第2阶段第13讲 Servlet进阶(上)

课程回顾

XML解析: DOM4J、DOM、SAX、JDOM, getParent() 获取父节点，再删除

HTTP协议: 0.9、1.0、1.1 无状态协议

反射技术: Class类反射入口、获取类信息、属性信息、方法信息、构造方法信息、main方法、创建对象(newInstance())、调用方法( invoke )、强制访问( setAccessible(true) )

动态代理: Proxy.newInstance( 类加载器, 接口数组，InvocationHandler ) MyBatis框架使用动态代理、SpringAOP也是

概述

我们在编写Servlet的时候，重写的doGet方法、doPost方法包括两个参数: HttpServletRequest, HttpServletResponse ;这两个参数表示的请求和响应对象。请求和响应对象的创建是由Tomcat服务器来实现的，我们开发人员并不需要显示的创建这两个对象；可以直接使用。Web服务器收到一个http请求，会针对每个请求创建一个HttpServletRequest和HttpServletResponse对象，从客户端取数据找HttpServletRequest，向客户端发送数据就是HttpServletResponse。

特别感谢: CSDN博客——扬俊的小屋做的动画

HttpServletResponse接口

接口定义

public interface HttpServletResponse extends ServletResponse

所在的包： javax.servlet.http,常见的属性和方法见文档。

HttpServletResponse对象代表服务器的响应。该对象可以向客户端发送三种类型的数据:

响应头：响应的头部信息
响应码：响应的状态码
响应体：响应的具体数据

查看HttpServletResponse的API，可以看到这些相关的方法。查看响应的相关信息:

发送响应头

package com.ujiuye.web;import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.GZIPOutputStream;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/resp2")
public class MyResponse2 extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String str = "对于IO操作来说，使用频率最高（也是最容易被遗忘）的就是close操作，好在Java规范使用了优雅的Closeable接口，这样我们只需简单封装调用此接口的方法即可。";System.out.println("原始字节长度:"+str.getBytes().length);//创建字节数组输出流,作为容器，默认长度32个字节ByteArrayOutputStream bos = new ByteArrayOutputStream();//创建压缩输出流,压缩，不存储GZIPOutputStream zip = new GZIPOutputStream(bos);//将原始字符串写到压缩输出流zip.write(str.getBytes());zip.close();//把容器转换成字节数组byte[] array = bos.toByteArray();System.out.println("压缩后的长度:"+array.length);//操作响应头response.setHeader("Content-Encoding", "gzip");response.setHeader("Content-Length", array.length+"");response.setHeader("Accept-Range", "bytes");response.setHeader("Cache-Control", "no-cache");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

执行结果:

发送响应头控制浏览器内容类型

text/html;charset=utf8 文本或者HTML代码
jpeg 图片格式
pdf pdf文件

内容类型参考文件: apache-tomcat-8.5.51/conf/web.xml

package com.ujiuye.web;import java.io.IOException;
import java.io.InputStream;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/image")
public class MyResponseImage extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//设置响应头response.setHeader("Content-Type", "jpeg");//加载图片获取输入流InputStream in = this.getServletContext().getResourceAsStream("/WEB-INF/01.jpeg");//创建缓冲数组byte[] b = new byte[1024];//定义读取数据长度int len = 0;//循环读取并写到浏览器ServletOutputStream sos =  response.getOutputStream();while( (len=in.read(b) ) != -1) {sos.write(b, 0, len);}sos.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

http://localhost:8080/chapter13/image

发送响应头控制浏览器禁止缓存

protected void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException { response.setDateHeader("expries", -1);response.setHeader("Cache-Control", "no-cache");response.setHeader("Pragma", "no-cache");
}

发送响应头控制浏览器定时刷新

protected void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException { response.setHeader("refresh", "5");//设置refresh响应头控制浏览器每隔5秒钟刷新一次//response.setHeader("refresh", "3;url=https://www.baidu.com");//3秒钟跳转页面
}

发送响应码

Servlet在接收用户请求并进行业务处理之后要转向到另一个页面，譬如成功或失败页面，这个页面跳转过程称为重定向。HttpServletResponse中一般用sendRedirect进行重定向，也就是跳转到另一个页面或者Servlet。sendRedirect进行重定向做了下面2件事：

设置HTTP响应报头中的Status为302
设置HTTP响应报头中的Location值为指定的URL

HttpServletResponse定义了很多状态码的常量(具体可以查看Servlet的API)，当需要向客户端发送响应状态码时，可以使用这些常量，避免了直接写数字，常见的状态码对应的常量：

状态码404对应的常量 SC_NOT_FOUND
状态码200对应的常量 SC_OK
状态码500对应的常量 SC_INTERNAL_SERVER_ERROR

用法

HttpServletResponse.sendRedirect("url?参数名1=参数值&参数名2=参数值");

实例

protected void doGet(HttpServletRequest request,  HttpServletResponse response) throws ServletException, IOException {  /*方法一：使用response.sendRedirect*/  //response.sendRedirect("index.html");  /*方法二：设置响应头和重定向地址*/  response.setHeader("Location", "index.html");  response.setStatus(HttpServletResponse.SC_FOUND);//设置302状态码，等同于response.setStatus(302);
}

发送响应体

通过response对象返回具体数据到浏览器是需要的数据传输媒介，分为: 字节流和字符流。

package com.ujiuye.web;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/refresh")
public class MyResponseRefresh extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/html;charset=utf8");/*** 多学一招：使用HTML语言里面的标签来控制浏览器行为，模拟通过设置响应头控制浏览器行为* response.setHeader("content-type", "text/html;charset=UTF-8");*/String str = "3秒钟跳转页面";//输出中文: 字节流//ServletOutputStream sos = response.getOutputStream();//sos.write(str.getBytes());//out.write("使用OutputStream输出数字:".getBytes("utf-8"));//out.write( (1+"").getBytes());//字母d， //字符流PrintWriter out = response.getWriter();out.println("字符流:" + str);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

注意：getOutputStream()和getWriter()这两个方法互相排斥，调用了其中的任何一个方法后，就不能再调用另一方法。

综合案例：文件下载

编写Servlet

package com.ujiuye.web;import java.io.IOException;
import java.io.InputStream;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/download")
public class MyResponseDownload extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//设置文件下载响应头response.setHeader("Content-disposition", "attachment;filename=01.jpeg");//加载图片获取输入流InputStream in = getServletContext().getResourceAsStream("/WEB-INF/01.jpeg");//获取输出流ServletOutputStream out = response.getOutputStream();//创建缓冲池byte[] b = new byte[1024];int len = 0;while(  (len = in.read(b)) != -1 ) {out.write(b, 0, len);}out.close();in.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

编写HTML页面

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="download">文件下载</a>
</body>
</html>

支持中文文件名

package com.ujiuye.web;import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/download")
public class MyResponseDownload extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//加载图片获取输入流String realPath = getServletContext().getRealPath("/WEB-INF/美女.jpeg");String fileName = realPath.substring(realPath.lastIndexOf("/") + 1);System.out.println("文件名称:"+fileName);//设置文件下载响应头response.setHeader("Content-disposition", "attachment;filename="+URLEncoder.encode(fileName, "utf-8"));//InputStream in = getServletContext().getResourceAsStream("/WEB-INF/01.jpeg");//获取流FileInputStream in  = new FileInputStream(realPath);ServletOutputStream out = response.getOutputStream();//创建缓冲池byte[] b = new byte[1024];int len = 0;while(  (len = in.read(b)) != -1 ) {out.write(b, 0, len);}in.close();out.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

综合案例：图片验证码

package com.ujiuye.web;import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/code")
public class MyResponseCode extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 0.设置refresh响应头控制浏览器每隔5秒钟刷新一次response.setHeader("refresh", "5");// 1.在内存中创建一张图片BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);// 2.得到图片// Graphics g = image.getGraphics();Graphics2D g = (Graphics2D) image.getGraphics();g.setColor(Color.WHITE);// 设置图片的背景色g.fillRect(0, 0, 80, 20);// 填充背景色// 3.向图片上写数据g.setColor(Color.BLUE);// 设置图片上字体的颜色g.setFont(new Font(null, Font.BOLD, 20));g.drawString(makeNum(), 0, 20);// 4.设置响应头控制浏览器浏览器以图片的方式打开response.setContentType("image/jpeg");// 等同于response.setHeader("Content-Type", "image/jpeg");// 5.设置响应头控制浏览器不缓存图片数据response.setDateHeader("expries", -1);response.setHeader("Cache-Control", "no-cache");response.setHeader("Pragma", "no-cache");// 6.将图片写给浏览器ImageIO.write(image, "jpg", response.getOutputStream());}/*** 生成随机数字*/private String makeNum() {Random random = new Random();String num = random.nextInt(9999999) + "";StringBuffer sb = new StringBuffer();for (int i = 0; i < 7 - num.length(); i++) {sb.append("0");}num = sb.toString() + num;return num;}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

访问地址: http://localhost:8080/chapter13/code

HttpServletRequest接口

接口定义

HttpServletRequest接口的定义

public interface HttpServletRequest extends ServletRequest

父接口: ServletRequest接口的定义, 从定义可以看出ServletRequest是根接口。

public interface ServletRequest

Defines an object to provide client request information to a servlet. The servlet container creates a ServletRequest object and passes it as an argument to the servlet’s service method.

定义一个提供客户端请求信息到一个Servlet的对象，Servlet容器创建一个ServletRequest对象并作为一个参数传递给Servlet的seivice方法。

A ServletRequest object provides data including parameter name and values, attributes, and an input stream. Interfaces that extend ServletRequest can provide additional protocol-specific data (for example, HTTP data is provided by HttpServletRequest.

一个ServletRequest对象提供的数据包括: 参数名称和参数值、属性值、输入流。继承自ServletRequest接口可以提供额外指定的协议参数，( 例如Http协议 )

实现类: HttpServletRequestWrapper

public class HttpServletRequestWrapper extends ServletRequestWrapperimplements HttpServletRequest

查看请求的相关信息:

获取请求行信息

package com.ujiuye.web2;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/line")
public class RequestLine extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String scheme   = request.getScheme();//获取协议String method   = request.getMethod(); //请求方法String url      = request.getRequestURL().toString();//请求的URLString uri      = request.getRequestURI();//请求的URIString param    = request.getQueryString();//请求的参数String protocol = request.getProtocol();//请求的协议String path     = request.getContextPath();//获取项目名称response.setContentType("text/html;charset=utf8");PrintWriter out = response.getWriter();out.println("scheme:"   + scheme + "<br/>");out.println("method:"   + method + "<br/>");out.println("url:"      + url + "<br/>");out.println("uri:"      + uri + "<br/>");out.println("param:"    + param + "<br/>");out.println("protocol:" + protocol + "<br/>");out.println("path:"     + path + "<br/>");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

http://localhost:8080/chapter13/line?username=admin&password=123456

获取请求头信息

获取请求的报文头信息：

request.getHeader(“xx”) 根据指定的请求头获取值
request.getHeaders(“xx”)根据指定的请求头获取值,值是多个；Accept-Language: zh-CN,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6
request.getHeaderNames()获取所有的请求头的名称，然后就可以根据名称再获取值

package com.ujiuye.web2;import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/header")
public class RequestHeader extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/html;charset=utf8"); PrintWriter out = response.getWriter();Enumeration<String> en =  request.getHeaderNames();//Iteratorwhile(en.hasMoreElements()) {String name =  en.nextElement();String value = request.getHeader(name);out.println(name + "-->" + value + "<br/>");}out.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

执行结果:

获取请求体信息

获得客户机请求参数(客户端提交的数据)

getParameter(String)方法**(常用)**
getParameterValues(String name)方法**(常用)**
getParameterNames()方法(不常用)
getParameterMap()方法**(编写框架时常用)**

注册页面

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="download">文件下载</a><h1>用户注册</h1>
<form name="regForm" action="registerServlet" method="post" id="regForm">
姓名: <input type="text" name="name" id="name"><br>
性别: 男<input type="radio" name="sex" id="radio1" value="男" checked>女<input type="radio" name="sex" id="radio2" value="女"><br>
爱好:
抽烟<input type="checkbox" name="hobbies" value="抽烟">
喝酒<input type="checkbox" name="hobbies" value="喝酒">
打豆豆<input type="checkbox" name="hobbies" value="打豆豆" checked>
泡妞<input type="checkbox" name="hobbies" value="泡妞"><br/>
简介: <textarea name="mark" id="" cols="30" rows="10"></textarea><br>
学历: <select name="education" id="selEdu"><optgroup label="非正常学历"><option value="野鸡大学">野鸡大学</option><option value="家里蹲大学">家里蹲大学</option><option value="社会大学">社会大学</option></optgroup><optgroup label="正常学历"><option value="初中">初中</option><option value="高中" selected="selected">高中</option><option value="大学">大学</option></optgroup>
</select><br>
<input type="submit" value="提交"/>
<input type="reset" value="重置"/>
</form>
</body>
</html>

注册Servlet

package com.ujiuye.web2;import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Map;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/registerServlet")
public class RequestBody extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();//第一种方法: 根据表单组件名称获取值String name      = request.getParameter("name");String sex       = request.getParameter("sex");String hobbies[] = request.getParameterValues("chk_hobbies");String mark      = request.getParameter("mark");String edu       = request.getParameter("education");out.println("name:" + name + "<br/>");out.println("sex:" + sex + "<br/>");out.println("hobbies:" + Arrays.toString(hobbies) + "<br/>");out.println("mark:" + mark + "<br/>");out.println("edu:" + edu + "<br/>");out.println("<hr/>");//第二种方法: 如果表单的内容不详，如何获取表单数据？ MapMap<String,String[]> map = request.getParameterMap();for(Map.Entry<String, String[]> entry : map.entrySet()) {String names = entry.getKey();String values[] = entry.getValue();out.println(names + "--->" + Arrays.toString(values).replace("[", "").replace("]", "")+"<br/>");}//第三种方法: 先获取所有的名称，再跟据名字获取内容out.println("<hr/>");Enumeration<String> en =  request.getParameterNames();while(en.hasMoreElements()) {String namess = en.nextElement();if(namess.startsWith("chk_")) {String [] values = request.getParameterValues(namess);out.println(namess + "--->" + Arrays.toString(values).replace("[", "").replace("]", "")+"<br/>");}else {String value = request.getParameter(namess);//多选的问题out.println(namess + "--->" + value+"<br/>");}}out.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

执行效果

获取请求客户端信息

package com.ujiuye.web2;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/remote")
public class RequestRemote  extends HttpServlet{@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String addr = request.getRemoteAddr();//客户端IP地址String host = request.getRemoteHost();//客户端主机int port    = request.getRemotePort();//客户端端口String user = request.getRemoteUser();//客户端用户名称request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();out.println("addr:" + addr+"<br/>");out.println("host:" + host+"<br/>");out.println("port:" + port+"<br/>");out.println("user:" + user+"<br/>");}
}

获取本地服务器信息

package com.ujiuye.web2;import java.io.IOException;
import java.io.PrintWriter;
import java.util.Locale;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/local")
public class RequestLocal  extends HttpServlet{@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String addr = request.getLocalAddr();//服务器IPString host = request.getLocalName();//服务器名称int port    = request.getLocalPort();//服务器端口//具体的服务器String serverName = request.getServerName();int serverPort    = request.getServerPort();//代表的本地信息，国家、语言Locale local = request.getLocale();request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();out.println("addr:" + addr+"<br/>");out.println("host:" + host+"<br/>");out.println("port:" + port+"<br/>");out.println("local:" + local.getDisplayCountry() + ","+local.getDisplayLanguage() +"<br/>");out.println("serverName:" + serverName+"<br/>");out.println("serverPort:" + serverPort+"<br/>");}
}