Request

获取请求参数通用方式

  1. 1
    String getParameter(String name)

    根据参数名称获取参数值

  2. 1
    String[] getParameterValues(String name)

    根据参数名称获取参数值的数组
    hobby=xx&hobby=game，多用于复选框

  3. 1
    Enumeration<String> getParameterNames()

    获取所有请求的参数名称

  4. 1
    Map<String,String[]> getParameterMap()

    获取所有请求的键值对集合

演示

getParameter

创建一个regist2.html

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="/hello/request6" method="post">
    <input type="text" placeholder="请输入用户名" name="username"><br>
    <input type="password" placeholder="请输入密码" name="password"><br>
    <input type="submit" value="注册">
</form>
</body>
</html>

再创建RequestDemo6
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package 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(name = "RequestDemo6",urlPatterns = "/request6")
public class RequestDemo6 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post获取请求参数

        //根据参数名称获取参数值
        String username = request.getParameter("username");
        System.out.println("post");
        System.out.println("username");
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数
        String username = request.getParameter("username");
        System.out.println("get");
        System.out.println("username");
    }
}

首先在html的method为POST请求时，测试一下，打开提交表单，得到反馈
运行结果

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post
username

再把method改为GET请求
运行结果
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get
username

这样就可以看到getParameter是通用的操作
无论是get还是post都可以使用

这种写法其实比较麻烦，所以可以将RequestDemon6改为

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package 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(name = "RequestDemo6",urlPatterns = "/request6")
public class RequestDemo6 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post获取请求参数

        //根据参数名称获取参数值
        String username = request.getParameter("username");
        System.out.println("post");
        System.out.println("username");
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数
//        String username = request.getParameter("username");
//        System.out.println("get");
//        System.out.println("username");
        this.doPost(request,response);
    }
}

getParameterValues

刚才提到这个适用于复选框

修改regist2.html

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="/hello/request6" method="get">
    <input type="text" placeholder="请输入用户名" name="username"><br>
    <input type="password" placeholder="请输入密码" name="password"><br>


    <input type="checkbox" name="hobby" value="game">游戏
    <input type="checkbox" name="hobby" value="study">学习
    <br>


    <input type="submit" value="注册">
</form>
</body>
</html>

同时修改Servlet

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package 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(name = "RequestDemo6",urlPatterns = "/request6")
public class RequestDemo6 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post获取请求参数

        //根据参数名称获取参数值
        String username = request.getParameter("username");
//        System.out.println("post");
//        System.out.println("username");

        //根据参数名称获取参数值的数组
        String[] hobbies = request.getParameterValues("hobby");
        for(String hobby:hobbies){
            System.out.println(hobby);
        }
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数
//        String username = request.getParameter("username");
//        System.out.println("get");
//        System.out.println("username");
        this.doPost(request,response);
    }
}

再次访问regist2.html，勾选游戏和学习，点击注册
运行结果

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game
study

getParameterNames

修改Servlet

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package 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;
import java.util.Enumeration;

@WebServlet(name = "RequestDemo6",urlPatterns = "/request6")
public class RequestDemo6 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post获取请求参数

        //根据参数名称获取参数值
        String username = request.getParameter("username");
//        System.out.println("post");
//        System.out.println("username");

        //根据参数名称获取参数值的数组
        String[] hobbies = request.getParameterValues("hobby");
//        for(String hobby:hobbies){
//            System.out.println(hobby);
//        }


        //获取所有请求的参数名称
        Enumeration<String> parameterNames = request.getParameterNames();
        while (parameterNames.hasMoreElements()){
            String name = parameterNames.nextElement();
            System.out.println(name);
            String value = request.getParameter(name);
            System.out.println(value);
            System.out.println("--------------------------------");
        }



    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数
//        String username = request.getParameter("username");
//        System.out.println("get");
//        System.out.println("username");
        this.doPost(request,response);
    }
}

访问regist2.html

运行结果

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username
51nd0re1
--------------------------------
password
123
--------------------------------
hobby
game
--------------------------------

会发现一个问题，hobby明明勾选了两个但是却只输出了一个，这是因为getParameter是String类型，而不是数组

getParameterMap

修改Servlet

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package 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;
import java.util.*;

@WebServlet(name = "RequestDemo6",urlPatterns = "/request6")
public class RequestDemo6 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post获取请求参数

        //根据参数名称获取参数值
        String username = request.getParameter("username");
//        System.out.println("post");
//        System.out.println("username");

        //根据参数名称获取参数值的数组
        String[] hobbies = request.getParameterValues("hobby");
//        for(String hobby:hobbies){
//            System.out.println(hobby);
//        }


        //获取所有请求的参数名称
        Enumeration<String> parameterNames = request.getParameterNames();
//        while (parameterNames.hasMoreElements()){
//            String name = parameterNames.nextElement();
//            System.out.println(name);
//            String value = request.getParameter(name);
//            System.out.println(value);
//            System.out.println("--------------------------------");
//        }

        //获取所有参数的map集合
        Map<String,String[]> parameterMap = request.getParameterMap();
        //循环
        Set<String> keySet = parameterMap.keySet();
        for(String name : keySet){
            //根据key获取值
            String[] values = parameterMap.get(name);
            System.out.println(name);
            for(String value : values){
                System.out.println(value);
            }
            System.out.println("--------------------");
        }



    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get获取请求参数
//        String username = request.getParameter("username");
//        System.out.println("get");
//        System.out.println("username");
        this.doPost(request,response);
    }
}

运行结果
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username
51nd0re1
--------------------
password
123
--------------------
hobby
game
study
--------------------

这里看到已经获取到了game和study，这样就解决了上一个获取不完整的问题

中文乱码问题

get方式 tomcat8已经将中文乱码问题解决了

post方式解决办法

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package 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;
import java.util.*;

@WebServlet(name = "RequestDemo7",urlPatterns = "/request7")
public class RequestDemo7 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.设置流的编码
        request.setCharacterEncoding("utf-8");

        //获取请求参数
        String username = request.getParameter("username");

        System.out.println(username);
    }

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

设置为utf-8即可

请求转发

一种在服务器内部的资源跳转方式

  1. 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)

  2. 使用RequestDispatcher对象来进行转发

演示

RequestDemo8

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package Request;

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;
import java.util.*;

@WebServlet(name = "RequestDemo8",urlPatterns = "/request8")
public class RequestDemo8 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo8被访问了----");
        //转发到demo9资源

//        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/request9");
//        requestDispatcher.forward(request, response);
        request.getRequestDispatcher("/request9").forward(request, response);
    }

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

RequestDemo9

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package 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;
import java.util.*;

@WebServlet(name = "RequestDemo9",urlPatterns = "/request9")
public class RequestDemo9 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo9被访问了----");
    }

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

访问request8
运行结果

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demo8被访问了----
demo9被访问了----

特点

  1. 浏览器地址栏路径不发生变化
  2. 只能转发到当前的服务器内部资源中
  3. 转发是一次请求

共享数据

  • 域对象：一个有作用范围的对象，可以在范围内共享数据

  • request域：代表一次请求的范围，一般用于请求转发的多个资源中共享数据

方法：

  1. setAttribute(String name,Object obj)：存储数据

  2. Object getAttitude(String name):通过键获取值

  3. removeAttribute(String name):通过键移除键值对

演示

修改request8

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package Request;

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;
import java.util.*;

@WebServlet(name = "RequestDemo8",urlPatterns = "/request8")
public class RequestDemo8 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo8被访问了----");
        //转发到demo9资源

//        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/request9");
//        requestDispatcher.forward(request, response);

        //存储数据到request域中
        request.setAttribute("msg","hello");

        request.getRequestDispatcher("/request9").forward(request, response);
    }

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

在转发之前将数据存储到request域中

修改request9

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package 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;
import java.util.*;

@WebServlet(name = "RequestDemo9",urlPatterns = "/request9")
public class RequestDemo9 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //获取数据
        Object msg = request.getAttribute("msg");
        System.out.println(msg);


        System.out.println("demo9被访问了----");
    }

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

访问request8
运行结果

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demo8被访问了----
hello
demo9被访问了----

这里可以知道，只有在转发的情况下才可以进行数据共享

获取ServletContext

1
ServletContext getServletContext()

演示

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package Request;

import javax.servlet.ServletContext;
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.*;

@WebServlet(name = "RequestDemo10",urlPatterns = "/request10")
public class RequestDemo10 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext = request.getServletContext();

        System.out.println(servletContext);
    }

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

运行结果
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org.apache.catalina.core.ApplicationContextFacade@672c0e6b