: GET
RequestURI: /http_request/request_line
RequestURL: http://localhost:8080/http_request/request_line
Protocol: HTTP/1.1
ContextPath: /http_request
ServletPath: /request_line

小结

• request.getContextPath()

项目路径

• request.getServletPath()

资源路径

获取请求头信息

Host: localhost:8080

Connection: keep-alive

Content-Type: application/x-www-form-urlencoded

User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36

Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8

Accept-Language: zh-CN,zh;q=0.9,en-US;q=0.8,en;q=0.7,en-GB;q=0.6

相关API

• 【重点】String getHeader(String headName)

  指定请求头中键，得到相应的值

• Enumeration<String> getHeaderNames()

  得到请求头中所有的键

Enumeration接口

Enumeration是枚举类型的集合，类似于迭代器

Iterator	Enumeration
hasNext()	hasMoreElements()
next()	nextElement()

• boolean hasMoreElements()

  判断是否还有下一个元素，如果有返回true

• E nextElement()

  得到当前元素，并且向下移动一个元素

案例1

需求

• 获取请求头信息并显示在终端上

实现

• RequestHeaderServlet.java

  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.util.Enumeration;
  
  @WebServlet("/request_header")
  public class RequestHeaderServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
          Enumeration<String> headerNames = request.getHeaderNames();
          while (headerNames.hasMoreElements()) {
              String headerName = headerNames.nextElement();
              System.out.println(headerName + ": " + request.getHeader(headerName));
          }
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

输出

host: localhost:8080
connection: keep-alive
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36
accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
accept-encoding: gzip, deflate, br
accept-language: zh-CN,zh;q=0.9,en-US;q=0.8,en;q=0.7,en-GB;q=0.6
cookie: JSESSIONID=7D790A7277BAFB203442AA8F084217F7

案例2

需求

• 获取浏览器版本并显示在命令行上

  判断是Edge、Chrome、Safari、Firefox或IE浏览器

实现

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

@WebServlet("/request_header")
public class RequestHeaderServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String userAgent = request.getHeader("User-Agent");
        if (userAgent.contains("Edge")) {
            System.out.println("Edge浏览器");
        } else if (userAgent.contains("Chrome")) {
            System.out.println("Chrome浏览器");
        } else if (userAgent.contains("Safari")) {
            System.out.println("Safari浏览器");
        } else if (userAgent.contains("Firefox")) {
            System.out.println("Firefox浏览器");
        } else {
            System.out.println("IE浏览器");
        }
    }

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

输出

Chrome
Firefox
Safari

小结

• 请求行

  • getContextPath

  获取项目路径

  • getServletPath

  获取资源路径

• 请求头

  • getHeader

  传入请求头的键，值作为getHeader函数的返回值

获取请求参数[重点]

• POST

  username=user&password=pass

• GET

  GET /http_request/login?username=user&password=pass HTTP/1.1

相关API

• String getParameter(String name)

  通过参数名得到参数的值

• String[] getParameterValues(String name)

  通过参数名得到一组参数值，返回是字符串的数组

• 【非重点】Enumeration<String> getParameterNames()

  得到所有参数的名字，返回是枚举的类型

• Map<String, String[]> getParameterMap()

  得到表单提交的所有参数名和参数值，封装成一个Map集合

• Part request.getPart(String name)

  Gets the Part with the given name.

• Collection<Part> getParts()

  Gets all the Part components of this request, provided that it is of type multipart/form-data.

案例

• 获取注册表单提交的数据并输出到页面上

实现

• index.html

  <html>
  <head>
      <meta charset="utf-8">
      <title></title>
  </head>
  <body>
  <form action="request_body" method="get">
      <input type="text" name="username" placeholder="用户名"/><br/>
      <input type="password" name="password" placeholder="密码"/><br/>
      爱好：
      <input type="checkbox" name="hobby" value="eat"/>吃饭
      <input type="checkbox" name="hobby" value="sleep"/>睡觉
      <input type="checkbox" name="hobby" value="hit dodo"/>打豆豆
  
      <input type="submit" value="登录"/>
  </form>
  </body>
  </html>

• RequestBodyServlet.java

  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.Enumeration;
  import java.util.Map;
  import java.util.Set;
  
  @WebServlet("/request_body")
  public class RequestBodyServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
          
          System.out.println("username: " + request.getParameter("username"));
          System.out.println("password: " + request.getParameter("password"));
          System.out.println("hobby: " + Arrays.toString(request.getParameterValues("hobby")));
  
          System.out.println("----");
          Enumeration<String> names = request.getParameterNames();
          while(names.hasMoreElements()) {
              String pname = names.nextElement();
              System.out.println(pname + ": " + request.getParameter(pname));
          }
  
          System.out.println("----");
          Map<String, String[]> map = request.getParameterMap();
          Set<Map.Entry<String, String[]>> entries = map.entrySet();
          for (Map.Entry<String, String[]> entry : entries) {
              System.out.println(entry.getKey() + ": " + Arrays.toString(entry.getValue()));
          }
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

输出

namename: user
password: pass
hobby: [eat, sleep]
----
namename: user
password: pass
hobby: eat
----
username: [user]
password: [pass]
hobby: [eat, sleep]

小结

• String getParameter(String name)

  获取参数值(一个名字，对应一个值)

• String[] getParameterValues(String name)

  获取参数值(一个名字，对应多个值)

• Map<String, String[]> getParameterMap()

  获取参数值(获取所有的参数名和参数值)

参数乱码问题

• GET 方式的乱码解决方案

  Tomcat 8.5，GET方式无乱码问题

• POST 方式的乱码解决方案

  request.setCharacterEncoding("utf-8");

小结

http://localhost:8080/JavaWeb_day02_Request_war_exploded/request_body

• 获取请求行信息

  • getContextPath

  获取项目路径

  • getServletPath

  获取资源路径

• 获取请求头信息

  • String getHeader("name")

  获取请求头，参数传入name，value作为返回值

• 获取请求参数信息

  • getParameter

  传一个key，返回一个value

  • getParameterValues

  传一个key，返回所有value

  • getParameterMap

  不传参数，返回所有的key和value

• 参数乱码问题

  request.setCharacterEncoding("utf-8")

• 注意

  utf-8不是解决乱码问题的万金油

  乱码是因为编码和解码不一致造成的

Request - 深入

转发

定义

用于资源跳转，从一个资源跳转到另一个资源

相关API

request.getRequestDispatcher("/resourceB").forward(request, response);

方法	说明
RequestDispatcher getRequestDispatcher(String path)	获取请求转发器（request对象方法）
void forward(ServletRequest request, ServletResponse response)	将请求转发到另一个资源（Servlet）上

特点【重点】

• 地址不变
• 服务器内部跳转
• 一次请求

案例

• 浏览器请求 AServlet，转发至 BServlet

实现

package com.futureweaver.request;

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

@WebServlet("/resourceA")
public class AServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("AServlet接收到了用户的请求");
        //... 处理自己所负责的业务

        // 通过getRequestDispatcher，获得一个请求调度器
        // 让调度器，转发到"/resourceB"
        // 并且通过forward进行转发
        // 转发时，需要两个参数，一个是request，一个是response
        request.getRequestDispatcher("/resourceB").forward(request, response);
    }

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

请求域【重点】

问题

相关API

• Object getAttribute(String key)

从作用域中取出值

• void setAttribute(String key, Object obj)

向作用域中添加键和值，如果之前没有这个键则是添加，如果有就是修改

• void removeAttribute(String key)

删除指定的键和值

作用

服务器内存区域，用于数据存储

一个盒子，在盒子里面可以存储物品(Object)

小结

• request.getRequestDispatcher("/资源路径").forward(request, response)
• void request.setAttribute(String key, Object obj);
• Object request.getAttribute(String key)
• void request.removeAttribute(String key)

Request 对象生命周期【难点】

一个对象从创建到销毁的全过程

• 什么时候创建

  当服务器接收到了浏览器的请求时

• 什么时候销毁

  当响应结束时

• 由谁创建

  Tomcat

• 由谁销毁

  Tomcat

小结

• 转发的特点

  1. 一次请求
  2. 地址不变
  3. 服务器内部跳转

• 转发

  request.getRequestDispatcher("/资源路径").forward(request, response)

• Request 的生命周期

  • 创建

    服务器接收到浏览器的请求时，由Tomcat创建

  • 销毁

    响应结束时，由Tomcat销毁

案例

需求

• 静态资源-HTML 登录页面(帐号框、密码框、登录按钮)

• 登录表单提交至 LoginServlet

  利用MyBatis获取真实数据并进行比对

• 若登录成功，转发至登录成功(LoginSuccessServlet)

• 若登录失败，转发至登录失败(LoginFailureServlet)

ver 0.1 原生方式

实现

• index.html

  <html>
  <head>
      <meta charset="utf-8">
      <title></title>
  </head>
  <body>
  <form action="login" method="post">
      <input type="text" name="username" placeholder="用户名"/><br/>
      <input type="password" name="password" placeholder="密码"/><br/>
      爱好：
      <input type="checkbox" name="hobby" value="吃饭"/>吃饭
      <input type="checkbox" name="hobby" value="睡觉"/>睡觉
      <input type="checkbox" name="hobby" value="打豆豆"/>打豆豆
  
      <input type="submit" value="登录"/>
  </form>
  </body>
  </html>

• LoginServlet.java

  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.io.PrintWriter;
  
  @WebServlet("/login")
  public class LoginServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
  
          String username = request.getParameter("username");
          String password = request.getParameter("password");
  
          if (username.equals("user") && password.equals("pass")) {
              request.getRequestDispatcher("/login_success").forward(request, response);
          } else {
              request.getRequestDispatcher("/login_failure").forward(request, response);
          }
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

• LoginSuccessServlet.java

  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  
  @WebServlet("/login_success")
  public class LoginSuccessServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
          System.out.println(request.getParameter("username") + " login success!");
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

• LoginFailureServlet.java

  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  
  @WebServlet("/login_failure")
  public class LoginFailureServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
          System.out.println(request.getParameter("username") + " login failure!");
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

ver 0.2 JavaBean方式

什么是JavaBean

• 类必须用 public 修饰

• 提供 publi 无参数的构造器

• 提供 getter 和 setter 方法访问属性

JavaBean的两个概念

• 字段

就是成员变量，字段名就是成员变量名

• 属性
  • 通过 setter 或 getter 方法获得
  • 属性名: setter/getter 方法去掉 set/get 前缀，首字母小写
  • 比如: setName() -> Name -> name
  • 一般情况下，字段名称和属性名称是一致的

实现

• index.html

  <html>
    <head>
      <meta charset="UTF-8">
      <title></title>
    </head>
    <body>
    <form action="login" method="post">
      <input type="text" name="username" placeholder="用户名"/><br/>
      <input type="password" name="password" placeholder="密码"/><br/>
      <input type="submit" value="登录"/>
    </form>
    </body>
  </html>

• UserInfo.java

  public class UserInfo {
      private String username;
      private String password;
  
      public String getUsername() {
          return username;
      }
  
      public void setUsername(String username) {
          this.username = username;
      }
  
      public String getPassword() {
          return password;
      }
  
      public void setPassword(String password) {
          this.password = password;
      }
  
      public UserInfo() {
      }
  
      public UserInfo(String username, String password) {
          this.username = username;
          this.password = password;
      }
  }

• LoginServlet.java

  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.io.PrintWriter;
  
  @WebServlet("/login")
  public class LoginServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
  
          UserInfo userInfo = new UserInfo();
          userInfo.setUsername(request.getParameter("username"));
          userInfo.setPassword(request.getParameter("password"));
  
          if (userInfo.getUsername().equals("user") && userInfo.getPassword().equals("pass")) {
              request.getRequestDispatcher("/login_success").forward(request, response);
          } else {
              request.getRequestDispatcher("/login_failure").forward(request, response);
          }
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

ver 1.0 BeanUtil方式

问题

• LoginServlet.java

UserInfo userInfo = new UserInfo();
userInfo.setUsername(request.getParameter("username"));
userInfo.setPassword(request.getParameter("password"));

• RegisterServlet.java

UserProfile userProfile = new UserProfile();
userProfile.setUsername(request.getParameter("username"));
userProfile.setPassword(request.getParameter("password"));
userProfile.setGender(request.getParameter("gender"));
userProfile.setMobile(request.getParameter("mobile"));
userProfile.setAvatar(request.getParameter("avatar"));

BeanUtils 工具包

• commons-beanutils-1.9.3.jar

  核心工具包

• commons-logging-1.2.jar

  日志记录包

• commons-collection-3.2.2.jar

  增强集合包

BeanUtils常用方法

• setProperty(Object obj, String name, Object value)

  给指定对象obj的指定属性name附值指定的值value
  如果属性不存在，则什么也不发生

• getProperty(Object obj, String name)

  获取指定对象obj指定属性name的值
  如果属性不存在，则会抛出异常

• copyProperties(Object dest, Object orig)

  将一个对象的值赋值给另一个对象
  只有相同属性名才会赋值
  简单记忆: "后付钱" -> 即将后一个对象的值赋值给前一个对象

• populateObject bean, Map<String, String[]> properties

  将Map集合中的数据封装到JavaBean对象中

实现

• LoginServlet.java

  import org.apache.commons.beanutils.BeanUtils;
  
  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.lang.reflect.InvocationTargetException;
  import java.util.Map;
  
  @WebServlet("/login")
  public class LoginServlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          request.setCharacterEncoding("utf-8");
  
          Map<String, String[]> parameterMap = request.getParameterMap();
          UserInfo userInfo = new UserInfo();
          try {
              BeanUtils.populate(userInfo, parameterMap);
          } catch (IllegalAccessException e) {
              e.printStackTrace();
          } catch (InvocationTargetException e) {
              e.printStackTrace();
          }
  
          if (userInfo.getUsername().equals("user") && userInfo.getPassword().equals("pass")) {
              request.getRequestDispatcher("/login_success").forward(request, response);
          } else {
              request.getRequestDispatcher("/login_failure").forward(request, response);
          }
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          this.doPost(request, response);
      }
  }

ver 2.0 MyBatis方式

项目结构

• resources
  • log4j.properties
  • mybatis-config.xml
  • UserMapper.xml
• src
  • com.futureweaver
    • domain
      • User.java
    • mapper
      • UserMapper.java
    • utils
      • SessionFactoryUtil.java
    • service
      • UserService.java
    • web
      • LoginServlet.java
• web
  • WEB-INF
    • lib
      • commons-beanutils-1.9.3.jar
      • commons-logging-1.2.jar
      • commons-collection-3.2.2.jar
      • log4j-1.2.17.jar
      • mybatis-3.5.3.jar
      • mysql-connector-j-8.2.0.jar
    • web.xml
  • index.html

学习目标总结

• 能够应用 Request 对象的方法
• 能够了解 Request 请求头信息
• 能够应用 Request 对象解决获取请求参数中文乱码问题
• 能够应用 BeanUtils 工具类对请求参数数据进行封装
• 请求域
• 转发的三个特点
• 能够独立运用 Servlet 技术完成登录功能