我知道如何上传文件：
<html>
<head>
<title>File Uploading Form</title>
</head>
<body>
<form action="UploadServlet" method="post"
enctype="multipart/form-data">
File :<input type="file" name="file" size="50" />
<input type="submit" value="Upload File"/>
</form>
</body>
</html>
这是读取文件的类：
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class BufferedReaderExample {
public static void main(String[] args) {
try (BufferedReader br = new BufferedReader(new FileReader("C:\\testing.txt")))
{
String sCurrentLine;
while ((sCurrentLine = br.readLine()) != null) {
System.out.println(sCurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
现在如何将这两者联系起来。用户将文件上载到服务器上，服务器对其进行处理。即，它接受文件并打印它的内容。我可以使用struts框架吗？我想上传excel表并将内容打印到jsp页面。我有使用apache poi在java中读取excel表的代码。但是读取excel文件的路径是硬编码的。你如何从上传的文件中获取它？
这是阅读Excel工作表的文件：
public class ReadExcelDemo
{
public static void main(String[] args)
{
try
{
FileInputStream file = new FileInputStream(new File("howtodoinjava_demo.xlsx"));
//Create Workbook instance holding reference to .xlsx file
XSSFWorkbook workbook = new XSSFWorkbook(file);
//Get first/desired sheet from the workbook
XSSFSheet sheet = workbook.getSheetAt(0);
//Iterate through each rows one by one
Iterator<Row> rowIterator = sheet.iterator();
while (rowIterator.hasNext())
{
Row row = rowIterator.next();
//For each row, iterate through all the columns
Iterator<Cell> cellIterator = row.cellIterator();
while (cellIterator.hasNext())
{
Cell cell = cellIterator.next();
//Check the cell type and format accordingly
switch (cell.getCellType())
{
case Cell.CELL_TYPE_NUMERIC:
System.out.print(cell.getNumericCellValue() + "t");
break;
case Cell.CELL_TYPE_STRING:
System.out.print(cell.getStringCellValue() + "t");
break;
}
}
System.out.println("");
}
file.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
输出：
ID NAME LASTNAME
1.0 Amit Shukla
2.0 Lokesh Gupta
3.0 John Adwards
4.0 Brian Schultz
但是如何将上传的和servlet文件拼接在一起呢？你如何阅读上传的文件？
答案 0 :(得分：3)
你可以通过两个步骤打破整个过程来实现它
1）上传文件
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
if (!isMultipart) {
return;
}
// Create a factory for disk-based file items
DiskFileItemFactory factory = new DiskFileItemFactory();
// Sets the size threshold beyond which files are written directly to
// disk.
factory.setSizeThreshold(MAX_MEMORY_SIZE);
// Sets the directory used to temporarily store files that are larger
// than the configured size threshold. We use temporary directory for
// java
factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
// constructs the folder where uploaded file will be stored
String uploadFolder = getServletContext().getRealPath("")
+ File.separator + DATA_DIRECTORY;
// Create a new file upload handler
ServletFileUpload upload = new ServletFileUpload(factory);
// Set overall request size constraint
upload.setSizeMax(MAX_REQUEST_SIZE);
try {
// Parse the request
List items = upload.parseRequest(request);
Iterator iter = items.iterator();
while (iter.hasNext()) {
FileItem item = (FileItem) iter.next();
if (!item.isFormField()) {
String fileName = new File(item.getName()).getName();
String filePath = uploadFolder + File.separator + fileName;
File uploadedFile = new File(filePath);
System.out.println(filePath);
// saves the file to upload directory
item.write(uploadedFile);
}
}
// displays done.jsp page after upload finished
getServletContext().getRequestDispatcher("/done.jsp").forward(
request, response);
} catch (FileUploadException ex) {
throw new ServletException(ex);
} catch (Exception ex) {
throw new ServletException(ex);
}
2）上传后传递文件位置到使用apche poi读取文件数据的方法。使用File uploadedFile = new File(filePath);对象获取文件位置。
答案 1 :(得分：2)
与Java中的许多操作一样，读取文件上载是不必要的复杂，并且难以从javadoc中解决。 您已经计划使用Apache库来读取上传的文件，因此我建议您使用apache.commons.fileupload上传文件。
此代码片段将CSV文件上传到字符串中：
...
import org.apache.commons.fileupload.*;
import org.apache.commons.fileupload.disk.*;
import org.apache.commons.fileupload.servlet.*;
...
if (ServletFileUpload.isMultipartContent(request)) {
int i=0;
DiskFileItemFactory factory = new DiskFileItemFactory();
// files smaller than 5MB will be held in memory
factory.setSizeThreshold(5000000);
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setFileSizeMax(10000000); // max size of attachment 10MB
List list = upload.parseRequest(request);
Iterator iter = list.iterator();
String csv = null;
while (iter.hasNext()) {
FileItem param = (FileItem)iter.next();
if (!param.isFormField()) {
csv = param.getString();
break;
}
}
if (csv==null) {
throw new Exception("CSV buffer not uploaded");
}
}
答案 2 :(得分：0)
我明白了。索引文件（html）用于上传文件（如上所述qquestion） 它的java类是：
import java.io.*;
import java.util.*;
import javax.servlet.ServletConfig;
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.output.*;
public class UploadServlet extends HttpServlet {
private boolean isMultipart;
private String filePath;
private int maxFileSize = 50 * 1024;
private int maxMemSize = 4 * 1024;
private File file ;
public void init( ){
// Get the file location where it would be stored.
filePath =
getServletContext().getInitParameter("file-upload");
}
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, java.io.IOException {
// Check that we have a file upload request
isMultipart = ServletFileUpload.isMultipartContent(request);
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter( );
if( !isMultipart ){
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet upload</title>");
out.println("</head>");
out.println("<body>");
out.println("<p>No file uploaded</p>");
out.println("</body>");
out.println("</html>");
return;
}
DiskFileItemFactory factory = new DiskFileItemFactory();
// maximum size that will be stored in memory
factory.setSizeThreshold(maxMemSize);
// Location to save data that is larger than maxMemSize.
factory.setRepository(new File("c:\\temp"));
// Create a new file upload handler
ServletFileUpload upload = new ServletFileUpload(factory);
// maximum file size to be uploaded.
upload.setSizeMax( maxFileSize );
try{
// Parse the request to get file items.
List fileItems = upload.parseRequest(request);
// Process the uploaded file items
Iterator i = fileItems.iterator();
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet upload</title>");
out.println("</head>");
out.println("<body>");
String fileName = "";
while ( i.hasNext () )
{
FileItem fi = (FileItem)i.next();
if ( !fi.isFormField () )
{
// Get the uploaded file parameters
String fieldName = fi.getFieldName();
fileName = fi.getName();
String contentType = fi.getContentType();
boolean isInMemory = fi.isInMemory();
long sizeInBytes = fi.getSize();
// Write the file
if( fileName.lastIndexOf("\\") >= 0 ){
file = new File( filePath +
fileName.substring( fileName.lastIndexOf("\\"))) ;
}else{
file = new File( filePath +
fileName.substring(fileName.lastIndexOf("\\")+1)) ;
}
fi.write( file ) ;
out.println("Uploaded Filename: " + fileName + "<br>");
out.println("Uploaded in location: "+filePath);
}
}
out.println("</body>");
out.println("</html>");
ReadExcelDemo rd = new ReadExcelDemo();
System.out.println("file name: "+fileName.substring(fileName.lastIndexOf("\\")));
String s = fileName.substring(fileName.lastIndexOf("\\"));
System.out.println(filePath);
System.out.println(s);
String fileP = filePath.concat(s+"\\");
System.out.println(fileP);
rd.read(fileP);
}catch(Exception ex) {
System.out.println(ex);
}
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, java.io.IOException {
throw new ServletException("GET method used with " +
getClass( ).getName( )+": POST method required.");
}
}
这是使用apache poi jars阅读excel表的类：
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.Iterator;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class ReadExcelDemo {
public static void read(String filePath) {
// public static void main(String[] args){
try {
FileInputStream file = new FileInputStream(new File(filePath));
// FileInputStream file = new FileInputStream(new File("C:\\work\\demo.xlsx"));
//Create Workbook instance holding reference to .xlsx file
XSSFWorkbook workbook = new XSSFWorkbook(file);
//Get first/desired sheet from the workbook
XSSFSheet sheet = workbook.getSheetAt(0);
//Iterate through each rows one by one
Iterator<Row> rowIterator = sheet.iterator();
while (rowIterator.hasNext()) {
Row row = rowIterator.next();
//For each row, iterate through all the columns
Iterator<Cell> cellIterator = row.cellIterator();
while (cellIterator.hasNext()) {
Cell cell = cellIterator.next();
//Check the cell type and format accordingly
switch (cell.getCellType()) {
case Cell.CELL_TYPE_NUMERIC: System.out.print(cell.getNumericCellValue() + "\t");
break;
case Cell.CELL_TYPE_STRING: System.out.print(cell.getStringCellValue() + "\t");
break;
}
}
System.out.println("");
}
/* int row=0;
int k=1;
Row myRow = sheet.createRow ((short)row);
myRow.createCell(k).setCellValue ("new data");
myRow = sheet.createRow ((short)row++); */
// Cell cell1 = sheet. // Access the second cell in second row to update the value
// cell1.setCellValue("OverRide Last Name");
Cell cell1 = null; // declare a Cell object
cell1 = sheet.getRow(2).getCell(2); // Access the second cell in second row to update the value
cell1.setCellValue("OverRide Last Name");
file.close();
/* FileOutputStream out = new FileOutputStream(new File("write_demo1.xlsx"));
workbook.write(out);
out.close(); */
}
catch (Exception e) {
e.printStackTrace();
}
}
}