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社区首页 >专栏 >第73节：Java中的HTTPServletReauest和HTTPServletResponse

第73节：Java中的HTTPServletReauest和HTTPServletResponse

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达达前端
发布于 2019-07-03 15:05:49
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发布于 2019-07-03 15:05:49
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文章被收录于专栏：达达前端

第73节：Java中的HTTPServletReauest和HTTPServletResponse

HTTP协议

客户端与服务器端通讯的一种规则。

request: 请求行 请求头 请求体

response: 响应行 响应头 响应体

Get: 请求的时候带上的数据，在url上拼接，数据长度有限制

POST: 以流的方式写数据，数据没有限制

代码语言：javascript
复制
Content-Type: 数据类型
Content-Length: 多少长度的数据

Servlet入门：

代码语言：javascript
复制
写一个类，实现接口Servlet
注册 web.xml
<servlet>
 servlet-name: 自定义
 servlet-class: 全路径
 <init-params> 不必要写 -servletconfig
</servlet>
<servlet-mapping>
 <servlet-name>: 上面的servlet-name
 <url-patter>: 以正斜杠开头
</servlet-mapping>

servlet的生命周期：

代码语言：javascript
复制
init: 默认情况下初次访问时就会执行，服务器启动时，只能执行一次
提前：
<servlet>
 servlet-name:
 servlet-class:
 <load-on-startup>2</load-on-startup>
</servlet>

service: 可以执行多次，只要进行请求
destory：销毁的使用，销毁在从服务器中移除托管或shutdown.bat
代码语言：javascript
复制
// servlet
public class Demo implements Servlet {
 @Override
 void service(){
 ...
 }
}

// 优化
继承接口已有的实现类
// 抽象类一定有抽象方法，不一定，有抽象方法的，一定是抽象类
class Demo2 extends HttpServlet {
 void doGet();
 void doPost();
}
代码语言：javascript
复制
// 源码
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
 HttpServletRequest request;
 HttpServletResponse response;
 
 try{
  request = (HttpServletRequest) req;
  response = (HttpServletResponse) res;
 }catch(ClassCastException e){
  throw new ServletException("non-HTTP request or response");
 }
 service(request,response);
}

HttpServletRequest和HttpServletResponse

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("来了一个请求。。。");
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}
代码语言：javascript
复制
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>ServletRegister</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
   <servlet-name>demo</servlet-name>
   <servlet-class>com.dashucoding.servlet.Demo</servlet-class>
  </servlet>
  <servlet-mapping>
   <servlet-name>demo</servlet-name>
   <url-pattern>/demo</url-pattern>
  </servlet-mapping>
</web-app>

效果

结果

创建Server

效果

代码语言：javascript
复制
// 创建ServletRegister ->  选择Servlet
package com.dashucoding.servlet;

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

/**
 * Servlet implementation class ServletRegister
 */
@WebServlet("/ServletRegister")
public class ServletRegister extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ServletRegister() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
代码语言：javascript
复制
package com.dashucoding.servlet;

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

/**
 * Servlet implementation class ServletRegister
 */
public class ServletRegister extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
代码语言：javascript
复制
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>TestRegister</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>ServletRegister</display-name>
    <servlet-name>ServletRegister</servlet-name>
    <servlet-class>com.dashucoding.servlet.ServletRegister</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ServletRegister</servlet-name>
    <url-pattern>/ServletRegister</url-pattern>
  </servlet-mapping>
</web-app>

效果

Servlet配置路径方式：

代码语言：javascript
复制
* : 就是个通配符，匹配任意文字。
/a*
*.aa

ServletContext

代码语言：javascript
复制
// web.xml
// 用于配置全局的参数
<context-param>
 <param-name>dashu</param-name>
 <param-value>dashucoding</param-value>
</context-param>

// <init-param></init-param>
代码语言：javascript
复制
// 获取对象
ServletContext context = getServletContext();
// 获取参数值
String name = context.getInitParameter("dashu");
System.out.println("name=" + name);
代码语言：javascript
复制
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // 获取对象
    ServletContext context = getServletContext();
    // 获取参数值
    String name = context.getInitParameter("dashu");
    System.out.println("name=" + name);
}

获取资源文件

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo03
 */
public class Demo03 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        // 获取ServletContext对象
        ServletContext context = getServletContext();
        // 获取给定的文件在服务器上面的绝对路径
        String path = context.getRealPath("");
        System.out.println("path=" + path);
        
        /*// 创建属性对象
        Properties properties = new Properties();

        // 指定载入的数据源
        InputStream is = new FileInputStream(path);
        properties.load(is);

        // 获取属性的值
        String name = properties.getProperty("name");
        System.out.println("name=" + name);*/
    }

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

效果

效果

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo03
 */
public class Demo03 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        // 获取ServletContext对象
        ServletContext context = getServletContext();
        // 获取给定的文件在服务器上面的绝对路径
        String path = context.getRealPath("/file/config.properties");
        System.out.println("path=" + path);
        
        // 创建属性对象
        Properties properties = new Properties();

        // 指定载入的数据源
        InputStream is = new FileInputStream(path);
        properties.load(is);

        // 获取属性的值
        String name = properties.getProperty("name");
        System.out.println("name=" + name);
    }

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

效果

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo03
 */
public class Demo03 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
//      test01();
        test02();
    }
    // alt + shift + z
    private void test02() {
        try {
            // 获取ServletContext对象
            ServletContext context = getServletContext();
            
            // 创建属性对象
            Properties properties = new Properties();

            // 指定载入的数据源
            InputStream is = context.getResourceAsStream("/file/config.properties");
            properties.load(is);

            // 获取属性的值
            String name = properties.getProperty("name");
            System.out.println("name02=" + name);
            is.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    // alt + shift + m
    private void test01() throws FileNotFoundException, IOException {
        // 获取ServletContext对象
        ServletContext context = getServletContext();
        // 获取给定的文件在服务器上面的绝对路径
        String path = context.getRealPath("/file/config.properties");
        System.out.println("path=" + path);
        
        // 创建属性对象
        Properties properties = new Properties();

        // 指定载入的数据源
        InputStream is = new FileInputStream(path);
        properties.load(is);

        // 获取属性的值
        String name = properties.getProperty("name");
        System.out.println("name=" + name);
    }

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

效果

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo03
 */
public class Demo03 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
//      test01();
//      test02();
        test03();
    }
    private void test03() {
        // TODO Auto-generated method stub
        try {
            // 获取ServletContext对象
            ServletContext context = getServletContext();
            
            // 创建属性对象
            Properties properties = new Properties();

            // 指定载入的数据源
            InputStream is = getClass().getClassLoader().getResourceAsStream("../../file/config.properties");
            properties.load(is);

            // 获取属性的值
            String name = properties.getProperty("name");
            System.out.println("name02=" + name);
            is.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    // alt + shift + z
    private void test02() {
        try {
            // 获取ServletContext对象
            ServletContext context = getServletContext();
            
            // 创建属性对象
            Properties properties = new Properties();

            // 指定载入的数据源
            InputStream is = context.getResourceAsStream("/file/config.properties");
            properties.load(is);

            // 获取属性的值
            String name = properties.getProperty("name");
            System.out.println("name02=" + name);
            is.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    // alt + shift + m
    private void test01() throws FileNotFoundException, IOException {
        // 获取ServletContext对象
        ServletContext context = getServletContext();
        // 获取给定的文件在服务器上面的绝对路径
        String path = context.getRealPath("/file/config.properties");
        System.out.println("path=" + path);
        
        // 创建属性对象
        Properties properties = new Properties();

        // 指定载入的数据源
        InputStream is = new FileInputStream(path);
        properties.load(is);

        // 获取属性的值
        String name = properties.getProperty("name");
        System.out.println("name=" + name);
    }

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

效果

ServletContext可以获取全局配置参数，可以获取web工程中的资源，存储数据，servlet简共享数据。

使用ServletContext获取数据

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

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

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 别人把数据给你了,你就要进行获取数据
        
        String userName = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println("usrName=" + userName + "==password==" + password );
        // 校验数据
        
        if("dashu".equals(userName)&&"123".equals(password)) {
            System.out.println("登录成功");
        }else {
            System.out.println("登录失败");
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
代码语言：javascript
复制
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h2>登录</h2>
    
    
    <form action="LoginServlet" method="get">
        账号:<input type="text" name="username"/><br>
        密码:<input type="text" name="password"/><br>
        <input type="submit" value="登录"/>
    </form>
</body>
</html>

效果

效果

效果

效果

效果

登录

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 别人把数据给你了,你就要进行获取数据
        
        String userName = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println("usrName=" + userName + "==password==" + password );
        // 校验数据
        // response
        
        PrintWriter pw = response.getWriter();
        
        if("dashu".equals(userName)&&"123".equals(password)) {
            // System.out.println("登录成功");
            pw.write("login success");
        }else {
            // System.out.println("登录失败");
            pw.write("login failed");
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

效果

效果

效果

代码语言：javascript
复制
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h2>登录成功</h2>
    <a href="CountSrevlet">获取网站登录成功总数 </a>
</body>
</html>
代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 别人把数据给你了,你就要进行获取数据
        
        String userName = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println("usrName=" + userName + "==password==" + password );
        // 校验数据
        // response
        
        PrintWriter pw = response.getWriter();
        
        if("dashu".equals(userName)&&"123".equals(password)) {
            // System.out.println("登录成功");
            // pw.write("login success");
            // 成功跳转 login_success.html
            // 设置状态码
            response.setStatus(302);
            response.setHeader("Location", "login_success.html");
        }else {
            // System.out.println("登录失败");
            pw.write("login failed");
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

登录次数

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

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

/**
 * Servlet implementation class CountServlet
 */
public class CountServlet extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 取值
        int count = (int)getServletContext().getAttribute("count");
        
        // 输出界面
        response.getWriter().write("login success count == "+count);
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 别人把数据给你了,你就要进行获取数据
        
        String userName = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println("usrName=" + userName + "==password==" + password );
        // 校验数据
        // response
        
        PrintWriter pw = response.getWriter();
        
        if("dashu".equals(userName)&&"123".equals(password)) {
            // System.out.println("登录成功");
            // pw.write("login success");
            // 成功跳转 login_success.html
            // 成功次数累加 存东西
            
            
            // 获取以前旧的值,然后给它赋新值
            Object obj = getServletContext().getAttribute("count");
            
            int totalCount = 0;
            
            if(obj != null) {
                totalCount = (int)obj;
            }
            
            System.out.println("登录成功的此时是" + totalCount);
        
            // 给count赋新值 set add put
            getServletContext().setAttribute("count",totalCount+1);

            
            // 设置状态码
            response.setStatus(302);
            response.setHeader("Location", "login_success.html");
        }else {
            // System.out.println("登录失败");
            pw.write("login failed");
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
代码语言：javascript
复制
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h2>登录成功</h2>
    <a href="CountServlet">获取网站登录成功总数 </a>
</body>
</html>
代码语言：javascript
复制
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h2>登录</h2>
    
    
    <form action="LoginServlet" method="get">
        账号:<input type="text" name="username"/><br>
        密码:<input type="text" name="password"/><br>
        <input type="submit" value="登录"/>
    </form>
</body>
</html>

效果

效果

路径：

代码语言：javascript
复制
    <form action="login" method="get">
        账号:<input type="text" name="username"/><br>
        密码:<input type="text" name="password"/><br>
        <input type="submit" value="登录"/>
    </form>
代码语言：javascript
复制
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/login</url-pattern>
  </servlet-mapping>
代码语言：javascript
复制
// ServletContext 销毁，服务器移除，关闭服务器
只要同一个应用程序就行

作用：

  1. 获取全局配置
  2. 获取web工程中的资源
  3. 存储数据
  4. 共享数据

HttpServletRequest获取请求头

获取所有的头信息:

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo01
 */
public class Demo01 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // request封装了客户端提交过来的一切数据
        // 拿所有的头 得到一个枚举 List集合
        Enumeration<String> headerNames = request.getHeaderNames();
        while(headerNames.hasMoreElements()) {
            String name = (String) headerNames.nextElement();
            System.out.println("name=" + name);
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

效果

效果

得到所有

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo01
 */
public class Demo01 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // request封装了客户端提交过来的一切数据
        // 拿所有的头 得到一个枚举 List集合
        Enumeration<String> headerNames = request.getHeaderNames();
        while(headerNames.hasMoreElements()) {
            String name = (String) headerNames.nextElement();
            String value = request.getHeader(name);
            System.out.println("name=" + name + ";value=" + value);
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

效果

获取提交的信息

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo01
 */
public class Demo01 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // request封装了客户端提交过来的一切数据
        // 拿所有的头 得到一个枚举 List集合
        Enumeration<String> headerNames = request.getHeaderNames();
        while(headerNames.hasMoreElements()) {
            String name = (String) headerNames.nextElement();
            String value = request.getHeader(name);
            System.out.println("name=" + name + ";value=" + value);
        }
        
        System.out.println("----------");
        
        // 请求体，拼接过来的数据 获取客户端提交过来的数据
        String name = request.getParameter("name");

        System.out.println("name=" + name);
        // http://localhost:8080/RequestDemo01/Demo01?name=dashucoding
        // http://localhost:8080/RequestDemo01/Demo01?name=dashucoding&address=GD
        
        System.out.println("----------");
        // 获取所有参数
        // Enumeration<String> parameterNames = request.getParameterNames();
        
        Map<String, String[]> map = request.getParameterMap();
        
        Set<String> keySet = map.keySet();
        Iterator<String> iterator = keySet.iterator();
        while(iterator.hasNext()) {
            String key = (String) iterator.next();
            System.out.println("key="+key+"，的值总数" + map.get(key).length);
            String value = map.get(key)[0];
            String value1 = map.get(key)[1];
            String value2 = map.get(key)[2];
            
            System.out.println(key+" == "+value + "=" + value1 + "=" + value2);
            // http://localhost:8080/RequestDemo01/Demo01?name=dashucoding&address=GD
            // name=zhangsan&name=lisi
        }
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

get请求过来的数据已经在url地址栏上进行过编码了，所以取到的是乱码。

getParameter默认使用ISO-8859-1去解码

代码语言：javascript
复制
username = new String(username.getBytes("ISO-8859-1"), "UTF-8");
System.out.println("userName="+username+"==password="+password);

post

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // 设置请求体的文字编码
        request.setCharacterEncoding("UTF-8");
        
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        // test01(username, password);
        
        //post过来的数据乱码处理：
        System.out.println("post:userName="+username+"==password="+password);
    }

    private void test01(String username, String password) throws UnsupportedEncodingException {
        System.out.println("username" + username +"password" + password);
        // 转成ISO-8859-1字节数组，再utf-8去拼接
        username = new String(username.getBytes("ISO-8859-1"),"UTF-8");
        System.out.println("userName="+username+"==password="+password);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("来了一个post请求");
        doGet(request, response);
    }

}
代码语言：javascript
复制
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h2>登录</h2>
    
    
    <form action="login" method="post">
        账号:<input type="text" name="username"/><br>
        密码:<input type="text" name="password"/><br>
        <input type="submit" value="登录"/>
    </form>
</body>
</html>

HttpServletResponse

效果

代码语言：javascript
复制
package com.dashucoding.servlet;

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

/**
 * Servlet implementation class Demo01
 */
public class Demo01 extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // 字符流的方式
        // response.getWriter().write("hello response");
        
        response.getOutputStream().write("hello".getBytes());
        // 设置当前请求的处理状态码
        // response.setStatus("");
        // 设置一个头
        // response.setHeader(name, value);
        // 设置响应内容的类型，以及编码
        // response.setContentType(type);
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.IOException;
import java.nio.charset.Charset;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo01
 */
public class Demo01 extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        
        // test01(response);
        // test02(response);
        // 字节流 默认是使用utf-8
        // response.getOutputStream().write("我是谁".getBytes());
        // 参数可以指定编码方式
        String csn = Charset.defaultCharset().name();
        
        response.setHeader("Content-Type", "text/html; charset=UTF-8");
        response.getOutputStream().write("我是谁".getBytes("UTF-8"));
    }
    
    void test02(HttpServletResponse response){
        
        try {
            // 中文乱码

            // 默认编码ISO-8859-1
            response.setCharacterEncoding("UTF-8");
            // 规定浏览器用什么编码去看
            response.setHeader("Content-Type", "text/html; charset=UTF-8");
            response.getWriter().write("我是谁");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    // Ctrl + shift + f
    void test01(HttpServletResponse response) {
        // 字符流的方式
        // response.getWriter().write("hello response");

        try {
            response.getOutputStream().write("hello".getBytes());
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        // 设置当前请求的处理状态码
        // response.setStatus("");
        // 设置一个头
        // response.setHeader(name, value);
        // 设置响应内容的类型，以及编码
        // response.setContentType(type);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

下载资源文件

效果

代码语言：javascript
复制
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

    默认servlet去下载<br>
    <a href="download/aa.jpg">aa.jpg</a><br>
    <a href="download/bb.txt">bb.txt</a><br>
    <a href="download/cc.rar">cc.rar</a><br>
    
</body>
</html>

效果

手动下载

代码语言：javascript
复制
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

    默认servlet去下载<br>
    <a href="download/aa.jpg">aa.jpg</a><br>
    <a href="download/bb.txt">bb.txt</a><br>
    <a href="download/cc.rar">cc.rar</a><br>

    <br>手动下载<br>
    <a href="Demo01?filename=aa.jpg">aa.jpg</a><br>
    <a href="Demo01?filename=bb.txt">bb.txt</a><br>
    <a href="Demo01?filename=cc.rar">cc.rar</a><br>
    
</body>
</html>

用于用户下载

代码语言：javascript
复制
package com.dashucoding.servlet;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Demo01
 */
public class Demo01 extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // 获取要下载的文件名字
        String fileName = request.getParameter("filename");
        // 获取这个文件在tomcat里面的绝对路径地址
        String path = getServletContext().getRealPath("download/"+fileName);
        
        // 用于用户下载
        response.setHeader("Content-Disposition", "attachment; filename="+fileName);
        
        // 转化成输入流
        InputStream is = new FileInputStream(path);
        OutputStream os = response.getOutputStream();
        
        int len = 0;
        byte[] buffer = new byte[1024];
        while( (len = is.read(buffer)) != -1) {
            os.write(buffer, 0, len);
        }
        
        os.close();
        is.close();
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

小结重点

代码语言：javascript
复制
HttpServletRequest：获取请求头
HttpServletResponse：对请求作出响应

如果看了觉得不错

点赞！转发！

达叔小生：往后余生，唯独有你 You and me, we are family ! 90后帅气小伙，良好的开发习惯；独立思考的能力；主动并且善于沟通 简书博客： 达叔小生 https://www.jianshu.com/u/c785ece603d1

结语

  • 下面我将继续对 其他知识 深入讲解 ，有兴趣可以继续关注
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原始发表：2019.01.21 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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目录
  • 创建Server
  • 登录
  • HttpServletRequest获取请求头
  • HttpServletResponse
  • 小结重点
  • 结语
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