項目代碼：https://github.com/PeiranZhang/springmvc-fileupload
使用文件下載步驟
- 對請求處理方法使用void或null作為返回類型，並在方法中添加HttpServletResponse參數
- 將響應的內容類型設為文件的內容類型
- 添加一個名為Content-Disposition的HTTP響應標題，並賦值attachment; filename= fileName，這里的fileName是默認文件名，應該出現在File Download（文件下載）對話框中。它通常與文件同名，但是也並非一定如此。（可選）
例子：下載服務器上的pdf文件
指定用戶、密碼登錄表單之后，設置session，然后才可以下載文件:/WEB-INF/data/secret.pdf
Controller代碼
@Controller
public class ResourceController {
private static final Log logger = LogFactory.getLog(ResourceController.class);
/**
* @param login @ModelAttribute 注解接受表單中的login對象
* @param session
* @param model
* @return
*/
@RequestMapping(value="/login")
public String login(@ModelAttribute Login login, HttpSession session, Model model) {
System.out.println(login);
//與jsp中的標簽綁定
model.addAttribute("login", new Login());
if ("paul".equals(login.getUserName()) &&
"secret".equals(login.getPassword())) {
//設置session
session.setAttribute("loggedIn", Boolean.TRUE);
return "Main";
} else {
return "LoginForm";
}
}
@RequestMapping(value="/resource_download")
public String downloadResource(HttpSession session, HttpServletRequest request,
HttpServletResponse response) {
if (session == null ||
session.getAttribute("loggedIn") == null) {
return "LoginForm";
}
String dataDirectory = request.
getServletContext().getRealPath("/WEB-INF/data");
System.out.println(dataDirectory);
File file = new File(dataDirectory, "secret.pdf");
if (file.exists()) {
//設置響應類型，這里是下載pdf文件
response.setContentType("application/pdf");
//設置Content-Disposition，設置attachment，瀏覽器會激活文件下載框；filename指定下載后默認保存的文件名
//不設置Content-Disposition的話，文件會在瀏覽器內打卡，比如txt、img文件
response.addHeader("Content-Disposition",
"attachment; filename=secret.pdf");
byte[] buffer = new byte[1024];
FileInputStream fis = null;
BufferedInputStream bis = null;
// if using Java 7, use try-with-resources
try {
fis = new FileInputStream(file);
bis = new BufferedInputStream(fis);
OutputStream os = response.getOutputStream();
int i = bis.read(buffer);
while (i != -1) {
os.write(buffer, 0, i);
i = bis.read(buffer);
}
} catch (IOException ex) {
// do something,
// probably forward to an Error page
} finally {
if (bis != null) {
try {
bis.close();
} catch (IOException e) {
}
}
if (fis != null) {
try {
fis.close();
} catch (IOException e) {
}
}
}
}
return null;
}
}
LoginForm.jsp
Main.jsp
結果
例子：瀏覽器內顯示圖片。圖片放在WEN-INF目錄下面，可以禁止直接請求
Controller代碼
@Controller
public class ImageController {
private static final Log logger = LogFactory.getLog(ImageController.class);
@RequestMapping(value="/image_get/{id}", method = RequestMethod.GET)
public void getImage(@PathVariable String id,
HttpServletRequest request,
HttpServletResponse response,
@RequestHeader String referer) {
//referer記錄了該請求是從哪個鏈接過來的，可以用來判斷請求是否合法
if (referer != null) {
System.out.println(referer);
String imageDirectory = request.getServletContext().
getRealPath("/WEB-INF/image");
File file = new File(imageDirectory,
id + ".jpg");
if (file.exists()) {
response.setContentType("image/jpg");
//不設置Content-Disposition的，圖像在瀏覽器內打卡
byte[] buffer = new byte[1024];
FileInputStream fis = null;
BufferedInputStream bis = null;
// if you're using Java 7, use try-with-resources
try {
fis = new FileInputStream(file);
bis = new BufferedInputStream(fis);
OutputStream os = response.getOutputStream();
int i = bis.read(buffer);
while (i != -1) {
os.write(buffer, 0, i);
i = bis.read(buffer);
}
} catch (IOException ex) {
// do something here
} finally {
if (bis != null) {
try {
bis.close();
} catch (IOException e) {
}
}
if (fis != null) {
try {
fis.close();
} catch (IOException e) {
}
}
}
}
}
}
}
html文件
結果
直接請求html文件，html里面的img標簽的src記錄了請求地址，發出請求，后台控制，將圖片的內容輸出到瀏覽器上
參考
- 《JSP、Servlet和SpringMVC學習指南》