## 3. 响应消息数据格式
## 3.1 Request：
![Alt Text](/images/posts/20210222160701981.png)
### 3.1.1 request对象和response对象的原理
1. `request`和`response`对象是由服务器创建的。我们来使用它们
2. `request`对象是来获取请求消息，`response`对象是来设置响应消息

### 3.1.2 request对象继承体系结构：	

| ||
|--|--|
| ServletRequest		 |接口  |
|	继承
| HttpServletRequest	  | 接口  |
|	实现

- `org.apache.catalina.connector.RequestFacade@5b3cad0e`
- `org.apache.catalina.connector.RequestFacade 类(tomcat)`

### 3.1.3 request功能：

#### 3.1.3.1 获取请求消息数据
##### 1. 获取请求行数据
* `GET /day14/demo1?name=zhangsan HTTP/1.1`
* 方法：
	1. 获取请求方式 ：`GET`
		 `String getMethod()`  
	2. `(*)`获取虚拟目录：`/day14`
		 `String getContextPath()`
	3. 获取`Servlet`路径: `/demo1`
		 `String getServletPath()`
	4. 获取`get`方式请求参数：`name=zhangsan`
		 `String getQueryString()`
	5. `(*)`获取请求URI：`/day14/demo1`
		 `String getRequestURI():	/day14/demo1`
		 `StringBuffer getRequestURL()  :http://localhost/day14/demo1`

		 `URL`:统一资源定位符 ： `http://localhost/day14/demo1	中华人民共和国`（范围小）
		 `URI`:统一资源标识符 : `/day14/demo1	   共和国`(范围大)
	
	6. 获取协议及版本：`HTTP/1.1`
		 `String getProtocol()`

	7. 获取客户机的IP地址：
		 `String getRemoteAddr()`
```java
package com.example.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;

/**
 * 演示Request对象获取请求行数据
 */

@WebServlet("/requestDemo1")
public class RequestDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /*
            1. 获取请求方式 ：GET
                * String getMethod()
            2. (*)获取虚拟目录：/day14
                * String getContextPath()
            3. 获取Servlet路径: /requestDemo1
                * String getServletPath()
            4. 获取get方式请求参数：name=zhangsan
                * String getQueryString()
            5. (*)获取请求URI：/day14/demo1
                * String getRequestURI():		/day14/requestDemo1
                * StringBuffer getRequestURL()  :http://localhost/day14/requestDemo1
            6. 获取协议及版本：HTTP/1.1
                * String getProtocol()

            7. 获取客户机的IP地址：
                * String getRemoteAddr()

         */
        //1. 获取请求方式 ：GET
        String method = request.getMethod();
        System.out.println(method);
        //2.(*)获取虚拟目录：/day14
        String contextPath = request.getContextPath();
        System.out.println(contextPath);
        //3. 获取Servlet路径: /demo1
        String servletPath = request.getServletPath();
        System.out.println(servletPath);
        //4. 获取get方式请求参数：name=zhangsan
        String queryString = request.getQueryString();
        System.out.println(queryString);
        //5.(*)获取请求URI：/day14/demo1
        String requestURI = request.getRequestURI();
        StringBuffer requestURL = request.getRequestURL();
        System.out.println(requestURI);
        System.out.println(requestURL);
        //6. 获取协议及版本：HTTP/1.1
        String protocol = request.getProtocol();
        System.out.println(protocol);
        //7. 获取客户机的IP地址：
        String remoteAddr = request.getRemoteAddr();
        System.out.println(remoteAddr);
    }
}
/*
		GET
		/day14
		/requestDemo1
		name=zhangsan
		/day14/requestDemo1
		http://localhost:8080/day14/requestDemo1
		HTTP/1.1
		0:0:0:0:0:0:0:1
*/

}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //演示获取请求头数据
    
    //1.获取所有请求头名称
    Enumeration<String> headerNames = request.getHeaderNames();
    //2.遍历
    while(headerNames.hasMoreElements()){
        String name = headerNames.nextElement();
        //根据名称获取请求头的值
        String value = request.getHeader(name);
        System.out.println(name+"---"+value);
    }

} } ``` ```java package com.example.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;

    String agent = request.getHeader("user-agent");
    //判断agent的浏览器版本
    if(agent.contains("Chrome")){
        //谷歌
        System.out.println("谷歌来了...");
    }else if(agent.contains("Firefox")){
        //火狐
        System.out.println("火狐来了...");
    }
} } ``` ```java 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;

}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //演示获取请求头数据:referer

    String referer = request.getHeader("referer");
    System.out.println(referer);//http://localhost/day14/login.html

    //防盗链
    if(referer != null ){
        if(referer.contains("/day14")){
            //正常访问
           // System.out.println("播放电影....");
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("播放电影....");
        }else{
            //盗链
            //System.out.println("想看电影吗？来优酷吧...");
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("想看电影吗？来优酷吧...");
        }
    }

} } ```

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

    System.out.println(username);
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    this.doPost(request,response);
} } ``` ![Alt Text](/images/posts/20210222173537483.png)

4. **创建包cn.example.util,编写工具类JDBCUtils**
```java
import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import javax.xml.crypto.Data;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
 * JDBC工具类 使用Durid连接池
 */
public class JDBCUtils {

    private static DataSource ds ;

    static {

        try {
            //1.加载配置文件
            Properties pro = new Properties();
            //使用ClassLoader加载配置文件，获取字节输入流
            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
            pro.load(is);

            //2.初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);

        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取连接池对象
     */
    public static DataSource getDataSource(){
        return ds;
    }


    /**
     * 获取连接Connection对象
     */
    public static Connection getConnection() throws SQLException {
        return  ds.getConnection();
    }
}

6. **编写cn.example.web.servlet.LoginServlet类**
```java
import cn.example.dao.UserDao;
import cn.example.domain.User;

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("/loginServlet")
public class LoginServlet extends HttpServlet {


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.设置编码
        req.setCharacterEncoding("utf-8");
        //2.获取请求参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //3.封装user对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);

        //4.调用UserDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser);

        //5.判断user
        if(user == null){
            //登录失败
            req.getRequestDispatcher("/failServlet").forward(req,resp);
        }else{
            //登录成功
            //存储数据
            req.setAttribute("user",user);
            //转发
            req.getRequestDispatcher("/successServlet").forward(req,resp);
        }

    }

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

    //设置编码
    response.setContentType("text/html;charset=utf-8");
    //输出
    response.getWriter().write("登录失败，用户名或密码错误");

}

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