Servlet--Request请求对象

1.请求对象的概述

请求：获取资源。在BS架构中，就是客户端浏览器向服务器端发出询问

请求对象：就是在项目当中用于发送请求的对象

2.获取各种路径的方法

返回值	方法名	说明
String	getContextPath()	获取虚拟目录名称
String	getServletPath()	获取Servlet映射路径
String	getRemoteAddr()	获取访问者ip地址
String	getQueryString()	获取请求的消息数据
String	getRequersURI()	获取统一资源标识符
StringBuffer	getRequestURL()	获取统一资源定位符

package servlet;

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("/servletDemo01")
public class ServletDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取虚拟目录名称 getContextPath()
        String contextPath = req.getContextPath();
        System.out.println(contextPath);
        //2.获取Servlet映射路径 getServletPath()
        String servletPath = req.getServletPath();
        System.out.println(servletPath);
        //3.获取访问者ip getRemoteAddr()
        String ip = req.getRemoteAddr();
        System.out.println(ip);
        //4.获取请求消息的数据 getQueryString()  url?后边的字符串（查询字符串）
        String queryString = req.getQueryString();
        System.out.println(queryString);
        //5.获取统一资源标识符 getRequestURI()    /request/servletDemo01   共和国
        String requestURI = req.getRequestURI();
        System.out.println(requestURI);
        //6.获取统一资源定位符 getRequestURL()    http://localhost:8080/request/servletDemo01  中华人民共和国
        StringBuffer requestURL = req.getRequestURL();
        System.out.println(requestURL);
    }

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

}

3.获取请求头信息的方法

返回值	方法名	说明
String	getHeader(String name)	根据请求头名称获取一个值
Enumeration<String>	getHeaders(String name)	根据请求头名称获取多个值
Enumeration<String>	getHeaderNames()	获取所有请求头名称

package servlet;

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;

/*
    获取请求头信息的相关方法
 */
@WebServlet("/servletDemo02")
public class ServletDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.根据请求头名称获取一个值
        String connection = req.getHeader("connection");
        System.out.println(connection);
        System.out.println("-------------------");
        //2.根据请求头名称获取多个值
        Enumeration<String> values = req.getHeaders("accept-encoding");
        while(values.hasMoreElements()) {
            String value = values.nextElement();
            System.out.println(value);
        }
        System.out.println("-------------------");
        //3.获取所有的请求头名称
        Enumeration<String> names = req.getHeaderNames();
        while(names.hasMoreElements()) {
            String name = names.nextElement();
            String value = req.getHeader(name);
            System.out.println(name + "," + value);
        }
    }

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

4. 获取请求参数信息的方法

返回值	方法名	说明
String	getParameter(String name)	根据名称获取数据
String[]	getParameterValues(String name)	根据名称获取所有数据
Enumeration<String>	getParameterNames()	获取所有名称
Map<String,String[]>	getParameterMap()	获取所有参数的键值对

在web目录下创建regist.html文件

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>
<form action="/request/servletDemo03" method="get" autocomplete="off">
    姓名：<input type="text" name="username"> <br>
    密码：<input type="password" name="password"> <br>
    爱好：<input type="checkbox" name="hobby" value="study">学习
    <input type="checkbox" name="hobby" value="game">游戏 <br>
    <button type="submit">注册</button>
</form>
</body>
</html>

package servlet;

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;
import java.util.Map;

/*
    获取请求参数信息的相关方法
 */
@WebServlet("/servletDemo03")
public class ServletDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.根据名称获取数据   getParameter()
        String username = req.getParameter("username");
        System.out.println(username);
        String password = req.getParameter("password");
        System.out.println(password);
        System.out.println("--------------------");
        //2.根据名称获取所有数据 getParameterValues()
        String[] hobbies = req.getParameterValues("hobby");
        for(String hobby : hobbies) {
            System.out.println(hobby);
        }
        System.out.println("--------------------");
        //3.获取所有名称  getParameterNames()
        Enumeration<String> names = req.getParameterNames();
        while(names.hasMoreElements()) {
            String name = names.nextElement();
            System.out.println(name);
        }
        System.out.println("--------------------");
        //4.获取所有参数的键值对 getParameterMap()
        Map<String, String[]> map = req.getParameterMap();
        for(String key : map.keySet()) {
            String[] values = map.get(key);
            System.out.print(key + ":");
            for(String value : values) {
                System.out.print(value + " ");
            }
            System.out.println();
        }
    }

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

5.获取参数手动封装对象

三种封装方式

1.手动封装反射

2.反射封装方式

3.工具类封装方式

新建bean.Student类

package bean;

import java.util.Arrays;

public class Student {
    private String username;
    private String password;
    private String[] hobby;

    public Student() {
    }

    public Student(String username, String password, String[] hobby) {
        this.username = username;
        this.password = password;
        this.hobby = hobby;
    }

    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 String[] getHobby() {
        return hobby;
    }

    public void setHobby(String[] hobby) {
        this.hobby = hobby;
    }

    @Override
    public String toString() {
        return "Student{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", hobby=" + Arrays.toString(hobby) +
                '}';
    }
}

package servlet;
import bean.Student;

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;
/*
    封装对象--手动方式
 */

@WebServlet("/servletDemo04")
public class ServletDemo04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取所有的数据
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String[] hobbies = req.getParameterValues("hobby");
        //2.封装学生对象
        Student stu = new Student(username,password,hobbies);
        //3.输出对象
        System.out.println(stu);
    }

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

修改regist.html

<form action="/request/servletDemo04" method="get" autocomplete="off">

6.获取参数反射封装对象

package servlet;
import bean.Student;

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.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Map;
/*
    封装对象--反射方式
 */

@WebServlet("/servletDemo05")
public class ServletDemo05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取所有的数据
        Map<String, String[]> map = req.getParameterMap();
        //2.封装学生对象
        Student stu = new Student();
        //2.1遍历集合
        for(String name : map.keySet()) {
            String[] value = map.get(name);
            try {
                //2.2获取Student对象的属性描述器
                //构造函数的第一个参数决定是哪个属性的描述器。第二个参数是当前属性所属对象的字节码
                PropertyDescriptor pd = new PropertyDescriptor(name,stu.getClass());
                //2.3获取对应的setXxx方法
                Method writeMethod = pd.getWriteMethod();
                //2.4执行方法
                if(value.length > 1) {
                    writeMethod.invoke(stu,(Object)value);//如果是多个属性值（爱好），需要转换为object
                }else {
                    writeMethod.invoke(stu,value);//通过当前属性描述器的写入方法，将value写入stu对象的这个属性身上
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        //3.输出对象
        System.out.println(stu);

    }

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

<form action="/request/servletDemo05" method="get" autocomplete="off">

7.获取参数工具类封装对象

导入jar包

package servlet;

import bean.Student;
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.util.Map;

/*
    封装对象--工具类方式
 */

@WebServlet("/servletDemo06")
public class ServletDemo06 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取所有的数据
        Map<String, String[]> map = req.getParameterMap();
        //2.封装学生对象
        Student stu = new Student();
        try {
            BeanUtils.populate(stu,map);//将map中的数据，封装到stu对象中（就这么一句话就搞定了）
        } catch (Exception e) {
            e.printStackTrace();
        }
        //3.输出对象
        System.out.println(stu);
    }

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

<form action="/request/servletDemo06" method="get" autocomplete="off">

8.流对象获取请求信息

返回值	方法名	说明
BufferedReader	getReader()	获取字符输入流
ServletInputStream	getInputStream()	获取字节输入流

package servlet;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
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("/servletDemo07")
public class ServletDemo07 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //字符流(必须是post方式)
        /*BufferedReader br = req.getReader();
        String line;
        while((line = br.readLine()) != null) {
            System.out.println(line);
        }*/
        //br.close();//这个流是从req对象中获取的，不是自己创建的，所以不需要关闭

        //字节流 （应用场景，请求参数中有二进制文件（图片）时）
        ServletInputStream is = req.getInputStream();
        byte[] arr = new byte[1024];
        int len;
        while((len = is.read(arr)) != -1) {
            System.out.println(new String(arr,0,len));
        }
    }

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

<!--如果是字符流，post请求方式-->
<form action="/request/servletDemo06" method="post" autocomplete="off">

流方式获取到的中文，会进行编码，所以看到的姓名是编码后的

解决乱码问题

GET 方式

没有乱码问题。在 Tomcat 8版本后已经解决

POST 方式

有乱码问题。可以通过 setCharacterEncoding() 方法来解决

//设置编码格式
req.setCharacterEncoding("UTF-8");

9.请求域

请求域(request域)：可以在一次请求范围内进行共享数据。

一般用于请求转发的多个资源中共享数据。

返回值	方法名	说明
void	setAttribute(String name,Object value)	向请求域对象中储存数据
Object	getAttribute(String name)	通过名称获取请求域对象中的数据
void	removeAttribute(String name)	通过名称移除请求域对象中的数据

请求到ServletA，实现的功能，需要用到ServletB，那这时候就可以在ServletA将请求转发到ServletB

那ServletB中可能会用到ServletA中的数据，那这时候就涉及到数据共享了

在这里如果使用应用域来共享数据，就有点浪费了，因为我们只是在这次请求中需要共享数据，不是整个应用

所以就用到了请求域

10.请求转发

请求转发：客户端的一次请求到达后，发现需要借助其他Servle来实现功能

特点：

浏览器地址栏不变

域对象中的数据不丢失

负责转发的 Servlet 转发前后的响应正文会丢失 (ServletA的响应正文会丢失，由ServletB响应客户端)

由转发的目的地来响应客户端

返回值	方法名	说明
RequestDispatcher	getRequestDispatcher(String name)	获取请求调度对象
void	forward(ServletRequest req,ServletResponse resp)	实现转发

package servlet;

import javax.servlet.RequestDispatcher;
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;

/*
    请求转发
 */
@WebServlet("/servletDemo09")
public class ServletDemo09 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置共享数据
        req.setAttribute("encoding","gbk");
        //获取请求调度对象
        RequestDispatcher rd = req.getRequestDispatcher("/servletDemo10");
        //实现转发功能
        rd.forward(req,resp);
    }

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

package servlet;

import javax.servlet.RequestDispatcher;
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;

/*
    请求转发
 */
@WebServlet("/servletDemo10")
public class ServletDemo10 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取共享数据
        Object encoding = req.getAttribute("encoding");
        System.out.println(encoding);
        System.out.println("servletDemo10执行了...");
    }

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

11.请求包含

在实际开发中，我们可能需要把两个Servlet的内容合并到一起来响应浏览器，而HTTP协议的特点是一请求，一响应的方式

所以绝对不可能出现有两个Servlet同时响应方式。那么我们就需要用到请求包含，把两个Servlet的响应内容合并输出

请求包含：可以合并其他 Servlet 中的功能一起响应给客户端

特点：

浏览器地址栏不变

域对象中的数据不丢失

被包含的 Servlet 响应头会丢失

返回值	方法名	说明
RequestDispatcher	getRequestDispatcher(String name)	获取请求调度对象
void	include(ServletRequest req,ServletResponse resp)	实现包含

package servlet;

import javax.servlet.RequestDispatcher;
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;

/*
    请求包含
 */
@WebServlet("/servletDemo11")
public class ServletDemo11 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("servletDemo11执行了...");
        //获取请求调度对象
        RequestDispatcher rd = req.getRequestDispatcher("/servletDemo12");
        //实现包含功能
        rd.include(req,resp);
    }

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

package servlet;

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;

/*
    请求包含
 */
@WebServlet("/servletDemo12")
public class ServletDemo12 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("servletDemo12执行了...");
    }

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