在server.xml
我的tomcat文件夹中,我在<Host>
标记下有一个虚拟文件夹:
<Context docBase="C:\app_files\" path="/app_files"/>
因此,我可以通过url从此文件夹中访问文件:http:// localhost:8080 / app_files / some_file.jpg
但这仅在启动服务器之前图像或文件已经存在的情况下才有效。如果我转到指向服务器启动后创建的图像的URL,则会出现404错误。重新启动服务器后,映像将正确加载。
如何解决这个问题?
实际上,在不使用server.xml的上下文的情况下,我确实设法完成了所需的操作。它基于BalusC的解决方案来通过servlet提供静态文件,方法如下:
public String imageUrl;
public void createAndShowImage() {
try {
String imageName = "/nice_images_folder/cool_image.jpg";
File imageFile = new File(System.getenv("MANAGEMENT_FILES") + imageName);
//Here goes your logic to create the file
createImage(imageFile);
//Here i use a fixed URL, you can do it as you see fit
this.imageUrl = "http://localhost:8080/MyCoolApp/" + CoolFileServlet.BASE_URL + imageName + "?delete=true";
} catch (Exception e) {
e.printStackTrace();
}
}
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLDecoder;
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(name="CoolFileServlet", urlPatterns={CoolFileServlet.BASE_URL + "*"})
public class CoolFileServlet extends HttpServlet {
public static final String BASE_URL = "/shiny_happy_files/";
private static final int DEFAULT_BUFFER_SIZE = 10240;
private String filePath;
public void init() throws ServletException {
this.filePath = System.getenv("MANAGEMENT_FILES");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
String requestedFile = request.getPathInfo();
if (requestedFile == null) {
response.sendError(HttpServletResponse.SC_NOT_FOUND); // 404.
return;
}
File file = new File(filePath, URLDecoder.decode(requestedFile, "UTF-8"));
if (!file.exists()) {
response.sendError(HttpServletResponse.SC_NOT_FOUND); // 404.
return;
}
String contentType = getServletContext().getMimeType(file.getName());
if (contentType == null) {
contentType = "application/octet-stream";
}
response.reset();
response.setBufferSize(DEFAULT_BUFFER_SIZE);
response.setContentType(contentType);
response.setHeader("Content-Length", String.valueOf(file.length()));
response.setHeader("Content-Disposition", "attachment; filename=\"" + file.getName() + "\"");
BufferedInputStream input = null;
BufferedOutputStream output = null;
try {
input = new BufferedInputStream(new FileInputStream(file), DEFAULT_BUFFER_SIZE);
output = new BufferedOutputStream(response.getOutputStream(), DEFAULT_BUFFER_SIZE);
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
int length;
while ((length = input.read(buffer)) > 0) {
output.write(buffer, 0, length);
}
} finally {
close(output);
close(input);
try {
if ("true".equals(request.getParameter("delete"))) {
if (!file.delete()) {
throw new RuntimeException("File could not be deleted");
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
private static void close(Closeable resource) {
if (resource != null) {
try {
resource.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
请注意,您可以在访问URL时将其参数delete = true传递给url,以便在恢复后立即将其删除(以防万一不再需要它)。
在我的情况下,我需要在用户执行某些操作后在页面上显示图像,所以我要做的就是显示图像url:
<h:graphicImage url="#{myManagedBean.imageUrl}"/>
就是这样,您可以使用此servlet提供任何类型的文件,并且该文件将立即返回您想要的文件,并且该文件将在服务器重新启动/重新部署之间保持活动状态(如果未通过删除)delete=true
。
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