5.Servlet接口

5.1 servletConfig

5.2 servletContext

5.3.HttpServletRequest

• ServletRequest接口被定义为用于封装请求的信息，ServletRequest对象由Servlet容器在用户每次请求Servlet时创建并传入Servlet的service()方法中；

• HttpServletRequest接口继承了ServletRequest接口，是专用于HTTP协议的子接口，用于封装HTTP请求信息；

• 在HttpServlet类的service()方法中，传入的ServletRequest对象被强制转换为HttpServletRequest对象来进行HTTP请求信息的处理。

• HttpServletRequest接口提供了具有如下功能类型的方法：

  • 获取请求报文信息（包括请求行、请求头、请求正文）的方法；

  • 获取网络连接信息的方法；

  • 存取请求域属性的方法。

• HttpServletRequest接口对请求行各部分信息的获取方法

  • getMethod(),获取请求使用的HTTP方法，例如，GET、POST、PUT
  • getRequestURI(),获取请求行中的资源名部分
  • getProtocol(),获取使用的协议及版本号。例如，HTTP/1.1、HTTP/1.0
  • getQueryString(),获取请求URL后面的查询字符串，只对GET有效
  • getServletPath(),获取Servlet所映射的路径
  • getContextPath(),获取请求资源所属于的Web应用的路径

package com.neuedu.servlet;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.Enumeration;
import java.util.Map;

/**
 * 项目：      usermanager
 * 类名:       ${NAME}
 * 创建时间：  2020/12/9  10:42
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 *
 * http://127.0.0.1:8080/mis/req
 */
@WebServlet(name = "RequestServlet",urlPatterns = "/req")
public class RequestServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

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

        //请求的http 行方法（客户端)
        String method = request.getMethod();
        String uri = request.getRequestURI();
        String protocol = request.getProtocol();
        String queryString = request.getQueryString();
        String servletPath = request.getServletPath();
        String contextPath = request.getContextPath();

        System.out.println("method:"+method);
        System.out.println("uri:"+uri);
        System.out.println("protocol:"+protocol);
        System.out.println("queryString:"+queryString);
        System.out.println("servletPath:"+servletPath);
        System.out.println("contextPath:"+contextPath);


        System.out.println("++++++++++++++++++++++++++++++++++++++++++++++++++++");

        //请求头
        Enumeration<String> names = request.getHeaderNames();
        while (names.hasMoreElements()){
            String name = names.nextElement();
            String value = request.getHeader(name);
            System.out.printf("%s:\t%s\r\n",name,value);
        }


        System.out.println("-------------------------------------------------------------");
        String contentType = request.getContentType();
        int contentLength = request.getContentLength();
        System.out.println("contentType:"+contentType);
        System.out.println("contentLength:"+contentLength);


//        System.out.println("-----------------------------------------------------");
//        Reader r = new InputStreamReader(request.getInputStream());
//        BufferedReader br = new BufferedReader(r);
//
//        String line= null;
//        while( (line =br.readLine() ) != null){
//            System.out.println(line);
//        }


        System.out.println("---------------------------------------------");
        Map<String,String[]> paramMap = request.getParameterMap();
        String[] usernames = paramMap.get("username");
        System.out.println(usernames[0]);

    }
}

存储在HttpServletRequest对象中的对象称之为请求域属性，属于同一个请求的多个处理组件之间可以通过请求域属性来传递对象数据。

HttpServletRequest接口提供了如下与请求域属性相关的方法：

• void setAtrribute(String name,Object value)，设定name属性的值为value,保存在request范围内；
• Object getAttribute(String name)，从request范围内获取name属性的值；
• void removeAttribute(String name)，从request范围内移除name属性的值；
• Enumeration getAttributeNames()，获取所有request范围的属性

UserControllerServlet

package com.neuedu.servlet;

import com.neuedu.dao.UserDao;
import com.neuedu.entity.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;
import java.util.List;

/**
 * 项目：      usermanager
 * 类名:       ${NAME}
 * 创建时间：  2020/12/9  13:39
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
@WebServlet(name = "UserControllerServlet",urlPatterns = "/usecontroller")
public class UserControllerServlet extends HttpServlet {
    UserDao userDao = new UserDao();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String sql = "select * from user";
        List<User> userList = userDao.list(sql);

        //共享数据
        request.setAttribute("userList",userList);
        request.getRequestDispatcher("userlist").forward(request,response);
    }

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

UserListServlet

package com.neuedu.servlet;

import com.neuedu.entity.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;
import java.io.PrintWriter;
import java.util.List;

/**
 * 项目：      usermanager
 * 类名:       ${NAME}
 * 创建时间：  2020/12/9  13:40
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
@WebServlet(name = "UserListServlet",urlPatterns = "/userlist")
public class UserListServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        List<User> userList = (List) request.getAttribute("userList");

        //通知浏览器 内容的类型
        response.setContentType("text/html;charset=utf-8");

        StringBuffer html = new StringBuffer();
        html.append(" <a href='user?type=toAdd'>添加</a>");
        html.append(" <table border='1' width='100%'  cellpadding='0' cellspacing='0'>			");
        html.append(" <tr>               ");
        html.append(" 	<td>序号</td>   ");
        html.append(" 	<td>用户名</td> ");
        html.append(" 	<td>昵称</td>   ");
        html.append(" 	<td>密码</td>   ");
        html.append(" 	<td>出生日期</td>   ");
        html.append(" 	<td>性别</td>   ");
        html.append(" 	<td>邮箱 </td>   ");
        html.append(" 	<td>操作 </td>   ");
        html.append(" </tr>              ");

        for (User user : userList) {

            html.append(" <tr>               ");
            html.append(" 	<td>" + user.getId() + "</td>       ");
            html.append(" 	<td>" + user.getUsername() + "</td>       ");
            html.append(" 	<td>" + user.getDisplayname() + "</td>       ");
            html.append(" 	<td>" + user.getPassword() + "</td>       ");
            html.append(" 	<td>" + user.getBirthday() + "</td>       ");
            html.append(" 	<td>" + user.getGender() + "</td>       ");
            html.append(" 	<td>" + user.getEmail() + "</td>       ");
            html.append(" 	<td><a href='user?type=toEdit&id=" + user.getId() + "'>编辑</a>  <a href='user?type=delete&id=" + user.getId() + "'>删除</a></td>       ");
            html.append(" </tr>              ");
        }

        html.append(" </table>           ");

        PrintWriter out = response.getWriter();
        out.print(html.toString());


        out.flush();
        out.close();
    }

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

5.4 HttpServletResponse

5.4.1 响应输出中文乱码问题

设置响应字符集

• 由于Java程序中的字符文本在内存中以Unicode编码的形式存在，因此PrintWriter对象在输出字符文本时，需要先将它们转换成其他某种字符集编码的字节数组后输出。

• PrintWriter对象默认使用ISO-8859-1字符集进行Unicode字符串到字节数组的转换，由于ISO-8859-1字符集中没有中文字符，因此Unicode编码的中文字符将被转换成无效的字符编码后输出给客户端，这就是Servlet中文输出乱码问题的原因。

• ServletResponse接口中定义了三种方等方法来指定getWriter()方法返回的PrintWriter对象所使用的字符集编码。

  • response.setCharacterEncoding("UTF-8");
    • 只能用来设置PrintWriter输出流中字符的编码方式，它的优先权最高。
  • response.setContentType("text/html;charset=UTF-8");
    • 既可以设置PrintWriter输出流中字符的编码方式，也可以设置浏览器接收到这些字符后以什么编码方式来解码，它的优先权低于第一种方法。
  • response.setLocale(new java.util.Locale("zh","CN"));
    • 只能用来设置PrintWriter输出流中字符的编码方式，它的优先权最低，在已经使用前两种方法中的一个设置了编码方式以后，它将被覆盖而不再起作用。

package com.neuedu.servlet;

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

/**
 * 项目：      usermanager
 * 类名:       ${NAME}
 * 创建时间：  2020/12/9  14:40
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
@WebServlet(name = "ResponseServlet", urlPatterns = "/resp")
public class ResponseServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//            response.setStatus();

        response.addHeader("class","java1");
        response.addHeader("Content-Type","text/html;charset=utf-8");

//        response.setContentType("text/html;charset=utf-8");

        PrintWriter writer = response.getWriter();
//        ServletOutputStream out = response.getOutputStream();
        
        //正文
        writer.write("<h1>响应内容</h1>");
        writer.flush();
        writer.close();
    }

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

5.4.2 HTTP响应代码

1××：信息，表示请求收到，继续处理 2××：成功，表示请求成功 3××：重定向，为完成请求客户需进一步细化请求

4××：由客户端引发的错误 5××：由服务器引发的错误

状态码	说明
400	Bad Request ：错误请求
401	Unauthorized：未经授权
404	Not Found ：找不到文件或目录，URL错误
405	Method Not Allowed ：表示这个特定的资源不允许该请求方法
500	Unsupported Media Type：服务器内部错误
501	Not Implemented ：服务器不支持能够满足该请求的功能
503	Service Unavailable：服务不可用

5.4.3向客户端输出信息

MIME类型，

类型/子类型	扩展名
application/envoy	evy
application/fractals	fif
application/futuresplash	spl
application/hta	hta
application/internet-property-stream	acx
application/mac-binhex40	hqx
application/msword	doc
application/msword	dot
application/octet-stream	*
application/octet-stream	bin
application/octet-stream	class
application/octet-stream	dms
application/octet-stream	exe
application/octet-stream	lha
application/octet-stream	lzh
application/oda	oda
application/olescript	axs
application/pdf	pdf
application/pics-rules	prf
application/pkcs10	p10
application/pkix-crl	crl
application/postscript	ai
application/postscript	eps
application/postscript	ps
application/rtf	rtf
application/set-payment-initiation	setpay
application/set-registration-initiation	setreg
application/vnd.ms-excel	xla
application/vnd.ms-excel	xlc
application/vnd.ms-excel	xlm
application/vnd.ms-excel	xls
application/vnd.ms-excel	xlt
application/vnd.ms-excel	xlw
application/vnd.ms-outlook	msg
application/vnd.ms-pkicertstore	sst
application/vnd.ms-pkiseccat	cat
application/vnd.ms-pkistl	stl
application/vnd.ms-powerpoint	pot
application/vnd.ms-powerpoint	pps
application/vnd.ms-powerpoint	ppt
application/vnd.ms-project	mpp
application/vnd.ms-works	wcm
application/vnd.ms-works	wdb
application/vnd.ms-works	wks
application/vnd.ms-works	wps
application/winhlp	hlp
application/x-bcpio	bcpio
application/x-cdf	cdf
application/x-compress	z
application/x-compressed	tgz
application/x-cpio	cpio
application/x-csh	csh
application/x-director	dcr
application/x-director	dir
application/x-director	dxr
application/x-dvi	dvi
application/x-gtar	gtar
application/x-gzip	gz
application/x-hdf	hdf
application/x-internet-signup	ins
application/x-internet-signup	isp
application/x-iphone	iii
application/x-javascript	js
application/x-latex	latex
application/x-msaccess	mdb
application/x-mscardfile	crd
application/x-msclip	clp
application/x-msdownload	dll
application/x-msmediaview	m13
application/x-msmediaview	m14
application/x-msmediaview	mvb
application/x-msmetafile	wmf
application/x-msmoney	mny
application/x-mspublisher	pub
application/x-msschedule	scd
application/x-msterminal	trm
application/x-mswrite	wri
application/x-netcdf	cdf
application/x-netcdf	nc
application/x-perfmon	pma
application/x-perfmon	pmc
application/x-perfmon	pml
application/x-perfmon	pmr
application/x-perfmon	pmw
application/x-pkcs12	p12
application/x-pkcs12	pfx
application/x-pkcs7-certificates	p7b
application/x-pkcs7-certificates	spc
application/x-pkcs7-certreqresp	p7r
application/x-pkcs7-mime	p7c
application/x-pkcs7-mime	p7m
application/x-pkcs7-signature	p7s
application/x-sh	sh
application/x-shar	shar
application/x-shockwave-flash	swf
application/x-stuffit	sit
application/x-sv4cpio	sv4cpio
application/x-sv4crc	sv4crc
application/x-tar	tar
application/x-tcl	tcl
application/x-tex	tex
application/x-texinfo	texi
application/x-texinfo	texinfo
application/x-troff	roff
application/x-troff	t
application/x-troff	tr
application/x-troff-man	man
application/x-troff-me	me
application/x-troff-ms	ms
application/x-ustar	ustar
application/x-wais-source	src
application/x-x509-ca-cert	cer
application/x-x509-ca-cert	crt
application/x-x509-ca-cert	der
application/ynd.ms-pkipko	pko
application/zip	zip
audio/basic	au
audio/basic	snd
audio/mid	mid
audio/mid	rmi
audio/mpeg	mp3
audio/x-aiff	aif
audio/x-aiff	aifc
audio/x-aiff	aiff
audio/x-mpegurl	m3u
audio/x-pn-realaudio	ra
audio/x-pn-realaudio	ram
audio/x-wav	wav
image/bmp	bmp
image/cis-cod	cod
image/gif	gif
image/ief	ief
image/jpeg	jpe
image/jpeg	jpeg
image/jpeg	jpg
image/pipeg	jfif
image/svg+xml	svg
image/tiff	tif
image/tiff	tiff
image/x-cmu-raster	ras
image/x-cmx	cmx
image/x-icon	ico
image/x-portable-anymap	pnm
image/x-portable-bitmap	pbm
image/x-portable-graymap	pgm
image/x-portable-pixmap	ppm
image/x-rgb	rgb
image/x-xbitmap	xbm
image/x-xpixmap	xpm
image/x-xwindowdump	xwd
message/rfc822	mht
message/rfc822	mhtml
message/rfc822	nws
text/css	css
text/h323	323
text/html	htm
text/html	html
text/html	stm
text/iuls	uls
text/plain	bas
text/plain	c
text/plain	h
text/plain	txt
text/richtext	rtx
text/scriptlet	sct
text/tab-separated-values	tsv
text/webviewhtml	htt
text/x-component	htc
text/x-setext	etx
text/x-vcard	vcf
video/mpeg	mp2
video/mpeg	mpa
video/mpeg	mpe
video/mpeg	mpeg
video/mpeg	mpg
video/mpeg	mpv2
video/quicktime	mov
video/quicktime	qt
video/x-la-asf	lsf
video/x-la-asf	lsx
video/x-ms-asf	asf
video/x-ms-asf	asr
video/x-ms-asf	asx
video/x-msvideo	avi
video/x-sgi-movie	movie
x-world/x-vrml	flr
x-world/x-vrml	vrml
x-world/x-vrml	wrl
x-world/x-vrml	wrz
x-world/x-vrml	xaf
x-world/x-vrml	xof

​ 渲染普通文本

package com.neuedu.servlet;

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;

/**
 * 
 *   http://127.0.0.1:8080/web05/plain
 * @author Administrator
 *
 */
@WebServlet("/plain")
public class PlainServlet extends HttpServlet {
	
	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/plain;charset=utf-8");
		
		//输出内容
		PrintWriter out = response.getWriter();
		
		out.append("<h1>欢迎访问Servlet </h1>");
		out.flush();
		out.close();
	}

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

}

渲染html

package com.neuedu.servlet;

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;

/**
 * 
 *   http://127.0.0.1:8080/web05/html
 * @author Administrator
 *
 */
@WebServlet("/html")
public class HtmlServlet extends HttpServlet {
	
	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		
		//输出内容
		PrintWriter out = response.getWriter();
		out.append("<h1>欢迎访问Servlet </h1>");
		out.flush();
		out.close();
	}

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

}

输出文件

package com.neuedu.servlet;

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

/**
 * 
 *   http://127.0.0.1:8080/web05/doc
 * @author Administrator
 *
 */
@WebServlet("/doc")
public class DocServlet extends HttpServlet {
	
//	 html  文本也好，浏览器能直接打开，直接打开打不开的 提示让你下载
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		//告诉浏览器下载文件的时候 文件名字叫啥
		response.setContentType("application/msword");
		response.addHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode("下载文件.doc","utf-8") +"");
		
		
		
		
		//发送文件
		//1 读取文件
		ServletOutputStream out = response.getOutputStream();//浏览器的输出流
		FileInputStream fis = new FileInputStream("D:\\a.doc");
		byte[] bts = new byte[1024];
		int len = -1;
		while(  (len = fis.read(bts)) != -1) {//将读取的doc文件 输出到浏览器
			
			out.write(bts,0,len);
			out.flush();
			
		}
		fis.close();
		out.close();
				
		
		//2 发送给 客户端
		//输出内容
		
		
	}

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

}