public static Integer getTomcatPortFromConfigXml(File serverXml) {     Integer port;     try {        DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();        domFactory.setNamespaceAware(true); // never forget this!        DocumentBuilder builder = domFactory.newDocumentBuilder();        Document doc = builder.parse(serverXml);        XPathFactory factory = XPathFactory.newInstance();        XPath xpath = factory.newXPath();        XPathExpression expr = xpath.compile          ("/Server/Service[@name='Catalina']/Connector[count(@scheme)=0]/@port[1]");        String result = (String) expr.evaluate(doc, XPathConstants.STRING);        port =  result != null && result.length() > 0 ? Integer.valueOf(result) : null;     } catch (Exception e) {       port = null;     }     return port;  }

另外：System.getProperty()中的字符串参数如下： System.getProperty()参数大全 # java.version                                Java Runtime Environment version # java.vendor                                Java Runtime Environment vendor # java.vendor.url                           Java vendor URL # java.home                                Java installation directory # java.vm.specification.version   Java Virtual Machine specification version # java.vm.specification.vendor    Java Virtual Machine specification vendor # java.vm.specification.name      Java Virtual Machine specification name # java.vm.version                        Java Virtual Machine implementation version # java.vm.vendor                        Java Virtual Machine implementation vendor # java.vm.name                        Java Virtual Machine implementation name # java.specification.version        Java Runtime Environment specification version # java.specification.vendor         Java Runtime Environment specification vendor # java.specification.name           Java Runtime Environment specification name # java.class.version                    Java class format version number # java.class.path                      Java class path # java.library.path                 List of paths to search when loading libraries # java.io.tmpdir                       Default temp file path # java.compiler                       Name of JIT compiler to use # java.ext.dirs                       Path of extension directory or directories # os.name                              Operating system name # os.arch                                  Operating system architecture # os.version                       Operating system version # file.separator                         File separator ("/" on UNIX) # path.separator                  Path separator (":" on UNIX) # line.separator                       Line separator ("\n" on UNIX) # user.name                        User's account name # user.home                              User's home directory # user.dir                               User's current working directory

# 对于getCanonicalPath()函数，“."就表示当前的文件夹，而”..“则表示当前文件夹的上一级文件夹 # 对于getAbsolutePath()函数，则不管”.”、“..”，返回当前的路径加上你在new File()时设定的路径 # 至于getPath()函数，得到的只是你在new File()时设定的路径 比如当前的路径为 C:\test ： File directory = new File("abc"); directory.getCanonicalPath(); //得到的是C:\test\abc directory.getAbsolutePath();    //得到的是C:\test\abc direcotry.getPath();                    //得到的是abc File directory = new File("."); directory.getCanonicalPath(); //得到的是C:\test directory.getAbsolutePath();    //得到的是C:\test\. direcotry.getPath();                    //得到的是. File directory = new File(".."); directory.getCanonicalPath(); //得到的是C:\ directory.getAbsolutePath();    //得到的是C:\test\.. direcotry.getPath();                    //得到的是..