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使用Servlet處理上傳的文件?相信很多沒有經(jīng)驗(yàn)的人對此束手無策,為此本文總結(jié)了問題出現(xiàn)的原因和解決方法,通過這篇文章希望你能解決這個問題。
一.使用getReader()和getInputStream()
Demo1
<!-- 這是HTML代碼塊,窗體網(wǎng)頁上顯示的是一個選擇文件的input框和一個upload的button --> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title></title> </head> <body> <form action="upload" method="post" enctype="multipart/form-data"> 選擇文件:<input type="file" name="filename" value="" /><br> <input type="submit" value="Upload" name="upload" /> </form> </body> </html>
//這是Servlet處理部分 import java.io.DataInputStream; import java.io.FileOutputStream; 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 uploadServlet @WebServlet("/upload") public class UploadServlet extends HttpServlet { private static final long serialVersionUID = 1L; //@see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //讀取請求Body byte[] body = readBody(request); //取得所有Body內(nèi)容的字符串表示 String textBody = new String(body, "ISO-8859-1"); //取得上傳的文件的文件名(取得路徑并分離) String filename = getFilename(textBody); //取得文件內(nèi)容在Body中的首尾索引 Position p = getFilePosition(request, textBody); //將內(nèi)容輸出到文件 writeTo(filename, body, p); } //存放索引的類 class Position{ int begin; int end; Position(int begin, int end) { this.begin = begin; this.end = end; } } //讀取請求body private byte[] readBody(HttpServletRequest request) throws IOException { int formDataLength = request.getContentLength(); //獲得ServletInputStream對象 //getReader()和getInputStream()只能則一調(diào)用,否則會拋出IllegalStateException異常 DataInputStream dataStream = new DataInputStream(request.getInputStream()); byte[] body = new byte[formDataLength]; int totalBytes = 0; while(totalBytes < formDataLength) { int bytes = dataStream.read(body, totalBytes, formDataLength); totalBytes += bytes; } return body; } //取得上傳文件名稱 private String getFilename(String reqBody) { //獲取filename的value,10是filename="的長度 //通過后臺調(diào)試我發(fā)現(xiàn)filename=后加的是帶著雙引號的路徑名,在獲取路徑名時不需要分號所以在分離時就將分號也分離掉了 String filename = reqBody.substring(reqBody.indexOf("filename=\"") + 10); //找到文件名這行的末尾,過濾掉對于獲取文件名而言的無用信息 filename = filename.substring(0, filename.indexOf("\n")); //獲取不包含路徑名的文件名 filename = filename.substring(filename.lastIndexOf("\\") + 1, filename.lastIndexOf("\"")); //此時后臺打印分離路徑后的文件名并將其作為返回值返回 System.out.println(filename); return filename; } //取得文件開始和結(jié)束位置 private Position getFilePosition(HttpServletRequest request, String textBody) throws IOException { //取得文件區(qū)段邊界信息 String contentType = request.getContentType(); String boundaryText = contentType.substring( contentType.lastIndexOf("=") + 1, contentType.length()); //取得實(shí)際上傳文件的起始與結(jié)束位置 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("ISO-8859-1")).length; int end = ((textBody.substring(0, boundaryLoc)).getBytes("ISO-8859-1")).length; return new Position(begin, end); } //輸出至文件 private void writeTo(String filename, byte[] body, Position p) throws IOException { //默認(rèn)上傳的文件是在F:\\javaeeAroundFiles目錄下 FileOutputStream fos = new FileOutputStream("F:\\javaeeAroundFiles\\later\\" + filename); fos.write(body, p.begin, (p.end - p.begin)); fos.flush(); fos.close(); } }
二.使用getPart()和getInputStream()
Demo2
//HTML代碼塊 <!-- 該HTML供uploadPartDemo和uploadPartDemo2共同使用,使用時通過更改body的form的action屬性值控制 --> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title></title> </head> <body> <form action="uploadPhoto" method="post" enctype="multipart/form-data"> 上傳相片:<input type="file" name="photo" /><br><br> <input type="submit" value="上傳" name="upload" /> </form> </body> </html>
//uploadPhotoDemo.java import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; 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 uploadPartDemo //Tomcat中必須設(shè)置@MutipartConfig標(biāo)注才能使用getPart()相關(guān)API @MultipartConfig @WebServlet("/uploadPhoto") public class uploadPartDemo extends HttpServlet { private static final long serialVersionUID = 1L; //@see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub //getPart()獲取Part對象 Part part = request.getPart("photo"); String filename = getFilename(part); writeTo(filename, part); } private String getFilename(Part part) { String header = part.getHeader("Content-Disposition"); //獲取完整路徑 String filename = header.substring(header.indexOf("filename=\"") + 10, header.lastIndexOf("\"")); //filename after substring is: F:\Entertainment\pictures\e5e893df874df44d99f06bc52504a65c.jpg System.out.println("filename after substring is: " + filename); //獲取文件名 filename = filename.substring(filename.lastIndexOf("\\") + 1); //filename after 2 substring is: e5e893df874df44d99f06bc52504a65c.jpg System.out.println("filename after 2 substring is: " + filename); return filename; } private void writeTo(String filename, Part part) throws IOException, FileNotFoundException { InputStream is = part.getInputStream(); FileOutputStream fos = new FileOutputStream("F:\\javaeeAroundFiles\\later\\" + filename); byte[] buffer = new byte[1024]; int length = -1; while((length = is.read(buffer)) != -1) { fos.write(buffer, 0, length); } is.close(); fos.close(); } }
這個Demo和第一個代碼最大的區(qū)別就是,通過getPart()方法獲得了Part對象,通過part對象的getHeader()方法指定標(biāo)頭獲得對應(yīng)的值。
在Tomcat中要在Servlet上設(shè)置@MultipartConfig才能取得Part對象,否則getPart會得到null
@MultipartConfig含有的屬性如下:
fileSizeThreshold:整數(shù)值設(shè)置,若上傳文件大小超過設(shè)置門檻,則先寫入緩存文件,默認(rèn)值為0
location:字符串設(shè)置,設(shè)置寫入文件時的目錄,使用時與write方法一起使用,下一個Demo中演示如何使用,默認(rèn)是空字符串
maxFileSize:限制上傳文件大小,默認(rèn)-1L即無限制
maxRequestSize:限制multipart/form-data請求個數(shù),默認(rèn)值為-1L
Demo3
使用Part的write方法進(jìn)行文件的寫入,HTML文件查看Demo2注釋部分
//uploadPhotoDemo2.java import java.io.IOException; 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 uploadPartDemo2 //設(shè)置屬性,這里的最后一級不用分隔符,可以與Demo2中writeTo方法的路徑做一下對比 @MultipartConfig(location="F:\\javaeeAroundFiles\\later") @WebServlet("/uploadPhoto2") public class uploadPartDemo2 extends HttpServlet { private static final long serialVersionUID = 1L; //@see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //文件名中可能有中文字符所以進(jìn)行編碼設(shè)置,使用setCharacterEncoding()方法 request.setCharacterEncoding("UTF-8"); Part part = request.getPart("photo"); String filename = getFilename(part); //使用Part的write方法,寫入location指定路徑 part.write(filename); } //獲取文件名與Demo2相同不放代碼 private String getFilename(Part part) {} }
若要實(shí)現(xiàn)同時上傳多個文件則可以使用getParts()方法,獲取到的Part對象被保存在一個Collection中
Demo4
<!-- 該HTML是三個input選框,選擇三個文件 --> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title></title> </head> <body> <form action="uploadParts" 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" value="上傳" name="upload" /> </form> </body> </html>
import java.io.IOException; 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 uploadPartsDemo @MultipartConfig(location="F:\\javaeeAroundFiles\\later") @WebServlet("/uploadParts") public class uploadPartsDemo extends HttpServlet { private static final long serialVersionUID = 1L; //@see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); //使用foreach遍歷獲取每一個Part對象 for(Part part : request.getParts()) { if(part.getName().startsWith("file")) { String filename = getFilename(part); part.write(filename); } } } //與之前的getFilename()方法相同 private String getFilename(Part part) { }
看完上述內(nèi)容,你們掌握使用Servlet處理上傳的文件的方法了嗎?如果還想學(xué)到更多技能或想了解更多相關(guān)內(nèi)容,歡迎關(guān)注億速云行業(yè)資訊頻道,感謝各位的閱讀!
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