WEB_32【檔案上傳】
阿新 • • 發佈：2018-12-10
特此說明：本文參考傳智播客、黑馬程式設計師視訊講座 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
檔案上傳介紹
檔案上傳程式碼如下，細節點需要滿足的條件已經註釋標註
<form action="/WEB32/upload" method="post" enctype="multipart/form-data">
<!-- type型別是file,name值必須有，enctype值必須是multipart/form-data -->
<input type="file" name 點選上傳按鈕，抓包得到下面情況：
<form action="/WEB32/upload" method="post" enctype="multipart/form-data">
<input type="text" name="text"><br>
<input type="file" name="fileName" 上面程式碼執行後，點選提交按鈕，抓包得到：
檔案上傳demo
（1）建立工程：
（3）書寫程式碼**
form.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/WEB32/upload" method="post" enctype="multipart/form-data">
<input type="text" name="text"><br>
<input type="file" name="fileName"><br>
<input type="submit" value="上傳">
</form>
</body>
</html>UploadServlet.java
package servlet;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class UploadServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
//接受上傳檔案
//1、建立磁碟檔案項工廠
DiskFileItemFactory factory = new DiskFileItemFactory();
//2、建立檔案上傳的核心類
ServletFileUpload upload = new ServletFileUpload(factory);
//3、解析request---獲得檔案項集合
List<FileItem> parseRequest = upload.parseRequest(request);
//4、遍歷檔案項集合
for(FileItem item : parseRequest){
//5、判斷普通表單項/檔案上傳項
boolean formField = item.isFormField();//是否是一個普通表單項
if(formField){
//普通表單項
String fieldName = item.getFieldName();
String fieldValue = item.getString();
System.out.println(fieldName+":"+fieldValue);
}else{
//檔案上傳項
//獲得上傳檔案的名稱
String fileName = item.getName();
//獲得上傳檔案的內容
InputStream in = item.getInputStream();
//將in中的資料拷貝伺服器上
String path = this.getServletContext().getRealPath("/upload");
OutputStream out = new FileOutputStream(path+"/"+fileName);
int len = 0;
byte[] buffer = new byte[1024];
while((len=in.read(buffer))>0){
out.write(buffer, 0, len);
}
in.close();
out.close();
}
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
檔案上傳的API的詳解
(1) DiskFileItemFactory 設定快取大小：factory.setSizeThreshold() 單位是位元組 設定臨時檔案的目錄：factory.setRepository(File) 上傳到快取中，達到一定大小後會放到臨時檔案中。臨時檔案大小達到和上傳的檔案大小一樣的時候就說明上傳成功了 (2) ServletFileUpload 判斷是否是一個檔案上傳的表單：ServletFileUpload.isMultipartContent(request); 解析request獲得表單項的集合：upload.parseRequest(request)； 設定上傳的檔名的編碼方式：upload.setHeaderEncoding(“UTF-8”);
(3) FileItem 判斷是否是普通表單項：item.isFormField(); 獲得表單的name屬性值：item.getFieldName(); 獲得表單的value值：item.getString(“UTF-8”) — UTF-8表示獲得中文時的編碼 獲得上傳檔案的名稱：item.getName() 獲得上傳檔案：item.getInputStream(); 刪除臨時檔案：item.delete();
詳解程式碼:
package com.itheima;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.IOUtils;
public class FileuploadServlet2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
//1、建立磁碟檔案項工廠
//作用：設定快取檔案的大小 設定臨時檔案儲存的位置
String path_temp = this.getServletContext().getRealPath("temp");
//DiskFileItemFactory factory = new DiskFileItemFactory(1024*1024, new File(path_temp));
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(1024*1024);
factory.setRepository(new File(path_temp));
//2、建立檔案上傳的核心類
ServletFileUpload upload = new ServletFileUpload(factory);
//設定上傳檔案的名稱的編碼
upload.setHeaderEncoding("UTF-8");
//ServletFileUpload的API
boolean multipartContent = upload.isMultipartContent(request);//判斷表單是否是檔案上傳的表單
if(multipartContent){
//是檔案上傳的表單
//***解析request獲得檔案項集合
List<FileItem> parseRequest = upload.parseRequest(request);
if(parseRequest!=null){
for(FileItem item : parseRequest){
//判斷是不是一個普通表單項
boolean formField = item.isFormField();
if(formField){
//username=zhangsan
String fieldName = item.getFieldName();
String fieldValue = item.getString("UTF-8");//對普通表單項的內容進行編碼
System.out.println(fieldName+"----"+fieldValue);
//當表單是enctype="multipart/form-data"時 request.getParameter相關的方法
//String parameter = request.getParameter("username");
}else{
//檔案上傳項
//檔案的名
String fileName = item.getName();
//獲得上傳檔案的內容
InputStream in = item.getInputStream();
String path_store = this.getServletContext().getRealPath("upload");
OutputStream out = new FileOutputStream(path_store+"/"+fileName);
IOUtils.copy(in, out);
in.close();
out.close();
//刪除臨時檔案
item.delete();
}
}
}
}else{
//不是檔案上傳表單
//使用原始的表單資料的獲得方式 request.getParameter();
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}