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FileUpload
一upload原理：
1.表单的method必须是post方法
2.enctype属性必须是“mutipatr/form-data”类型
enctype默认的属性是“application/x-www-form-urlencoded”
enctype的作用是：告知服务器请求正文的MIME类型
application/x-www-form-urlencoded:username=aaa&password=123
ServletRequest.getParameter(String name)，该方法是专门用来读取enctype是“application/x-www-form-urlencoded”时的方法
3.在Servlet里面通过request.getInputStream()方法就可以获得文件输入流
byte[] b= new byte[1024];
int len=0;
InputStream is = request.getInputStream();
while((len=is.read(b)) != -1){
System.out.println(new String(b,0 ,len));
}
代码示例
1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2 pageEncoding="UTF-8"%> 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 4 <html> 5 <head> 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 7 <title>Insert title here</title> 8 </head> 9 <body>10 <form action="${pageContext.request.contextPath}/UploadServlet" method="post" enctype="multipart/form-data">11 请输入FileName<input type="text" name="FileName"/>12 <input type="file"name="file"/>13 <input type="submit" value=http://www.mamicode.com/"提交"/>14 ${pageContext.request.contextPath}15 16 17 18 19 </form>20 21 </body>22 </html>
1 package jcbc.ds.test1; 2 3 import java.io.IOException; 4 import java.io.InputStream; 5 import java.util.List; 6 7 import javax.servlet.ServletException; 8 import javax.servlet.http.HttpServlet; 9 import javax.servlet.http.HttpServletRequest;10 import javax.servlet.http.HttpServletResponse;11 12 import org.apache.commons.fileupload.FileItem;13 import org.apache.commons.fileupload.FileUploadException;14 import org.apache.commons.fileupload.disk.DiskFileItemFactory;15 import org.apache.commons.fileupload.servlet.ServletFileUpload;16 17 /**18 * Servlet implementation class UploadServlet19 */20 public class UploadServlet extends HttpServlet {21 private static final long serialVersionUID = 1L;22 23 /**24 * @see HttpServlet#HttpServlet()25 */26 public UploadServlet() {27 super();28 29 }30 31 /**32 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)33 */34 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {35 36 //创建DiskFileItemFactory对象37 //DiskFileItemFactory dis = new DiskFileItemFactory();38 //创建ServletFileUpload对象39 /*ServletFileUpload servletupload = new ServletFileUpload(dis);*/40 byte[] b= new byte[1024];41 int len=0;42 InputStream is = request.getInputStream();43 while((len=is.read(b)) != -1){44 System.out.println(new String(b,0 ,len));45 }46 /*try {47 List<FileItem> fileItem = servletupload.parseRequest(request);48 for(FileItem items : fileItem) {49 System.out.println(items.getName());50 //进行解析传过来的数据进行封装51 }52 is.close();53 54 } catch (FileUploadException e) {55 // TODO Auto-generated catch block56 e.printStackTrace();57 }*/58 59 }60 61 }
二借助第三方组件实现文件上传：
步骤：
1.拷贝jar包commons-fileupload.jar commons-io.jar
具体参考http://commons.apache.org/proper/commons-fileupload/using.html
2.//创建DiskFileItemFactory对象
DiskFileItemFactory disfileitemfactory = new DiskFileItemFactory();
//创建ServletFileUpload对象
ServletFileUpload servletupload = new ServletFileUpload(disfileitemfactory);
3.获取封装信息
List<FileItem> fileItem = servletupload.parseRequest(request);//这里会抛异常
具体步骤代码如下：
1 package jcbc.ds.test1; 2 3 import java.io.File; 4 import java.io.IOException; 5 import java.io.InputStream; 6 import java.io.OutputStream; 7 import java.util.List; 8 9 import javax.servlet.ServletException;10 import javax.servlet.http.HttpServlet;11 import javax.servlet.http.HttpServletRequest;12 import javax.servlet.http.HttpServletResponse;13 14 import org.apache.commons.fileupload.FileItem;15 import org.apache.commons.fileupload.FileUploadException;16 import org.apache.commons.fileupload.disk.DiskFileItemFactory;17 import org.apache.commons.fileupload.servlet.ServletFileUpload;18 import org.apache.commons.io.FileUtils;19 20 /**21 * Servlet implementation class UploadServlet22 */23 public class UploadServlet extends HttpServlet {24 private static final long serialVersionUID = 1L;25 26 /**27 * @see HttpServlet#HttpServlet()28 */29 public UploadServlet() {30 super();31 32 }33 34 /**35 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)36 */37 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {38 response.setContentType("text/html; charset=gbk");39 //创建DiskFileItemFactory对象40 DiskFileItemFactory disfileitemfactory = new DiskFileItemFactory();41 //创建ServletFileUpload对象42 ServletFileUpload servletupload = new ServletFileUpload(disfileitemfactory);43 44 try {45 //封装46 List<FileItem> fileItem = servletupload.parseRequest(request);47 for(FileItem files : fileItem ){48 if(files.isFormField()){49 System.out.println(files.getFieldName());50 }51 else{52 InputStream is = files.getInputStream();53 String name = files.getName();54 //截取文件名55 String fileName = name.substring(name.lastIndexOf("\\")+1);56 System.out.println(fileName);//打印结果为huxuebing.txt57 58 System.out.println(request.getServletContext().getRealPath("/fileName"));59 //创建File类对象60 File file = new File(request.getServletContext().getRealPath("/")+fileName);61 //判断该文件是否存在如果不存在就创建，存在就不创建62 if(file.exists()==false){63 System.out.println("==================");64 file.createNewFile();65 System.out.println("==================");66 }67 try {68 //向创建的文件写入69 files.write(file);70 } catch (Exception e) {71 // TODO Auto-generated catch block72 e.printStackTrace();73 }74 75 }76 77 }78 79 } catch (FileUploadException e) {80 // TODO Auto-generated catch block81 e.printStackTrace();82 }83 84 }85 86 }
FileNamehuxuebing.txtD:\workSpace\web2\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\day18\fileName====================================
FileUpload
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