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本文实例为大家分享了java实现文件上传下载的具体代码,供大家参考,具体内容如下
一.上传
1.前端:
<form method="post" action="fileupload" enctype="multipart/form-data"> <input type="file" name="uploadfile" /> <br/> <input type="submit" value="上传" /> </form>
2.后台:
import java.io.file; import java.io.ioexception; import java.io.printwriter; import java.util.list; import javax.servlet.servletexception; import javax.servlet.annotation.webservlet; 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.disk.diskfileitemfactory; import org.apache.commons.fileupload.servlet.servletfileupload; import dao.filedao; @webservlet("/fileupload") public class fileupload extends httpservlet { private static final long serialversionuid = 1l; // 上传配置 private static final int memory_threshold = 1024 * 1024 * 3; // 3mb private static final int max_file_size = 1024 * 1024 * 40; // 40mb private static final int max_request_size = 1024 * 1024 * 50; // 50mb public fileupload() { super(); } protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { request.setcharacterencoding("utf-8"); response.setcharacterencoding("utf-8"); response.setcontenttype("text/html;charset=utf-8"); printwriter out = response.getwriter(); if (!servletfileupload.ismultipartcontent(request)) { // 如果不是则停止 out.println("error: 表单必须包含 enctype=multipart/form-data"); out.flush(); return; } // 配置上传参数 diskfileitemfactory factory = new diskfileitemfactory(); // 设置内存临界值 - 超过后将产生临时文件并存储于临时目录中 factory.setsizethreshold(memory_threshold); // 设置临时存储目录 factory.setrepository(new file(system.getproperty("java.io.tmpdir"))); servletfileupload upload = new servletfileupload(factory); // 设置最大文件上传值 upload.setfilesizemax(max_file_size); // 设置最大请求值 (包含文件和表单数据) upload.setsizemax(max_request_size); // 中文处理 upload.setheaderencoding("utf-8"); string uploadpath = request.getservletcontext().getrealpath("/files"); file uploaddir = new file(uploadpath); if (!uploaddir.exists()) { uploaddir.mkdir(); } try { // 解析请求的内容提取文件数据 list<fileitem> formitems = upload.parserequest(request); if (formitems != null && formitems.size() > 0) { // 迭代表单数据 for (fileitem item : formitems) { // 处理不在表单中的字段 if (!item.isformfield()) { string filename = new file(item.getname()).getname(); string filepath = uploadpath + file.separator + filename; file storefile = new file(filepath); // 在控制台输出文件的上传路径 // system.out.println(filepath); // 保存文件到硬盘 if(storefile.exists()) { out.println("上传失败,文件已存在!"); }else { item.write(storefile); out.println("文件上传成功!"); } } } } } catch (exception ex) { response.getwriter().println("文件上传成功!"); } } protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { doget(request, response); } }
二.下载
1.下载链接:
filedownload?filename="+urlencoder.encode(filename,"utf-8") --------- 需要对url中的中文参数进行编码,否则会出现乱码
2.后台:
import java.io.file; import java.io.fileinputstream; import java.io.ioexception; import java.io.printwriter; import java.net.urlencoder; import javax.servlet.servletexception; import javax.servlet.annotation.webservlet; import javax.servlet.http.httpservlet; import javax.servlet.http.httpservletrequest; import javax.servlet.http.httpservletresponse; @webservlet("/filedownload") public class filedownload extends httpservlet { private static final long serialversionuid = 1l; public filedownload() { super(); } protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { request.setcharacterencoding("utf-8"); response.setcharacterencoding("utf-8"); printwriter out = response.getwriter(); string dirpath = request.getservletcontext().getrealpath("/files"); string filename = urlencoder.encode(request.getparameter("filename"),"utf-8"); //需要对url中的中文参数进行编码,否则出现乱码 response.getwriter().println(filename); string filepath = dirpath + file.separator + filename; response.setcontenttype("application/octet-stream"); response.setheader("content-disposition", "attachment; filename=\"" + filename + "\""); fileinputstream fileinputstream = new fileinputstream(filepath); int i = 0; while ((i = fileinputstream.read()) != -1) { out.write(i); } fileinputstream.close(); out.close(); } protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { doget(request, response); } }
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