// no nulls
        if ((null==userId) || (null==password)) {
         System.out.print("userid is null");
            throw new UserDirectoryException();
        }

        try {

            // conform userId to uppercase when stored
            p.put(fixId(userId), password);
            String o = this.getClass().getClassLoader().getResource(UserDirectoryFile).getFile();
            p.store(new FileOutputStream(o), UserDirectoryHeader);

           
        }

        catch (IOException e) {
            throw new UserDirectoryException();

       }
    }

修改为：
    public void setUser(String userId, String password) throws
            UserDirectoryException {

        // no nulls
        if ((null==userId) || (null==password)) {
         System.out.print("userid is null");
            throw new UserDirectoryException();
        }

        try {

            // conform userId to uppercase when stored
            p.put(fixId(userId), password);
            String o = this.getClass().getClassLoader().getResource(UserDirectoryFile).getFile();
     System.out.println(o); //o is /D:/myregister/WEB-INF/classes/resources/users.properties
     String ostr=o.substring(1); // the  line must be add is to use to remove the "/" in  String o
     System.out.println(ostr); //ostr is D:/myregister/WEB-INF/classes/resources/users.properties
            p.store(new FileOutputStream(ostr), UserDirectoryHeader);//modify o as ostr

           
        }

        catch (IOException e) {
            throw new UserDirectoryException();

       }
    }

注意最关键的是将：this.getClass().getClassLoader().getResource(UserDirectoryFile).getFile();所获得的字符串进行处理因为它前面多了一个"/"。需要去掉。



英文：

I found a solution to your problem

first step:
you must deploy the application build a folder  make sure you don't use
a directory which has any spaces in the path (such as the Program Files directory on Windows)as this may
cause the UserDirectoryException.
such as build a folder "myregister"  in Driver D and copy the program in it.

add the following codes to server.xml:

<Context path="/myregister"
docBase="d:\myregister\"
crossContext="false"
debug="0"
reloadable="true" >

<Logger className="org.apache.catalina.logger.FileLogger"
prefix="localhost_dbtest_log." suffix=".txt"
timestamp="true"/>

</Context>

second step:
just find the following code within the 'UserDirectory.java'
    public void setUser(String userId, String password) throws
            UserDirectoryException {

        // no nulls
        if ((null==userId) || (null==password)) {
         System.out.print("userid is null");
            throw new UserDirectoryException();
        }

        try {

            // conform userId to uppercase when stored
            p.put(fixId(userId), password);
            String o = this.getClass().getClassLoader().getResource(UserDirectoryFile).getFile();
            p.store(new FileOutputStream(o), UserDirectoryHeader);

           
        }

        catch (IOException e) {
            throw new UserDirectoryException();

       }
    }

modify as follow:
    public void setUser(String userId, String password) throws
            UserDirectoryException {

        // no nulls
        if ((null==userId) || (null==password)) {
         System.out.print("userid is null");
            throw new UserDirectoryException();
        }

        try {

            // conform userId to uppercase when stored
            p.put(fixId(userId), password);
            String o = this.getClass().getClassLoader().getResource(UserDirectoryFile).getFile();
     System.out.println(o); //o is /D:/myregister/WEB-INF/classes/resources/users.properties
     String ostr=o.substring(1); // the  line must be add is to use to remove the "/" in  String o
     System.out.println(ostr); //ostr is D:/myregister/WEB-INF/classes/resources/users.properties
            p.store(new FileOutputStream(ostr), UserDirectoryHeader);//modify o as ostr

           
        }

        catch (IOException e) {
            throw new UserDirectoryException();

       }
    }

by the way,the String o is /D:/myregister/WEB-INF/classes/resources/users.properties
the String ostr is D:/myregister/WEB-INF/classes/resources/users.properties