五、Request学习笔记

1、关于请求

简单来说就是客户端向服务器发出的请求

Servlet中定义了协议相关的对象 HttpServletRequest 接口和协议无关的对象 ServletRequest 接口

2、Request请求对象常用方法

1）获取路径

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@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
        String contextPath =req.getContextPath();
        System.out.println(contextPath);
        //2.获取Servlet映射路线
        String servletPath = req.getServletPath();
        System.out.println(servletPath);
        //3.获取访问者ip ipv6
        String remoteUser = req.getRemoteUser();
        System.out.println(remoteUser);
        //4.获取请求的消息数据
        String queryString = req.getQueryString();
        System.out.println(queryString);
        //5.获取统一资源标识符
        String requestURI = req.getRequestURI();
        System.out.println(requestURI);
        //6.获取统一资源定位符
        StringBuffer requestURL = req.getRequestURL();
        System.out.println(requestURL);
    }
}

/crm /servletDemo01 0:0:0:0:0:0:0:1 null /crm/servletDemo01 http://localhost:8080/crm/servletDemo01

2) 请求头信息

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@WebServlet("/servletDemo01")
public class ServletDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //7.根据请求头获得一个值
        String cookie = req.getHeader("Cookie");
        System.out.println(cookie);
        //8.根据请求头名称获取多个值
        Enumeration<String> headers = req.getHeaders("Accept-Encoding");
        while (headers.hasMoreElements()) {
            String value = headers.nextElement();
            System.out.println(value);
        }
        //9.获取所有请求头名称
        Enumeration<String> headerNames = req.getHeaderNames();
        while (headerNames.hasMoreElements()){
            String value = headerNames.nextElement();
            System.out.println(value);
        }

3）获取请求参数信息

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>
    <form action="/crm/servletDemo02" 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>

@WebServlet("/servletDemo02")
public class servletDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.根据名称获取数据
        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
        String[] hobbies = req.getParameterValues("hobby");
        for (String hobby : hobbies) {
            System.out.println(hobby);
        }
        System.out.println("====================");
        //3.获取所有名称
        Enumeration<String> parameterNames = req.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            String s = parameterNames.nextElement();
            System.out.println(s);
        }
        System.out.println("=======================");
        //4.获取所有参数的键值对
        Map<String, String[]> parameterMap = req.getParameterMap();
        for (String s : parameterMap.keySet()){
            String[] strings = parameterMap.get(s);
            for (String string : strings) {
                System.out.println(string);
            }
        }
    }
}

3、获取参数封装对象

1）手动封装

@WebServlet("/servletDemo02")
public class servletDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.根据名称获取数据
        String username = req.getParameter("username");
        System.out.println(username);
        String password = req.getParameter("password");
        System.out.println(password);

       User user= new User();
       user.setUsername(username);
       user.setPassword(password);

       System.out.println(user.toString());
    }

2）反射封装

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

    public String[] getHobby() {
        return hobby;
    }

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

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

@WebServlet("/servletDemo02")
public class servletDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取所有数据
        Map<String, String[]> parameterMap = req.getParameterMap();
        //2.封装User对象
        User user = new User();
        //3.遍历集合
        for (String name : parameterMap.keySet()){
            String[] strings = parameterMap.get(name);
            try {
                //4.获取User对象的属性选择器
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(name,user.getClass());
                //5.获取对应的setXXX方法
                Method writeMethod = propertyDescriptor.getWriteMethod();
                //6.执行对应方法
                if(strings.length>1){
                    writeMethod.invoke(user,(Object) strings);
                }else {
                    writeMethod.invoke(user, strings);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        System.out.println(user.toString());
    }
}

3）工具类封装

下载如下jar包引入WEB-INF下的libs 记得在项目管理中二次引入

commons-beanutils-1.9.4.jar

commons-logging-1.2.jar

@WebServlet("/servletDemo02")
public class servletDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取所有数据
        Map<String, String[]> parameterMap = req.getParameterMap();
        //2.封装User对象
        User user = new User();
        try {
            BeanUtils.populate(user,parameterMap);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        System.out.println(user.toString());
    }
}

3、流对象获取请求信息

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1）字符流

@WebServlet("/servletDemo02")
public class servletDemo02 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       //字符流
        BufferedReader reader = req.getReader();
        String line;
        while ((line = reader.readLine()) != null){
            System.out.println(line);
        }
        //不需要手动关闭，不是自己创建的，而是通过req获得的
        //reader.close();
    }
}

2) 字节流

@WebServlet("/servletDemo02")
public class servletDemo02 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       //字符流
        ServletInputStream inputStream = req.getInputStream();
        byte[] arr = new byte[1024];
        int len;
        while ((len = inputStream.read(arr)) != -1){
            System.out.println(new String(arr,0,len));
        }
    }
}

4、中文乱码

Get方式无乱码问题在tomcat8后被解决
Post方式需要通过setCharacterEncoding()解决

req.setCharacterEncoding("UTF-8");

tips：流对象不生效

5、请求域

可以在一次请求范围内共享数据

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6、请求转发

服务端接收到请求后发现需要借助其他Servlet实现功能

浏览器地址不变
域对象数据不丢失
负责转发的Servlet转发前后的响应正文会丢失（响应正文就是服务器返回的HTML页面）
由转发的目的地来响应客户端
比重定向效率高

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@WebServlet("/servletDemo02")
public class servletDemo02 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setAttribute("encoding","css");
        RequestDispatcher requestDispatcher = req.getRequestDispatcher("/peopleServlet");
        requestDispatcher.forward(req,resp);
    }

public class PeopleServlet  extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("PeopleServlet");
        Object encoding = req.getAttribute("encoding");
        System.out.println(encoding);
    }
}

tips:前后请求方式要一致

7、请求包含

合并其他Servlet中的功能一起响应给客户端

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

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请求包含大多数是在jsp页面中，完成多页面的合并
请求转发大多是在Servlet中，转发目标大多是jsp页面

点此查看原文

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本文作者：柠檬zz7

本文链接：https://www.cnblogs.com/codeui/p/16699841.html

posted @ 2022-09-16 14:38 柠檬zz7 阅读(36) 评论(0) 编辑收藏举报

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柠檬zz7

五、Request学习笔记

1、关于请求

2、Request请求对象常用方法

1）获取路径

2) 请求头信息

3）获取请求参数信息

3、获取参数封装对象

1）手动封装

2）反射封装

3）工具类封装

3、流对象获取请求信息

1）字符流

2) 字节流

4、中文乱码

5、请求域

6、请求转发

7、请求包含

点此查看原文

公告

搜索

常用链接

随笔分类

随笔档案

阅读排行榜

推荐排行榜

柠檬zz7

五、Request学习笔记

1、关于请求

2、Request请求对象常用方法

1）获取路径

2) 请求头信息

3）获取请求参数信息

3、获取参数封装对象

1） 手动封装

2）反射封装

3）工具类封装

3、流对象获取请求信息

1）字符流

2) 字节流

4、中文乱码

5、请求域

6、请求转发

7、请求包含

点此查看原文

公告

搜索

常用链接

随笔分类

随笔档案

阅读排行榜

推荐排行榜

1）手动封装