tomcat 5.5 - 读取资源文件的问题

Question

I'm using Tomcat 5.5 as my servlet container. My web application deploys via .jar and has some resource files (textual files with strings and configuration parameters) located under its WEB-INF directory. Tomcat 5.5 runs on ubuntu linux. The resource file is read with a file reader:
fr = new FileReader("messages.properties");

The problem is that sometimes the servlet can't find the resource file, but if i restart it a couple of times it works, then again after some time it stops working. Can someone suggest what's the best way of reading resource strings from a servlet? Or a workaround for this problem? Putting the resource files under WEB-INF/classes doesn't help either.

Answer 1

If you are trying to access this file from a Servlet-aware class, such as a ContextListener or other lifecycle listener, you can use the ServletContext object to get the path to a resource.

These three are roughly equivalent. (Don't confuse getResourceAsStream as the same as the one provided by the ClassLoader class. They behave very differently)

void myFunc(ServletContext context) {
   //returns full path. Ex: C:\tomcat\5.5\webapps\myapp\web-inf\message.properties 
   String fullCanonicalPath = context.getRealPath("/WEB-INF/message.properties");

   //Returns a URL to the file. Ex: file://c:/tomcat..../message.properties
   URL urlToFile = context.getResource("/WEB-INF/message.properties");

   //Returns an input stream. Like calling getResource().openStream();
   InputStream inputStream = context.getResourceAsStream("/WEB-INF/message.properties");
   //do something
}

Answer 2

I'm guessing the problem is you're trying to use a relative path to access the file. Using absolute path should help (ie "/home/tomcat5/properties/messages.properties").

However, the usual solution to this problem is to use the getResourceAsStream method of the ClassLoader. Deploying the properties file to "WEB-INF/classes" will make it available to the class loader and you'll be able to access the properties stream.

Untested proto-code:

Properties props = new Properties();

InputStream is =
getClass().getClassLoader().getResourceAsStream("messages.properties");

props.load(is);

Answer 3

I use the following code to load a properties file from within a servlet:

public void init(ServletConfig config) throws ServletException {
    String pathToFile = config.getServletContext().getRealPath("")
        + "/WEB-INF/config.properties";
    Properties properties = new Properties();
    properties.load(new FileInputStream(pathToPropertiesFile));
}

This works with Tomcat 6.0

Answer 4

If you use

new FileReader("message.properties");

Then the FileReader will attempt to read that file from the base directory - which in Tomcat is likely to be the /bin folder.

As diciu mentioned, use an absolute path or load it as a resource the classloader.

Answer 5

我用过Jboss Seam：

ServletLifecycle.getServletContext().getRealPath("")