Java File download

We will go directly to the topic, file download only need four steps:

1. Set the file ContentType type

2. Setting the file header

3. Get Servletoutputstream object (out) via response

4. Write to the output stream (out)

Download code:

I'm using SPRINGMVC here, but the only purpose here is to get the ServletContext object, the object's purpose, as explained in the following example

Download, need to use two jar package: Commons-fileupload.jar and Commons-io.jar

Java code

2. Import Org.springframework.stereotype.Controller;
4. Import org.springframework.web.bind.annotation.RequestMapping;
6. Import Org.springframework.web.context.ServletContextAware;
10. Import Javax.servlet.ServletContext;
12. Import Javax.servlet.ServletOutputStream;
14. Import Javax.servlet.http.HttpServletResponse;
16. Import java.io.*;
20. @Controller
22. Public class Filecontroller implements servletcontextaware{
24. //spring here is to inject the ServletContext object by implementing the Servletcontextaware interface
26. private ServletContext ServletContext;
32. @RequestMapping ("File/download")
34. public void FileDownload (httpservletresponse response) {
36. //Get Site Deployment path (via ServletContext object) to determine the location of the download file for download
38. String path = Servletcontext.getrealpath ("/");
42. //1. Set the file contenttype type so that it will automatically determine the type of download file
44. Response.setcontenttype ("Multipart/form-data");
46. //2. Setting the file header: The last parameter is to set the download file name (if we call A.pdf)
48. Response.setheader ("content-disposition", "attachment;filename=" +"a.pdf");
50. Servletoutputstream out;
52. //The file object is obtained through the path of the files (false there is a download.pdf file in this path)
54. File File = new file (path + "download/" + "download.pdf");
58. try {
60. FileInputStream InputStream = new FileInputStream (file);
64. //3. Getting Servletoutputstream objects by response (out)
66. out = Response.getoutputstream ();
70. int b = 0;
72. byte[] buffer = new byte[512];
74. While (b! =-1) {
76. b = inputstream.read (buffer);
78. //4. Writing to the output stream (out)
80. Out.write (buffer,0,b);
82. }
84. Inputstream.close ();
86. Out.close ();
88. Out.flush ();
92. } catch (IOException e) {
94. E.printstacktrace ();
96. }
98. }
102. @Override
104. public void Setservletcontext (ServletContext servletcontext) {
106. this.servletcontext = ServletContext;
108. }
110. }

Java File download