Servlet的请求HttpServletRequest

时间：2023-03-08 17:23:03
Servlet的请求HttpServletRequest

一、从容器到HttpServlet

1、web容器作了什么

　　web容器做的事情就是，创建Servlet实例，并完成Servlet的名称注册及URL模式的对应。在请求来到时，web容器会转发给正确的Servlet来处理请求。

　　当请求来到http服务器时，而http服务器转交请求给容器时，容器会创建一个代表档次请求的HttpServletRequest对象，并将请求相关信息设置给该对象。同时，容器会创建一个HttpServletResponse对象，作为稍后要对客户端进行相应的java对象。

　　　　　Servlet的请求HttpServletRequest

　　接着，容器会根据读取的@webServlet标注或者xml的设置，找出处理该请求的servlet，调用它的service()方法，将创建的HttpServletRequest对象、HttpServletResponse对象传入作为参数，service()方法中会根据HTTP请求的方式，调用对应的doXXX()方法。接着再doXXX()方法中，可以使用request、resposne对象，如：getParameter()取得请求参数，使用getWriter()取得输出用的PrintWriter对象，并进行各项响应处理。对PrintWriter做的输出操作，最后由容器转换为HTTP响应，再由HTTP服务器对浏览器响应。之后容器将对象销毁。

　　　　Servlet的请求HttpServletRequest

2、关于HttpServletRequest

2.1 处理请求参数与标头

　　String username = request.getParameter("name");指定请求参数名称来取得对应的值。如果传来的是"123"这样的字符串值，必须使用Integer.parseInt()这类方法剖析为基本类型。

　　String[] values = request.getParameterValues("param");就像param=10&param=20&param=30，此时用getParameterValues()取得一个String数组。

　　如果想要知道请求中有多少请求参数，则可以使用getParameterNames()方法，会返回一个Enumeration对象。

　　　　Enumeration<String> e = request.getParameterNames();

　　　　while(e.hasMoreElements()){

　　　　　　String param = e.nextElement();

　　　　　　...

　　　　}

　　对于HTTP标头的信息(Header)，可以通过以下方法取得：

　　　　1、getHeader()：使用方式与getParameter类似。

　　　　2、getHeaders()：与getParameterValues类似。

　　　　3、getHeaderNames()：与getParameterNames类似。

　　以下的实例如何取得并显示浏览器送出的标头信息。

 package cc.openhome;

 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;

 /**

  * Servlet implementation class HeaderServlet

  */

 @WebServlet("/header.view")

 public class HeaderServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;

     /**

      * @see HttpServlet#HttpServlet()

      */

     public HeaderServlet() {

         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

         PrintWriter out=response.getWriter();

         out.println("<html>");

         out.println("<head>");

         out.println("<title>HeadServlet</title>");

         out.println("</head>");

         out.println("<body>");

         out.println("<h1>HeaderServlet at "+request.getContextPath()+"</h1>");//取得应用程序环境路径

         Enumeration<String> names=request.getHeaderNames();//取得所有标头名称

         while(names.hasMoreElements()){

             String name=names.nextElement();

             out.println(name+": "+request.getHeader(name)+"<br>");//输出所有的标头值

         }

         out.println("</body>");

         out.println("</html>");

          out.close();

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

     }

 }

HeaderServlet

　　运行结果：

　　　　Servlet的请求HttpServletRequest

2.2 getReader()、getInputStream()读取Body内容

　　getReader()方法，可以取得一个BufferedReader对象，可以读取Body数据。

　　例子1：读取请求Body内容

 package cc.openhome;

 import java.io.BufferedReader;

 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;

 /**

  * Servlet implementation class BodyServlet

  */

 @WebServlet("/body.view")

 public class BodyServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;

     /**

      * @see HttpServlet#HttpServlet()

      */

     public BodyServlet() {

         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

     }

     private String readBody(HttpServletRequest request) throws IOException {

         // TODO Auto-generated method stub

         BufferedReader reader=request.getReader();//取得BufferedReader对象

         String input=null;

         String requestBody="";

         while((input=reader.readLine())!=null){

             requestBody=requestBody+input+"<br>";

         }

         return requestBody;

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

         String body=readBody(request);

         PrintWriter out=response.getWriter();//取得响应输出对象

         out.println("<html>");

         out.println("<head>");

         out.println("<title>Servlet BodyView</title>");

         out.println("</head>");

         out.println("<body>");

         out.println(body);

         out.println("</body>");

         out.println("</html>");

         out.close();

     }

 }

BodyServlet

 <!DOCTYPE html>

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

 <title>Insert title here</title>

 </head>

 <body>

     <form action="body.view" method="post">

         名称：<input type="text" name="user"><br>

         密码：<input type="password" name="passwd"><br><br>

         <input type="submit" name="login" value="送出">

     </form>

 </body>

 </html>

form.html

　在名称字段上输入“良葛格”，密码上输入“123456”，单机送出按钮，得到：

　　　　Servlet的请求HttpServletRequest

2.3 getPart()、getParts()取得上传文件

　　Servlet3.0中，新增了Part接口，可以方便进行文件上传处理。可以通过request对象的getPart()方法取得Part对象。

　　例1：上传文件到指定目录。

 package cc.openhome;

 import java.io.FileOutputStream;

 import java.io.IOException;

 import java.io.InputStream;

 import java.io.OutputStream;

 import javax.servlet.ServletException;

 import javax.servlet.annotation.MultipartConfig;

 import javax.servlet.annotation.WebServlet;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import javax.servlet.http.Part;

 /**

  * Servlet implementation class PhotoServlet

  */

 @MultipartConfig(location="e:/java web/workspace/")//设置location属性

 @WebServlet("/photo.do")

 public class PhotoServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;

     /**

      * @see HttpServlet#HttpServlet()

      */

     public PhotoServlet() {

         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

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

         request.setCharacterEncoding("UTF-8");

         Part part=request.getPart("photo");

         String filename=getFilename(part);

         //writeTo(filename,part);

         part.write(filename);//将文件写入location的指定目录

     }

 //    private void writeTo(String filename, Part part) throws IOException {

 //        // TODO Auto-generated method stub

 //        InputStream in=part.getInputStream();

 //        OutputStream out=new FileOutputStream("e:/java web/workspace/"+filename);

 //        byte[] buffer=new byte[1024];

 //        int length=-1;

 //        while((length=in.read(buffer))!=-1){

 //            out.write(buffer,0,length);

 //        }

 //        in.close();

 //        out.close();

 //    }

     private String getFilename(Part part) {

         // TODO Auto-generated method stub

         String header=part.getHeader("Content-Disposition");

         String filename=header.substring(header.indexOf("filename=\"")+10,header.lastIndexOf("\""));

         return filename;

     }

 }

UploadServlet.java

 <!DOCTYPE html>

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" >

 <title>Insert title here</title>

 </head>

 <body>

     <form action="photo.do" method="post" enctype="multipart/form-data">

         上传相片：<input type="file" name="photo" value="" /><br>

         <input type="submit" name="upload" value="上传">

     </form>

 </body>

 </html>

upload.html

　　在Tomcat中必须设置@MultipartConfig标注才能使用getPart()相关API。@MultipartConfig也可以设置属性，比如location。@MultipartConfig(location="c:/workspace")，则上例子就可以修改为：

 package cc.openhome;

 import java.io.FileOutputStream;

 import java.io.IOException;

 import java.io.InputStream;

 import java.io.OutputStream;

 import javax.servlet.ServletException;

 import javax.servlet.annotation.MultipartConfig;

 import javax.servlet.annotation.WebServlet;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import javax.servlet.http.Part;

 /**

  * Servlet implementation class PhotoServlet

  */

 @MultipartConfig(location="e:/java web/workspace/")//设置location属性

 @WebServlet("/photo.do")

 public class PhotoServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;

     /**

      * @see HttpServlet#HttpServlet()

      */

     public PhotoServlet() {

         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

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

         request.setCharacterEncoding("UTF-8");

         Part part=request.getPart("photo");

         String filename=getFilename(part);

         //writeTo(filename,part);

         part.write(filename);//将文件写入location的指定目录

     }

 //    private void writeTo(String filename, Part part) throws IOException {

 //        // TODO Auto-generated method stub

 //        InputStream in=part.getInputStream();

 //        OutputStream out=new FileOutputStream("e:/java web/workspace/"+filename);

 //        byte[] buffer=new byte[1024];

 //        int length=-1;

 //        while((length=in.read(buffer))!=-1){

 //            out.write(buffer,0,length);

 //        }

 //        in.close();

 //        out.close();

 //    }

     private String getFilename(Part part) {

         // TODO Auto-generated method stub

         String header=part.getHeader("Content-Disposition");

         String filename=header.substring(header.indexOf("filename=\"")+10,header.lastIndexOf("\""));

         return filename;

     }

 }

UploadServlet.java

　　如果有多个文件要上传，可以使用getParts方法，这回返回一个Collection<Part>，其中是每个上传文件的part对象。　　

　　例子2：上传多个文件

 package cc.openhome;

 import java.io.DataInputStream;

 import java.io.FileOutputStream;

 import java.io.IOException;

 import java.io.UnsupportedEncodingException;

 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 UploadServlet

  */

 @WebServlet("/upload.do")

 public class UploadServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;

     /**

      * @see HttpServlet#HttpServlet()

      */

     public UploadServlet() {

         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

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

         request.setCharacterEncoding("UTF-8");

         //锟斤拷取锟斤拷锟斤拷Body

         byte[] body=readBody(request);

         //取锟斤拷锟斤拷锟斤拷Body锟斤拷锟捷碉拷锟街凤拷锟斤拷锟斤拷示

         String textBody=new String(body,"UTF-8");

         //取锟斤拷锟较达拷锟斤拷锟斤拷锟斤拷锟侥硷拷

         String filename=getFilename(textBody);

         //取锟斤拷锟侥硷拷锟斤拷始锟斤拷锟斤拷锟轿伙拷锟�

         Position p=getFilePosition(request,textBody);

         //锟斤拷锟斤拷锟斤拷募锟�

         writeTo(filename,body,p);

     }

     private void writeTo(String filename, byte[] body, Position p) throws IOException {

         // TODO Auto-generated method stub

         FileOutputStream fileOutputStream=new FileOutputStream("e:/java web/workspace/"+filename);

         fileOutputStream.write(body,p.begin,(p.end-p.begin));

         fileOutputStream.flush();

         fileOutputStream.close();

     }

     private Position getFilePosition(HttpServletRequest request, String textBody) throws UnsupportedEncodingException {

         // TODO Auto-generated method stub

         //取得实际上传的文件

         String contentType=request.getContentType();

         String boundaryText=contentType.substring(contentType.lastIndexOf("=")+1,contentType.length());

         //取得实际上传的文件

         int pos=textBody.indexOf("filename=\"");

         pos=textBody.indexOf("\n",pos)+1;

         pos=textBody.indexOf("\n",pos)+1;

         pos=textBody.indexOf("\n",pos)+1;

         int boundaryLoc=textBody.indexOf(boundaryText,pos)-4;

         int begin=((textBody.substring(0,pos)).getBytes("GBK")).length;

         int end=((textBody.substring(0,boundaryLoc)).getBytes("GBK")).length;

         return new Position(begin, end);

     }

     private String getFilename(String textBody) {

         // TODO Auto-generated method stub

         String filename=textBody.substring(textBody.indexOf("filename=\"")+10);

         filename=filename.substring(0,filename.indexOf("\n"));

         filename=filename.substring(filename.lastIndexOf("\\")+1,filename.indexOf("\""));

         return filename;

     }

     private byte[] readBody(HttpServletRequest request) throws IOException {

         // TODO Auto-generated method stub

         int formatDataLength=request.getContentLength();

         DataInputStream dataStream=new DataInputStream(request.getInputStream());//取锟斤拷InputStraem锟侥讹拷锟斤拷

         byte body[]=new byte[formatDataLength];

         int totalBytes=0;

         while(totalBytes<formatDataLength){

             int bytes=dataStream.read(body,totalBytes,formatDataLength);

             totalBytes+=bytes;

         }

         return body;

     }

 }

 class Position{

     int begin;

     int end;

     public Position(int begin,int end) {

         // TODO Auto-generated constructor stub

         this.begin=begin;

         this.end=end;

     }

 }

UploadServlet2.java

 <!DOCTYPE html>

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" >

 <title>Insert title here</title>

 </head>

 <body>

     <form action="upload1.do" method="post" enctype="multipart/form-data">

         文件1：<input type="file" name="file1" value="" /><br>

         文件2：<input type="file" name="file2" value="" /><br>

         文件3：<input type="file" name="file3" value="" /><br><br>

         <input type="submit" name="upload" value="上传"/>

     </form>

 </body>

 </html>

multi-upload.html

2.4 使用RequestDispatcher调派请求

　　在web应用程序中，经常需要多个Servlet来完成请求。例如，将另一个Servlet的请求处理流程包含进来，或者将请求转发forward给别的servlet处理。可以使用：

　　　　RequestDispatcher dispatcher = request.getRequestDispatcher("some.do");

　　(1)、使用include()方法

　　　　将另一个servlet的操作流程包括至目前的servlet操作之中。

　　　　例1：include方法

 package cc.openhome;

 import java.io.IOException;

 import java.io.PrintWriter;

 import javax.servlet.RequestDispatcher;

 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 Some

  */

 @WebServlet("/some.view")

 public class Some extends HttpServlet {

     private static final long serialVersionUID = 1L;

     /**

      * @see HttpServlet#HttpServlet()

      */

     public Some() {

         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

         PrintWriter out=response.getWriter();

         out.println("Some do one...");

         RequestDispatcher dispatcher=request.getRequestDispatcher("other.view?data=123456");

         dispatcher.include(request, response);

         out.println("Some do two...");

         out.close();

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

     }

 }

some.java

 package cc.openhome;

 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;

 /**

  * Servlet implementation class OtherServlet

  */

 @WebServlet("/other.view")

 public class OtherServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;

     /**

      * @see HttpServlet#HttpServlet()

      */

     public OtherServlet() {

         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

         PrintWriter out=response.getWriter();

         out.println("Other do one..");

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

     }

 }

othersome.java

　　　运行结果：网页上看到响应顺序是Some do one ... Other do one... Some do two.. .　　　　

　　(2)、使用forward()方法

　　　　将处理请求转发给别的Servlet。

　　　　例2：forwod方法

 package cc.openhome;

 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;

 import com.sun.javafx.sg.prism.NGShape.Mode;

 import com.sun.media.sound.ModelAbstractChannelMixer;

 /**

  * Servlet implementation class HelloController

  */

 @WebServlet("/hello.do")

 public class HelloController extends HttpServlet {

     private static final long serialVersionUID = 1L;

     private HelloModel model=new HelloModel();

     /**

      * @see HttpServlet#HttpServlet()

      */

     public HelloController() {

         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

         String name=request.getParameter("user");//收集请求参数

         String message=model.doHello(name);//委托HelloModel对象处理

         request.setAttribute("message", message);//将结果信息设置至请求对像成属性

         request.getRequestDispatcher("hello1.view").forward(request, response);

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

     }

 }

HelloController.java

 package cc.openhome;

 import java.util.*;

 public class HelloModel {

     private Map<String, String>messages=new HashMap<String,String>();

     public HelloModel(){

         messages.put("caterpillar", "Hello");

         messages.put("Justin", "Welcome");

         messages.put("momor", "Hi");

     }

     public String doHello(String user){

         String message=messages.get(user);

         return message+", "+user+"!";

     }

 }

HelloModel.java

 package cc.openhome;

 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 HelloView

  */

 @WebServlet("/hello1.view")

 public class HelloView extends HttpServlet {

     private static final long serialVersionUID = 1L;

     private String htmlTemplate=

               "<html>"

             +     "<head>"

             +        "<meta http-equiv='Content-Type'"

             +            "content='text/html; charset=UTF-8'>"

             +        "<title>%s</title>"

             +    "</head>"

             +    "<body>"

             +        "<h1>%s</h1>"

             +    "</body>"

             +"</html>";

     /**

      * @see HttpServlet#HttpServlet()

      */

     public HelloView() {

         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

         String user=request.getParameter("user");//取得请求参数

         String message=(String) request.getAttribute("message");//取得请求属性

         String html=String.format(htmlTemplate, user,message);//产生html结果

         response.getWriter().print(html);//输出html结果

     }

     /**

      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

      */

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

         // TODO Auto-generated method stub

     }

 }

HelloView.java

　　运行结果：(Model2架构)

　　　　Servlet的请求HttpServletRequest

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