文件上传下载

2019-05-16 23:56:56来源:博客园 阅读 ()

新老客户大回馈,云服务器低至5折

 

1、文件上传的核心点

1:用<input type=”file”/> 来声明一个文件域。File:_____ <浏览>.

2:必须要使用post方式的表单。

3:必须设置表单的类型为multipart/form-data.是设置这个表单传递的不是key=value值。传递的是字节码.

对于一个普通的表单来说只要它是post类型。默认就是

Content-type:application/x-www-from-urlencoded

表现形式

       1:在request的请求头中出现。

       2:在form声明时设置一个类型enctype="application/x-www-form-urlencoded";

      

如果要实现文件上传,必须设置enctype=“multipart/form-data”

 

表单与请求的对应关系:

2、如何获取上传的文件的内容-以下是自己手工解析txt文档

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 如果一个表单的类型是post且enctype为multipart/form-date
 * 则所有数据都是以二进制的方式向服务器上传递。
 * 所以req.getParameter("xxx")永远为null。
 * 只可以通过req.getInputStream()来获取数据,获取正文的数据
 * 
 * @author wangjianme
 *
 */
public class UpServlet extends HttpServlet {
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        String txt = req.getParameter("txt");//返回的是null
        System.err.println("txt is :"+txt);
        System.err.println("=========================================");
        InputStream in = req.getInputStream();
//        byte[] b= new byte[1024];
//        int len = 0;
//        while((len=in.read(b))!=-1){
//            String s = new String(b,0,len);
//            System.err.print(s);
//        }
        BufferedReader br = new BufferedReader(new InputStreamReader(in));
        String firstLine = br.readLine();//读取第一行,且第一行是分隔符号
        String fileName = br.readLine();
        fileName = fileName.substring(fileName.lastIndexOf("\\")+1);// bafasd.txt"
        fileName = fileName.substring(0,fileName.length()-1);
        
        br.readLine();
        br.readLine();
        String data = null;
        //获取当前项目的运行路径
        String projectPath = getServletContext().getRealPath("/up");
        PrintWriter out  = new PrintWriter(projectPath+"/"+fileName);
        while((data=br.readLine())!=null){
            if(data.equals(firstLine+"--")){
                break;
            }
            out.println(data);
        }
        out.close();
    }
}

3、使用apache-fileupload处理文件上传

框架:是指将用户经常处理的业务进行一个代码封装。让用户可以方便的调用。

       目前文件上传的(框架)组件:

       Apache----fileupload -

       Orialiy – COS – 2008() -

       Jsp-smart-upload – 200M。

用fileupload上传文件:

 需要导入第三方包:

       Apache-fileupload.jar – 文件上传核心包。

       Apache-commons-io.jar – 这个包是fileupload的依赖包。同时又是一个工具包。

核心类:

       DiskFileItemFactory – 设置磁盘空间,保存临时文件。只是一个具类。

       ServletFileUpload  - 文件上传的核心类,此类接收request,并解析reqeust。

       servletfileUpload.parseRequest(requdest)  - List<FileItem>

       一个FileItem就是一个标识的开始:---------243243242342 到 ------------------245243523452—就是一个FileItem

第一步:导入包

第二步:书写一个servlet完成doPost方法

/**
 * DiskFileItemFactory构造的两个参数
 *     第一个参数:sizeThreadHold - 设置缓存(内存)保存多少字节数据,默认为10K
 *                如果一个文件没有大于10K,则直接使用内存直接保存成文件就可以了。
 *              如果一个文件大于10K,就需要将文件先保存到临时目录中去。
 * 第二个参数 File 是指临时目录位置
 *
 */
public class Up2Servlet extends HttpServlet {
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        req.setCharacterEncoding("UTf-8");
        //获取项目的路径
        String path = getServletContext().getRealPath("/up");
        //第一步声明diskfileitemfactory工厂类,用于在指的磁盘上设置一个临时目录
        DiskFileItemFactory disk = 
                new DiskFileItemFactory(1024*10,new File("d:/a"));
        //第二步:声明ServletFileUpoload,接收上面的临时目录
        ServletFileUpload up = new ServletFileUpload(disk);
        //第三步:解析request
        try {
            List<FileItem> list =  up.parseRequest(req);
            //如果就一个文件
            FileItem file = list.get(0);
            //获取文件名,带路径
            String fileName = file.getName();
            fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
            //获取文件的类型
            String fileType = file.getContentType();
            //获取文件的字节码
            InputStream in = file.getInputStream();
            //声明输出字节流
            OutputStream out = new FileOutputStream(path+"/"+fileName);
            //文件copy
            byte[] b = new byte[1024];
            int len = 0;
            while((len=in.read(b))!=-1){
                out.write(b,0,len);
            }
            out.close();
            
            long size = file.getInputStream().available();
            
            //删除上传的临时文件
            file.delete();
            //显示数据
            resp.setContentType("text/html;charset=UTf-8");
            PrintWriter op = resp.getWriter();
            op.print("文件上传成功<br/>文件名:"+fileName);
            op.print("<br/>文件类型:"+fileType);
            op.print("<br/>文件大小(bytes)"+size);
            
            
            
        } catch (Exception e) {
            e.printStackTrace();
        }
        
    }

}

4、上传多个文件

第一步:修改页面的表单为多个input type=”file”

<form action="<c:url value='/Up3Servlet'/>" method="post" enctype="multipart/form-data">
        File1:<input type="file" name="txt"><br/>
        File2:<input type="file" name="txt"><br/>
        <input type="submit"/>
 </form>

第二步:遍历list<fileitem>

public class Up3Servlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String path = getServletContext().getRealPath("/up");
        //声明disk
        DiskFileItemFactory disk = new DiskFileItemFactory();
        disk.setSizeThreshold(1024*1024);
        disk.setRepository(new File("d:/a"));
        //声明解析requst的servlet
        ServletFileUpload up = new ServletFileUpload(disk);
        try{
            //解析requst
            List<FileItem> list = up.parseRequest(request);
            //声明一个list<map>封装上传的文件的数据
            List<Map<String,String>> ups = new ArrayList<Map<String,String>>();
            for(FileItem file:list){
                Map<String,String> mm = new HashMap<String, String>();
                //获取文件名
                String fileName = file.getName();
                fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
                String fileType = file.getContentType();
                InputStream in = file.getInputStream();
                int size = in.available();
                //使用工具类
                FileUtils.copyInputStreamToFile(in,new File(path+"/"+fileName));
                mm.put("fileName",fileName);
                mm.put("fileType",fileType);
                mm.put("size",""+size);
                
                ups.add(mm);
                file.delete();
            }
            request.setAttribute("ups",ups);
            //转发
            request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
            
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

5、动态上传多个文件

核心问题:

    在页面上应该可以控制<input type=”file”/>多少。

第一步:用table的格式化

 <form name="xx" action="<c:url value='/Up3Servlet'/>" method="post" enctype="multipart/form-data">
    <table id="tb" border="1">
        <tr>
            <td>
                File:
            </td>
            <td>
                <input type="file" name="file">
                <button onclick="_del(this);">删除</button>
            </td>
        </tr>
    </table>
    <br/>
    <input type="button" onclick="_submit();" value="上传">
    <input onclick="_add();" type="button" value="增加">
    </form>
  </body>
  <script type="text/javascript">
      function _add(){
          var tb = document.getElementById("tb");
          //写入一行
          var tr = tb.insertRow();
          //写入列
          var td = tr.insertCell();
          //写入数据
          td.innerHTML="File:";
          //再声明一个新的td
          var td2 = tr.insertCell();
          //写入一个input
          td2.innerHTML='<input type="file" name="file"/><button onclick="_del(this);">删除</button>';
      }
      function _del(btn){
          var tr = btn.parentNode.parentNode;
          //alert(tr.tagName);
          //获取tr在table中的下标
          var index = tr.rowIndex;
          //删除
          var tb = document.getElementById("tb");
          tb.deleteRow(index);
      }
      function _submit(){
          //遍历所的有文件
          var files = document.getElementsByName("file");
          if(files.length==0){
              alert("没有可以上传的文件");
              return false;
          }
          for(var i=0;i<files.length;i++){
              if(files[i].value==""){
                  alert(""+(i+1)+"个文件不能为空");
                  return false;
              }
          }
        document.forms['xx'].submit();
      }
  </script>
</html>

6、解决文件的重名的问题

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

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

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FileUtils;

public class UpImgServlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String path = getServletContext().getRealPath("/up");
        DiskFileItemFactory disk = 
                new DiskFileItemFactory(1024*10,new File("d:/a"));
        ServletFileUpload up = new ServletFileUpload(disk);
        try{
            List<FileItem> list = up.parseRequest(request);
            //只接收图片*.jpg-iamge/jpege.,bmp/imge/bmp,png,
            List<String> imgs = new ArrayList<String>();
            for(FileItem file :list){
                if(file.getContentType().contains("image/")){
                    String fileName = file.getName();
                    fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
                    
                    //获取扩展
                    String extName = fileName.substring(fileName.lastIndexOf("."));//.jpg
                    //UUID
                    String uuid = UUID.randomUUID().toString().replace("-", "");
                    //新名称
                    String newName = uuid+extName;
                    
                    
                    FileUtils.copyInputStreamToFile(file.getInputStream(),
                            new File(path+"/"+newName));
                    //放到list
                    imgs.add(newName);
                }
                file.delete();
            }
            request.setAttribute("imgs",imgs);
            request.getRequestDispatcher("/jsps/imgs.jsp").forward(request, response);
        }catch(Exception e){
            e.printStackTrace();
        }
    
    }

}

7、处理带说明信息的图片

List<FileItem> :

    FileItem:

 void

delete()
          
删除保存在临时目录中的文件。

 

 

String

getContentType()  获取文档的类型
          Returns the content type passed by the browser or null if not defined.

 String

getFieldName() 获取字段的名称,即name=xxxx
          Returns the name of the field in the multipart form corresponding to this file item.

<input type=”file” name=”img”/>

 InputStream

getInputStream()
          Returns an InputStream that can be used to retrieve the contents of the file.

 String

getName()
          Returns the original filename in the client's filesystem, as provided by the browser (or other client software).

获取文件名称。

如果是在IE获取的文件为 c\aaa\aaa\xxx.jpg –即完整的路径。

IE;文件名称只是 xxx.jpg

 

 

long

getSize()  获取文件大小 相当于in.avilivable();
          Returns the size of the file item

如果你上传是一普通的文本元素,则可以通过以下方式获取元素中的数据

<form enctype=”multipart/form-data”>

    <input type=”text” name=”name”/>

String

getString()  用于获取普通的表单域的信息。
          Returns the contents of the file item as a String, using the default character encoding.
IOS-8859-1

 String

getString(String encoding) 可以指定编码格式
          Returns the contents of the file item as a String, using the specified encoding.

 void

write(File file) 直接将文件保存到另一个文件中去。
          A convenience method to write an uploaded item to disk.

以下文件用判断一个fileItem是否是filetype=file)对象或是text(type=text|checkbox|radio)对象:

 boolean

isFormField()  如果是text|checkbox|radio|select这个值就是true.
          Determines whether or not a
FileItem instance represents a simple form field.

示例:

public class UpDescServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");//可以获取中文的文件名
        String path = getServletContext().getRealPath("/up");
        DiskFileItemFactory disk = 
                new DiskFileItemFactory();
        disk.setRepository(new File("d:/a"));
        try{
            ServletFileUpload up = 
                    new ServletFileUpload(disk);
            List<FileItem> list = up.parseRequest(request);
            for(FileItem file:list){
                //第一步:判断是否是普通的表单项
                if(file.isFormField()){
                    String fileName = file.getFieldName();//<input type="text" name="desc">=desc
                    String value = file.getString("UTF-8");//默认以ISO方式读取数据
                    System.err.println(fileName+"="+value);
                }else{//说明是一个文件
                    String fileName = file.getName();
                    fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
                    file.write(new File(path+"/"+fileName));
                    System.err.println("文件名是:"+fileName);
                    System.err.println("文件大小是:"+file.getSize());
                    file.delete();
                }
            }
        }catch(Exception e){
            e.printStackTrace();
        }
    }

}

8、目录打散-hash算法

会根据文件名计算一个目录出来,计算的这个目录必须是可再计算的。

       原文件名为:你的相片.jpg

       修改名称:8383902829432oiwowf.jpg

       根据这个新的名称字符串,获取这个字符串的hash值 int hash = newName.hashCode();

       hashCode =””+ 898987878;

       获取后两位作为一个目录:78.

       目录的个数:up/00-99/00-99 共100个目录

       Up

              01

                     01

                     ..

                     99

        02

              ..

        99

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import java.util.UUID;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
/**
 * 处理目录打散。
 * 思想:对新生成的文件名进行二进制运算。
 * 先取后一位 int x = hashcode & 0xf;
 * 再取后第二位:int y = (hashCode >> 4) & 0xf;
 * @author wangjianme
 *
 */
public class DirServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String path = getServletContext().getRealPath("/up");
        DiskFileItemFactory disk = 
                new DiskFileItemFactory();
        disk.setRepository(new File("d:/a"));
        try{
            ServletFileUpload up = new ServletFileUpload(disk);
            List<FileItem> list = up.parseRequest(request);
            for(FileItem file:list){
                if(!file.isFormField()){
                    String fileName = file.getName();
                    fileName=fileName.substring(fileName.lastIndexOf("\\")+1);
                    String extName = fileName.substring(fileName.lastIndexOf("."));
                    String newName = UUID.randomUUID().toString().replace("-","")+extName;
                    //第一步:获取新名称的hashcode
                    int code = newName.hashCode();
                    //第二步:获取后一位做为第一层目录
                    String dir1 = 
                            Integer.toHexString(code & 0xf);
                    //获取第二层的目录
                    String dir2 = 
                            Integer.toHexString((code>>4)&0xf);
                    String savePath = dir1+"/"+dir2;
                    //组成保存的目录
                    savePath=path+"/"+savePath;
                    //判断目录是否存在
                    File f = new File(savePath);
                    if(!f.exists()){
                        //创建目录
                        f.mkdirs();
                    }
                    //保存文件
                    file.write(new File(savePath+"/"+newName));
                    file.delete();
                    //带路径保存到request
                    request.setAttribute("fileName",dir1+"/"+dir2+"/"+newName);
                }
            }
            
            request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
        }catch(Exception e){
            e.printStackTrace();
        }
    }

}

9、性能提升

核心点用FileItemIterator it= up.getItemIterator(request);处理文件上传。

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.RequestContext;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.servlet.ServletRequestContext;
import org.apache.commons.io.FileUtils;

public class FastServlet extends HttpServlet {

    
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String path = getServletContext().getRealPath("/up");
        DiskFileItemFactory disk = 
                new DiskFileItemFactory();
        disk.setRepository(new File("d:/a"));
        try{
            ServletFileUpload up = new ServletFileUpload(disk);
            //以下是迭代器模式
            FileItemIterator it= up.getItemIterator(request);
            while(it.hasNext()){
                FileItemStream item =  it.next();
                String fileName = item.getName();
                fileName=fileName.substring(fileName.lastIndexOf("\\")+1);
                InputStream in = item.openStream();
                FileUtils.copyInputStreamToFile(in,new File(path+"/"+fileName));
            }
        }catch(Exception e){
            e.printStackTrace();
        }
        
    }

}

10、限制上传大小

1:限制总文件的大小     上传10文件,设置最多总上传大小为100M

      

void

setSizeMax(long sizeMax)
          Sets the maximum allowed size of a complete request, as opposed to setFileSizeMax(long).

104857600

153046512  

 

       2:设置第每一个文件的大小 ,如果设置每 一个文件大小10M

 void

setFileSizeMax(long fileSizeMax)
          Sets the maximum allowed size of a single uploaded file, as opposed to getSizeMax().

11、用COS实现文件上传

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.UUID;

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

import com.oreilly.servlet.MultipartRequest;
import com.oreilly.servlet.multipart.DefaultFileRenamePolicy;
import com.oreilly.servlet.multipart.FileRenamePolicy;
/**
 * 在Cos中就一个类,
 * MultipartRequest它是request的包装类。
 */
public class CosServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse resp)
            throws ServletException, IOException {
        //第一步:声明文件的保存目录
        String path = getServletContext().getRealPath("/up");
        //第二步:文件传
        //声明文件重新取名的策略
        FileRenamePolicy rename = new DefaultFileRenamePolicy();
        MultipartRequest req = 
                new MultipartRequest(request,path,1024*1024*100,"UTF-8",new MyRename());
        
//        //第三步:显示信息,
        resp.setContentType("text/html;charset=UTf-8");
        PrintWriter out = resp.getWriter();
        
        out.print("文件名称1:"+req.getOriginalFileName("img1"));
        out.print("<br/>新名称:"+req.getFilesystemName("img1"));
        out.print("<br/>类型1:"+req.getContentType("img1"));
        out.print("<br/>大小1:"+req.getFile("img1").length());
        out.print("<br/>说明:"+req.getParameter("desc1"));
        if(req.getContentType("img1").contains("image/")){
            out.print("<img src='"+request.getContextPath()+"/up/"+req.getFilesystemName("img1")+"'></img>");
        }
        
//        out.print("<hr/>");
//        out.print("文件名称2:"+req.getOriginalFileName("img2"));
//        out.print("<br/>类型2:"+req.getContentType("img2"));
//        out.print("<br/>大小2:"+req.getFile("img2").length());
//        out.print("<br/>说明2:"+req.getParameter("desc2"));
//        
//        
//        out.print("<hr/>");
//        out.print("文件名称3:"+req.getOriginalFileName("img3"));
//        out.print("<br/>类型3:"+req.getContentType("img3"));
//        out.print("<br/>大小3:"+req.getFile("img3").length());
//        out.print("<br/>说明3:"+req.getParameter("desc3"));
    }
}
class MyRename implements FileRenamePolicy{
    public File rename(File file) {
        String fileName = file.getName();
        String extName = fileName.substring(fileName.lastIndexOf("."));
        String uuid = UUID.randomUUID().toString().replace("-","");
        String newName = uuid+extName;//abc.jpg
        file = new File(file.getParent(),newName);
        return file;
    }
    
}

12、下载

即可以是get也可以是post

public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        String name = req.getParameter("name");
        //第一步:设置响应的类型
        resp.setContentType("application/force-download");
        //第二读取文件
        String path = getServletContext().getRealPath("/up/"+name);
        InputStream in = new FileInputStream(path);
        //设置响应头
        //对文件名进行url编码
        name = URLEncoder.encode(name, "UTF-8");
        resp.setHeader("Content-Disposition","attachment;filename="+name);
        resp.setContentLength(in.available());
        
        //第三步:开始文件copy
        OutputStream out = resp.getOutputStream();
        byte[] b = new byte[1024];
        int len = 0;
        while((len=in.read(b))!=-1){
            out.write(b,0,len);
        }
        out.close();
        in.close();
    }

13、单线程断点下载

服务使用断点下载时,响应的信息是206

       UrlConnection HttpurlConnection-通过URL来获取urlconnection实例。

 

第一步:正常下载

import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigDecimal;
import java.net.HttpURLConnection;
import java.net.URL;
public class CommonDown {
    public static void main(String[] args) throws Exception {
        String path = "http://localhost:6666/day22_cos/up/video.avi";
        URL url = new URL(path);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");
        con.setDoInput(true);
        con.connect();
        int code = con.getResponseCode();
        System.err.println(code);
        if (code == 200) {
            //获取文件大小
            long size = con.getContentLength();
            System.err.println("总大小是:"+size);
            //声明下载到的字节
            long sum=0;
            BigDecimal bd = new BigDecimal(0D);
            double already = 0D;
            InputStream in = con.getInputStream();
            byte[] b = new byte[1024];
            int len = -1;
            OutputStream out = new FileOutputStream("d:/a/video.avi");
            while ((len = in.read(b)) != -1) {
                out.write(b, 0, len);
                sum=sum+len;
                double percent = ((double)sum)/((double)size);
                percent*=100;
                bd = new BigDecimal(percent);
                bd = bd.divide(new BigDecimal(1),0,BigDecimal.ROUND_HALF_UP);
                if(bd.doubleValue()!=already){
                    System.err.println(bd.intValue()+"%");
                    already=bd.doubleValue();
                }
            }
            out.close();
        }
    }
}

第二步:断点下载

1:如何通知服务器只给我3以后数据。

   req.setHeader("range","bytes=0-"); 从第0字节以后的所有字节

 

   range=”bytes=3-”

2:我如何知道自己已经下载的3K数据。

   读取文件大小。

   file.length();

 

3:如果从当前已经下载的文件后面开始追加数据。

  FileRandomAccess 随机访问文件对象

  seek(long);

  skip(long);

 

 

14URLConnection

此类用于在java代码中模拟浏览器组成http协议向服务发请求(get/post)。

 

 

代码:

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;

public class OneServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse resp)
            throws ServletException, IOException {
        String name = request.getParameter("name");
        System.err.println("这是get、、、、"+name);
        resp.setContentType("text/html;charset=UTF-8");
        resp.getWriter().print("你好:"+name);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse resp)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String name = request.getParameter("name");
        System.err.println("这是post请求......."+name);
        resp.setContentType("text/html;charset=UTF-8");
        resp.getWriter().print("你好:"+name);
    }

}

urlconnection访问oneSerlvet

import java.io.File;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import org.junit.Test;
public class Demo {
    /**
     * 发送get请求
     * @throws Exception
     */
    @Test
    public void testConn() throws Exception{
        //第一步:声明url
        String urlPath = "http://localhost:6666/day22_cos/OneServlet?name=Jack";
        //第二步:声明URL对象
        URL url = new URL(urlPath);
        //第三步:从url上获取连接
        HttpURLConnection con=  (HttpURLConnection) url.openConnection();
        //第四步:设置访问的类型
        con.setRequestMethod("GET");
        //第五步:设置可以向服务器发信息。也可以从服务器接收信息
        con.setDoInput(true); //也可以从服务器接收信息
        con.setDoOutput(true); //设置可以向服务器发信息
        //第六步:连接
        con.connect();
        //7:检查连接状态
        int code = con.getResponseCode();
        if(code==200){
            //8:从服务器读取数据
            InputStream in = con.getInputStream();
            byte[] b = new byte[1024];
            int len = 0;
            while((len=in.read(b))!=-1){
                String s = new String(b,0,len,"UTF-8");
                System.err.print(s);
            }
        }
        //9:断开
        con.disconnect();
    }
    /**
     * 以下发送post请求
     */
    @Test
    public void post() throws Exception{
        //第一步:声明url
        String urlPath = "http://localhost:6666/day22_cos/OneServlet";
        //第二步:声明URL对象
        URL url = new URL(urlPath);
        //第三步:从url上获取连接
        HttpURLConnection con=  (HttpURLConnection) url.openConnection();
        //第四步:设置访问的类型
        con.setRequestMethod("POST");
        con.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
        //第五步:设置可以向服务器发信息。也可以从服务器接收信息
        con.setDoInput(true);//设置可以向服务器发信息
        con.setDoOutput(true);//也可以从服务器接收信息
        //第六步:发信息
        //获取输出流
        OutputStream out = con.getOutputStream();
        out.write("name=张三".getBytes("UTF-8"));
        
        
        //7:检查连接状态
        int code = con.getResponseCode();
        if(code==200){
            //8:从服务器读取数据
            InputStream in = con.getInputStream();
            byte[] b = new byte[1024];
            int len = 0;
            while((len=in.read(b))!=-1){
                String s = new String(b,0,len,"UTF-8");
                System.err.print(s);
            }
        }
        //9:断开
        con.disconnect();
    }
}

 


原文链接:https://www.cnblogs.com/dnn179/p/10863455.html
如有疑问请与原作者联系

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