图片或者HTML文件这样的静态资源 ，在浏览器中打开 正确的URL就可以下载，只要资源是放在应用程序的目录下面，或者是应用程序的子目录下面，而不是放在WEB-INF下，Servlet/jsp容器就
会将这个资源发送到浏览器。然而，有时候静态资源是保存一应用程序目录以外或者是数据库中，则要通过编程来发送资源。
例子
- 工程目录
- ResourceController
@Controller
public class ResourceController {
private static final Log logger = LogFactory.getLog(ResourceController.class );
@RequestMapping(value ="/login")
public String login(@ModelAttribute Login login, HttpSession session, Model model){
model.addAttribute("login" , new Login()) ; // for what
if ("lsj".equals(login.getUserName())&& "123".equals(login.getPassword())){
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 dataDir= request.getServletContext().getRealPath("/WEB-INF/data") ;
File file = new File(dataDir , "secret.pdf") ;
if (file.exists()){
response.setContentType("application/pdf");
response.addHeader("Content-Disposition",
"attachment; filename=secret.pdf");
byte [] buffer = new byte[1024];
FileInputStream fis = null;
BufferedInputStream bis = null;
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 (Exception e) {
e.printStackTrace();
}finally{
if (bis!= null){
try {
bis.close();
} catch (IOException e2) {
}
}
if (fis!= null){
try {
fis.close();
} catch (IOException e2) {
}
}
}
}
return null;//不进行跳转
}
}
- Login
public class Login implements Serializable {
private static final long serialVersionUID = -38L;
private String userName;
private String password;
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
- LoginForm.jsp
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML>
<html>
<head>
<title>Login</title>
<style type="text/css">@import url("<c:url value="/css/main.css"/>");</style>
</head>
<body>
<div id="global">
<form:form commandName="login" action="login" method="post">
<fieldset>
<legend>Login</legend>
<p>
<label for="userName">User Name: </label>
<form:input id="userName" path="userName" cssErrorClass="error"/>
</p>
<p>
<label for="password">Password: </label>
<form:password id="password" path="password" cssErrorClass="error"/>
</p>
<p id="buttons">
<input id="reset" type="reset" tabindex="4">
<input id="submit" type="submit" tabindex="5"
value="Login">
</p>
</fieldset>
</form:form>
</div>
</body>
</html>
- Main.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE HTML>
<html>
<head>
<title>Download Page</title>
<style type="text/css">@import url("<c:url value="/css/main.css"/>");</style>
</head>
<body>
<div id="global">
<h4>Please click the link below.</h4>
<p>
<a href="resource_download">Download</a>
</p>
</div>
</body>
</html>