Tomcat服务器在war webapp中的绝对文件访问 [英] Tomcat server absolute file access in war webapp

问题描述

我有一个Spring webapp，它的 .war 文件已经上传到Tomcat服务器。大部分基本功能都是按照预期工作 - 页面浏览和表单提交。现在我的问题是，我的web应用程序需要读取和写入文件，我不知道如何实现这一点（文件I / O返回显示java.lang.NullPointerException ）。

我使用以下代码来获取给定文件的绝对路径建议通过 Titi Wangsa Bin Damhore 了解相对于服务器的路径：

  HttpSession session = request.getSession（）; 
 ServletContext sc = session.getServletContext（）; 
 String file = sc.getRealPath（src / test.arff）; 
 logger.info（文件路径：+文件）; 
  

以下是输出路径：

 /home/username/tomcat/webapps/appname/src/test.arff 
  

但是当我通过 WinSCP 检查文件目录时，文件的实际路径是：

  /home/username/tomcat/webapps/appname/WEB-INF/classes/test.arff 
  
 
 
 
 以下是我的问题：
 
 
 
 
如何将这些路径转换为像 C：/Users/Workspace/appname/src/test.arff 机器，完美的作品）？它的服务器是 Apache Tomcat 6.0.35 和 Apache Tomcat 6.0.35 。
 
 
为什么代码返回与实际路径不同的路径？ 
 
 
如果文件I / O不适用，我可以使用哪些替代方法？ 
 
 <我只需要访问两个文件（每个<1MB），所以我不认为我可能需要使用数据库来包含它们，如所示。在这个线程中减去 /减去。
 
 
 
 文件I / O  
 
 
 
以下是我用来访问我需要的文件的代码。  
 
 
  BufferedWriter writer; 
尝试{
 URI uri = new URI（/ test.arff）; 
 writer = new BufferedWriter（new FileWriter（
 calcModelService.getAbsolutePath（）+ uri））; 
 
 writer.write（data.toString（））; 
 writer.flush（）; 
 writer.close（）; 
} catch（IOException e）{
 e.printStackTrace（）; 
} catch（URISyntaxException e）{
 e.printStackTrace（）; 
 
  
 
 
解决方案
 p> 
 
 
  ServletContext application = ...; 
 InputStream in = null; 
 
尝试{
 in = application.getResourceAtStream（/ WEB-INF / web.xml）; //示例
 
 //读取文件
} finally {
 if（null！= in）try {in.close（）; } 
 catch（IOException ioe）{/ * log this * /} 
} 
  
 
 
 <要写文件： 
 
 
  ServletContext application = ...; 
文件tmpdir =（File）application.getAttribute（javax.servlet.context.tempdir）; 
 
 if（null == tmpdir）
 throw new IllegalStateException（容器不提供临时目录）; //或者另外处理
 
文件targetFile = new File（tmpDir，my-temp-filename.txt）; 
 BufferedWriter out = null; 
 
尝试{
 out = new BufferedWriter（new FileWriter（targetFile））; 
 
 //写入输出流
} finally {
 if（null！= out）try {out.close（）; } 
 catch（IOException ioe）{/ * log this * /} 
} 
  
 
 
 <如果你不想使用servlet容器提供的tmpdir，那么你应该使用完全在servlet上下文的purvue之外的某个地方，比如 / path / to / temporary / files 或类似的东西。你绝对不希望使用容器的临时目录，除了真正的临时文件，可以删除重新部署等。
 
I have a Spring webapp whose .war file has been uploaded to a Tomcat server. Most of the basic functions are working as intended - page views and form submission. 

My problem now is that my webapp needs to read and write files and I am clueless as to how I can achieve this (the file I/O returns java.lang.NullPointerException). 

I used the following code to get the absolute path of a given file suggested by Titi Wangsa Bin Damhore to know the path relative to the server:
HttpSession session = request.getSession();
ServletContext sc = session.getServletContext();
String file = sc.getRealPath("src/test.arff");
logger.info("File path: " + file);
Here is the output path:
/home/username/tomcat/webapps/appname/src/test.arff
But when I checked the file directory via WinSCP, the file's actual path is:
/home/username/tomcat/webapps/appname/WEB-INF/classes/test.arff
Here are my questions:

How do I transform these paths into something like C:/Users/Workspace/appname/src/test.arff (the original path in my local machine that works perfectly)? It's servers are Apache Tomcat 6.0.35 and Apache Tomcat 6.0.35.
Why is the code returning a different path as opposed to the actual path? 
If file I/O is not applicable, what alternatives can I use?
PS I just need to access two files (< 1MB each) so I don't think I may need to use a database to contain them as suggested by minus in this thread.

File I/O

Below is the code I use for accessing the file I need. 
BufferedWriter writer;
    try {
        URI uri = new URI("/test.arff");
        writer = new BufferedWriter(new FileWriter(
            calcModelService.getAbsolutePath() + uri));

        writer.write(data.toString());
        writer.flush();
        writer.close();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (URISyntaxException e) {
        e.printStackTrace();
    }

解决方案
To read files:
ServletContext application = ...;
InputStream in = null;

try {
  in = application.getResourceAtStream("/WEB-INF/web.xml"); // example

  // read your file
} finally {
  if(null != in) try { in.close(); }
   catch (IOException ioe) { /* log this */ }
}
To write files:
ServletContext application = ...;
File tmpdir = (File)application.getAttribute("javax.servlet.context.tempdir");

if(null == tmpdir)
  throw new IllegalStateException("Container does not provide a temp dir"); // Or handle otherwise

File targetFile = new File(tmpDir, "my-temp-filename.txt");
BufferedWriter out = null;

try {
  out = new BufferedWriter(new FileWriter(targetFile));

  // write to output stream
} finally {
  if(null != out) try { out.close(); }
  catch (IOException ioe) { /* log this */ }
}
If you don't want to use the tmpdir provided by the servlet container, then you should use someplace that is entirely outside of the servlet context's purvue, like /path/to/temporary/files or something like that. You definitely don't want to use the container's temporary directory for anything other than truly temporary files which are okay to delete on re-deployment, etc.

                        
这篇关于Tomcat服务器在war webapp中的绝对文件访问的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！