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  • 第73节：Java中的HTTPServletReauest和HTTPServletResponse

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    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

    Content-Type: 数据类型
Content-Length: 多少长度的数据

    Servlet入门：

    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：

    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

    // 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();
}

    // 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

    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);
	}
}

    <?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

    // 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);
	}

}

    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);
	}

}

    <?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：

    * : 就是个通配符，匹配任意文字。
/a*
*.aa

    ServletContext

    // 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>

    // 获取对象
ServletContext context = getServletContext();
// 获取参数值
String name = context.getInitParameter("dashu");
System.out.println("name=" + name);

    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

    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

    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

    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

    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

    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);
	}

}

    <!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

    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

    <!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>

    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

    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);
	}

}

    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);
	}

}

    <!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>

    <!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：

    	<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>

      <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/login</url-pattern>
  </servlet-mapping>

    // 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:

    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

    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

    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

    username = new String(username.getBytes("ISO-8859-1"), "UTF-8");
System.out.println("userName="+username+"==password="+password);

    post

    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);
	}

}

    <!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

    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);
	}

}

    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

    <!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

    <!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

    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

    HttpServletRequest：获取请求头
HttpServletResponse：对请求作出响应

    如果看了觉得不错

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    结语

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  • 原文地址：https://www.cnblogs.com/dashucoding/p/11140346.html
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