servlet中可以使用post请求上传文件，使用getreader()和getinputstream()自己处理，也可以使用getpart()或getparts()封装了一些功能的方法处理，getparts()可以同时上传多个文件。接下来使用四个demo来练习一下使用方法
一.使用getreader()和getinputstream()
demo1
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<!-- 这是html代码块，窗体网页上显示的是一个选择文件的input框和一个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"> 选择文件：<input type="file" name="filename" value="" /><br> <input type="submit" value="upload" name="upload" /> </form> </body></html> |
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//这是servlet处理部分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 { //读取请求body byte[] body = readbody(request); //取得所有body内容的字符串表示 string textbody = new string(body, "iso-8859-1"); //取得上传的文件的文件名(取得路径并分离) string filename = getfilename(textbody); //取得文件内容在body中的首尾索引 position p = getfileposition(request, textbody); //将内容输出到文件 writeto(filename, body, p); } //存放索引的类 class position{ int begin; int end; position(int begin, int end) { this.begin = begin; this.end = end; } } //读取请求body private byte[] readbody(httpservletrequest request) throws ioexception { int formdatalength = request.getcontentlength(); //获得servletinputstream对象 //getreader()和getinputstream()只能则一调用，否则会抛出illegalstateexception异常 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; } //取得上传文件名称 private string getfilename(string reqbody) { //获取filename的value,10是filename="的长度 //通过后台调试我发现filename=后加的是带着双引号的路径名，在获取路径名时不需要分号所以在分离时就将分号也分离掉了 string filename = reqbody.substring(reqbody.indexof("filename=\"") + 10); //找到文件名这行的末尾，过滤掉对于获取文件名而言的无用信息 filename = filename.substring(0, filename.indexof("\n")); //获取不包含路径名的文件名 filename = filename.substring(filename.lastindexof("\\") + 1, filename.lastindexof("\"")); //此时后台打印分离路径后的文件名并将其作为返回值返回 system.out.println(filename); return filename; } //取得文件开始和结束位置 private position getfileposition(httpservletrequest request, string textbody) throws ioexception { //取得文件区段边界信息 string contenttype = request.getcontenttype(); string boundarytext = contenttype.substring( contenttype.lastindexof("=") + 1, contenttype.length()); //取得实际上传文件的起始与结束位置 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); } //输出至文件 private void writeto(string filename, byte[] body, position p) throws ioexception { //默认上传的文件是在f:\\javaeearoundfiles目录下 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
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//html代码块<!-- 该html供uploadpartdemo和uploadpartdemo2共同使用，使用时通过更改body的form的action属性值控制 --><!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"> 上传相片：<input type="file" name="photo" /><br><br> <input type="submit" value="上传" name="upload" /> </form> </body></html> |
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//uploadphotodemo.javaimport 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中必须设置@mutipartconfig标注才能使用getpart()相关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()获取part对象 part part = request.getpart("photo"); string filename = getfilename(part); writeto(filename, part); } private string getfilename(part part) { string header = part.getheader("content-disposition"); //获取完整路径 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); //获取文件名 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(); }} |
这个demo和第一个代码最大的区别就是，通过getpart()方法获得了part对象，通过part对象的getheader()方法指定标头获得对应的值。
在tomcat中要在servlet上设置@multipartconfig才能取得part对象，否则getpart会得到null
@multipartconfig含有的属性如下：
- filesizethreshold：整数值设置，若上传文件大小超过设置门槛，则先写入缓存文件，默认值为0
- location：字符串设置，设置写入文件时的目录，使用时与write方法一起使用，下一个demo中演示如何使用，默认是空字符串
- maxfilesize：限制上传文件大小，默认-1l即无限制
- maxrequestsize：限制multipart/form-data请求个数，默认值为-1l
demo3
使用part的write方法进行文件的写入，html文件查看demo2注释部分
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//uploadphotodemo2.javaimport 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//设置属性，这里的最后一级不用分隔符，可以与demo2中writeto方法的路径做一下对比@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进行编码设置，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，写入location指定路径 part.write(filename); } //获取文件名与demo2相同不放代码 private string getfilename(part part) {}} |
若要实现同时上传多个文件则可以使用getparts()方法，获取到的part对象被保存在一个collection中
demo4
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<!-- 该html是三个input选框，选择三个文件 --><!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="上传" name="upload" /> </form> </body></html> |
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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遍历获取每一个part对象 for(part part : request.getparts()) { if(part.getname().startswith("file")) { string filename = getfilename(part); part.write(filename); } } } //与之前的getfilename()方法相同 private string getfilename(part part) {} |
总结
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原文链接：https://blog.csdn.net/sdr_zd/article/details/77952196
